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Zhu T, Yang Y, Hu C, Ma L, Sheng J, Chang R, Liao Y, Wang L, Zhu Y, Zhao M, Li B, Li T, Liao C. Effects of Enterobacter cloacae insecticidal protein on the Duox-ROS system and midgut bacterial community and function of Galleria mellonella larvae. Toxicon 2024; 247:107850. [PMID: 38971137 DOI: 10.1016/j.toxicon.2024.107850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2023] [Revised: 07/01/2024] [Accepted: 07/03/2024] [Indexed: 07/08/2024]
Abstract
BACKGROUND Enterobacter cloacae insecticidal proteins have been reported to kill Galleria mellonella larvae through affecting their midgut microbiome. However, the mechanisms involved remain unclear. Here we aim to investigate how the insecticidal proteins act on the midgut Duox-ROS system and microbial community of G. mellonella larvae. METHODS Reverse transcription qPCR and fluorescence probes were utilized to assess the Duox expression levels and to evaluate quantitative changes of the ROS levels. Sequencing of the 16S rRNA gene sequences of the midgut bacteria of G. mellonella larvae was conducted for further analyses of bacterial diversity, composition, and abundance. RESULTS After the injection of the insecticidal proteins, the Duox expression levels first increased within 28 h, then dramatically peaked at 36 h, and slowly decreased thereafter. Simultaneously, the ROS levels increased significantly at 36 h, peaked at 48 h, and rapidly declined to the normal level at 60 h. Responsive to the change of the ROS levels, the structure of the midgut microbial community was altered substantially, compared to that of the untreated larvae. The relative abundance of Enterobacteriaceae and other specific pathogenic bacteria increased significantly, whereas that of Lactobacillus decreased sharply. Importantly, notable shifts were observed in the crucial midgut predicted metabolic functions, including membrane transportation, carbohydrate metabolism, and amino acid metabolism. CONCLUSION Insecticidal proteins of E. cloacae kill G. mellonella larvae mainly through generation of high oxidative stress, alterations of the midgut microbial community and function, and damage to the physiological functions. These findings provide insights into the inhibition mechanism of E. cloacae insecticidal proteins to G. mellonella larvae.
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Affiliation(s)
- Tao Zhu
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China; Laboratory of Water Pollution Control and Rehabilitation Technology, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Yi Yang
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Chao Hu
- Pingdingshan Academy of Agricultural Sciences, China
| | - Liang Ma
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Jiaqing Sheng
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Ruiying Chang
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Yanfei Liao
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Lianzhe Wang
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China; Laboratory of Water Pollution Control and Rehabilitation Technology, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Yutao Zhu
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Mei Zhao
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China
| | - Bingbing Li
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China; Laboratory of Water Pollution Control and Rehabilitation Technology, Henan University of Urban Construction, Pingdingshan, Henan, China.
| | - Taotao Li
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China; Laboratory of Water Pollution Control and Rehabilitation Technology, Henan University of Urban Construction, Pingdingshan, Henan, China.
| | - Chunli Liao
- College of Life Science and Engineering, Henan University of Urban Construction, Pingdingshan, Henan, China; Center of Healthy Food Engineering and Technology of Henan, Henan University of Urban Construction, Pingdingshan, Henan, China; Laboratory of Water Pollution Control and Rehabilitation Technology, Henan University of Urban Construction, Pingdingshan, Henan, China.
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Chen G, Li Q, Zhang C, Zhao W, Jurat-Fuentes JL, Zhou X, Chen F, Yang X, Han L. Synergism of Cry1Ca toxicity by gut resident Enterococcus spp. in the rice stem borer, Chilo suppressalis. Int J Biol Macromol 2024; 257:128654. [PMID: 38065453 DOI: 10.1016/j.ijbiomac.2023.128654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 11/29/2023] [Accepted: 12/05/2023] [Indexed: 01/26/2024]
Abstract
The bacterium Bacillus thuringiensis (Bt) is the most economically successful biopesticide to date, and Bt insecticidal proteins are produced in transgenic crops for pest control. However, relevant details in the Bt-mediated killing process remain undefined. In our previous research, we observed reduced larval susceptibility to Bt Cry1Ca in Chilo suppressalis, a major rice pest in China, after gut microbiota elimination. Here, we tested the hypothesis that gut microbiota, particularly abundant Enterococcus spp., influences C. suppressalis susceptibility to Cry1Ca. We isolated and identified four Enterococcus spp. from C. suppressalis gut microbiota and evaluated their impact on Cry1Ca toxicity. Among the four Enterococcus spp. identified, three of them (E. casseliflavus, E. faecalis, and E. mundtii) dramatically increased larval mortality when introduced in axenic C. suppressalis challenged with Cry1Ca. Gut epithelial damage by Cry1Ca promoted the translocation of Enterococcus spp. from the gut lumen into the hemocoel, where they proliferated and induced larval melanization and hemocyte apoptosis. Our combined findings demonstrate that the presence of specific gut microbiota can greatly affect susceptibility to Cry1Ca through melanization and apoptosis of hemocytes. Better understanding of the Bt intoxication process guides the development of bio-enhancers for Bt-based microbial biopesticides and potential improvement of transgenic crops.
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Affiliation(s)
- Geng Chen
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Qianwen Li
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Chen Zhang
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Wanxuan Zhao
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | | | - Xuguo Zhou
- Department of Entomology, University of Kentucky, Lexington 40546, USA
| | - Fajun Chen
- Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Xiaowei Yang
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
| | - Lanzhi Han
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
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Polenogova OV, Klementeva TN, Kabilov MR, Alikina TY, Krivopalov AV, Kruykova NA, Glupov VV. A Diet with Amikacin Changes the Bacteriobiome and the Physiological State of Galleria mellonella and Causes Its Resistance to Bacillus thuringiensis. INSECTS 2023; 14:889. [PMID: 37999088 PMCID: PMC10672437 DOI: 10.3390/insects14110889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/10/2023] [Accepted: 11/14/2023] [Indexed: 11/25/2023]
Abstract
Environmental pollution with antibiotics can cause antibiotic resistance in microorganisms, including the intestinal microbiota of various insects. The effects of low-dose aminoglycoside antibiotic (amikacin) on the resident gut microbiota of Galleria mellonella, its digestion, its physiological parameters, and the resistance of this species to bacteria Bacillus thuringiensis were investigated. Here, 16S rDNA analysis revealed that the number of non-dominant Enterococcus mundtii bacteria in the eighteenth generation of the wax moth treated with amikacin was increased 73 fold compared to E. faecalis, the dominant bacteria in the native line of the wax moth. These changes were accompanied by increased activity of acidic protease and glutathione-S-transferase in the midgut tissues of larvae. Ultra-thin section electron microscopy detected no changes in the structure of the midgut tissues. In addition, reduced pupa weight and resistance of larvae to B. thuringiensis were observed in the eighteenth generation of the wax moth reared on a diet with amikacin. We suggest that long-term cultivation of wax moth larvae on an artificial diet with an antibiotic leads to its adaptation due to changes in both the gut microbiota community and the physiological state of the insect organism.
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Affiliation(s)
- Olga V. Polenogova
- Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630091, Russia; (T.N.K.); (A.V.K.); (N.A.K.); (V.V.G.)
| | - Tatyana N. Klementeva
- Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630091, Russia; (T.N.K.); (A.V.K.); (N.A.K.); (V.V.G.)
| | - Marsel R. Kabilov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (M.R.K.); (T.Y.A.)
| | - Tatyana Y. Alikina
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia; (M.R.K.); (T.Y.A.)
| | - Anton V. Krivopalov
- Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630091, Russia; (T.N.K.); (A.V.K.); (N.A.K.); (V.V.G.)
| | - Natalya A. Kruykova
- Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630091, Russia; (T.N.K.); (A.V.K.); (N.A.K.); (V.V.G.)
| | - Viktor V. Glupov
- Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630091, Russia; (T.N.K.); (A.V.K.); (N.A.K.); (V.V.G.)
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Upfold J, Rejasse A, Nielsen-Leroux C, Jensen AB, Sanchis-Borja V. The immunostimulatory role of an Enterococcus-dominated gut microbiota in host protection against bacterial and fungal pathogens in Galleria mellonella larvae. FRONTIERS IN INSECT SCIENCE 2023; 3:1260333. [PMID: 38469511 PMCID: PMC10926436 DOI: 10.3389/finsc.2023.1260333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 10/09/2023] [Indexed: 03/13/2024]
Abstract
Understanding the intricate interplay between the gut microbiota and the immune response in insects is crucial, given its diverse impact on the pathogenesis of various microbial species. The microbiota's modulation of the host immune system is one such mechanism, although its complete impact on immune responses remains elusive. This study investigated the tripartite interaction between the gut microbiota, pathogens, and the host's response in Galleria mellonella larvae reared under axenic (sterile) and conventional (non-sterile) conditions. The influence of the microbiota on host fitness during infections was evaluated via two different routes: oral infection induced by Bacillus thuringiensis subsp. galleriae (Btg), and topical infection induced by Metarhizium robertsii (Mr). We observed that larvae without a microbiota can successfully fulfill their life cycle, albeit with more variation in their developmental time. We subsequently performed survival assays on final-instar larvae, using the median lethal dose (LD50) of Btg and Mr. Our findings indicated that axenic larvae were more vulnerable to an oral infection of Btg; specifically, a dose that was calculated to be half-lethal for the conventional group resulted in a 90%-100% mortality rate in the axenic group. Through a dual-analysis experimental design, we could identify the status of the gut microbiota using 16S rRNA sequencing and assess the level of immune-related gene expression in the same group of larvae at basal conditions and during infection. This analysis revealed that the microbiota of our conventionally reared population was dominated entirely by four Enterococcus species, and these species potentially stimulated the immune response in the gut, due to the increased basal expression of two antimicrobial peptides (AMPs)-gallerimycin and gloverin-in the conventional larvae compared with the axenic larvae. Furthermore, Enterococcus mundtii, isolated from the gut of conventional larvae, showed inhibition activity against Btg in vitro. Lastly, other immune effectors, namely, phenoloxidase activity in the hemolymph and total reactive oxygen/nitrogen species (ROS/RNS) in the gut, were tested to further investigate the extent of the stimulation of the microbiota on the immune response. These findings highlight the immune-modulatory role of the Enterococcus-dominated gut microbiota, an increasingly reported microbiota assemblage of laboratory populations of Lepidoptera, and its influence on the host's response to oral and topical infections.
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Affiliation(s)
- Jennifer Upfold
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Agnès Rejasse
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | | | - Annette Bruun Jensen
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Vincent Sanchis-Borja
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
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Mi L, Gu Z, Li Y, Xu W, Shu C, Zhang J, Bai X, Geng L. Enterobacter Strain IPPBiotE33 Displays a Synergistic Effect with Bacillus thuringiensis Bt185. Int J Mol Sci 2023; 24:14193. [PMID: 37762496 PMCID: PMC10531557 DOI: 10.3390/ijms241814193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 09/08/2023] [Accepted: 09/08/2023] [Indexed: 09/29/2023] Open
Abstract
The discovery and isolation of new non-Bt insecticidal bacteria and genes are significant for the development of new biopesticides against coleopteran pests. In this study, we evaluated the insecticidal activity of non-Bt insecticidal bacteria, PPBiotE33, IPPBiotC41, IPPBiotA42 and IPPBiotC43, isolated from the peanut rhizosphere. All these strains showed insecticidal activity against first- and third-instar larvae of Holotrichia parallela, Holotrichia oblita, Anomala corpulenta and Potosia brevitarsis. IPPBiotE33 showed the highest toxicity among the four strains and exhibited virulence against Colaphellus bowringi. The genome of IPPBiotE33 was sequenced, and a new protein, 03673, with growth inhibition effects on C. bowringi was obtained. In addition, IPPBiotE33 had a synergistic effect with Bacillus thuringiensis Bt185 against H. parallela in bioassays and back-inoculation experiments with peanut seedlings. IPPBiotE33 induced a decrease in hemocytes and an increase in phenol oxidase activity in H. parallela hemolymph, known as the immunosuppressive effect, which mediated synergistic activity with Bt185. This study increased our knowledge of the new insecticidal strain IPPBiotE33 and shed new light on the research on new insecticidal coaction mechanisms and new blended pesticides.
