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Wang Y, Luo J, Guan X, Zhao Y, Sun L. Bacillus cereus cereolysin O induces pyroptosis in an undecapeptide-dependent manner. Cell Death Discov 2024; 10:122. [PMID: 38458999 PMCID: PMC10923922 DOI: 10.1038/s41420-024-01887-7] [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: 11/03/2023] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 03/10/2024] Open
Abstract
Bacillus cereus is a clinically significant foodborne pathogen that causes severe gastrointestinal and non-gastrointestinal disease. Cereolysin O (CLO) is a putative virulence factor of B. cereus, and its function remains to be investigated. In this study, we examined the biological activity of CLO from a deep sea B. cereus isolate. CLO was highly toxic to mammalian cells and triggered pyroptosis through NLRP3 inflammasome-mediated caspase 1 and gasdermin D activation. CLO-induced cell death involved ROS accumulation and K+ efflux, and was blocked by serum lipids. CLO bound specifically to cholesterol, and this binding was essential to CLO cytotoxicity. The structural integrity of the three tryptophan residues in the C-terminal undecapeptide was vital for CLO to interact with membrane lipids and cause membrane perforation. Taken together, these results provided new insights into the molecular mechanism of B. cereus CLO-mediated cytotoxicity.
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Affiliation(s)
- Yujian Wang
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, CAS Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
| | - Jingchang Luo
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, CAS Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- College of Marine Sciences, University of Chinese Academy of Sciences, Qingdao, China
| | - Xiaolu Guan
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, CAS Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- College of Marine Sciences, University of Chinese Academy of Sciences, Qingdao, China
| | - Yan Zhao
- Tsinghua-Peking Joint Center for Life Sciences, School of Medicine, Tsinghua University, Beijing, China.
| | - Li Sun
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, CAS Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China.
- College of Marine Sciences, University of Chinese Academy of Sciences, Qingdao, China.
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2
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Harirchi S, Sar T, Ramezani M, Aliyu H, Etemadifar Z, Nojoumi SA, Yazdian F, Awasthi MK, Taherzadeh MJ. Bacillales: From Taxonomy to Biotechnological and Industrial Perspectives. Microorganisms 2022; 10:microorganisms10122355. [PMID: 36557608 PMCID: PMC9781867 DOI: 10.3390/microorganisms10122355] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/18/2022] [Accepted: 11/21/2022] [Indexed: 12/02/2022] Open
Abstract
For a long time, the genus Bacillus has been known and considered among the most applicable genera in several fields. Recent taxonomical developments resulted in the identification of more species in Bacillus-related genera, particularly in the order Bacillales (earlier heterotypic synonym: Caryophanales), with potential application for biotechnological and industrial purposes such as biofuels, bioactive agents, biopolymers, and enzymes. Therefore, a thorough understanding of the taxonomy, growth requirements and physiology, genomics, and metabolic pathways in the highly diverse bacterial order, Bacillales, will facilitate a more robust designing and sustainable production of strain lines relevant to a circular economy. This paper is focused principally on less-known genera and their potential in the order Bacillales for promising applications in the industry and addresses the taxonomical complexities of this order. Moreover, it emphasizes the biotechnological usage of some engineered strains of the order Bacillales. The elucidation of novel taxa, their metabolic pathways, and growth conditions would make it possible to drive industrial processes toward an upgraded functionality based on the microbial nature.
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Affiliation(s)
- Sharareh Harirchi
- Swedish Centre for Resource Recovery, University of Borås, 50190 Borås, Sweden
| | - Taner Sar
- Swedish Centre for Resource Recovery, University of Borås, 50190 Borås, Sweden
| | - Mohaddaseh Ramezani
- Microorganisms Bank, Iranian Biological Resource Centre (IBRC), Academic Center for Education, Culture and Research (ACECR), Tehran, Iran
| | - Habibu Aliyu
- Institute of Process Engineering in Life Science II: Technical Biology, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Zahra Etemadifar
- Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan 8174673441, Iran
| | - Seyed Ali Nojoumi
- Microbiology Research Center, Pasteur Institute of Iran, Tehran 1316943551, Iran
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran 1316943551, Iran
| | - Fatemeh Yazdian
- Department of Life Science Engineering, Faculty of New Sciences and Technologies, University of Tehran, Tehran 1439957131, Iran
| | - Mukesh Kumar Awasthi
- College of Natural Resources and Environment, Northwest A&F University, Taicheng Road 3#, Yangling, Xianyang 712100, China
| | - Mohammad J. Taherzadeh
- Swedish Centre for Resource Recovery, University of Borås, 50190 Borås, Sweden
- Correspondence:
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3
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Cationic protein 8 plays multiple roles in Galleria mellonella immunity. Sci Rep 2022; 12:11737. [PMID: 35817811 PMCID: PMC9273619 DOI: 10.1038/s41598-022-15929-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 07/01/2022] [Indexed: 11/08/2022] Open
Abstract
Galleria mellonella cationic protein 8 (GmCP8) is a hemolymph protein previously identified as an opsonin and an inhibitor of fungal proteases. In this work, we showed its bactericidal activity toward Pseudomonas entomophila, Pseudomonas aeruginosa, Bacillus thuringiensis, Staphylococcus aureus, and Escherichia coli and against yeast-like fungi Candida albicans. The activity against E. coli was correlated with bacterial membrane permeabilization. In turn, in the case of P. entomophila, B. thuringiensis, and C. albicans, the atomic force microscopy analysis of the microbial surface showed changes in the topography of cells and changes in their nanomechanical properties. GmCP8 also showed the inhibitory activity toward the serine protease trypsin and the metalloproteinase thermolysin. The expression of the gene encoding the GmCP8 protein did not increase either in the gut or in the fat body of G. mellonella after oral infection with P. entomophila. Similarly, the amount of GmCP8 in the hemolymph of G. mellonella did not change in immune-challenged insects. However, when GmCP8 was injected into the G. mellonella hemocel, a change in the survival curve was observed in the infected larvae. Our results shed new light on the function of GmCP8 protein in insect immunity, indicating its role in humoral defence mechanisms.
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Bacillus thuringiensis Spores and Cry3A Toxins Act Synergistically to Expedite Colorado Potato Beetle Mortality. Toxins (Basel) 2021; 13:toxins13110746. [PMID: 34822531 PMCID: PMC8624055 DOI: 10.3390/toxins13110746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 10/06/2021] [Accepted: 10/16/2021] [Indexed: 11/17/2022] Open
Abstract
The insect integument (exoskeleton) is an effective physiochemical barrier that limits disease-causing agents to a few portals of entry, including the gastrointestinal and reproductive tracts. The bacterial biopesticide Bacillus thuringiensis (Bt) enters the insect host via the mouth and must thwart gut-based defences to make its way into the body cavity (haemocoel) and establish infection. We sought to uncover the main antibacterial defences of the midgut and the pathophysiological features of Bt in a notable insect pest, the Colorado potato beetle Leptinotarsa decemlineata (CPB). Exposing the beetles to both Bt spores and their Cry3A toxins (crystalline δ-endotoxins) via oral inoculation led to higher mortality levels when compared to either spores or Cry3A toxins alone. Within 12 h post-exposure, Cry3A toxins caused a 1.5-fold increase in the levels of reactive oxygen species (ROS) and malondialdehyde (lipid peroxidation) within the midgut - key indicators of tissue damage. When Cry3A toxins are combined with spores, gross redox imbalance and 'oxidation stress' is apparent in beetle larvae. The insect detoxification system is activated when Bt spores and Cry3A toxins are administered alone or in combination to mitigate toxicosis, in addition to elevated mRNA levels of candidate defence genes (pattern-recognition receptor, stress-regulation, serine proteases, and prosaposin-like protein). The presence of bacterial spores and/or Cry3A toxins coincides with subtle changes in microbial community composition of the midgut, such as decreased Pseudomonas abundance at 48 h post inoculation. Both Bt spores and Cry3A toxins have negative impacts on larval health, and when combined, likely cause metabolic derangement, due to multiple tissue targets being compromised.
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5
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Comparative genome analysis of Bacillus thuringiensis strain HD521 and HS18-1. Sci Rep 2021; 11:16590. [PMID: 34400725 PMCID: PMC8368016 DOI: 10.1038/s41598-021-96133-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 07/22/2021] [Indexed: 02/07/2023] Open
Abstract
Bacillus thuringiensis (Bt) is an important biological insecticide used to management of different agricultural pests by producing toxic parasporal crystals proteins. Strain HD521 has an antagonistic effect against Rhizoctonia solani AG1IA, the causal agent of rice sheath blight. This strain with three cry7 genes can the formation of bipyramidal parasporal crystals (BPCs). BPCs are used for insecticidal activities against Henosepilachna vigintioctomaculata larva (Coleoptera). Strain HS18-1 contains different types of BPCs encoding genes and has effective toxicity for Lepidoptera and Diptera insects. Here we report the whole genome sequencing and assembly of HD521 and HS18-1 strains and analyzed the genome constitution covering virulence factors, types of plasmid, insertion sequences, and prophage sequences. The results showed that the genome of strain HD521 contains a circular chromosome and six circular plasmids, encoding eight types of virulence protein factors [Immune Inhibitor A, Hemolytic Enterotoxin, S-layer protein, Phospholipase C, Zwittermicin A-resistance protein, Metalloprotease, Chitinase, and N-acyl homoserine lactonase (AiiA)], four families of insertion sequence, and comprises six pro-phage sequences. The genome of strain HS18-1 contains one circular chromosome and nine circular plasmids, encoding five types of virulence protein factors [Hemolytic Enterotoxin, S-layer protein, Phospholipase C, Chitinase, and N-acyl homoserine lactonase (AiiA)] and four families of insertion sequence, and comprises of three pro-phage sequences. The obtained results will contribute to deeply understand the B. thuringiensis strain HD521 and HS18-1 at the genomic level.