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Affiliation(s)
- Liang Mi
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
- College of Life Sciences, Northeast Agricultural University, Harbin 150038, China
| | - Ziqiong Gu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Ying Li
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Wenyue Xu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Changlong Shu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Xi Bai
- College of Life Sciences, Northeast Agricultural University, Harbin 150038, China
| | - Lili Geng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
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Castañeda-Molina Y, Marulanda-Moreno SM, Saldamando-Benjumea C, Junca H, Moreno-Herrera CX, Cadavid-Restrepo G. Microbiome analysis of Spodoptera frugiperda (Lepidoptera, Noctuidae) larvae exposed to Bacillus thuringiensis (Bt) endotoxins. PeerJ 2023; 11:e15916. [PMID: 37719127 PMCID: PMC10503500 DOI: 10.7717/peerj.15916] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 07/27/2023] [Indexed: 09/19/2023] Open
Abstract
Background Spodoptera frugiperda (or fall armyworm, FAW) is a polyphagous pest native to Western Hemisphere and recently discovered in the Eastern Hemisphere. In Colombia, S. frugiperda is recognized as a pest of economic importance in corn. The species has genetically differentiated into two host populations named "corn" and "rice" strains. In 2012, a study made in central Colombia demonstrated that the corn strain is less susceptible to Bacillus thuringiensis (Bt) endotoxins (Cry1Ac and Cry 1Ab) than the rice strain. In this country, Bt transgenic corn has been extensively produced over the last 15 years. Since gut microbiota plays a role in the physiology and immunity of insects, and has been implicated in promoting the insecticidal activity of Bt, in this study an analysis of the interaction between Bt endotoxins and FAW gut microbiota was made. Also, the detection of endosymbionts was performed here, as they might have important implications in the biological control of a pest. Methods The composition and diversity of microbiomes associated with larval specimens of S. frugiperda(corn strain) was investigated in a bioassay based on six treatments in the presence/absence of Bt toxins and antibiotics (Ab) through bacterial isolate analyses and by high throughput sequencing of the bacterial 16S rRNA gene. Additionally, species specific primers were used, to detect endosymbionts from gonads in S. frugiperda corn strain. Results Firmicutes, Proteobacteria and Bacteroidota were the most dominant bacterial phyla found in S. frugiperda corn strain. No significant differences in bacteria species diversity and richness among the six treatments were found. Two species of Enterococcus spp., E. mundtii and E. casseliflavus were detected in treatments with Bt and antibiotics, suggesting that they are less susceptible to both of them. Additionally, the endosymbiont Arsenophonus was also identified on treatments in presence of Bt and antibiotics. The results obtained here are important since little knowledge exists about the gut microbiota on this pest and its interaction with Bt endotoxins. Previous studies made in Lepidoptera suggest that alteration of gut microbiota can be used to improve the management of pest populations, demonstrating the relevance of the results obtained in this work.
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Affiliation(s)
- Yuliana Castañeda-Molina
- Departamento de Biociencias/Grupo de investigación Microbiodiversidad y Bioprospección/Laboratorio de Biología Celular y Molecular, Universidad Nacional de Colombia, Medellín, Antioquia, Colombia
| | - Sandra María Marulanda-Moreno
- Departamento de Biociencias/Grupo de investigación Microbiodiversidad y Bioprospección/Laboratorio de Biología Celular y Molecular, Universidad Nacional de Colombia, Medellín, Antioquia, Colombia
| | - Clara Saldamando-Benjumea
- Departamento de Biociencias/Grupo de Biotecnologia Vegetal UNALMED-CIB/Laboratorio de Ecología y Evolución de Insectos, Universidad Nacional de Colombia, Medellin, Antioquia, Colombia
| | - Howard Junca
- RG Microbial Ecology: Metabolism, Genomics & Evolution, Div. Ecogenomics & Holobionts, Microbiomas Foundation, Chía, Cundinamarca, Colombia
| | - Claudia Ximena Moreno-Herrera
- Departamento de Biociencias/Grupo de investigación Microbiodiversidad y Bioprospección/Laboratorio de Biología Celular y Molecular, Universidad Nacional de Colombia, Medellín, Antioquia, Colombia
| | - Gloria Cadavid-Restrepo
- Departamento de Biociencias/Grupo de investigación Microbiodiversidad y Bioprospección/Laboratorio de Biología Celular y Molecular, Universidad Nacional de Colombia, Medellín, Antioquia, Colombia
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Zhao C, Wang L, Zhang K, Zhu X, Li D, Ji J, Luo J, Cui J. Variation of Helicoverpa armigera symbionts across developmental stages and geographic locations. Front Microbiol 2023; 14:1251627. [PMID: 37744901 PMCID: PMC10513443 DOI: 10.3389/fmicb.2023.1251627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 08/18/2023] [Indexed: 09/26/2023] Open
Abstract
Cotton bollworm (Helicoverpa armigera) poses a global problem, causing substantial economic and ecological losses. Endosymbionts in insects play crucial roles in multiple insect biological processes. However, the interactions between H. armigera and its symbionts have not been well characterized to date. We investigated the symbionts of H. armigera in the whole life cycle from different geographical locations. In the whole life cycle of H. armigera, Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were the dominant bacteria at the phylum level, while Enterococcus, Enterobacter, Glutamicibacter, and Bacillus were the four dominant bacteria at the genus level. Furthermore, high similarity in symbiotic bacterial community was observed in different stages of H. armigera, which were dominated by Enterococcus and Enterobacter. In fields, the dominant bacteria were Proteobacteria and Bacteroidetes, whereas, in the laboratory, the dominant bacteria were Proteobacteria. At the genus level, the dominant bacteria in cotton bollworm eggs of wild populations were Enterobacter, Morganella, Lactococcus, Asaia, Apibacter, and Enterococcus, and the subdominant bacteria were Bartonella, Pseudomonas, and Orbus. Moreover, the symbionts varied with geographical locations, and the closer the geographical distance, the more similar the microbial composition. Taken together, our study identifies and compares the symbiont variation along with geographical gradients and host development dynamic and reveals the high flexibility of microbiome communities in H. armigera, which probably benefits for the successful survival in a complicated changing environment.
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Affiliation(s)
- Chenchen Zhao
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Henan International Laboratory for Green Pest Control, College of Plant Protection, Henan Agricultural University, Zhengzhou, Henan, China
| | - Li Wang
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, Henan, China
| | - Kaixin Zhang
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, Henan, China
- Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, China
| | - Xiangzhen Zhu
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, Henan, China
- Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, China
| | - Dongyang Li
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, Henan, China
- Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, China
| | - Jichao Ji
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, Henan, China
- Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, China
| | - Junyu Luo
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, China
| | - Jinjie Cui
- National Key Laboratory of Cotton Bio-breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, Henan, China
- Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji, China
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Zhao D, Wu H, Li Y, Wang Q, Ji Y, Guo X, Guo W. Effects of the pyrE deletion mutant from Bacillus thuringiensis on gut microbiota and immune response of Spodoptera exigua. Front Microbiol 2023; 14:1182699. [PMID: 37333629 PMCID: PMC10272597 DOI: 10.3389/fmicb.2023.1182699] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 05/12/2023] [Indexed: 06/20/2023] Open
Abstract
The gut microbiota is essential for the growth and development of insects, and the intestinal immune system plays a critical role in regulating the homeostasis of intestinal microorganisms and their interactions with pathogenic bacteria. Infection with Bacillus thuringiensis (Bt) can disrupt the gut microbiota of insects, but the regulatory factors governing the interaction between Bt and gut bacteria are not well understood. Uracil secreted by exogenous pathogenic bacteria can activate DUOX-mediated reactive oxygen species (ROS) production, which helps maintain intestinal microbial homeostasis and immune balance. To elucidate the regulatory genes involved in the interaction between Bt and gut microbiota, we investigate the effects of uracil derived from Bt on gut microbiota, and host immunity using a uracil deficient Bt strain (Bt GS57△pyrE) obtained by homologous recombination. We analyze the biological characteristics of the uracil deficient strain and found that the deletion of uracil in Bt GS57 strain changed the diversity of gut bacteria in Spodoptera exigua, as investigated using Illumina HiSeq sequencing. Furthermore, qRT-PCR analysis showed that compared with Bt GS57 (control), the expression of the SeDuox gene and the level of ROS were significantly decreased after feeding with Bt GS57△pyrE. Adding uracil to Bt GS57△pyrE restored the expression level of DUOX and ROS to a higher level. Additionally, we observed that PGRP-SA, attacin, defensin and ceropin genes were significant different in the midgut of S. exigua infected by Bt GS57 and Bt GS57△pyrE, with a trend of increasing first and then decreasing. These results suggest that uracil regulates and activates the DUOX-ROS system, affects the expression of antimicrobial peptide genes, and disturb intestinal microbial homeostasis. We preliminarily speculate that uracil is a key factor in the interaction between Bt and gut microbiota, and these findings provide a theoretical basis for clarifying the interaction between Bt, host, and intestinal microorganisms, as well as for gaining new insights into the insecticidal mechanism of B. thuringiensis in insects.
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Affiliation(s)
- Dan Zhao
- College of Plant Protection, Hebei Agricultural University, Baoding, China
| | - Han Wu
- College of Plant Protection, Hebei Agricultural University, Baoding, China
- Graduate School of Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yazi Li
- College of Plant Protection, Hebei Agricultural University, Baoding, China
| | - Qian Wang
- College of Plant Protection, Hebei Agricultural University, Baoding, China
| | - Yujie Ji
- Graduate School of Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xiaochang Guo
- College of Plant Protection, Hebei Agricultural University, Baoding, China
| | - Wei Guo
- College of Plant Protection, Hebei Agricultural University, Baoding, China
- Graduate School of Chinese Academy of Agricultural Sciences, Beijing, China
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9
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Muita BK, Baxter SW. Temporal Exposure to Bt Insecticide Causes Oxidative Stress in Larval Midgut Tissue. Toxins (Basel) 2023; 15:toxins15050323. [PMID: 37235357 DOI: 10.3390/toxins15050323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 04/27/2023] [Accepted: 05/01/2023] [Indexed: 05/28/2023] Open
Abstract
Bacillus thuringiensis (Bt) three-domain Cry toxins are highly successful biological pesticides; however, the mechanism through which they cause death to targeted larval midgut cells is not fully understood. Herein, we challenged transgenic Bt-susceptible Drosophila melanogaster larvae with moderate doses of activated Cry1Ac toxin and assessed the midgut tissues after one, three, and five hours using transmission electron microscopy and transcriptome sequencing. Larvae treated with Cry1Ac showed dramatic changes to their midgut morphology, including shortened microvilli, enlarged vacuoles, thickened peritrophic membranes, and swelling of the basal labyrinth, suggesting water influx. Transcriptome analysis showed that innate immune responses were repressed, genes involved with cell death pathways were largely unchanged, and mitochondria-related genes were strongly upregulated following toxin exposure. Defective mitochondria produced after toxin exposure were likely to contribute to significant levels of oxidative stress, which represent a common physiological response to a range of toxic chemicals. Significant reductions in both mitochondrial aconitase activity and ATP levels in the midgut tissue supported a rapid increase in reactive oxygen species (ROS) following exposure to Cry1Ac. Overall, these findings support the role of water influx, midgut cell swelling, and ROS activity in response to moderate concentrations of Cry1Ac.
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Affiliation(s)
- Biko K Muita
- School of Biological Sciences, University of Adelaide, Adelaide 5005, Australia
| | - Simon W Baxter
- School of BioSciences, University of Melbourne, Melbourne 3010, Australia
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10
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Li Y, Chang L, Xu K, Zhang S, Gao F, Fan Y. Research Progresses on the Function and Detection Methods of Insect Gut Microbes. Microorganisms 2023; 11:1208. [PMID: 37317182 DOI: 10.3390/microorganisms11051208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 03/20/2023] [Accepted: 04/27/2023] [Indexed: 06/16/2023] Open
Abstract
The insect gut is home to an extensive array of microbes that play a crucial role in the digestion and absorption of nutrients, as well as in the protection against pathogenic microorganisms. The variety of these gut microbes is impacted by factors such as age, diet, pesticides, antibiotics, sex, and caste. Increasing evidence indicates that disturbances in the gut microbiota can lead to compromised insect health, and that its diversity has a far-reaching impact on the host's health. In recent years, the use of molecular biology techniques to conduct rapid, qualitative, and quantitative research on the host intestinal microbial diversity has become a major focus, thanks to the advancement of metagenomics and bioinformatics technologies. This paper reviews the main functions, influencing factors, and detection methods of insect gut microbes, in order to provide a reference and theoretical basis for better research utilization of gut microbes and management of harmful insects.