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6
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Consentino L, Rejasse A, Crapart N, Bevilacqua C, Nielsen-LeRoux C. Laser capture microdissection to study Bacillus cereus iron homeostasis gene expression during Galleria mellonella in vivo gut colonization. Virulence 2021; 12:2104-2121. [PMID: 34374318 PMCID: PMC8366545 DOI: 10.1080/21505594.2021.1959790] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Bacillus cereus is a Gram-positive opportunistic pathogen closely related to the entomopathogen, Bacillus thuringiensis, both of which are involved in intestinal infections. Iron is an essential micronutrient for full growth and virulence of pathogens during infection. However, little is known about iron homeostasis during gut infection. Therefore, we aimed to assess the expression of B. cereus genes related to bacterial iron homeostasis, virulence and oxidative stress. The hypothesis is that the expression of such genes would vary between early and later stage colonization in correlation to gut cell damage. To perform the study, a germ-free Galleria mellonella model was set up in order to adapt the use of Laser-capture microdissection (LCM), to select precise areas in the gut lumen from frozen whole larval cryo-sections. Analyses were performed from alive larvae and the expression of targeted genes was assessed byspecific pre-amplification of mRNA followed by quantitative PCR. Firstly, the results reinforce the reliability of LCM, despite a low amount of bacterial RNA recovered. Secondly, bacterial genes involved in iron homeostasis are expressed in the lumen at both 3 and 16 hours post force-feeding. Thirdly, iron gene expression is slightly modulated during gut infection, and lastly, the mRNA of G. mellonella encoding for ferritin and transferrin iron storage and transport are recovered too. Therefore, iron homeostasis should play a role in B. cereus gut colonization. Furthermore, we demonstrate for the first time the value of using LCM for specific in situ gene expression analysis of extracellular bacteria in a whole animal.
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Affiliation(s)
- Laurent Consentino
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Agnès Rejasse
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France
| | - Nicolas Crapart
- Université Paris Saclay, INRAE, AgroParisTech, UMR GABI, Abridge, Jouy En Josas, France.,Exilone, Elancourt, France
| | - Claudia Bevilacqua
- Université Paris Saclay, INRAE, AgroParisTech, UMR GABI, Abridge, Jouy En Josas, France
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7
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Immune Inhibitor A Metalloproteases Contribute to Virulence in Bacillus Endophthalmitis. Infect Immun 2021; 89:e0020121. [PMID: 34097460 DOI: 10.1128/iai.00201-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endophthalmitis is a devastating infection that can cause blindness. Over half of Bacillus endophthalmitis cases result in significant loss of useful vision. Bacillus produces many virulence factors that may contribute to retinal damage and robust inflammation. We analyzed Bacillus immune inhibitor A (InhA) metalloproteases in the context of this disease, hypothesizing that InhAs contribute to Bacillus intraocular virulence and inflammation. We analyzed phenotypes and infectivity of wild type (WT), InhA1-deficient (ΔinhA1), InhA2-deficient (ΔinhA2), or InhA1, A2, and A3-deficient (ΔinhA1-3) Bacillus thuringiensis. In vitro analysis of growth, proteolysis, and cytotoxicity were compared. WT and InhA mutants were similarly cytotoxic to retinal cells. Mutants ΔinhA1 and ΔinhA2 entered log phase growth earlier than WT. Proteolysis by the ΔinhA1-3 mutant was decreased, but this strain grew similar to WT in vitro. Experimental endophthalmitis was initiated by intravitreally infecting C57BL/6J mice with 200 CFU of B. thuringiensis WT or InhA mutants. Eyes were analyzed for intraocular Bacillus and myeloperoxidase concentrations, retinal function loss, and gross histological changes. Eyes infected with ΔinhA1 or ΔinhA2 strains contained greater numbers of bacteria than eyes infected with WT throughout the infection course. Eyes infected with single mutants had inflammation and retinal function loss similar to eyes infected with WT strain. Eyes infected with ΔinhA1-3 cleared the infection. RT-PCR results suggested that there may be compensatory expression of the other InhAs in the single InhA mutant. These results indicate that together, the InhA metalloproteases contribute to the severity of infection and inflammation in Bacillus endophthalmitis.
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8
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The Food Poisoning Toxins of Bacillus cereus. Toxins (Basel) 2021; 13:toxins13020098. [PMID: 33525722 PMCID: PMC7911051 DOI: 10.3390/toxins13020098] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/14/2021] [Accepted: 01/25/2021] [Indexed: 12/13/2022] Open
Abstract
Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide and CytK are also presented, as well as methods for toxin detection, and the contribution of further putative virulence factors to the diarrheal disease.
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Genomics and Proteomics Analyses Revealed Novel Candidate Pesticidal Proteins in a Lepidopteran-Toxic Bacillus thuringiensis Strain. Toxins (Basel) 2020; 12:toxins12110673. [PMID: 33114565 PMCID: PMC7693509 DOI: 10.3390/toxins12110673] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/12/2020] [Accepted: 10/20/2020] [Indexed: 11/17/2022] Open
Abstract
Discovery and identification of novel insecticidal proteins in Bacillus thuringiensis (Bt) strains are of crucial importance for efficient biological control of pests and better management of insect resistance. In this study, the Bt strain KhF, toxic for Plodia interpunctella and Grapholita molesta larvae, underwent genomics and proteomics analyses to achieve a better understanding of the bases of its pathogenicity. The whole-genome sequencing results revealed that the KhF strain contained nine coding sequences with homologies to Bt insecticidal genes. The lepidopteran toxic mixture of spores and crystals of this Bt strain was subjected to liquid chromatography and tandem mass spectrometry (LC-MS/MS) to assess the protein composition. The results of the proteomic analyses, combined with the toxin gene sequences, revealed that two of the main components of the crystals were two new candidate pesticidal proteins, named KhFA and KhFB. These proteins showed a similarity lower than 36% to the other known Bt toxins. The phylogenetic analysis showed that the KhFA and KhFB grouped with the newly denominated Xpp and Mpp (former ETX/Mtx) pesticidal protein groups, respectively. Altogether, this study has led to the discovery of two novel candidate pesticidal toxins in the lepidopteran toxic KhF strain.
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10
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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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Abstract
The Bacillus cereus group includes several Bacillus species with closely related phylogeny. The most well-studied members of the group, B. anthracis, B. cereus, and B. thuringiensis, are known for their pathogenic potential. Here, we present the historical rationale for speciation and discuss shared and unique features of these bacteria. Aspects of cell morphology and physiology, and genome sequence similarity and gene synteny support close evolutionary relationships for these three species. For many strains, distinct differences in virulence factor synthesis provide facile means for species assignment. B. anthracis is the causative agent of anthrax. Some B. cereus strains are commonly recognized as food poisoning agents, but strains can also cause localized wound and eye infections as well as systemic disease. Certain B. thuringiensis strains are entomopathogens and have been commercialized for use as biopesticides, while some strains have been reported to cause infection in immunocompromised individuals. In this article we compare and contrast B. anthracis, B. cereus, and B. thuringiensis, including ecology, cell structure and development, virulence attributes, gene regulation and genetic exchange systems, and experimental models of disease.
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12
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Zhao Y, Chen C, Gu HJ, Zhang J, Sun L. Characterization of the Genome Feature and Toxic Capacity of a Bacillus wiedmannii Isolate From the Hydrothermal Field in Okinawa Trough. Front Cell Infect Microbiol 2019; 9:370. [PMID: 31750261 PMCID: PMC6842932 DOI: 10.3389/fcimb.2019.00370] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 10/10/2019] [Indexed: 11/13/2022] Open
Abstract
The Bacillus cereus group is frequently isolated from soil, plants, food, and other environments. In this study, we report the first isolation and characterization of a B. cereus group member, Bacillus wiedmannii SR52, from the hydrothermal field in the Iheya Ridge of Okinawa Trough. SR52 was isolated from the gills of shrimp Alvinocaris longirostris, an invertebrate species found abundantly in the ecosystems of the hydrothermal vents, and is most closely related to B. wiedmannii FSL W8-0169. SR52 is aerobic, motile, and able to form endospores. SR52 can grow in NaCl concentrations up to 9%. SR52 has a circular chromosome of 5,448,361 bp and a plasmid of 137,592 bp, encoding 5,709 and 189 genes, respectively. The chromosome contains 297 putative virulence genes, including those encoding enterotoxins and hemolysins. Fourteen rRNA operons, 107 tRNAs, and 5 sRNAs are present in the chromosome, and 7 tRNAs are present in the plasmid. SR52 possesses 13 genomic islands (GIs), all on the chromosome. Comparing to FSL W8-0169, SR52 exhibits several streaking features in its genome, notably an exceedingly large number of non-coding RNAs and GIs. In vivo studies showed that following intramuscular injection into fish, SR52 was able to disseminate in tissues and cause mortality; when inoculated into mice, SR52 induced acute mortality and disseminated transiently in tissues. In vitro studies showed that SR52 possessed hemolytic activity, and the extracellular product of SR52 exhibited a strong cytotoxic effect. These results provided the first insight into the cytotoxicity and genomic feature of B. wiedmannii from the deep-sea hydrothermal environment.