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Affiliation(s)
- Yazi Li
- Tangshan Key Laboratory of Agricultural Pathogenic Fungi and Toxins, Department of Life Science, Tangshan Normal University, Tangshan 063000, China
| | - Liyun Chang
- Tangshan Key Laboratory of Agricultural Pathogenic Fungi and Toxins, Department of Life Science, Tangshan Normal University, Tangshan 063000, China
| | - Ke Xu
- Tangshan Key Laboratory of Agricultural Pathogenic Fungi and Toxins, Department of Life Science, Tangshan Normal University, Tangshan 063000, China
| | - Shuhong Zhang
- Tangshan Key Laboratory of Agricultural Pathogenic Fungi and Toxins, Department of Life Science, Tangshan Normal University, Tangshan 063000, China
| | - Fengju Gao
- Tangshan Key Laboratory of Agricultural Pathogenic Fungi and Toxins, Department of Life Science, Tangshan Normal University, Tangshan 063000, China
| | - Yongshan Fan
- Tangshan Key Laboratory of Agricultural Pathogenic Fungi and Toxins, Department of Life Science, Tangshan Normal University, Tangshan 063000, China
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11
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Lei X, Zhang F, Zhang J. Gut Microbiota Accelerate the Insecticidal Activity of Plastid-Expressed Bacillus thuringiensis Cry3Bb to a Leaf Beetle, Plagiodera versicolora. Microbiol Spectr 2023; 11:e0504922. [PMID: 36976001 PMCID: PMC10101071 DOI: 10.1128/spectrum.05049-22] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/27/2023] [Indexed: 03/29/2023] Open
Abstract
Bacillus thuringiensis is widely used as a biopesticide, and its crystal protein expressed in transgenic crops has been successfully used for the management of insect pests. However, whether the midgut microbiota contribute to the Bt insecticidal mechanism remains controversial. We previously demonstrated that transplastomic poplar plants expressing Bt Cry3Bb are highly lethal to willow leaf beetle (Plagiodera versicolora), one of the major pests causing severe damage to Salicaceae plants such as willows and poplars. Here, we demonstrate that feeding poplar leaves expressing Cry3Bb to nonaxenic P. versicolora larvae leads to significantly accelerated mortality, and overgrowth and dysbiosis of the gut microbiota, compared with axenic larvae. Corroborating work done with Lepidopteran insects, plastid-expressed Cry3Bb can cause the lysis of the beetle's intestinal cells, lead to the entry of intestinal bacteria into the body cavity, and thus cause the dynamic changes in the flora of the midgut and blood cavity in P. versicolora. Reintroduction of Pseudomonas putida, a gut bacterium of P. versicolora, into axenic P. versicolora larvae further enhances mortality upon feeding on Cry3Bb-expressing poplar. Our results indicate the important contribution of host gut microbiota in promoting the B. thuringiensis crystal protein insecticidal activity and provide new insights into the mechanism of pest control by Bt-transplastomic approaches. IMPORTANCE The contribution of gut microbiota to Bacillus thuringiensis Cry3Bb insecticidal activity in a leaf beetle was demonstrated using transplastomic poplar plants, providing a potential new approach to improve the efficiency of plastid transformation technology for pest control by expression of Bt toxins.
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Affiliation(s)
- Xiaoyu Lei
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Hongshan Laboratory, School of Life Sciences, Hubei University, Wuhan, China
| | - Fengjuan Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Hongshan Laboratory, School of Life Sciences, Hubei University, Wuhan, China
| | - Jiang Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, Hubei Hongshan Laboratory, School of Life Sciences, Hubei University, Wuhan, China
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China
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12
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Chen H, Hao D, Chen C, Sun Y, Yu X. Effects of midgut bacteria in Hyphantria cunea (Lepidoptera: Erebidae) on nuclear polyhedrosis virus and Bacillus thuringiensis (Bacillales: Bacillaceae). JOURNAL OF INSECT SCIENCE (ONLINE) 2023; 23:1. [PMID: 36916277 PMCID: PMC10011879 DOI: 10.1093/jisesa/iead009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 12/05/2022] [Accepted: 02/02/2023] [Indexed: 06/18/2023]
Abstract
Hyphantria cunea Drury (Lepidoptera: Erebidae) is a quarantine pest in China that can cause damage to hundreds of plants. As biological control agents, Nuclear Polyhedrosis Virus (NPV) and Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) (Bt) are commonly used to inhibit the prevalence of H. cunea. To investigate the role of midgut bacteria in the infection of NPV and Bt in H. cunea, we performed a series of tests, including isolating the dominant culturable bacteria in the midgut, eliminating intestinal bacteria, and respectively inoculating the dominant strains with NPV and Bt for bioassay. Two dominant bacteria, Klebsiella oxytoca Lautrop (Enterobacterales: Enterobacteriaceae) and Enterococcus mundtii Collins (Lactobacillales: Enterococcaceae), in the midgut of H. cunea were identified, and a strain of H. cunea larvae without intestinal bacteria was successfully established. In the bioassays of entomopathogen infection, K. oxytoca showed significant synergistic effects with both NPV and Bt on the death of H. cunea. In contrast, E. mundtii played antagonistic effects. This phenomenon may be attributed to the differences in the physico-chemical properties of the two gut bacteria and the alkaline environment required for NPV and Bt to infect the host. It is worth noting that the enhanced insecticidal activity of K. oxytoca on NPV and Bt provides a reference for future biological control of H. cunea by intestinal bacteria.
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Affiliation(s)
- Hongjian Chen
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | | | - Changyu Chen
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | - Yuhang Sun
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | - Xiaohang Yu
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
- College of Forestry, Nanjing Forestry University, Nanjing 210037, China
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13
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Yoon SA, Harrison JG, Smilanich AM, Forister ML. Experimental removal of extracellular egg‐associated microbes has long‐lasting effects for larval performance. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Su’ad A. Yoon
- Okinawa Institute of Science and Technology Okinawa Japan
| | | | - Angela M. Smilanich
- University of Nevada Reno, Department of Biology, Program of Ecology, Evolution, and Conservation Biology Reno NV
| | - Matthew L. Forister
- University of Nevada Reno, Department of Biology, Program of Ecology, Evolution, and Conservation Biology Reno NV
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14
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Deguenon JM, Dhammi A, Ponnusamy L, Travanty NV, Cave G, Lawrie R, Mott D, Reisig D, Kurtz R, Roe RM. Bacterial Microbiota of Field-Collected Helicoverpa zea (Lepidoptera: Noctuidae) from Transgenic Bt and Non-Bt Cotton. Microorganisms 2021; 9:microorganisms9040878. [PMID: 33923893 PMCID: PMC8072973 DOI: 10.3390/microorganisms9040878] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 04/07/2021] [Accepted: 04/16/2021] [Indexed: 12/15/2022] Open
Abstract
The bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is an important agricultural pest in U.S. cotton and is managed using transgenic hybrids that produce insecticidal proteins from the bacterium, Bacillus thuringiensis (Bt). The reduced efficacy against H. zea caterpillars of Bt plants expressing Cry toxins is increasing in the field. In a first step towards understanding Bt cotton–bollworm–microbiota interactions, we investigated the internal bacterial microbiota of second–third stadium H. zea collected in the field from non-Bt versus Bt (WideStrike) cotton in close proximity (in North Carolina, USA). The bacterial populations were analyzed using culture-dependent and -independent molecular approaches. We found that WideStrike samples had a higher bacterial density and diversity per larva than insects collected from non-Bt cotton over two field seasons: 8.42 ± 0.23 and 5.36 ± 0.75 (log10 colony forming units per insect) for WideStrike compared to 6.82 ± 0.20 and 4.30 ± 0.56 for non-Bt cotton for seasons 1 and 2, respectively. Fifteen phyla, 103 families, and 229 genera were identified after performing Illumina sequencing of the 16S rRNA. At the family level, Enterobacteriaceae and Enterococcaceae were the most abundant taxa. The Enterococcaceae family was comprised mostly of Enterococcus species (E. casseliflavus and another Enterococcus sp.). Members of the Enterococcus genus can acidify their environment and can potentially reduce the alkaline activation of some Bt toxins. These findings argue for more research to better understand the role of cotton–bollworm–bacteria interactions and the impact on Bt toxin caterpillar susceptibility.
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Affiliation(s)
- Jean M. Deguenon
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Anirudh Dhammi
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Loganathan Ponnusamy
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
- Correspondence:
| | - Nicholas V. Travanty
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Grayson Cave
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Roger Lawrie
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Dan Mott
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Dominic Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
| | - Ryan Kurtz
- Cotton Incorporated, Cary, NC 27513, USA;
| | - R. Michael Roe
- Department of Entomology and Plant Pathology, North Carolina State University, 3230 Ligon Street, Campus Box 7647, Raleigh, NC 27695-7647, USA; (J.M.D.); (A.D.); (N.V.T.); (G.C.); (R.L.); (D.M.); (D.R.); (R.M.R.)
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15
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Paddock KJ, Pereira AE, Finke DL, Ericsson AC, Hibbard BE, Shelby KS. Host resistance to Bacillus thuringiensis is linked to altered bacterial community within a specialist insect herbivore. Mol Ecol 2021; 30:5438-5453. [PMID: 33683750 PMCID: PMC9290792 DOI: 10.1111/mec.15875] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 02/12/2021] [Accepted: 03/01/2021] [Indexed: 12/19/2022]
Abstract
Evolution of resistance to transgenic crops producing toxins from Bacillus thuringiensis (Bt) threatens the sustainability of the technology. Examination of resistance mechanisms has largely focused on characterization of mutations in proteins serving as Bt toxin binding sites. However, insect microbial communities have the potential to provide host resistance to pesticides in a myriad of ways. Previous findings suggest the killing mechanism of Bt relies on enteric bacteria becoming pathogenic in the disrupted gut environment of the insect following Bt intoxication. Thus, here we hypothesized that resistance to Bt would alter the microbiome composition of the insect. Previous studies have manipulated the microbiome of susceptible insects and monitored their response to Bt. In our study, we characterized the associated bacterial communities of Bt‐resistant and ‐susceptible western corn rootworms, a widespread pest of maize in the United States. We found resistant insects harbor a bacterial community that is less rich and distinct from susceptible insects. After feeding on Bt‐expressing maize, susceptible insects exhibited dysbiosis of the associated bacterial community, whereas the community within resistant insects remained relatively unchanged. These results suggest resistance to Bt produces alterations in the microbiome of the western corn rootworm that may contribute to resistance. We further demonstrated that by itself, feeding on Bt toxin‐expressing seedlings caused a shift in the microbiota. This work provides a broader picture of the effect stressors have on microbiome composition, and the potential heritable changes induced as a result of intense selection.
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Affiliation(s)
- Kyle J Paddock
- Division of Plant Sciences, University of Missouri, Columbia, MO, USA
| | - Adriano E Pereira
- Division of Plant Sciences, University of Missouri, Columbia, MO, USA
| | - Deborah L Finke
- Division of Plant Sciences, University of Missouri, Columbia, MO, USA
| | - Aaron C Ericsson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, USA
| | - Bruce E Hibbard
- Division of Plant Sciences, University of Missouri, Columbia, MO, USA.,USDA-ARS, University of Missouri, Columbia, MO, USA
| | - Kent S Shelby
- Division of Plant Sciences, University of Missouri, Columbia, MO, USA.,USDA-ARS, Columbia, MO, USA
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16
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Li S, Xu X, De Mandal S, Shakeel M, Hua Y, Shoukat RF, Fu D, Jin F. Gut microbiota mediate Plutella xylostella susceptibility to Bt Cry1Ac protoxin is associated with host immune response. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 271:116271. [PMID: 33401210 DOI: 10.1016/j.envpol.2020.116271] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 11/27/2020] [Accepted: 12/08/2020] [Indexed: 06/12/2023]
Abstract
Insect gut microbiotas have a variety of physiological functions for host growth, development, and immunity. Bacillus thuringiensis (Bt) is known to kill insect pests by releasing insecticidal protoxins, which are activated in the insect midgut. However, the interplay among Bt infection, host immunity, and gut microbiota are still unclear. Here we show that Bt Cry1Ac protoxin interacts with the gut microbiota to accelerate the mortality of P. xylostella larvae. Cry1Ac protoxin was found to cause a dynamic change in the midgut and hemocoel microbiota of P. xylostella, with a significant increase in bacterial load and a significant reduction in bacterial diversity. In turn, loss of gut microbiota significantly decreased the Bt susceptibility of P. xylostella larvae. The introduction of three gut bacterial isolates Enterococcus mundtii (PxG1), Carnobacterium maltaromaticum (PxCG2), and Acinetobacter guillouiae (PxCG3) restored sensitivity to Bt Cry1Ac protoxin. We also found that Cry1Ac protoxin and native gut microbiota can trigger host midgut immune response, which involves the up-regulation of expression of Toll and IMD pathway genes and most antimicrobial peptide genes, respectively. Our findings further shed light on the interplay between insect gut microbiota and host immunity under the Bt toxin killing pressure, and this may provide insights for improving the management of Bt resistance and lead to new strategies for biological control of insect pests.