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Affiliation(s)
- Yan Zhao
- CAS Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China.,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Chen Chen
- CAS Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China.,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Han-Jie Gu
- CAS Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China.,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jian Zhang
- CAS Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China.,Deep Sea Research Center, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Li Sun
- CAS Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China
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13
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Repertoire of the Bacillus thuringiensis Virulence Factors Unrelated to Major Classes of Protein Toxins and Its Role in Specificity of Host-Pathogen Interactions. Toxins (Basel) 2019; 11:toxins11060347. [PMID: 31212976 PMCID: PMC6628457 DOI: 10.3390/toxins11060347] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 05/21/2019] [Accepted: 06/10/2019] [Indexed: 12/28/2022] Open
Abstract
Bacillus thuringiensis (Bt) is a Gram-positive soil bacteria that infects invertebrates, predominantly of Arthropoda phylum. Due to its immense host range Bt has become a leading producer of biopesticides applied both in biotechnology and agriculture. Cytotoxic effect of Bt, as well as its host specificity, are commonly attributed either to proteinaceous crystal parasporal toxins (Cry and Cyt) produced by bacteria in a stationary phase or to soluble toxins of Vip and Sip families secreted by vegetative cells. At the same time, numerous non-toxin virulence factors of Bt have been discovered, including metalloproteases, chitinases, aminopolyol antibiotics and nucleotide-mimicking moieties. These agents act at each stage of the B. thuringiensis invasion and contribute to cytotoxic properties of Bt strains enhancing toxin activity, ensuring host immune response evasion and participating in extracellular matrix degeneration. In this review we attempt to classify Bt virulence factors unrelated to major groups of protein toxins and discuss their putative role in the establishment of Bt specificity to various groups of insects.
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14
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Buisson C, Gohar M, Huillet E, Nielsen-LeRoux C. Bacillus thuringiensis Spores and Vegetative Bacteria: Infection Capacity and Role of the Virulence Regulon PlcR Following Intrahaemocoel Injection of Galleria mellonella. INSECTS 2019; 10:insects10050129. [PMID: 31060274 PMCID: PMC6571593 DOI: 10.3390/insects10050129] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 04/19/2019] [Accepted: 04/30/2019] [Indexed: 11/16/2022]
Abstract
Bacillus thuringiensis is an invertebrate pathogen that produces insecticidal crystal toxins acting on the intestinal barrier. In the Galleria mellonella larvae infection model, toxins from the PlcR virulence regulon contribute to pathogenicity by the oral route. While B. thuringiensis is principally an oral pathogen, bacteria may also reach the insect haemocoel following injury of the cuticle. Here, we address the question of spore virulence as compared to vegetative cells when the wild-type Bt407cry- strain and its isogenic ∆plcR mutant are inoculated directly into G. mellonella haemocoel. Mortality dose-response curves were constructed at 25 and 37 °C using spores or vegetative cell inocula, and the 50% lethal dose (LD50) in all infection conditions was determined after 48 h of infection. Our findings show that (i) the LD50 is lower for spores than for vegetative cells for both strains, while the temperature has no significant influence, and (ii) the ∆plcR mutant is four to six times less virulent than the wild-type strain in all infection conditions. Our results suggest that the environmental resistant spores are the most infecting form in haemocoel and that the PlcR virulence regulon plays an important role in toxicity when reaching the haemocoel from the cuticle and not only following ingestion.
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Affiliation(s)
- Christophe Buisson
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
| | - Michel Gohar
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
| | - Eugénie Huillet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France.
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Yu WQ, Zheng GP, Qiu DW, Yan FC, Liu WZ, Liu WX. Draft genome sequence, disease-resistance genes, and phenotype of a Paenibacillus terrae strain (NK3-4) with the potential to control plant diseases. Genome 2018; 61:725-734. [PMID: 30184440 DOI: 10.1139/gen-2018-0113] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Paenibacillus terrae NK3-4 is a plant growth-promoting rhizobacterium that may be useful for controlling plant diseases. We conducted a genomic analysis and identified the genes mediating antimicrobial functions. Additionally, an extracellular antifungal protein component was isolated and identified. The draft genome sequence was assembled into 54 contigs, with 5 458 568 bp and a G+C content of 47%. Moreover, 4 690 015 bp encoded 5090 proteins, 7 rRNAs, and 54 tRNAs. Forty-four genes involved in antimicrobial functions were detected. They mainly encode 19 non-ribosomal peptide synthetases (NRPSs); one polyketide synthase/NRPSs hybrid enzyme; four Zn-dependent metalloproteases; three antilisterial bacteriocin subtilosin biosynthesis proteins (AlbA); four serine proteases; five pectate lyases; three beta-glucanases; and four 1,4-beta-xylanases. These include four novel NRPSs that have not been found in any species of Paenibacillus. Furthermore, five proteins exhibiting antifungal activity were identified from the antifungal extracellular protein component based on MS/MS and the strain NK3-4 predicted protein library. On the basis of these features, we propose that strain NK3-4 represents a promising biocontrol agent for protecting plant from diseases. The draft genome sequence described herein may provide the genetic basis for the characterization of the molecular mechanisms underlying the biocontrol functions. It may also facilitate the development of rational strategies for improving the strain.
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Affiliation(s)
- Wen Qing Yu
- a College of Agriculture, Heilongjiang Bayi Agricultural University, Daqing, 163319, Heilongjiang, China.,b Heilongjiang Academy of Land Reclamation, Haerbin, Heilongjiang Province, 150038, China.,c Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100094, China
| | - Gui Ping Zheng
- a College of Agriculture, Heilongjiang Bayi Agricultural University, Daqing, 163319, Heilongjiang, China
| | - De Wen Qiu
- c Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100094, China
| | - Feng Chao Yan
- b Heilongjiang Academy of Land Reclamation, Haerbin, Heilongjiang Province, 150038, China
| | - Wen Zhi Liu
- b Heilongjiang Academy of Land Reclamation, Haerbin, Heilongjiang Province, 150038, China
| | - Wan Xue Liu
- c Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100094, China
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Hollensteiner J, Poehlein A, Spröer C, Bunk B, Sheppard AE, Rosenstiel P, Schulenburg H, Liesegang H. Complete genome sequence of the nematicidal Bacillus thuringiensis MYBT18247. J Biotechnol 2017; 260:48-52. [PMID: 28899808 DOI: 10.1016/j.jbiotec.2017.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 09/08/2017] [Accepted: 09/08/2017] [Indexed: 11/28/2022]
Abstract
The Gram-positive spore forming bacterium Bacillus thuringiensis MYBT18247 encodes three cry toxin genes, (cry6Ba2, cry6Ba3 and cry21-like) which are active against nematodes. For a better understanding of the evolution of virulence and cry toxins, we present here the complete genome sequence of Bacillus thuringiensis MYBT18247. Various additional virulence factors such as bacteriocins, proteases and hemolysins were identified. In addition, the methylome and the metabolic potential of the strain were analyzed and the strain phylogenetically classified.
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Affiliation(s)
- Jacqueline Hollensteiner
- Department of Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, University of Goettingen, Germany
| | - Anja Poehlein
- Department of Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, University of Goettingen, Germany
| | - Cathrin Spröer
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Boyke Bunk
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Anna E Sheppard
- Department of Evolutionary Ecology and Genetics, Zoological Institute, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Philip Rosenstiel
- Institute of Clinical Molecular Biology, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Hinrich Schulenburg
- Department of Evolutionary Ecology and Genetics, Zoological Institute, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Heiko Liesegang
- Department of Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, University of Goettingen, Germany.
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Gupta V, Chaudhary N, Aggarwal S, Adlakha N, Gulati P, Bhatnagar R. Functional analysis of BAS2108-2109 two component system: Evidence for protease regulation in Bacillus anthracis. Int J Biochem Cell Biol 2017; 89:71-84. [PMID: 28602714 DOI: 10.1016/j.biocel.2017.06.004] [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: 03/09/2017] [Revised: 06/01/2017] [Accepted: 06/03/2017] [Indexed: 01/18/2023]
Abstract
BACKGROUND Bacillus anthracis (BA) is a major bioterrorism concern which has evolved complex regulatory mechanisms for its virulence factors. Secreted proteases play an imperative role in the pathogenesis of BA, however their regulation remains elusive. Two component systems (TCS) are often employed by bacteria to sense and adapt to the environmental perturbations. In several pathogens, TCS are commonly associated with the regulation of virulence factors including proteases. The genome of BA encodes 41 TCS pairs, however, the role of any TCS in regulation of its proteases is not known. PRINCIPAL FINDINGS The study established BAS2108-2109 as a prototypical TCS where BAS2108 functions as a histidine kinase and BAS2109 as the response regulator. The expression of BAS2109 was found to be elevated under host simulated conditions and in pellicle forming cells. Electrophoretic mobility shift assay (EMSA) and lacZ reporter assay revealed positive autoregulation of the BAS2108-2109 operon by BAS2109. Collective analysis of ANS assay and EMSA demonstrated Lys167, Thr179 and Thr182 residues are crucial for the DNA binding activity of BAS2109. EMSA analysis further highlighted BAS2109 as the transcriptional regulator for different genes of BA, particularly proteases. Upregulation of proteases in BA overexpressing BAS2109 further strengthen its role in protease regulation. SIGNIFICANCE This is the first report to identify a TCS pair for its role in the regulation of proteases of BA. Importance of proteases in the pathogenesis of BA is well documented, therefore, studying the regulatory networks governing their expression will help in identification of new drug targets.
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Affiliation(s)
- Vatika Gupta
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India, India; Medical Microbiology and Bioprocess Technology Laboratory, Department of Microbiology, Maharshi Dayanand University, Rohtak, Haryana, India
| | - Neha Chaudhary
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India, India
| | - Somya Aggarwal
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India, India
| | - Nidhi Adlakha
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India, India
| | - Pooja Gulati
- Medical Microbiology and Bioprocess Technology Laboratory, Department of Microbiology, Maharshi Dayanand University, Rohtak, Haryana, India
| | - Rakesh Bhatnagar
- Molecular Biology and Genetic Engineering Laboratory, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India, India.