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Affiliation(s)
- Shuzhong Li
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Xiaoxia Xu
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Surajit De Mandal
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Muhammad Shakeel
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Yanyan Hua
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Rana Fartab Shoukat
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Dongran Fu
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China
| | - Fengliang Jin
- College of Plant Protection, South China Agricultural University, Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province, Guangzhou, PR China.
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17
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Li Y, Schal C, Pan X, Huang Y, Zhang F. Effects of Antibiotics on the Dynamic Balance of Bacteria and Fungi in the Gut of the German Cockroach. JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:2666-2678. [PMID: 32968762 DOI: 10.1093/jee/toaa205] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Indexed: 06/11/2023]
Abstract
The German cockroach, Blattella germanica (L.) (Blattaria: Blattidae) harbored diverse microorganisms in the digestive tract, including bacteria, fungi, viruses, archaea, and protozoa. This diverse community maintains a relatively stable balance. Some bacteria have been confirmed to play crucial roles in the insect's physiology, biochemistry, and behavior. Antibiotics can effectively eliminate bacteria and disrupt the balance of gut microbiota, but the time-course of this process, the structure of the new microbial community, and the dynamics of re-assemblage of a bacterial community after antibiotic treatment have not been investigated. In the present study, antibiotic (levofloxacin and gentamicin) ingestion reduced bacterial diversity and abundance in the cockroach gut. Within 14 d of discontinuing antibiotic treatment, the number of culturable gut bacteria returned to its original level. However, the composition of the new bacterial community with greater abundance of antibiotic-resistant Enterococcus and Dysgonomonas was significantly different from the original community. Network analysis showed that antibiotic treatment made the interaction between bacteria and fungi closer and stronger in the cockroach gut during the recovery of gut microorganisms. The study on the composition change, recovery rules, and interaction dynamics between gut bacteria and fungi after antibiotic treatment are helpful to explore gut microbes' colonization and interaction with insects, which contributes to the selection of stable core gut bacteria as biological carriers of paratransgenesis for controlling Blattella germanica.
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Affiliation(s)
- Yaru Li
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, People of Republic of China
| | - Coby Schal
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC
| | - Xiaoyuan Pan
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, People of Republic of China
| | - Yanhong Huang
- State Key Laboratory of Biobased Material and Green Papermaking, Shandong Food Ferment Industry Research and Design Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250013, 41 Jiefang Road, People's Republic of China
| | - Fan Zhang
- Key Laboratory of Animal Resistance Biology of Shandong Province, College of Life Science, Shandong Normal University, Jinan, People of Republic of China
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18
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Strong Environment-Genotype Interactions Determine the Fitness Costs of Antibiotic Resistance In Vitro and in an Insect Model of Infection. Antimicrob Agents Chemother 2020; 64:AAC.01033-20. [PMID: 32661001 DOI: 10.1128/aac.01033-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 07/08/2020] [Indexed: 11/20/2022] Open
Abstract
The acquisition of antibiotic resistance commonly imposes fitness costs, a reduction in the fitness of bacteria in the absence of drugs. These costs have been quantified primarily using in vitro experiments and a small number of in vivo studies in mice, and it is commonly assumed that these diverse methods are consistent. Here, we used an insect model of infection to compare the fitness costs of antibiotic resistance in vivo to those in vitro Experiments explored diverse mechanisms of resistance in a Gram-positive pathogen, Bacillus thuringiensis, and a Gram-negative intestinal symbiont, Enterobacter cloacae Rifampin resistance in B. thuringiensis showed fitness costs that were typically elevated in vivo, although these were modulated by genotype-environment interactions. In contrast, resistance to cefotaxime via derepression of AmpC β-lactamase in E. cloacae resulted in no detectable costs in vivo or in vitro, while spontaneous resistance to nalidixic acid, and carriage of the IncP plasmid RP4, imposed costs that increased in vivo Overall, fitness costs in vitro were a poor predictor of fitness costs in vivo because of strong genotype-environment interactions throughout this study. Insect infections provide a cheap and accessible means of assessing the fitness consequences of resistance mutations, data that are important for understanding the evolution and spread of resistance. This study emphasizes that the fitness costs imposed by particular mutations or different modes of resistance are extremely variable and that only a subset of these mutations is likely to be prevalent outside the laboratory.
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19
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The Tripartite Interaction of Host Immunity- Bacillus thuringiensis Infection-Gut Microbiota. Toxins (Basel) 2020; 12:toxins12080514. [PMID: 32806491 PMCID: PMC7472377 DOI: 10.3390/toxins12080514] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 08/05/2020] [Accepted: 08/07/2020] [Indexed: 12/12/2022] Open
Abstract
Bacillus thuringiensis (Bt) is an important cosmopolitan bacterial entomopathogen, which produces various protein toxins that have been expressed in transgenic crops. The evolved molecular interaction between the insect immune system and gut microbiota is changed during the Bt infection process. The host immune response, such as the expression of induced antimicrobial peptides (AMPs), the melanization response, and the production of reactive oxygen species (ROS), varies with different doses of Bt infection. Moreover, B. thuringiensis infection changes the abundance and structural composition of the intestinal bacteria community. The activated immune response, together with dysbiosis of the gut microbiota, also has an important effect on Bt pathogenicity and insect resistance to Bt. In this review, we attempt to clarify this tripartite interaction of host immunity, Bt infection, and gut microbiota, especially the important role of key immune regulators and symbiotic bacteria in the Bt killing activity. Increasing the effectiveness of biocontrol agents by interfering with insect resistance and controlling symbiotic bacteria can be important steps for the successful application of microbial biopesticides.
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20
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Optimal Response to Quorum-Sensing Signals Varies in Different Host Environments with Different Pathogen Group Size. mBio 2020; 11:mBio.00535-20. [PMID: 32487754 PMCID: PMC7267880 DOI: 10.1128/mbio.00535-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Quorum sensing describes the ability of microbes to alter gene regulation according to their local population size. Some successful theory suggests that this is a form of cooperation, namely, investment in shared products is only worthwhile if there are sufficient bacteria making the same product. This theory can explain the genetic diversity in these signaling systems in Gram-positive bacteria, such as Bacillus and Staphylococcus sp. The possible advantages gained by rare genotypes (which can exploit the products of their more common neighbors) could explain why different genotypes can coexist. We show that while these social interactions can occur in simple laboratory experiments, they do not occur in naturalistic infections using an invertebrate pathogen, Bacillus thuringiensis. Instead, our results suggest that different genotypes are adapted to differently sized hosts. Overall, social models are not easily applied to this system, implying that a different explanation for this form of quorum sensing is required. The persistence of genetic variation in master regulators of gene expression, such as quorum-sensing systems, is hard to explain. Here, we investigated two alternative hypotheses for the prevalence of polymorphic quorum sensing in Gram-positive bacteria, i.e., the use of different signal/receptor pairs (‘pherotypes’) to regulate the same functions. First, social interactions between pherotypes or ‘facultative cheating’ may favor rare variants that exploit the signals of others. Second, different pherotypes may increase fitness in different environments. We evaluated these hypotheses in the invertebrate pathogen Bacillus thuringiensis, using three pherotypes expressed in a common genetic background. Facultative cheating could occur in well-mixed host homogenates provided there was minimal cross talk between competing pherotypes. However, facultative cheating did not occur when spatial structure was increased in static cultures or in naturalistic oral infections, where common pherotypes had higher fitness. There was clear support for environment-dependent fitness; pherotypes varied in responsiveness to signals and in mean competitive fitness. Notably, competitive fitness varied with group size. In contrast to typical social evolution models of quorum sensing which predict higher response to signal at larger group size, the pherotype with highest responsiveness to signals performed best in smaller hosts where infections have a lower pathogen group size. In this system, low signal abundance appears to limit fitness in hosts, while the optimal level of response to signals varies in different host environments.
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Heckel DG. How do toxins from Bacillus thuringiensis kill insects? An evolutionary perspective. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2020; 104:e21673. [PMID: 32212396 DOI: 10.1002/arch.21673] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 03/11/2020] [Accepted: 03/12/2020] [Indexed: 05/29/2023]
Abstract
Three-domain Cry toxins from the bacterium Bacillus thuringiensis (Bt) are increasingly used in agriculture to replace chemical insecticides in pest control. Most chemical insecticides kill pest insects swiftly, but are also toxic to beneficial insects and other species in the agroecosystem. Cry toxins enjoy the advantages of high selectivity and the possibility of the application by sprays or transgenic plants. However, these benefits are offset by the limited host range and the evolution of resistance to Bt toxins by insect pests. Understanding how Bt toxins kill insects will help to understand the nature of both problems. The recent realization that ABC transporters play a central role in the killing mechanism will play an important role in devising solutions.
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Affiliation(s)
- David G Heckel
- Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany
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Martínez-Solís M, Collado MC, Herrero S. Influence of Diet, Sex, and Viral Infections on the Gut Microbiota Composition of Spodoptera exigua Caterpillars. Front Microbiol 2020; 11:753. [PMID: 32435237 PMCID: PMC7218101 DOI: 10.3389/fmicb.2020.00753] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 03/30/2020] [Indexed: 11/25/2022] Open
Abstract
The gut microbiota plays essential roles in processes related with metabolism, physiology, and immunity in all organisms, including insects. In the present work, we performed a broad analysis of the Spodoptera exigua gut microbiota, a major agricultural pest. We analyzed the influence of multiple parameters such as diet, geographic location, sex, or viral infections on S. exigua caterpillar gut microbiota composition. Our study revealed a high variability in bacterial composition among individuals, and a major influence of environmental bacteria (including those acquired through diet) on the gut microbiota composition, supporting previous studies that claim resident microbiota are lacking in caterpillars. Previous studies with laboratory-reared insects showed that changes in caterpillar gut bacterial composition affect the insecticidal properties of entomopathogenic viruses and bacteria. Our study revealed different microbiota composition in field insects carrying a natural viral infection with Spodoptera exigua nucleopolyhedrovirus (SeMNPV) and/or Spodoptera exigua iflavirus 1 (SeIV1). Few taxa can be specifically associated with the infection, suggesting microbiota influence the infective process of these natural pathogens, and providing new strategies for insect pest management.