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Orozco-Flores AA, Valadez-Lira JA, Oppert B, Gomez-Flores R, Tamez-Guerra R, Rodríguez-Padilla C, Tamez-Guerra P. Regulation by gut bacteria of immune response, Bacillus thuringiensis susceptibility and hemolin expression in Plodia interpunctella. JOURNAL OF INSECT PHYSIOLOGY 2017; 98:275-283. [PMID: 28167070 DOI: 10.1016/j.jinsphys.2017.01.020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 01/09/2017] [Accepted: 01/16/2017] [Indexed: 06/06/2023]
Abstract
Plodia interpunctella (Hübner) is an important stored grain insect pest worldwide, and the first lepidopteran with reported resistance to Bacillus thuringiensis (Bt) toxins. Since gut bacteria may affect Bt insecticidal activity, we evaluated whether P. interpunctella lacking gut bacteria had differences in immune responses and susceptibility to the Bt formulation, Bactospeine. In order to clear gut bacteria, third instar larvae were reared on artificial diet containing antibiotics, or were obtained from sterilized eggs and reared under sterile conditions, and larvae were fed diets with or without Bt. Mortality was significantly lower (p<0.05) in bacteria-free larvae treated with Bt, compared with Bt-treated larvae with unaffected gut bacteria. The number of hemocytes was lower in control and Bt-treated larvae, but was significantly higher (p<0.001) in larvae treated with antibiotics and Bt, and larvae from presterilized eggs and reared on sterile diet had the highest number of hemocytes. Phenoloxidase activity was significantly lower (p<0.05) in Bt-treated larvae from presterilized eggs reared on antibiotics for 24h or in larvae reared on antibiotic-treated diets prior to Bt introduction compared with those fed control diet. Hemolin gene expression was reduced in larvae fed Bt diets compared with control and was not detected in larvae treated with antibiotics. Larvae from sterilized eggs and fed sterile diet never reached the pupal stage. Therefore, the loss of gut bacteria in P. interpunctella larvae affected the host immune response and expression of the hemolin gene, and significantly reduced susceptibility to Bt.
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Affiliation(s)
- Alonso A Orozco-Flores
- Universidad Autónoma de Nuevo León, Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Cd. Universitaria, San Nicolás de los Garza, N. L. 66455, Mexico
| | - Jose A Valadez-Lira
- Universidad Autónoma de Nuevo León, Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Cd. Universitaria, San Nicolás de los Garza, N. L. 66455, Mexico
| | - Brenda Oppert
- USDA, Agricultural Research Service, Center for Grain and Animal Health Research, 1515 College Ave., Manhattan, KS 66502, USA
| | - Ricardo Gomez-Flores
- Universidad Autónoma de Nuevo León, Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Cd. Universitaria, San Nicolás de los Garza, N. L. 66455, Mexico
| | - Reyes Tamez-Guerra
- Universidad Autónoma de Nuevo León, Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Cd. Universitaria, San Nicolás de los Garza, N. L. 66455, Mexico
| | - Cristina Rodríguez-Padilla
- Universidad Autónoma de Nuevo León, Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Cd. Universitaria, San Nicolás de los Garza, N. L. 66455, Mexico
| | - Patricia Tamez-Guerra
- Universidad Autónoma de Nuevo León, Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Cd. Universitaria, San Nicolás de los Garza, N. L. 66455, Mexico.
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Screening of Cytotoxic B. cereus on Differentiated Caco-2 Cells and in Co-Culture with Mucus-Secreting (HT29-MTX) Cells. Toxins (Basel) 2016; 8:toxins8110320. [PMID: 27827957 PMCID: PMC5127117 DOI: 10.3390/toxins8110320] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/09/2016] [Accepted: 10/31/2016] [Indexed: 12/18/2022] Open
Abstract
B. cereus is an opportunistic foodborne pathogen able to cause diarrhoea. However, the diarrhoeal potential of a B. cereus strain remains difficult to predict, because no simple correlation has yet been identified between the symptoms and a unique or a specific combination of virulence factors. In this study, 70 B. cereus strains with different origins (food poisonings, foods and environment) have been selected to assess their enterotoxicity. The B. cereus cell-free supernatants have been tested for their toxicity in vitro, on differentiated (21 day-old) Caco-2 cells, using their ATP content, LDH release and NR accumulation. The genetic determinants of the main potential enterotoxins and virulence factors (ces, cytK, entFM, entS, hbl, nhe, nprA, piplC and sph) have also been screened by PCR. This analysis showed that none of these genes was able to fully explain the enterotoxicity of B. cereus strains. Additionally, in order to assess a possible effect of the mucus layer in vitro, a cytotoxicity comparison between a monoculture (Caco-2 cells) and a co-culture (Caco-2 and HT29-MTX mucus-secreting cells) model has been performed with selected B. cereus supernatants. It appeared that, in these conditions, the mucus layer had no notable influence on the cytotoxicity of B. cereus supernatants.
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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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21
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An in-depth characterization of the entomopathogenic strain Bacillus pumilus 15.1 reveals that it produces inclusion bodies similar to the parasporal crystals of Bacillus thuringiensis. Appl Microbiol Biotechnol 2016; 100:3637-54. [PMID: 26782747 DOI: 10.1007/s00253-015-7259-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 12/13/2015] [Accepted: 12/19/2015] [Indexed: 01/05/2023]
Abstract
In the present work, the local isolate Bacillus pumilus 15.1 has been morphologically and biochemically characterized in order to gain a better understanding of this novel entomopathogenic strain active against Ceratitis capitata. This strain could represent an interesting biothechnological tool for the control of this pest. Here, we report on its nutrient preferences, extracellular enzyme production, motility mechanism, biofilm production, antibiotic suceptibility, natural resistance to chemical and physical insults, and morphology of the vegetative cells and spores. The pathogen was found to be β-hemolytic and susceptible to penicillin, ampicillin, chloramphenicol, gentamicin, kanamycin, rifampicin, tetracycline, and streptomycin. We also report a series of biocide, thermal, and UV treatments that reduce the viability of B. pumilus 15.1 by several orders of magnitude. Heat and chemical treatments kill at least 99.9 % of vegetative cells, but spores were much more resistant. Bleach was the only chemical that was able to completely eliminate B. pumilus 15.1 spores. Compared to the B. subtilis 168 spores, B. pumilus 15.1 spores were between 2.67 and 350 times more resistant to UV radiation while the vegetative cells of B. pumilus 15.1 were almost up to 3 orders of magnitude more resistant than the model strain. We performed electron microscopy for morphological characterization, and we observed geometric structures resembling the parasporal crystal inclusions synthesized by Bacillus thuringiensis. Some of the results obtained here such as the parasporal inclusion bodies produced by B. pumilus 15.1 could potentially represent virulence factors of this novel and potentially interesting strain.
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22
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Milutinović B, Höfling C, Futo M, Scharsack JP, Kurtz J. Infection of Tribolium castaneum with Bacillus thuringiensis: quantification of bacterial replication within cadavers, transmission via cannibalism, and inhibition of spore germination. Appl Environ Microbiol 2015; 81:8135-44. [PMID: 26386058 PMCID: PMC4651099 DOI: 10.1128/aem.02051-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Accepted: 09/14/2015] [Indexed: 12/18/2022] Open
Abstract
Reproduction within a host and transmission to the next host are crucial for the virulence and fitness of pathogens. Nevertheless, basic knowledge about such parameters is often missing from the literature, even for well-studied bacteria, such as Bacillus thuringiensis, an endospore-forming insect pathogen, which infects its hosts via the oral route. To characterize bacterial replication success, we made use of an experimental oral infection system for the red flour beetle Tribolium castaneum and developed a flow cytometric assay for the quantification of both spore ingestion by the individual beetle larvae and the resulting spore load after bacterial replication and resporulation within cadavers. On average, spore numbers increased 460-fold, showing that Bacillus thuringiensis grows and replicates successfully in insect cadavers. By inoculating cadaver-derived spores and spores from bacterial stock cultures into nutrient medium, we next investigated outgrowth characteristics of vegetative cells and found that cadaver-derived bacteria showed reduced growth compared to bacteria from the stock cultures. Interestingly, this reduced growth was a consequence of inhibited spore germination, probably originating from the host and resulting in reduced host mortality in subsequent infections by cadaver-derived spores. Nevertheless, we further showed that Bacillus thuringiensis transmission was possible via larval cannibalism when no other food was offered. These results contribute to our understanding of the ecology of Bacillus thuringiensis as an insect pathogen.
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Affiliation(s)
- Barbara Milutinović
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Christina Höfling
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Momir Futo
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Jörn P Scharsack
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Joachim Kurtz
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
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23
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Sheppard AE, Nakad R, Saebelfeld M, Masche AC, Dierking K, Schulenburg H. High instability of a nematicidal Cry toxin plasmid in Bacillus thuringiensis. J Invertebr Pathol 2015; 133:34-40. [PMID: 26592941 DOI: 10.1016/j.jip.2015.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 11/11/2015] [Accepted: 11/20/2015] [Indexed: 12/26/2022]
Abstract
In bacterial pathogens, virulence factors are often carried on plasmids and other mobile genetic elements, and as such, plasmid evolution is central in understanding pathogenicity. Bacillus thuringiensis is an invertebrate pathogen that uses plasmid-encoded crystal (Cry) toxins to establish infections inside the host. Our study aimed to quantify stability of two Cry toxin-encoding plasmids, BTI_23p and BTI_16p, under standard laboratory culturing conditions. These two plasmids are part of the genome of the B. thuringiensis strain MYBT18679, which is of particular interest because of its high pathogenicity towards nematodes. One of the plasmids, BTI_23p, was found to be highly unstable, with substantial loss occurring within a single growth cycle. Nevertheless, longer term experimental evolution in the absence of a host revealed maintenance of the plasmid at low levels in the bacterial populations. BTI_23p encodes two nematicidal Cry toxins, Cry21Aa2 and Cry14Aa1. Consistent with previous findings, loss of the plasmid abolished pathogenicity towards the nematode Caenorhabditis elegans, which could be rescued by addition of Cry21Aa2-expressing Escherichia coli. These results implicate BTI_23p as a plasmid that is required for successful infection, yet unstable when present at high frequency in the population, consistent with the role of Cry toxins as public goods.