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Affiliation(s)
- María Martínez-Solís
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Departamento de Genética, Universitat de València, Valencia, Spain
| | - María Carmen Collado
- Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas (IATA-CSIC), Valencia, Spain
| | - Salvador Herrero
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Departamento de Genética, Universitat de València, Valencia, Spain
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Sajjadian SM, Kim Y. Dual Oxidase-Derived Reactive Oxygen Species Against Bacillus thuringiensis and Its Suppression by Eicosanoid Biosynthesis Inhibitors. Front Microbiol 2020; 11:528. [PMID: 32292400 PMCID: PMC7120046 DOI: 10.3389/fmicb.2020.00528] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/11/2020] [Indexed: 12/26/2022] Open
Abstract
Two entomopathogenic bacteria, Xenorhabdus and Photorhabdus, are known to be able to synthesize and secrete eicosanoid biosynthesis inhibitors (EIBs) that can enhance pathogenicity of Bacillus thuringiensis (Bt) against different target insects. Such enhancements can be explained by the suppression of immune responses in the hemocoel by EIBs. However, little is known about the role of EIBs in the defense against Bt pathogenicity in the gut. This study was focused on the role of insect gut immunity in the defense against Bt pathogenicity, in which the cooperative effect of bacterial metabolites was assessed. Screening 14 different bacterial strains, bacterial culture broth of Photorhabdus temperata subsp. temperata ANU101 (Ptt) gave the highest cooperative effect on Bt virulence along with significant inhibitory activity against phospholipase A2 (PLA2) of Plutella xylostella. In gut lumen, Ptt culture broth suppressed the generation of reactive oxygen species (ROS) induced by Bt treatment and facilitated bacterial growth, similar to vitamin E, an antioxidant. To analyze the ROS source, dual oxidase (Px-Duox) and NADPH-dependent oxidase (Px-Nox) genes were predicted from P. xylostella genome and their expressions were confirmed in larval gut. RNA interference (RNAi) of Px-Duox expression reduced ROS levels in both gut epithelium and lumen while RNAi of Px-Nox expression reduced ROS levels only in gut epithelium. Ptt extract significantly suppressed gene expression levels of Px-Duox and Px-Nox, leading to lower ROS concentrations in the gut lumen. Three commercial PLA2 inhibitors significantly increased the insecticidal activity of Bt by suppressing ROS levels in the gut lumen. These results indicate that Ptt extract containing EBIs can prevent up-regulation of ROS level in the midgut in response to Bt infection and enhance the virulence of Bt against P. xylostella.
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Affiliation(s)
| | - Yonggyun Kim
- Department of Plant Medicals, Andong National University, Andong, South Korea
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Matthews AC, Mikonranta L, Raymond B. Shifts along the parasite-mutualist continuum are opposed by fundamental trade-offs. Proc Biol Sci 2020; 286:20190236. [PMID: 30940052 DOI: 10.1098/rspb.2019.0236] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Theory suggests that symbionts can readily evolve more parasitic or mutualistic strategies with respect to hosts. However, many symbionts have stable interactions with hosts that improve nutrient assimilation or confer protection from pathogens. We explored the potential for evolution of increased parasitism or decreased parasitism and mutualism in a natural gut symbiosis between larvae of Plutella xylostella and the microbe Enterobacter cloacae. We focused on interactions with the pathogen, Bacillus thuringiensis: selecting for parasitism in terms of facilitating pathogen infection, or increased mutualism in terms of host protection. Selection for parasitism led to symbionts increasing pathogen-induced mortality but reduced their competitive ability with pathogens and their in vitro growth rates. Symbionts did not evolve to confer protection from pathogens. However, several lineages evolved reduced parasitism, primarily in terms of moderating impacts on host growth, potentially because prudence pays dividends through increased host size. Overall, the evolution of increased parasitism was achievable but was opposed by trade-offs likely to reduce fitness. The evolution of protection may not have occurred because suppressing growth of B. thuringiensis in the gut might provide only weak protection or because evolution towards protective interactions was opposed by the loss of competitive fitness in symbionts.
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Affiliation(s)
- Andrew C Matthews
- 1 School of Biological Science, Royal Holloway University of London , Egham, Surrey TW20 0EX , UK.,2 University of Exeter , Penryn Campus, Penryn, Cornwall TR10 9FE , UK
| | - Lauri Mikonranta
- 2 University of Exeter , Penryn Campus, Penryn, Cornwall TR10 9FE , UK.,3 Department of Biology, University of York , Wentworth Way, York YO10 5DD , UK
| | - Ben Raymond
- 1 School of Biological Science, Royal Holloway University of London , Egham, Surrey TW20 0EX , UK.,2 University of Exeter , Penryn Campus, Penryn, Cornwall TR10 9FE , UK
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Erlandson MA, Toprak U, Hegedus DD. Role of the peritrophic matrix in insect-pathogen interactions. JOURNAL OF INSECT PHYSIOLOGY 2019; 117:103894. [PMID: 31175854 DOI: 10.1016/j.jinsphys.2019.103894] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 05/27/2019] [Accepted: 06/05/2019] [Indexed: 05/12/2023]
Abstract
The peritrophic matrix (PM) is an acellular chitin and glycoprotein layer that lines the invertebrate midgut. The PM has long been considered a physical as well as a biochemical barrier, protecting the midgut epithelium from abrasive food particles, digestive enzymes and pathogens infectious per os. This short review will focus on the latter function, as a barrier to pathogens infectious per os. We focus on the evidence confirming the role of the PM as protective barrier against pathogenic microorganisms of insects, mainly bacteria and viruses, as well as the evolution of a variety of mechanisms used by pathogens to overcome the PM barrier.
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Affiliation(s)
- Martin A Erlandson
- Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada; Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
| | - Umut Toprak
- Molecular Entomology Laboratory, Faculty of Agriculture, Ankara University, Ankara, Turkey
| | - Dwayne D Hegedus
- Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada; Department of Food and Bioproduct Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Somerville J, Zhou L, Raymond B. Aseptic Rearing and Infection with Gut Bacteria Improve the Fitness of Transgenic Diamondback Moth, Plutella xylostella. INSECTS 2019; 10:insects10040089. [PMID: 30925791 PMCID: PMC6523322 DOI: 10.3390/insects10040089] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 03/21/2019] [Accepted: 03/25/2019] [Indexed: 12/27/2022]
Abstract
Mass insect rearing can have a range of applications, for example in biological control of pests. The competitive fitness of released insects is extremely important in a number of applications. Here, we investigated how to improve the fitness of a transgenic diamondback moth, which has shown variation in mating ability when reared in different insectaries. Specifically we tested whether infection with a gut bacteria, Enterobacter cloacae, and aseptic rearing of larvae could improve insect growth and male performance. All larvae were readily infected with E. cloacae. Under aseptic rearing, pupal weights were reduced and there was a marginal reduction in larval survival. However, aseptic rearing substantially improved the fitness of transgenic males. In addition, under aseptic rearing, inoculation with E. cloacae increased pupal weights and male fitness, increasing the proportion of transgenic progeny from 20% to 30% relative to uninfected insects. Aseptic conditions may improve the fitness of transgenic males by excluding microbial contaminants, while symbiont inoculation could further improve fitness by providing additional protection against infection, or by normalizing insect physiology. The simple innovation of incorporating antibiotic into diet, and inoculating insects with symbiotic bacteria that are resistant to that antibiotic, could provide a readily transferable tool for other insect rearing systems.
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Affiliation(s)
- Jasmine Somerville
- Centre for Ecology and Conservation, Penryn campus, College of Life and Environmental Science, University of Exeter, TR10 9FE, UK.
| | - Liqin Zhou
- Centre for Ecology and Conservation, Penryn campus, College of Life and Environmental Science, University of Exeter, TR10 9FE, UK.
| | - Ben Raymond
- Centre for Ecology and Conservation, Penryn campus, College of Life and Environmental Science, University of Exeter, TR10 9FE, UK.
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Impact of Antibiotics on Efficacy of Cry Toxins Produced in Two Different Genetically Modified Bt Maize Varieties in Two Lepidopteran Herbivore Species, Ostrinia nubilalis and Spodoptera littoralis. Toxins (Basel) 2018; 10:toxins10120489. [PMID: 30477136 PMCID: PMC6316186 DOI: 10.3390/toxins10120489] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 11/09/2018] [Accepted: 11/15/2018] [Indexed: 01/02/2023] Open
Abstract
The insecticidal crystal proteins from Bacillus thuringiensis (Bt) are widely-used biopesticides that are used both as Bt spore-crystal preparations in sprayable formulations and as activated toxins in genetically modified (GM) plants. Models for their modes of action have been proposed but many issues remain unresolved. Among those is the role of commensal gut bacteria in target insect death: previous studies showed that antibiotics attenuate the toxicity of Bt sprays. We tested whether antibiotics interfere with the effects of GM plant-produced Bt toxins in larvae of two Lepidopteran species, the European corn borer Ostrinia nubilalis and the cotton leafworm Spodoptera littoralis. The larvae were reared on artificial diet with or without antibiotics and, thereafter, fed two varieties of Bt GM maize in comparison to conventional non-Bt maize leaves sprayed with antibiotic solution and/or with a Bt formulation. Antibiotics significantly reduced or delayed the toxicity of Cry toxins, although to a lesser extent than previously reported for Bt-sprays. This supports the hypothesis that Cry toxins induce mortality by themselves in the absence of Bt bacteria and spores, and of commensal gut bacteria. However, larvae that were not treated with antibiotics died faster and at a higher rate which was further compounded by plant variety and species sensitivity. These findings support a hypothesis that toxicemia alone can inflict significant mortality. However, in the absence of antibiotics, the gut bacteria likely enhance the Cry toxin effect by inflicting, additionally, bacterial septicemia. This has important implications in field situations where antibiotic substances are present—e.g., from manure of animals from conventional production systems—and for ecotoxicological testing schemes of Bt toxins and nontarget organisms that are often using artificial diets enriched with high concentrations of antibiotics.
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Interaction between Insects, Toxins, and Bacteria: Have We Been Wrong So Far? Toxins (Basel) 2018; 10:toxins10070281. [PMID: 29986377 PMCID: PMC6070883 DOI: 10.3390/toxins10070281] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/01/2018] [Accepted: 07/02/2018] [Indexed: 12/19/2022] Open
Abstract
Toxins are a major virulence factor produced by many pathogenic bacteria. In vertebrates, the response of hosts to the bacteria is inseparable from the response to the toxins, allowing a comprehensive understanding of this tripartite host-pathogen-toxin interaction. However, in invertebrates, this interaction has been investigated by two complementary but historically distinct fields of research: toxinology and immunology. In this article, I highlight how such dichotomy between these two fields led to a biased, or even erroneous view of the ecology and evolution of the interaction between insects, toxins, and bacteria. I focus on the reason behind such a dichotomy, on how to bridge the fields together, and on confounding effects that could bias the outcome of the experiments. Finally, I raise four questions at the border of the two fields on the cross-effects between toxins, bacteria, and spores that have been largely underexplored to promote a more comprehensive view of this interaction.
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Paniagua Voirol LR, Frago E, Kaltenpoth M, Hilker M, Fatouros NE. Bacterial Symbionts in Lepidoptera: Their Diversity, Transmission, and Impact on the Host. Front Microbiol 2018; 9:556. [PMID: 29636736 PMCID: PMC5881003 DOI: 10.3389/fmicb.2018.00556] [Citation(s) in RCA: 174] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 03/12/2018] [Indexed: 01/05/2023] Open
Abstract
The insect’s microbiota is well acknowledged as a “hidden” player influencing essential insect traits. The gut microbiome of butterflies and moths (Lepidoptera) has been shown to be highly variable between and within species, resulting in a controversy on the functional relevance of gut microbes in this insect order. Here, we aim to (i) review current knowledge on the composition of gut microbial communities across Lepidoptera and (ii) elucidate the drivers of the variability in the lepidopteran gut microbiome and provide an overview on (iii) routes of transfer and (iv) the putative functions of microbes in Lepidoptera. To find out whether Lepidopterans possess a core gut microbiome, we compared studies of the microbiome from 30 lepidopteran species. Gut bacteria of the Enterobacteriaceae, Bacillaceae, and Pseudomonadaceae families were the most widespread across species, with Pseudomonas, Bacillus, Staphylococcus, Enterobacter, and Enterococcus being the most common genera. Several studies indicate that habitat, food plant, and age of the host insect can greatly impact the gut microbiome, which contributes to digestion, detoxification, or defense against natural enemies. We mainly focus on the gut microbiome, but we also include some examples of intracellular endosymbionts. These symbionts are present across a broad range of insect taxa and are known to exert different effects on their host, mostly including nutrition and reproductive manipulation. Only two intracellular bacteria genera (Wolbachia and Spiroplasma) have been reported to colonize reproductive tissues of Lepidoptera, affecting their host’s reproduction. We explore routes of transmission of both gut microbiota and intracellular symbionts and have found that these microbes may be horizontally transmitted through the host plant, but also vertically via the egg stage. More detailed knowledge about the functions and plasticity of the microbiome in Lepidoptera may provide novel leads for the control of lepidopteran pest species.