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Affiliation(s)
- Anna E Sheppard
- Department of Evolutionary Ecology and Genetics, Christian-Albrechts University of Kiel, Kiel, Germany.
| | - Rania Nakad
- Department of Evolutionary Ecology and Genetics, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Manja Saebelfeld
- Department of Evolutionary Ecology and Genetics, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Anna C Masche
- Department of Evolutionary Ecology and Genetics, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Katja Dierking
- Department of Evolutionary Ecology and Genetics, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Hinrich Schulenburg
- Department of Evolutionary Ecology and Genetics, Christian-Albrechts University of Kiel, Kiel, Germany
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Omer H, Alpha-Bazin B, Brunet JL, Armengaud J, Duport C. Proteomics identifies Bacillus cereus EntD as a pivotal protein for the production of numerous virulence factors. Front Microbiol 2015; 6:1004. [PMID: 26500610 PMCID: PMC4595770 DOI: 10.3389/fmicb.2015.01004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 09/07/2015] [Indexed: 11/13/2022] Open
Abstract
Bacillus cereus is a Gram-positive pathogen that causes a wide variety of diseases in humans. It secretes into the extracellular milieu proteins that may contribute directly or indirectly to its virulence. EntD is a novel exoprotein identified by proteogenomics of B. cereus ATCC 14579. We constructed a ΔentD mutant and analyzed the impact of entD disruption on the cellular proteome and exoproteome isolated from early, late, and stationary-phase cultures. We identified 308 and 79 proteins regulated by EntD in the cellular proteome and the exoproteome, respectively. The contribution of these proteins to important virulence-associated functions, including central metabolism, cell structure, antioxidative ability, cell motility, and toxin production, are presented. The proteomic data were correlated with the growth defect, cell morphology change, reduced motility, and reduced cytotoxicity of the ΔentD mutant strain. We conclude that EntD is an important player in B. cereus virulence. The function of EntD and the putative EntD-dependent regulatory network are discussed. To our knowledge, this study is the first characterization of an Ent family protein in a species of the B. cereus group.
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Affiliation(s)
- Hélène Omer
- Université d'Avignon et des Pays de Vaucluse, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France ; INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France ; CEA-Marcoule, DSV/IBITEC-S/SPI/Li2D, Laboratory "Innovative technologies for Detection and Diagnostic" Bagnols-sur-Cèze, France
| | - Béatrice Alpha-Bazin
- CEA-Marcoule, DSV/IBITEC-S/SPI/Li2D, Laboratory "Innovative technologies for Detection and Diagnostic" Bagnols-sur-Cèze, France
| | | | - Jean Armengaud
- CEA-Marcoule, DSV/IBITEC-S/SPI/Li2D, Laboratory "Innovative technologies for Detection and Diagnostic" Bagnols-sur-Cèze, France
| | - Catherine Duport
- Université d'Avignon et des Pays de Vaucluse, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France ; INRA, UMR408 Sécurité et Qualité des Produits d'Origine Végétale Avignon, France
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Draft Genome Sequence of the Entomopathogenic Bacterium Bacillus pumilus 15.1, a Strain Highly Toxic to the Mediterranean Fruit Fly Ceratitis capitata. GENOME ANNOUNCEMENTS 2015; 3:3/5/e01019-15. [PMID: 26404596 PMCID: PMC4582572 DOI: 10.1128/genomea.01019-15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We present the draft whole-genome sequence of the entomopathogenic Bacillus pumilus 15.1 strain that consists of 3,795,691 bp and 3,776 predicted protein-coding genes. This genome sequence provides the basis for understanding the potential mechanism behind the toxicity and virulence of B. pumilus 15.1 against the Mediterranean fruit fly.
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Dammak I, Dammak M, Tounsi S. Histopathological and combinatorial effects of the metalloprotease InhA1 and Cry proteins of Bacillus thuringiensis against Spodoptera littoralis. Int J Biol Macromol 2015; 81:759-62. [PMID: 26358555 DOI: 10.1016/j.ijbiomac.2015.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 08/31/2015] [Accepted: 09/04/2015] [Indexed: 11/17/2022]
Abstract
The zinc metalloprotease (InhA) of Bacillus thuringiensis specifically hydrolyzes cecropins and attacins, two antibacterial peptides in the immune hemolymph of insects, leading to a high resistance of the bacteria to the humoral defense system of its host. In the present study, the inhA gene of B. thuringiensis strain BUPM28 was cloned and the nucleotide sequence analysis revealed that it was identical to that of B. thuringiensis 8010. The expressed InhA1 protein in Escherichia coli showed toxicity to neonate Spodoptera littoralis larvae with a LC50 of 2.07±0.72μg/cm(2). Study of the effect of combining Cry proteins with InhA1 showed that one improves the toxicity of the other one against S. littoralis. Investigation of the histopathological effect of this metalloprotease showed an extensive damage of S. littoralis epithelium tissue. These results provide an insight to the use of InhA as supplement to Cry toxins to improve the efficacy of B. thuringiensis formulations and to overcome possible resistance problems.
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Affiliation(s)
- Ines Dammak
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Mariam Dammak
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia
| | - Slim Tounsi
- Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
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Elmogy M, Bassal TTM, Yousef HA, Dorrah MA, Mohamed AA, Duvic B. Isolation, characterization, kinetics, and enzymatic and nonenzymatic microbicidal activities of a novel c-type lysozyme from plasma of Schistocerca gregaria (Orthoptera: Acrididae). JOURNAL OF INSECT SCIENCE (ONLINE) 2015; 15:iev038. [PMID: 25972507 PMCID: PMC4535491 DOI: 10.1093/jisesa/iev038] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 04/15/2015] [Indexed: 05/24/2023]
Abstract
A protein, designated as Sgl, showing a muramidase lytic activity to the cell wall of the Gram-positive bacterium Micrococcus lysodeikticus was isolated for the first time from plasma of Escherichia coli-immunized fifth instar Schistocerca gregaria. The isolated Sgl was detected as a single protein band, on both native- and SDS-PAGE, has a molecular weight of ∼15.7 kDa and an isoelectric point (pI) of ca 9.3 and its antiserum has specifically recognized its isolated form. Fifty-nine percentage of Sgl lytic activity was recovered in the isolated fractions and yielded ca 126-fold increase in specific activity than that of the crude. The partial N-terminal amino acid sequence of the Sgl has 55 and 40% maximum identity with Bombyx mori and Gallus gallus c-type lysozymes, respectively. The antibacterial activity against the Gram-positive and the Gram-negative bacteria were comparatively stronger than that of the hen egg white lysozyme (HEWL). The detected Sgl poration to the inner membrane that reach a maximum ability after 3 h was suggested to operate as a nonenzymatic mechanism for Gram-negative bacterial cell lysis, as tested in a permease-deficient E. coli, ML-35 strain. Sgl showed a maximal muramidase activity at pH 6.2, 30-50°C, and 0.05 M Ca(2+) or Mg(2+); and has a Km of 0.5 μg/ml and a Vmax of 0.518 with M. lysodeikticus as a substrate. The Sgl displayed a chitinase activity against chitin with a Km of 0.93 mg/ml and a Vmax of 1.63.
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Affiliation(s)
- Mohamed Elmogy
- Department of Entomology, Faculty of Science, Cairo University, P. O. Box 12613, Giza, Egypt Department of Biology, Faculty of Applied Science, Umm AlQura University, P.O. Box 673, Makkah, KSA
| | - Taha T M Bassal
- Department of Entomology, Faculty of Science, Cairo University, P. O. Box 12613, Giza, Egypt
| | - Hesham A Yousef
- Department of Entomology, Faculty of Science, Cairo University, P. O. Box 12613, Giza, Egypt
| | - Moataza A Dorrah
- Department of Entomology, Faculty of Science, Cairo University, P. O. Box 12613, Giza, Egypt
| | - Amr A Mohamed
- Department of Entomology, Faculty of Science, Cairo University, P. O. Box 12613, Giza, Egypt
| | - Bernard Duvic
- Institut National de la Recherche Agronomique (INRA), UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), 34095 Montpellier Cedex 05, France Université Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), 34095 Montpellier Cedex 05, France
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Ruiu L, Falchi G, Floris I, Marche MG, Mura ME, Satta A. Pathogenicity and characterization of a novel Bacillus cereus sensu lato isolate toxic to the Mediterranean fruit fly Ceratitis capitata Wied. J Invertebr Pathol 2015; 126:71-7. [DOI: 10.1016/j.jip.2015.01.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 01/27/2015] [Accepted: 01/28/2015] [Indexed: 10/24/2022]
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Taszłow P, Wojda I. Changes in the hemolymph protein profiles in Galleria mellonella infected with Bacillus thuringiensis involve apolipophorin III. The effect of heat shock. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2015; 88:123-143. [PMID: 25308190 DOI: 10.1002/arch.21208] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
This report concerns the effect of heat shock on host-pathogen interaction in Galleria mellonella infected with Bacillus thuringiensis. We show enhanced activity against Gram-positive bacteria in the hemolymph of larvae pre-exposed to heat shock before infection with B. thuringiensis. Heat shock influenced the protein pattern in the hemolymph of infected larvae: more peptides with a molecular weight below 10 kDa were detected in comparison with nonshocked animals. Additionally, we noticed that the amount of apolipophorin III (apoLp-III) in the hemolymph decreased transiently following infection, which was considerably higher in larvae pre-exposed to heat shock. On the other hand, its expression in the fat body showed a consequent infection-induced decline, observed equally in shocked and nonshocked animals. This suggests that the amount of apoLp-III in the hemolymph of G. mellonella larvae is regulated at multiple levels. We also report that this protein is more resistant to degradation in the hemolymph of larvae pre-exposed to heat shock in comparison to nonshocked larvae. Two-dimensional analysis revealed the presence of three isoforms of apoLp-III, all susceptible to proteolytic degradation. However, one of them was the most abundant, both in the protease-treated and untreated hemolymph. Taking into consideration that, in general, apoLp-III has a stimulative effect on different immune-related hemolymph proteins and peptides, the reported findings bring us closer to understanding the effect of heat shock on the resistance of G. mellonella to infection.