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Affiliation(s)
| | - Enric Frago
- Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Unité Mixte de Recherche Peuplements Végétaux et Bioagresseurs en Milieu Tropical, Saint-Pierre, La Réunion
| | - Martin Kaltenpoth
- Department for Evolutionary Ecology, Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Monika Hilker
- Institute of Biology, Freie Universität Berlin, Berlin, Germany
| | - Nina E Fatouros
- Biosystematics Group, Wageningen University and Research, Wageningen, Netherlands
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Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis. Parasit Vectors 2018; 11:121. [PMID: 29499735 PMCID: PMC5834902 DOI: 10.1186/s13071-018-2741-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 02/23/2018] [Indexed: 12/11/2022] Open
Abstract
Background Insect microbiota is a dynamic microbial community that can actively participate in defense against pathogens. Bacillus thuringiensis (Bt) is a natural entomopathogen widely used as a bioinsecticide for pest control. Although Bt’s mode of action has been extensively studied, whether the presence of microbiota is mandatory for Bt to effectively kill the insect is still under debate. An association between a higher tolerance and a modified microbiota was already evidenced but a critical point remained to be solved: is the modified microbiota a cause or a consequence of a higher tolerance to Bt? Methods In this study we focused on the mosquito species Aedes aegypti, as no work has been performed on Diptera on this topic to date, and on B. thuringiensis israelensis (Bti), which is used worldwide for mosquito control. To avoid using antibiotics to cure bacterial microbiota, mosquito larvae were exposed to an hourly increasing dose of Bti during 25 hours to separate the most susceptible larvae dying quickly from more tolerant individuals, with longer survival. Results Denaturing gradient gel electrophoresis (DGGE) fingerprinting revealed that mosquito larval bacterial microbiota was strongly affected by Bti infection after only a few hours of exposure. Bacterial microbiota from the most tolerant larvae showed the lowest diversity but the highest inter-individual differences. The proportion of Bti in the host tissue was reduced in the most tolerant larvae as compared to the most susceptible ones, suggesting an active control of Bti infection by the host. Conclusions Here we show that a modified microbiota is associated with a higher tolerance of mosquitoes to Bti, but that it is rather a consequence of Bti infection than the cause of the higher tolerance. This study paves the way to future investigations aiming at unraveling the role of host immunity, inter-species bacterial competition and kinetics of host colonization by Bti that could be at the basis of the phenotype observed in this study. Electronic supplementary material The online version of this article (10.1186/s13071-018-2741-8) contains supplementary material, which is available to authorized users.
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Xia X, Sun B, Gurr GM, Vasseur L, Xue M, You M. Gut Microbiota Mediate Insecticide Resistance in the Diamondback Moth, Plutella xylostella (L.). Front Microbiol 2018; 9:25. [PMID: 29410659 PMCID: PMC5787075 DOI: 10.3389/fmicb.2018.00025] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 01/08/2018] [Indexed: 01/23/2023] Open
Abstract
The development of insecticide resistance in insect pests is a worldwide concern and elucidating the underlying mechanisms is critical for effective crop protection. Recent studies have indicated potential links between insect gut microbiota and insecticide resistance and these may apply to the diamondback moth, Plutella xylostella (L.), a globally and economically important pest of cruciferous crops. We isolated Enterococcus sp. (Firmicutes), Enterobacter sp. (Proteobacteria), and Serratia sp. (Proteobacteria) from the guts of P. xylostella and analyzed the effects on, and underlying mechanisms of insecticide resistance. Enterococcus sp. enhanced resistance to the widely used insecticide, chlorpyrifos, in P. xylostella, while in contrast, Serratia sp. decreased resistance and Enterobacter sp. and all strains of heat-killed bacteria had no effect. Importantly, the direct degradation of chlorpyrifos in vitro was consistent among the three strains of bacteria. We found that Enterococcus sp., vitamin C, and acetylsalicylic acid enhanced insecticide resistance in P. xylostella and had similar effects on expression of P. xylostella antimicrobial peptides. Expression of cecropin was down-regulated by the two compounds, while gloverin was up-regulated. Bacteria that were not associated with insecticide resistance induced contrasting gene expression profiles to Enterococcus sp. and the compounds. Our studies confirmed that gut bacteria play an important role in P. xylostella insecticide resistance, but the main mechanism is not direct detoxification of insecticides by gut bacteria. We also suggest that the influence of gut bacteria on insecticide resistance may depend on effects on the immune system. Our work advances understanding of the evolution of insecticide resistance in this key pest and highlights directions for research into insecticide resistance in other insect pest species.
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Affiliation(s)
- Xiaofeng Xia
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, China
- Key Laboratory of Green Pest Control (Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Botong Sun
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, China
- Key Laboratory of Green Pest Control (Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Geoff M. Gurr
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
- Graham Centre, Charles Sturt University, Orange, NSW, Australia
| | - Liette Vasseur
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
- Department of Biological Sciences, Brock University, Ontario, ON, Canada
| | - Minqian Xue
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, China
- Key Laboratory of Green Pest Control (Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Minsheng You
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou, China
- Key Laboratory of Green Pest Control (Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
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Recombinant entomopathogenic agents: a review of biotechnological approaches to pest insect control. World J Microbiol Biotechnol 2017; 34:14. [DOI: 10.1007/s11274-017-2397-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 12/13/2017] [Indexed: 12/20/2022]
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Effects of antibiotics on biological activity of Cry1Ac in Bt-susceptible and Bt-resistant Helicoverpa armigera strains. J Invertebr Pathol 2017; 151:197-200. [PMID: 29111356 DOI: 10.1016/j.jip.2017.10.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/11/2017] [Accepted: 10/26/2017] [Indexed: 01/24/2023]
Abstract
In this study, the results showed that the population of midgut bacteria and larval mortality due to Cry1Ac are significantly reduced in antibiotic-treated larvae from Bt-susceptible, -resistant and field-collected strains (96S, BtR, FS respectively) of Helicoverpa armigera. The percentage reduction of larval mortality with increasing concentrations of antibiotics was significantly different among strains with the smallest effect observed in FS. It has been suggested that antibiotics could influence the toxicity of Cry1Ac, possibly by eliminating gut bacteria, hence gut bacteria might be playing essential roles in Bt-induced killing of H. armigera. But elimination of midgut microflora with antibiotics had no effect on resistance level.
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Castagnola A, Jackson J, Perera OP, Oppert C, Eda S, Jurat-Fuentes JL. Alpha-arylphorin is a mitogen in the Heliothis virescens midgut cell secretome upon Cry1Ac intoxication. PeerJ 2017; 5:e3886. [PMID: 29018619 PMCID: PMC5629956 DOI: 10.7717/peerj.3886] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 09/13/2017] [Indexed: 11/20/2022] Open
Abstract
Insecticidal crystal (Cry) proteins produced by the bacterium Bacillus thuringiensis (Bt) target cells in the midgut epithelium of susceptible larvae. While the mode of action of Cry toxins has been extensively investigated, the midgut response to Cry intoxication and its regulation are not well characterized. In this work, we describe the secreted proteome (secretome) of primary mature midgut cell cultures from Heliothis virescens larvae after exposure to Cry1Ac toxin compared to control buffer treatment. The Cry1Ac-induced secretome caused higher proliferation and differentiation and an overall reduction in total cell mortality over time in primary H. virescens midgut stem cell cultures when compared to treatment with control buffer secretome. Differential proteomics identified four proteins with significant differences in abundance comparing Cry1Ac-treated and control secretomes. The most significant difference detected in the Cry1Ac secretome was an arylphorin subunit alpha protein not detected in the control secretome. Feeding of purified alpha-arylphorin to H. virescens larvae resulted in midgut hyperplasia and significantly reduced susceptibility to Cry1Ac toxin compared to controls. These data identify alpha-arylphorin as a protein with a new putative role in the midgut regeneration process in response to Cry1Ac intoxication and possibly pathogen/abiotic stress, identifying alpha-arylphorin as a potential gene to target with insecticidal gene silencing for pest control.
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Affiliation(s)
- Anais Castagnola
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, United States of America.,Current affiliation: ManTech International Corporation, Herndon, VA, United States of America
| | - Jerreme Jackson
- Genome Science and Technology Program, University of Tennessee, Knoxville, TN, United States of America.,Current affiliation: Oklahoma State University, Department of Microbiology and Molecular Genetics, Stillwater, OK, United States of America
| | - Omaththage P Perera
- Southern Insect Management Research Unit, United States Department of Agriculture-Agricultural Research Service, Stoneville, MS, USA
| | - Cris Oppert
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, United States of America.,Current affiliation: Bayer CropScience, Morrisville, NC, United States of America
| | - Shigetoshi Eda
- Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, United States of America
| | - Juan Luis Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, United States of America.,Genome Science and Technology Program, University of Tennessee, Knoxville, TN, United States of America
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Raymond B, Federici BA. In defense of Bacillus thuringiensis, the safest and most successful microbial insecticide available to humanity - a response to EFSA. FEMS Microbiol Ecol 2017. [PMID: 28645183 PMCID: PMC5812528 DOI: 10.1093/femsec/fix084] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Bacillus cereus group contains vertebrate pathogens such as B. anthracis and B. cereus and the invertebrate pathogen B. thuringiensis (Bt). Microbial biopesticides based on Bt are widely recognised as being among the safest and least environmentally damaging insecticidal products available. Nevertheless, a recent food-poisoning incident prompted a European Food Safety Authority review which argued that Bt poses a health risk equivalent to B. cereus, a causative agent of diarrhoea. However, a critical examination of available data, and this latest incident, provides no solid evidence that Bt causes diarrhoea. Although relatively high levels of B. cereus-like spores can occur in foods, genotyping demonstrates that these are predominantly naturally occurring strains rather than biopesticides. Moreover, MLST genotyping of >2000 isolates show that biopesticide genotypes have never been isolated from any clinical infection. MLST data demonstrate that B. cereus group is heterogeneous and formed of distinct clades with substantial differences in biology, ecology and host association. The group posing the greatest risk (the anthracis clade) is distantly related to the clade containing all biopesticides. These recent data support the long-held view that Bt and especially the strains used in Bt biopesticides are very safe for humans.
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Affiliation(s)
- Ben Raymond
- University of Exeter, Penryn campus, Penryn, TR10 9FE, UK
| | - Brian A Federici
- Department of Entomology and Institute for Integrative Genome Biology, University of California, Riverside, Riverside, CA 92521 USA
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Peterson B, Bezuidenhout CC, Van den Berg J. An Overview of Mechanisms of Cry Toxin Resistance in Lepidopteran Insects. JOURNAL OF ECONOMIC ENTOMOLOGY 2017; 110:362-377. [PMID: 28334065 DOI: 10.1093/jee/tow310] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Indexed: 06/06/2023]
Abstract
Arthropods have the capacity to evolve resistance to insecticides and insecticidal traits in genetically modified crops. Resistance development among Lepidoptera is a common phenomenon, and a repertoire of resistance mechanisms to various Cry toxins have been identified from laboratory, greenhouse, and field studies in this insect order. Elucidation of such resistance mechanisms is crucial for developing IRM (insect resistance management) strategies to ensure sustainable use of genetically modified crops. This mini review provides a comprehensive overview of mechanisms of resistance that have been reported for lepidopteran pests. This study demonstrated that resistance mechanisms are highly complex, and the most common mechanism of resistance is altered binding sites. It is yet to be established whether all these altered binding sites are regulated by an MAPK signaling pathway, which might suggest a universal mechanism of resistance in lepidopterans.
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Affiliation(s)
- B Peterson
- Potchefstroom Campus, North-West University, Potchefstroom, 2531, South Africa (; ; )
| | - C C Bezuidenhout
- Potchefstroom Campus, North-West University, Potchefstroom, 2531, South Africa (; ; )
| | - J Van den Berg
- Potchefstroom Campus, North-West University, Potchefstroom, 2531, South Africa (; ; )
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37
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Wu K, Yang B, Huang W, Dobens L, Song H, Ling E. Gut immunity in Lepidopteran insects. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2016; 64:65-74. [PMID: 26872544 DOI: 10.1016/j.dci.2016.02.010] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 02/06/2016] [Accepted: 02/06/2016] [Indexed: 06/05/2023]
Abstract
Lepidopteran insects constitute one of the largest fractions of animals on earth, but are considered pests in their relationship with man. Key to the success of this order of insects is its ability to digest food and absorb nutrition, which takes place in the midgut. Because environmental microorganisms can easily enter Lepidopteran guts during feeding, the innate immune response guards against pathogenic bacteria, virus and microsporidia that can be devoured with food. Gut immune responses are complicated by both resident gut microbiota and the surrounding peritrophic membrane and are distinct from immune responses in the body cavity, which depend on the function of the fat body and hemocytes. Due to their relevance to agricultural production, studies of Lepidopteran insect midgut and immunity are receiving more attention, and here we summarize gut structures and functions, and discuss how these confer immunity against different microorganisms. It is expected that increased knowledge of Lepidopteran gut immunity may be utilized for pest biological control in the future.
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Affiliation(s)
- Kai Wu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Bing Yang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Wuren Huang
- Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou, Hainan 571101, China
| | - Leonard Dobens
- School of Biological Sciences, University of Missouri-Kansas City, 5007 Rockhill Road, Kansas City, MO 64110, USA
| | - Hongsheng Song
- College of Life Sciences, Shanghai University, Shanghai 200444, China.
| | - Erjun Ling
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
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38
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Affiliation(s)
- Nichole A Broderick
- a Department of Molecular and Cell Biology , University of Connecticut , Storrs , CT , USA
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39
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Regode V, Kuruba S, Mohammad AS, Sharma HC. Isolation and Characterization of Gut Bacterial Proteases Involved in Inducing Pathogenicity of Bacillus thuringiensis Toxin in Cotton Bollworm, Helicoverpa armigera. Front Microbiol 2016; 7:1567. [PMID: 27766093 PMCID: PMC5052264 DOI: 10.3389/fmicb.2016.01567] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/20/2016] [Indexed: 12/16/2022] Open
Abstract
Bacillus thuringiensis toxin proteins are deployed in transgenic plants for pest management. The present studies were aimed at characterization of gut bacterial proteases involved in activation of inactive Cry1Ac protoxin (pro-Cry1Ac) to active toxin in Helicoverpa armigera. Bacterial strains were isolated from H. armigera midgut and screened for their proteolytic activation toward pro-Cry1Ac. Among 12 gut bacterial isolates seven isolates showed proteolytic activity, and proteases from three isolates (IVS1, IVS2, and IVS3) were found to be involved in the proteolytic conversion of pro-Cry1Ac into active toxin. The proteases from IVS1, IVS2, and IVS3 isolates were purified to 11.90-, 15.50-, and 17.20-fold, respectively. The optimum pH and temperature for gut bacterial protease activity was 8.0 and 40°C. Maximum inhibition of total proteolytic activity was exerted by phenylmethane sulfonyl fluoride followed by EDTA. Fluorescence zymography revealed that proteases from IVS1, IVS2, and IVS3 were chymotrypsin-like and showing protease band at ~15, 65, and 15 kDa, respectively. Active Cry1Ac formed from processing pro-Cry1Ac by gut bacterial proteases exhibited toxicity toward H. armigera. The gut bacterial isolates IVS1, IVS2, and IVS3 showed homology with B. thuringiensis (CP003763.1), Vibrio fischeri (CP000020.2), and Escherichia coli (CP011342.1), respectively. Proteases produced by midgut bacteria are involved in proteolytic processing of B. thuringiensis protoxin and play a major role in inducing pathogenicity of B. thuringiensis toxins in H. armigera.
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Affiliation(s)
- Visweshwar Regode
- Department of Entomology, International Crops Research Institute for the Semi-Arid Tropics, PatancheruIndia; Department of Biochemistry, Gulbarga University, KalaburagiIndia
| | | | - Akbar S Mohammad
- Department of Entomology, International Crops Research Institute for the Semi-Arid Tropics, Patancheru India
| | - Hari C Sharma
- Department of Entomology, International Crops Research Institute for the Semi-Arid Tropics, Patancheru India
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Martemyanov VV, Belousova IA, Pavlushin SV, Dubovskiy IM, Ershov NI, Alikina TY, Kabilov MR, Glupov VV. Phenological asynchrony between host plant and gypsy moth reduces insect gut microbiota and susceptibility to Bacillus thuringiensis. Ecol Evol 2016; 6:7298-7310. [PMID: 28725398 PMCID: PMC5513265 DOI: 10.1002/ece3.2460] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/26/2016] [Accepted: 08/12/2016] [Indexed: 01/15/2023] Open
Abstract
The phenological synchrony between the emergence of overwintering herbivorous insects and the budding of host plants is considered a crucial factor in the population dynamics of herbivores. However, the mechanisms driving the interactions between the host plant, herbivores, and their pathogens are often obscure. In the current study, an artificially induced phenological asynchrony was used to investigate how the asynchrony between silver birch Betula pendula and gypsy moth Lymantria dispar affects the immunity of the insect to bacteria, its susceptibility to the entomopathogenic bacteria Bacillus thuringiensis, and the diversity in its midgut microbiota. The lysozyme-like activity in both the midgut and hemolymph plasma and the nonspecific esterase activity and antimicrobial peptide gene expression in the midgut were studied in both noninfected and B. thuringiensis-infected larvae. Our results provide the first evidence that phenologically asynchronous larvae are less susceptible to B. thuringiensis infection than phenologically synchronous larvae, and our results show that these effects are related to the high basic levels and B. thuringiensis-induced levels of lysozyme-like activities. Moreover, a 16S rRNA analysis revealed that dramatic decreases in the diversity of the larval gut bacterial consortia occurred under the effect of asynchrony. Larvae infected with B. thuringiensis presented decreased microbiota diversity if the larvae were reared synchronously with the host plant but not if they were reared asynchronously. Our study demonstrates the significant effect of phenological asynchrony on innate immunity-mediated interactions between herbivores and entomopathogenic bacteria and highlights the role of nonpathogenic gut bacteria in these interactions.
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Affiliation(s)
- Vyacheslav V. Martemyanov
- Laboratory of Ecological ParasitologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
- Biological InstituteNational Research Tomsk State UniversityTomskRussia
| | - Irina A. Belousova
- Laboratory of Ecological ParasitologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
- Institute of BiologyIrkutsk State UniversityIrkutskRussia
| | - Sergey V. Pavlushin
- Laboratory of Ecological ParasitologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Ivan M. Dubovskiy
- Laboratory of Insect PathologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Nikita I. Ershov
- Institute of Cytology and GeneticsSiberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Tatyana Y. Alikina
- Genomics Core FacilityInstitute of Chemical Biology and Fundamental MedicineSiberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Marsel R. Kabilov
- Genomics Core FacilityInstitute of Chemical Biology and Fundamental MedicineSiberian BranchRussian Academy of SciencesNovosibirskRussia
| | - Victor V. Glupov
- Laboratory of Insect PathologyInstitute of Systematics and Ecology of Animals Siberian BranchRussian Academy of SciencesNovosibirskRussia
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41
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Midgut microbiota and host immunocompetence underlie Bacillus thuringiensis killing mechanism. Proc Natl Acad Sci U S A 2016; 113:9486-91. [PMID: 27506800 DOI: 10.1073/pnas.1521741113] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacillus thuringiensis is a widely used bacterial entomopathogen producing insecticidal toxins, some of which are expressed in insect-resistant transgenic crops. Surprisingly, the killing mechanism of B. thuringiensis remains controversial. In particular, the importance of the septicemia induced by the host midgut microbiota is still debated as a result of the lack of experimental evidence obtained without drastic manipulation of the midgut and its content. Here this key issue is addressed by RNAi-mediated silencing of an immune gene in a lepidopteran host Spodoptera littoralis, leaving the midgut microbiota unaltered. The resulting cellular immunosuppression was characterized by a reduced nodulation response, which was associated with a significant enhancement of host larvae mortality triggered by B. thuringiensis and a Cry toxin. This was determined by an uncontrolled proliferation of midgut bacteria, after entering the body cavity through toxin-induced epithelial lesions. Consequently, the hemolymphatic microbiota dramatically changed upon treatment with Cry1Ca toxin, showing a remarkable predominance of Serratia and Clostridium species, which switched from asymptomatic gut symbionts to hemocoelic pathogens. These experimental results demonstrate the important contribution of host enteric flora in B. thuringiensis-killing activity and provide a sound foundation for developing new insect control strategies aimed at enhancing the impact of biocontrol agents by reducing the immunocompetence of the host.
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42
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Gut microbiota of Busseola fusca (Lepidoptera: Noctuidae). World J Microbiol Biotechnol 2016; 32:115. [PMID: 27263010 DOI: 10.1007/s11274-016-2066-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/05/2016] [Indexed: 12/21/2022]
Abstract
Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a stemborer pest that attacks maize (Zea mays) throughout sub-Saharan Africa. Genetically modified maize has been shown to be effective against B. fusca. However, resistance of B. fusca against Bt-maize has developed and spread throughout South Africa. Previous studies suggested that gut microbiota contribute to mortality across a range of Lepidoptera. To fully assess the role of microbiota within the gut, it is essential to understand the microbiota harboured by natural B. fusca populations. This study aimed to identify the gut-associated bacteria by 16S rRNA gene sequencing. A total of 78 bacterial strains were characterised from the midgut of B. fusca larvae that were collected from 30 sites across the maize producing region of South Africa. Molecular phylogenetic analyses revealed bacteria affiliated to Proteobacteria, Actinobacteria, and Firmicutes. Taxonomic distribution placed these isolates into 15 different genera representing 20 species. The majority of bacteria identified belong to the genera Bacillus, Enterococcus, and Klebsiella. The B. fusca gut represents an intriguing and unexplored niche for analysing microbial ecology. The study could provide opportunities for developing new targets for pest management and contribute to understanding the phenomenon of resistance evolution of this species.
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43
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Dubovskiy IM, Grizanova EV, Whitten MMA, Mukherjee K, Greig C, Alikina T, Kabilov M, Vilcinskas A, Glupov VV, Butt TM. Immuno-physiological adaptations confer wax moth Galleria mellonella resistance to Bacillus thuringiensis. Virulence 2016; 7:860-870. [PMID: 27029421 PMCID: PMC5160394 DOI: 10.1080/21505594.2016.1164367] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
Microevolutionary mechanisms of resistance to a bacterial pathogen were explored in a population of the Greater wax moth, Galleria mellonella, selected for an 8.8-fold increased resistance against the entomopathogenic bacterium Bacillus thuringiensis (Bt) compared with a non-selected (suspectible) line. Defense strategies of the resistant and susceptible insect lines were compared to uncover mechanisms underpinning resistance, and the possible cost of those survival strategies. In the uninfected state, resistant insects exhibited enhanced basal expression of genes related to regeneration and amelioration of Bt toxin activity in the midgut. In addition, these insects also exhibited elevated activity of genes linked to inflammation/stress management and immune defense in the fat body. Following oral infection with Bt, the expression of these genes was further elevated in the fat body and midgut of both lines and to a greater extent some of them in resistant line than the susceptible line. This gene expression analysis reveals a pattern of resistance mechanisms targeted to sites damaged by Bt with the insect placing greater emphasis on tissue repair as revealed by elevated expression of these genes in both the fat body and midgut epithelium. Unlike the susceptible insects, Bt infection significantly reduced the diversity and richness (abundance) of the gut microbiota in the resistant insects. These observations suggest that the resistant line not only has a more intact midgut but is secreting antimicrobial factors into the gut lumen which not only mitigate Bt activity but also affects the viability of other gut bacteria. Remarkably the resistant line employs multifactorial adaptations for resistance to Bt without any detected negative trade off since the insects exhibited higher fecundity.