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Affiliation(s)
- Paulina Taszłow
- Department of Immunobiology, Faculty of Biology and Biotechnology, Institute of Biology and Biochemistry, Maria Curie-Sklodowska University, Lublin, Poland
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Expression of prtA from Photorhabdus luminescens in Bacillus thuringiensis enhances mortality in lepidopteran larvae by sub-cutaneous but not oral infection. J Invertebr Pathol 2014; 121:85-8. [DOI: 10.1016/j.jip.2014.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Revised: 05/30/2014] [Accepted: 07/07/2014] [Indexed: 11/17/2022]
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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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Argôlo-Filho RC, Loguercio LL. Bacillus thuringiensis Is an Environmental Pathogen and Host-Specificity Has Developed as an Adaptation to Human-Generated Ecological Niches. INSECTS 2013; 5:62-91. [PMID: 26462580 PMCID: PMC4592628 DOI: 10.3390/insects5010062] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 12/03/2013] [Accepted: 12/13/2013] [Indexed: 11/16/2022]
Abstract
Bacillus thuringiensis (Bt) has been used successfully as a biopesticide for more than 60 years. More recently, genes encoding their toxins have been used to transform plants and other organisms. Despite the large amount of research on this bacterium, its true ecology is still a matter of debate, with two major viewpoints dominating: while some understand Bt as an insect pathogen, others see it as a saprophytic bacteria from soil. In this context, Bt's pathogenicity to other taxa and the possibility that insects may not be the primary targets of Bt are also ideas that further complicate this scenario. The existence of conflicting research results, the difficulty in developing broader ecological and genetics studies, and the great genetic plasticity of this species has cluttered a definitive concept. In this review, we gathered information on the aspects of Bt ecology that are often ignored, in the attempt to clarify the lifestyle, mechanisms of transmission and target host range of this bacterial species. As a result, we propose an integrated view to account for Bt ecology. Although Bt is indeed a pathogenic bacterium that possesses a broad arsenal for virulence and defense mechanisms, as well as a wide range of target hosts, this seems to be an adaptation to specific ecological changes acting on a versatile and cosmopolitan environmental bacterium. Bt pathogenicity and host-specificity was favored evolutionarily by increased populations of certain insect species (or other host animals), whose availability for colonization were mostly caused by anthropogenic activities. These have generated the conditions for ecological imbalances that favored dominance of specific populations of insects, arachnids, nematodes, etc., in certain areas, with narrower genetic backgrounds. These conditions provided the selective pressure for development of new hosts for pathogenic interactions, and so, host specificity of certain strains.
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Affiliation(s)
- Ronaldo Costa Argôlo-Filho
- Department of Biological Sciences, State University of Santa Cruz (UESC), Rod, Ilhéus-Itabuna, Km-16, Ilhéus-BA 45662-900, Brazil.
| | - Leandro Lopes Loguercio
- Department of Biological Sciences, State University of Santa Cruz (UESC), Rod, Ilhéus-Itabuna, Km-16, Ilhéus-BA 45662-900, Brazil.
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Wojda I, Taszłow P. Heat shock affects host-pathogen interaction in Galleria mellonella infected with Bacillus thuringiensis. JOURNAL OF INSECT PHYSIOLOGY 2013; 59:894-905. [PMID: 23834825 DOI: 10.1016/j.jinsphys.2013.06.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 06/23/2013] [Accepted: 06/27/2013] [Indexed: 06/02/2023]
Abstract
We report that Galleria mellonella larvae exposed to heat shock was more resistant to infection with entomopathogenic bacteria Bacillus thuringiensis. The insects were exposed to a temperature of 40°C for 30 min directly before injection of vegetative bacterial cells. It appeared that the kinetics of the immune response was affected in heat-shocked animals. The infection-induced antimicrobial activity of larval hemolymph was stronger in shocked animals in comparison to the non-shocked ones. Hemolymph proteins of molecular weight below 10 kDa, corresponding to the size of antimicrobial peptides, were responsible for this activity. Furthermore, the transcription level of genes encoding antimicrobial peptides: cecropin, gallerimycin, and galiomycin was increased in the fat bodies of insects exposed to heat shock before infection. On the contrary, the heat-shock treatment did not enhance expression of the metalloproteinase inhibitor-IMPI in the infected animals. The difference in the amount of antimicrobial peptides and, consequently, in the defense activity of insect hemolymph, persisted after the action of bacterial metalloproteinases, which are well-known virulence factors. Furthermore, peptides with antimicrobial activity in the hemolymph of infected larvae pre-exposed to heat shock appeared to be more resistant to proteolytic degradation both in vitro and in vivo. Our results point to the mechanism of cross-protection of thermal stress toward innate immune response.
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Affiliation(s)
- Iwona Wojda
- Department of Immunobiology, Institute of Biology and Biochemistry, Faculty of Biology and Biotechnology, Akademicka 19, 20-033 Lublin, Poland.
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Alteration in Bacillus thuringiensis toxicity by curing gut flora: novel approach for mosquito resistance management. Parasitol Res 2013; 112:3283-8. [DOI: 10.1007/s00436-013-3507-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/14/2013] [Indexed: 11/26/2022]
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Milutinović B, Stolpe C, Peuβ R, Armitage SAO, Kurtz J. The red flour beetle as a model for bacterial oral infections. PLoS One 2013; 8:e64638. [PMID: 23737991 PMCID: PMC3667772 DOI: 10.1371/journal.pone.0064638] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 04/17/2013] [Indexed: 01/03/2023] Open
Abstract
Experimental infection systems are important for studying antagonistic interactions and coevolution between hosts and their pathogens. The red flour beetle Tribolium castaneum and the spore-forming bacterial insect pathogen Bacillus thuringiensis (Bt) are widely used and tractable model organisms. However, they have not been employed yet as an efficient experimental system to study host-pathogen interactions. We used a high throughput oral infection protocol to infect T. castaneum insects with coleopteran specific B. thuringiensis bv. tenebrionis (Btt) bacteria. We found that larval mortality depends on the dietary spore concentration and on the duration of exposure to the spores. Furthermore, differential susceptibility of larvae from different T. castaneum populations indicates that the host genetic background influences infection success. The recovery of high numbers of infectious spores from the cadavers indicates successful replication of bacteria in the host and suggests that Btt could establish infectious cycles in T. castaneum in nature. We were able to transfer plasmids from Btt to a non-pathogenic but genetically well-characterised Bt strain, which was thereafter able to successfully infect T. castaneum, suggesting that factors residing on the plasmids are important for the virulence of Btt. The availability of a genetically accessible strain will provide an ideal model for more in-depth analyses of pathogenicity factors during oral infections. Combined with the availability of the full genome sequence of T. castaneum, this system will enable analyses of host responses during infection, as well as addressing basic questions concerning host-parasite coevolution.
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Affiliation(s)
- Barbara Milutinović
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Clemens Stolpe
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Robert Peuβ
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | | | - Joachim Kurtz
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
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Doll VM, Ehling-Schulz M, Vogelmann R. Concerted action of sphingomyelinase and non-hemolytic enterotoxin in pathogenic Bacillus cereus. PLoS One 2013; 8:e61404. [PMID: 23613846 PMCID: PMC3628865 DOI: 10.1371/journal.pone.0061404] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 03/10/2013] [Indexed: 11/18/2022] Open
Abstract
Bacillus cereus causes food poisoning and serious non-gastrointestinal-tract infections. Non-hemolytic enterotoxin (Nhe), which is present in most B. cereus strains, is considered to be one of the main virulence factors. However, a B. cereus ΔnheBC mutant strain lacking Nhe is still cytotoxic to intestinal epithelial cells. In a screen for additional cytotoxic factors using an in vitro model for polarized colon epithelial cells we identified B. cereus sphingomyelinase (SMase) as a strong inducer of epithelial cell death. Using single and double deletion mutants of sph, the gene encoding for SMase, and nheBC in B. cereus we demonstrated that SMase is an important factor for B. cereus cytotoxicity in vitro and pathogenicity in vivo. SMase substantially complemented Nhe induced cytotoxicity in vitro. In addition, SMase but not Nhe contributed significantly to the mortality rate of larvae in vivo in the insect model Galleria mellonella. Our study suggests that the role of B. cereus SMase as a secreted virulence factor for in vivo pathogenesis has been underestimated and that Nhe and SMase complement each other significantly to cause full B. cereus virulence hence disease formation.
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Affiliation(s)
- Viktoria M. Doll
- Abteilung Mikrobiologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung ZIEL, Technische Universität München, Freising Weihenstephan, Germany
| | - Monika Ehling-Schulz
- Functional Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Roger Vogelmann
- Second Department of Internal Medicine, Universitätsmedizin Mannheim, University Heidelberg, Mannheim, Germany
- * E-mail:
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Complete Genome Sequence of Bacillus thuringiensis Strain 407 Cry-. GENOME ANNOUNCEMENTS 2013; 1:genomeA00158-12. [PMID: 23405326 PMCID: PMC3569317 DOI: 10.1128/genomea.00158-12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 11/30/2012] [Indexed: 11/25/2022]
Abstract
Bacillus thuringiensis is an insect pathogen that has been used widely as a biopesticide. Here, we report the genome sequence of strain 407 Cry-, which is used to study the genetic determinants of pathogenicity. The genome consists of a 5.5-Mb chromosome and nine plasmids, including a novel 502-kb megaplasmid.
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Ramarao N, Nielsen-Leroux C, Lereclus D. The insect Galleria mellonella as a powerful infection model to investigate bacterial pathogenesis. J Vis Exp 2012:e4392. [PMID: 23271509 DOI: 10.3791/4392] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The study of bacterial virulence often requires a suitable animal model. Mammalian models of infection are costly and may raise ethical issues. The use of insects as infection models provides a valuable alternative. Compared to other non-vertebrate model hosts such as nematodes, insects have a relatively advanced system of antimicrobial defenses and are thus more likely to produce information relevant to the mammalian infection process. Like mammals, insects possess a complex innate immune system(1). Cells in the hemolymph are capable of phagocytosing or encapsulating microbial invaders, and humoral responses include the inducible production of lysozyme and small antibacterial peptides(2,3). In addition, analogies are found between the epithelial cells of insect larval midguts and intestinal cells of mammalian digestive systems. Finally, several basic components essential for the bacterial infection process such as cell adhesion, resistance to antimicrobial peptides, tissue degradation and adaptation to oxidative stress are likely to be important in both insects and mammals(1). Thus, insects are polyvalent tools for the identification and characterization of microbial virulence factors involved in mammalian infections. Larvae of the greater wax moth Galleria mellonella have been shown to provide a useful insight into the pathogenesis of a wide range of microbial infections including mammalian fungal (Fusarium oxysporum, Aspergillus fumigatus, Candida albicans) and bacterial pathogens, such as Staphylococcus aureus, Proteus vulgaris, Serratia marcescens Pseudomonas aeruginosa, Listeria monocytogenes or Enterococcus faecalis(4-7). Regardless of the bacterial species, results obtained with Galleria larvae infected by direct injection through the cuticle consistently correlate with those of similar mammalian studies: bacterial strains that are attenuated in mammalian models demonstrate lower virulence in Galleria, and strains causing severe human infections are also highly virulent in the Galleria model(8-11). Oral infection of Galleria is much less used and additional compounds, like specific toxins, are needed to reach mortality. G. mellonella larvae present several technical advantages: they are relatively large (last instar larvae before pupation are about 2 cm long and weight 250 mg), thus enabling the injection of defined doses of bacteria; they can be reared at various temperatures (20 °C to 30 °C) and infection studies can be conducted between 15 °C to above 37 °C(12,13), allowing experiments that mimic a mammalian environment. In addition, insect rearing is easy and relatively cheap. Infection of the larvae allows monitoring bacterial virulence by several means, including calculation of LD50(14), measurement of bacterial survival(15,16) and examination of the infection process(17). Here, we describe the rearing of the insects, covering all life stages of G. mellonella. We provide a detailed protocol of infection by two routes of inoculation: oral and intra haemocoelic. The bacterial model used in this protocol is Bacillus cereus, a Gram positive pathogen implicated in gastrointestinal as well as in other severe local or systemic opportunistic infections(18,19).
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Scott E, Dyer DW. Divergence of the SigB regulon and pathogenesis of the Bacillus cereus sensu lato group. BMC Genomics 2012; 13:564. [PMID: 23088190 PMCID: PMC3485630 DOI: 10.1186/1471-2164-13-564] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Accepted: 10/10/2012] [Indexed: 12/31/2022] Open
Abstract
Background The Bacillus cereus sensu lato group currently includes seven species (B. cereus, B. anthracis, B. mycoides, B. pseudomycoides, B. thuringiensis, B. weihenstephanensis and B. cytotoxicus) that recent phylogenetic and phylogenomic analyses suggest are likely a single species, despite their varied phenotypes. Although horizontal gene transfer and insertion-deletion events are clearly important for promoting divergence among these genomes, recent studies have demonstrated that a major basis for phenotypic diversity in these organisms may be differential regulation of the highly similar gene content shared by these organisms. To explore this hypothesis, we used an in silico approach to evaluate the relationship of pathogenic potential and the divergence of the SigB-dependent general stress response within the B. cereus sensu lato group, since SigB has been demonstrated to support pathogenesis in Bacillus, Listeria and Staphylococcus species. Results During the divergence of these organisms from a common “SigB-less” ancestor, the placement of SigB promoters at varied locations in the B. cereus sensu lato genomes predict alternative structures for the SigB regulon in different organisms. Predicted promoter changes suggesting differential transcriptional control of a common gene pool predominate over evidence of indels or horizontal gene transfer for explaining SigB regulon divergence. Conclusions Four lineages of the SigB regulon have arisen that encompass different gene contents and suggest different strategies for supporting pathogenesis. This is consistent with the hypothesis that divergence within the B. cereus sensu lato group rests in part on alternative strategies for regulation of a common gene pool.
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Affiliation(s)
- Edgar Scott
- Department of Microbiology and Immunology, Oklahoma University Health Sciences Center, Oklahoma City, 73117, USA
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Nielsen-LeRoux C, Gaudriault S, Ramarao N, Lereclus D, Givaudan A. How the insect pathogen bacteria Bacillus thuringiensis and Xenorhabdus/Photorhabdus occupy their hosts. Curr Opin Microbiol 2012; 15:220-31. [PMID: 22633889 DOI: 10.1016/j.mib.2012.04.006] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/26/2012] [Accepted: 04/27/2012] [Indexed: 10/28/2022]
Abstract
Insects are the largest group of animals on earth. Like mammals, virus, fungi, bacteria and parasites infect them. Several tissue barriers and defense mechanisms are common for vertebrates and invertebrates. Therefore some insects, notably the fly Drosophila and the caterpillar Galleria mellonella, have been used as models to study host-pathogen interactions for several insect and mammal pathogens. They are excellent tools to identify pathogen determinants and host tissue cell responses. We focus here on the comparison of effectors used by two different groups of bacterial insect pathogens to accomplish the infection process in their lepidopteran larval host: Bacillus thuringiensis and the nematode-associated bacteria, Photorhabdus and Xenorhabdus. The comparison reveals similarities in function and expression profiles for some genes, which suggest that such factors are conserved during evolution in order to attack the tissue encountered during the infection process.
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Affiliation(s)
- Christina Nielsen-LeRoux
- INRA, UMR1319, Micalis, Génétique microbienne et Environnement, La Minière, F-78280 Guyancourt, France.
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Proteomic analysis of Bacillus thuringiensis at different growth phases by using an automated online two-dimensional liquid chromatography-tandem mass spectrometry strategy. Appl Environ Microbiol 2012; 78:5270-9. [PMID: 22636013 DOI: 10.1128/aem.00424-12] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The proteome of a new Bacillus thuringiensis subsp. kurstaki strain, 4.0718, from the middle vegetative (T(1)), early sporulation (T(2)), and late sporulation (T(3)) phases was analyzed using an integrated liquid chromatography (LC)-based protein identification system. The system comprised two-dimensional (2D) LC coupled with nanoscale electrospray ionization (ESI) tandem mass spectrometry (MS/MS) on a high-resolution hybrid mass spectrometer with an automated data analysis system. After deletion of redundant proteins from the different batches and B. thuringiensis subspecies, 918, 703, and 778 proteins were identified in the respective three phases. Their molecular masses ranged from 4.6 Da to 477.4 Da, and their isoelectric points ranged from 4.01 to 11.84. Function clustering revealed that most of the proteins in the three phases were functional metabolic proteins, followed by proteins participating in cell processes. Small molecular and macromolecular metabolic proteins were further classified according to the Kyoto Encyclopedia of Genes and Genome and BioCyc metabolic pathway database. Three protoxins (Cry2Aa, Cry1Aa, and Cry1Ac) as well as a series of potential intracellular active factors were detected. Many significant proteins related to spore and crystal formation, including sporulation proteins, help proteins, chaperones, and so on, were identified. The expression patterns of two identified proteins, CotJc and glutamine synthetase, were validated by Western blot analysis, which further confirmed the MS results. This study is the first to use shotgun technology to research the proteome of B. thuringiensis. Valuable experimental data are provided regarding the methodology of analyzing the B. thuringiensis proteome (which can be used to produce insecticidal crystal proteins) and have been added to the related protein database.