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Affiliation(s)
- Ivan M Dubovskiy
- a Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science , Novosibirsk , Russia
| | - Ekaterina V Grizanova
- a Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science , Novosibirsk , Russia
| | - Miranda M A Whitten
- b Institute of Life Science, College of Medicine, Swansea University , Swansea , Wales , UK
| | - Krishnendu Mukherjee
- c Department of Bioresources , Fraunhofer Institute for Molecular Biology and Applied Ecology , Giessen , Germany
| | - Carolyn Greig
- d Department of Biosciences , College of Science, Swansea University , Swansea , Wales , UK
| | - Tatiana Alikina
- e Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Science , Novosibirsk , Russia
| | - Marsel Kabilov
- e Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Science , Novosibirsk , Russia
| | - Andreas Vilcinskas
- f Institute for Insect Biotechnology, Justus-Liebig University , Giessen , Germany
| | - Viktor V Glupov
- a Institute of Systematics and Ecology of Animals, Siberian Branch of Russian Academy of Science , Novosibirsk , Russia
| | - Tariq M Butt
- d Department of Biosciences , College of Science, Swansea University , Swansea , Wales , UK
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Keiser CN, Shearer TA, DeMarco AE, Brittingham HA, Knutson KA, Kuo C, Zhao K, Pruitt JN. Cuticular bacteria appear detrimental to social spiders in mixed but not monoculture exposure. Curr Zool 2016; 62:377-384. [PMID: 29491926 PMCID: PMC5829440 DOI: 10.1093/cz/zow015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 10/22/2015] [Indexed: 12/15/2022] Open
Abstract
Much of an animal’s health status, life history, and behavior are dictated by
interactions with its endogenous and exogenous bacterial communities. Unfortunately,
interactions between hosts and members of their resident bacterial community are often
ignored in animal behavior and behavioral ecology. Here, we aim to identify the nature of
host–microbe interactions in a nonmodel organism, the African social spider
Stegodyphus dumicola. We collected and identified bacteria from the
cuticles of spiders in situ and then exposed spiders to bacterial
monocultures cultures via topical application or injection. We also topically inoculated
spiders with a concomitant “cocktail” of bacteria and measured the behavior of spiders
daily for 24 days after inoculation. Lastly, we collected and identified bacteria from the
cuticles of prey items in the capture webs of spiders, and then fed spiders domestic
crickets which had been injected with these bacteria. We also injected 1 species of
prey-borne bacteria into the hemolymph of spiders. Only Bacillus
thuringiensis caused increased mortality when injected into the hemolymph of
spiders, whereas no bacterial monocultures caused increased mortality when applied
topically, relative to control solutions. However, a bacterial cocktail of cuticular
bacteria caused weight loss and mortality when applied topically, yet did not detectibly
alter spider behavior. Consuming prey injected with prey-borne bacteria was associated
with an elongated lifespan in spiders. Thus, indirect evidence from multiple experiments
suggests that the effects of these bacteria on spider survivorship appear contingent on
their mode of colonization and whether they are applied in monoculture or within a mixed
cocktail. We urge that follow-up studies should test these host–microbe interactions
across different social contexts to determine the role that microbes play in colony
performance.
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Affiliation(s)
- Carl N Keiser
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Taylor A Shearer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Alexander E DeMarco
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Hayley A Brittingham
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Karen A Knutson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Candice Kuo
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Katherine Zhao
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Jonathan N Pruitt
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260 USA
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45
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Johnston PR, Rolff J. Host and Symbiont Jointly Control Gut Microbiota during Complete Metamorphosis. PLoS Pathog 2015; 11:e1005246. [PMID: 26544881 PMCID: PMC4636265 DOI: 10.1371/journal.ppat.1005246] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 10/02/2015] [Indexed: 01/08/2023] Open
Abstract
Holometabolous insects undergo a radical anatomical re-organisation during metamorphosis. This poses a developmental challenge: the host must replace the larval gut but at the same time retain symbiotic gut microbes and avoid infection by opportunistic pathogens. By manipulating host immunity and bacterial competitive ability, we study how the host Galleria mellonella and the symbiotic bacterium Enterococcus mundtii interact to manage the composition of the microbiota during metamorphosis. Disenabling one or both symbiotic partners alters the composition of the gut microbiota, which incurs fitness costs: adult hosts with a gut microbiota dominated by pathogens such as Serratia and Staphylococcus die early. Our results reveal an interaction that guarantees the safe passage of the symbiont through metamorphosis and benefits the resulting adult host. Host-symbiont "conspiracies" as described here are almost certainly widespread in holometobolous insects including many disease vectors.
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Affiliation(s)
| | - Jens Rolff
- Freie Universität Berlin, Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Berlin, Germany
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46
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Elimination of Gut Microbes with Antibiotics Confers Resistance to Bacillus thuringiensis Toxin Proteins in Helicoverpa armigera (Hubner). Appl Biochem Biotechnol 2015; 177:1621-37. [DOI: 10.1007/s12010-015-1841-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/08/2015] [Indexed: 12/21/2022]
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47
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van Leeuwen E, O'Neill S, Matthews A, Raymond B. Making pathogens sociable: the [corrected] emergence of high relatedness through limited host invasibility. ISME JOURNAL 2015; 9:2315-23. [PMID: 26125685 PMCID: PMC4579463 DOI: 10.1038/ismej.2015.111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 04/16/2015] [Accepted: 05/19/2015] [Indexed: 12/31/2022]
Abstract
Cooperation depends upon high relatedness, the high genetic similarity of interacting partners relative to the wider population. For pathogenic bacteria, which show diverse cooperative traits, the population processes that determine relatedness are poorly understood. Here, we explore whether within-host dynamics can produce high relatedness in the insect pathogen Bacillus thuringiensis. We study the effects of host/pathogen interactions on relatedness via a model of host invasion and fit parameters to competition experiments with marked strains. We show that invasibility is a key parameter for determining relatedness and experimentally demonstrate the emergence of high relatedness from well-mixed inocula. We find that a single infection cycle results in a bottleneck with a similar level of relatedness to those previously reported in the field. The bottlenecks that are a product of widespread barriers to infection can therefore produce the population structure required for the evolution of cooperative virulence.
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Affiliation(s)
- Edwin van Leeuwen
- School of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Sarah O'Neill
- School of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Andrew Matthews
- School of Biological Sciences, Royal Holloway University of London, Egham, UK.,Department of Life Sciences, Imperial College London, Silwood Park campus, Ascot, UK
| | - Ben Raymond
- School of Biological Sciences, Royal Holloway University of London, Egham, UK.,Department of Life Sciences, Imperial College London, Silwood Park campus, Ascot, UK
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48
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Cornforth DM, Matthews A, Brown SP, Raymond B. Bacterial Cooperation Causes Systematic Errors in Pathogen Risk Assessment due to the Failure of the Independent Action Hypothesis. PLoS Pathog 2015; 11:e1004775. [PMID: 25909384 PMCID: PMC4409216 DOI: 10.1371/journal.ppat.1004775] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 03/03/2015] [Indexed: 11/19/2022] Open
Abstract
The Independent Action Hypothesis (IAH) states that pathogenic individuals (cells, spores, virus particles etc.) behave independently of each other, so that each has an independent probability of causing systemic infection or death. The IAH is not just of basic scientific interest; it forms the basis of our current estimates of infectious disease risk in humans. Despite the important role of the IAH in managing disease interventions for food and water-borne pathogens, experimental support for the IAH in bacterial pathogens is indirect at best. Moreover since the IAH was first proposed, cooperative behaviors have been discovered in a wide range of microorganisms, including many pathogens. A fundamental principle of cooperation is that the fitness of individuals is affected by the presence and behaviors of others, which is contrary to the assumption of independent action. In this paper, we test the IAH in Bacillus thuringiensis (B.t), a widely occurring insect pathogen that releases toxins that benefit others in the inoculum, infecting the diamondback moth, Plutella xylostella. By experimentally separating B.t. spores from their toxins, we demonstrate that the IAH fails because there is an interaction between toxin and spore effects on mortality, where the toxin effect is synergistic and cannot be accommodated by independence assumptions. Finally, we show that applying recommended IAH dose-response models to high dose data leads to systematic overestimation of mortality risks at low doses, due to the presence of synergistic pathogen interactions. Our results show that cooperative secretions can easily invalidate the IAH, and that such mechanistic details should be incorporated into pathogen risk analysis.
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Affiliation(s)
- Daniel M. Cornforth
- Department of Molecular Biosciences, The University of Texas, Austin, Austin, Texas, United States of America
- * E-mail: (DMC); (BR)
| | - Andrew Matthews
- Department of Life Sciences, Imperial College London, Silwood Park, Ascot, United Kingdom
| | - Sam P. Brown
- Centre for Immunity, Infection and Immunity, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Ben Raymond
- Department of Life Sciences, Imperial College London, Silwood Park, Ascot, United Kingdom
- * E-mail: (DMC); (BR)
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Paramasiva I, Shouche Y, Kulkarni GJ, Krishnayya PV, Akbar SM, Sharma HC. Diversity in gut microflora of Helicoverpa armigera populations from different regions in relation to biological activity of Bacillus thuringiensis δ-endotoxin Cry1Ac. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2014; 87:201-213. [PMID: 25195523 DOI: 10.1002/arch.21190] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Transgenic crops expressing toxin proteins from Bacillus thuringiensis (Bt) have been deployed on a large scale for management of Helicoverpa armigera. Resistance to Bt toxins has been documented in several papers, and therefore, we examined the role of midgut microflora of H. armigera in its susceptibility to Bt toxins. The susceptibility of H. armigera to Bt toxin Cry1Ac was assessed using Log-dose-Probit analysis, and the microbial communities were identified by 16S rRNA sequencing. The H. armigera populations from nine locations harbored diverse microbial communities, and had some unique bacteria, suggesting a wide geographical variation in microbial community in the midgut of the pod borer larvae. Phylotypes belonging to 32 genera were identified in the H. armigera midgut in field populations from nine locations. Bacteria belonging to Enterobacteriaceae (Order Bacillales) were present in all the populations, and these may be the common members of the H. armigera larval midgut microflora. Presence and/or absence of certain species were linked to H. armigera susceptibility to Bt toxins, but there were no clear trends across locations. Variation in susceptibility of F1 neonates of H. armigera from different locations to the Bt toxin Cry1Ac was found to be 3.4-fold. These findings support the idea that insect migut microflora may influence the biological activity of Bt toxins.
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Affiliation(s)
- Inakarla Paramasiva
- Department of Entomology, Agricultural College, Acharya N.G. Ranga Agriculture University, Bapatla, Andhra Pradesh, India; Entomology, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Telangana, India
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Paramasiva I, Sharma HC, Krishnayya PV. Antibiotics influence the toxicity of the delta endotoxins of Bacillus thuringiensis towards the cotton bollworm, Helicoverpa armigera. BMC Microbiol 2014; 14:200. [PMID: 25059716 PMCID: PMC4222728 DOI: 10.1186/1471-2180-14-200] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 07/12/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The cotton bollworm, Helicoverpa armigera is one of the most important crop pests worldwide. It has developed high levels of resistance to synthetic insecticides, and hence, Bacillus thuringiensis (Bt) formulations are used as a safer pesticide and the Bt genes have been deployed in transgenic crops for controlling this pest. There is an apprehension that H. armigera might develop resistance to transgenic crops in future. Therefore, we studied the role of gut microbes by eliminating them with antibiotics in H. armigera larvae on the toxicity of Bt toxins against this pest. RESULTS Commercial formulation of Bt (Biolep®) and the pure Cry1Ab and Cry1Ac toxin proteins were evaluated at ED50, LC50, and LC90 dosages against the H. armigera larvae with and without antibiotics (which removed the gut microbes). Lowest H. armigera larval mortality due to Bt formulation and the Bt toxins Cry1Ab and Cry1Ac was recorded in insects reared on diets with 250 and 500 μg ml-1 diet of each of the four antibiotics (gentamicin, penicillin, rifampicin, and streptomycin), while the highest larval mortality was recorded in insects reared on diets without the antibiotics. Mortality of H. armigera larvae fed on diets with Bt formulation and the δ-endotoxins Cry1Ab and Cry1Ac was inversely proportional to the concentration of antibiotics in the artificial diet. Nearly 30% reduction in larval mortality was observed in H. armigera larvae from F1 to F3 generation when the larvae were reared on diets without antibiotics (with gut microbes) and fed on 0.15% Bt or 12 μg Cry1Ab or Cry1Ac ml-1 diet, indicating development of resistance to Bt in the presence of gut microflora. However, there were no differences in larval mortality due to Bt, Cry1Ab or Cry1Ac across generations in insects when they were reared on diets with 250 μg of each antibiotic ml-1 diet (without gut microflora). CONCLUSIONS The results suggested that antibiotics which eliminated gut microflora influenced the toxicity of Bt towards H. armigera, and any variation in diversity and abundance of gut microflora will have a major bearing on development of resistance to Bt toxins applied as foliar sprays or deployed in transgenic crops for pest management.
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Affiliation(s)
| | - Hari C Sharma
- International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324 Andhra Pradesh, India.
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