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Song F, Peng Q, Brillard J, Buisson C, Been M, Abee T, Broussolle V, Huang D, Zhang J, Lereclus D, Nielsen‐LeRoux C. A multicomponent sugar phosphate sensor system specifically induced in
Bacillus cereus
during infection of the insect gut. FASEB J 2012; 26:3336-50. [DOI: 10.1096/fj.11-197681] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Fuping Song
- Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) 1319 MicalisGénétique Microbienne et Environnement Guyancourt France
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection Beijing China
| | - Qi Peng
- Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) 1319 MicalisGénétique Microbienne et Environnement Guyancourt France
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection Beijing China
| | - Julien Brillard
- INRA Avignon France
- Université d'Avignon et des Pays de Vaucluse, UMR408, Sécurité et Qualité des Produits d'Origine Végétale Avignon France
| | - Christophe Buisson
- Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) 1319 MicalisGénétique Microbienne et Environnement Guyancourt France
| | - Mark Been
- Top Institute (TI) Food and Nutrition and Laboratory of Food Microbiology Wageningen The Netherlands
| | - Tjakko Abee
- Top Institute (TI) Food and Nutrition and Laboratory of Food Microbiology Wageningen The Netherlands
| | - Véronique Broussolle
- INRA Avignon France
- Université d'Avignon et des Pays de Vaucluse, UMR408, Sécurité et Qualité des Produits d'Origine Végétale Avignon France
| | - Dafang Huang
- Biotechnology Research InstituteChinese Academy of Agricultural Sciences (CAAS) Beijing China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection Beijing China
| | - Didier Lereclus
- Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) 1319 MicalisGénétique Microbienne et Environnement Guyancourt France
| | - Christina Nielsen‐LeRoux
- Institut National de la Recherche Agronomique (INRA), Unité Mixte de Recherche (UMR) 1319 MicalisGénétique Microbienne et Environnement Guyancourt France
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant Protection Beijing China
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Li X, Ding X, Xia L, Sun Y, Yuan C, Yin J. Proteomic analysis of Bacillus thuringiensis strain 4.0718 at different growth phases. ScientificWorldJournal 2012; 2012:798739. [PMID: 22649324 PMCID: PMC3353320 DOI: 10.1100/2012/798739] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 11/16/2011] [Indexed: 01/23/2023] Open
Abstract
The growth process of Bacillus thuringiensis Bt4.0718 strain was studied using proteomic technologies. The proteins of Bt whole cells at three phases—middle vegetative, early sporulation, and late sporulation—were extracted with lysis buffer, followed with separation by 2-DE and identified by MALDI-TOF/TOF MS. Bioactive factors such as insecticidal crystal proteins (ICPs) including Cry1Ac(3), Cry2Aa, and BTRX28, immune inhibitor (InhA), and InhA precursor were identified. InhA started to express at the middle vegetative phase, suggesting its contribution to the survival of Bt in the host body. At the early sporulation phase, ICPs started their expression. CotJC, OppA, ORF1, and SpoIVA related to the formation of crystals and spores were identified, the expression characteristics of which ensured the stable formation of crystals and spores. This study provides an important foundation for further exploration of the stable expression of ICPs, the smooth formation of crystals, and the construction of recombinant strains.
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Affiliation(s)
- Xiaohui Li
- Key Laboratory of Microbial Molecular Biology of Hunan Province, College of Life Science, Hunan Normal University, Changsha 410081, China
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Temperature-dependent production of various PlcR-controlled virulence factors in Bacillus weihenstephanensis strain KBAB4. Appl Environ Microbiol 2012; 78:2553-61. [PMID: 22307282 DOI: 10.1128/aem.07446-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Bacillus cereus sensu lato complex has recently been divided into several phylogenetic groups with clear differences in growth temperature range. However, only a few studies have investigated the actual pathogenic potential of the psychrotolerant strains of the B. cereus group at low temperature, and little information is available concerning gene expression at low temperature. We found that vegetative cells of the psychrotolerant B. weihenstephanensis strain KBAB4 were pathogenic against the model insect Galleria mellonella at 15°C but not at 30°C. A similar temperature-dependent difference also was observed for the supernatant, which was cytotoxic to Vero epithelial cell lines and to murine macrophage J774 cells at 15°C but not at 30°C. We therefore determined the effect of low temperature on the production of various proteins putatively involved in virulence using two-dimensional protein gel electrophoresis, and we showed that the production of the Hbl enterotoxin and of two proteases, NprB and NprP2, was greater at a growth temperature of 15°C than at 30°C. The quantification of the mRNA levels for these virulence genes by real-time quantitative PCR at both temperatures showed that there was also more mRNA present at 15°C than at 30°C. We also found that at 15°C, hbl mRNA levels were maximal in the mid- to late exponential growth phase. In conclusion, we found that the higher virulence of the B. cereus KBAB4 strain at low temperature was accompanied by higher levels of the production of various known PlcR-controlled virulence factors and by a higher transcriptional activity of the corresponding genes.
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Whole-genome phylogenies of the family Bacillaceae and expansion of the sigma factor gene family in the Bacillus cereus species-group. BMC Genomics 2011; 12:430. [PMID: 21864360 PMCID: PMC3171730 DOI: 10.1186/1471-2164-12-430] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Accepted: 08/24/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Bacillus cereus sensu lato group consists of six species (B. anthracis, B. cereus, B. mycoides, B. pseudomycoides, B. thuringiensis, and B. weihenstephanensis). While classical microbial taxonomy proposed these organisms as distinct species, newer molecular phylogenies and comparative genome sequencing suggests that these organisms should be classified as a single species (thus, we will refer to these organisms collectively as the Bc species-group). How do we account for the underlying similarity of these phenotypically diverse microbes? It has been established for some time that the most rapidly evolving and evolutionarily flexible portions of the bacterial genome are regulatory sequences and transcriptional networks. Other studies have suggested that the sigma factor gene family of these organisms has diverged and expanded significantly relative to their ancestors; sigma factors are those portions of the bacterial transcriptional apparatus that control RNA polymerase recognition for promoter selection. Thus, examining sigma factor divergence in these organisms would concurrently examine both regulatory sequences and transcriptional networks important for divergence. We began this examination by comparison to the sigma factor gene set of B. subtilis. RESULTS Phylogenetic analysis of the Bc species-group utilizing 157 single-copy genes of the family Bacillaceae suggests that several taxonomic revisions of the genus Bacillus should be considered. Within the Bc species-group there is little indication that the currently recognized species form related sub-groupings, suggesting that they are members of the same species. The sigma factor gene family encoded by the Bc species-group appears to be the result of a dynamic gene-duplication and gene-loss process that in previous analyses underestimated the true heterogeneity of the sigma factor content in the Bc species-group. CONCLUSIONS Expansion of the sigma factor gene family appears to have preferentially occurred within the extracytoplasmic function (ECF) sigma factor genes, while the primary alternative (PA) sigma factor genes are, in general, highly conserved with those found in B. subtilis. Divergence of the sigma-controlled transcriptional regulons among various members of the Bc species-group likely has a major role in explaining the diversity of phenotypic characteristics seen in members of the Bc species-group.
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Wu D, He J, Gong Y, Chen D, Zhu X, Qiu N, Sun M, Li M, Yu Z. Proteomic analysis reveals the strategies of Bacillus thuringiensis
YBT-1520 for survival under long-term heat stress. Proteomics 2011; 11:2580-91. [DOI: 10.1002/pmic.201000392] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 03/04/2011] [Accepted: 03/14/2011] [Indexed: 11/05/2022]
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Abstract
Lepidopteran insects provide important model systems for innate immunity of insects, particularly for cell biology of hemocytes and biochemical analyses of plasma proteins. Caterpillars are also among the most serious agricultural pests, and understanding of their immune systems has potential practical significance. An early response to infection in lepidopteran larvae is the activation of hemocyte adhesion, leading to phagocytosis, nodule formation, or encapsulation. Plasmatocytes and granular cells are the hemocyte types involved in these responses. Infectious microorganisms are recognized by binding of hemolymph plasma proteins to microbial surface components. This "pattern recognition" triggers phagocytosis and nodule formation, activation of prophenoloxidase and melanization and the synthesis of antimicrobial proteins that are secreted into the hemolymph. Many hemolymph proteins that function in such innate immune responses of insects were first discovered in lepidopterans. Microbial proteinases and nucleic acids released from lysed host cells may also activate lepidopteran immune responses. Hemolymph antimicrobial peptides and proteins can reach high concentrations and may have activity against a broad spectrum of microorganisms, contributing significantly to clearing of infections. Serine proteinase cascade pathways triggered by microbial components interacting with pattern recognition proteins stimulate activation of the cytokine Spätzle, which initiates the Toll pathway for expression of antimicrobial peptides. A proteinase cascade also results inproteolytic activation of phenoloxidase and production of melanin coatings that trap and kill parasites and pathogens. The proteinases in hemolymph are regulated by specific inhibitors, including members of the serpin superfamily. New developments in lepidopteran functional genomics should lead to much more complete understanding of the immune systems of this insect group.
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Tran SL, Guillemet E, Ngo-Camus M, Clybouw C, Puhar A, Moris A, Gohar M, Lereclus D, Ramarao N. Haemolysin II is a Bacillus cereus virulence factor that induces apoptosis of macrophages. Cell Microbiol 2011; 13:92-108. [PMID: 20731668 DOI: 10.1111/j.1462-5822.2010.01522.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Bacillus cereus is a Gram-positive spore-forming bacterium causing food poisoning and serious opportunistic infections. These infections are characterized by bacterial accumulation despite the recruitment of phagocytic cells. The precise mechanisms and the bacterial factors allowing B. cereus to circumvent host immune responses remain to be elucidated. We have previously shown that B. cereus induces macrophage cell death by an unknown mechanism. Here we identified the toxic component from the B. cereus supernatant. We report that Haemolysin II (HlyII) provokes macrophage cell death by apoptosis through its pore-forming activity. The HlyII-induced apoptotic pathway is caspase 3 and 8 dependent, thus most likely mediated by the death receptor pathway. Using insects and mice as in vivo models, we show that deletion of hlyII strongly reduces virulence. In addition, we show that after infection of Bombyx mori larvae, the immune cells are apoptotic, demonstrating that HlyII induces apoptosis of phagocytic cells in vivo. Altogether, our results clearly unravel HlyII as a novel virulence protein that induces apoptosis in phagocytic cells in vitro and in vivo.
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Affiliation(s)
- Seav-Ly Tran
- INRA, Unité MICALIS, UMR 1319, équipe GME, La Minière, 78285 Guyancourt, France
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Stenfors Arnesen L, Granum PE, Buisson C, Bohlin J, Nielsen-LeRoux C. Using an insect model to assess correlation between temperature and virulence in Bacillus weihenstephanensis and Bacillus cereus. FEMS Microbiol Lett 2011; 317:196-202. [DOI: 10.1111/j.1574-6968.2011.02229.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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50
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Tran SL, Guillemet E, Ngo-Camus M, Clybouw C, Puhar A, Moris A, Gohar M, Lereclus D, Ramarao N. Haemolysin II is a Bacillus cereus virulence factor that induces apoptosis of macrophages. Cell Microbiol 2010. [DOI: 10.1111/j.1462-5822.2010.001522.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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