Effects of Different Hosts on Bacterial Communities of Parasitic Wasp Nasonia vitripennis

Host adaptability of Microplitis manilae (Hymenoptera: Braconidae) in Noctuidae

Biological control is an effective and sustainable method of integrated pest management. Microplitis manilae (Hymenoptera: Braconidae) is a common internal parasitoid wasp of the order Lepidoptera. To determine a suitable host species for the reproduction of parasitoids, it is essential to assess host suitability and parasitic potential of the parasitized pests. Herein, we investigated host selection and exploitation of M. manilae. We evaluated the parasitic efficacy of M. manilae in 4 pest species in the Spodoptera and Mythimna genera of the Noctuidae family. The results indicated that the parasitism rate of M. manilae on 3 species in the Spodoptera genus is higher than on Mythimna separata in the Mythimna genus, with M. manilae exhibiting a higher parasitism rate and shorter development duration on Spodoptera litura compared to other species. The parasitism rate for 1st instars hosts was 86.67 ± 0.04%, while the development duration was 14.1 ± 0.03 days. However, when parasitizing the 3rd instar of Spodoptera frugiperda, parasitoids showed a higher sex ratio, of 0.71 ± 0.05. Additionally, M. manilae had parasitic effect on M. separata, providing a new choice for its parasitism. The results identify the optimal host, which could enhance and reproduction rate and survival rate of M. manilae, thus facilitating their large-scale propagation. Understanding the parasitic effects of M. manilae on pests can further its field application, also plays a major role in promoting the development of biological control technologies and sustainable agricultural production.

Bacterial communities in Asecodes hispinarum (Hymenoptera: Eulophidae) and its host Brontispa longissima (Coleoptera: Chrysomelidae), with comparison of Wolbachia dominance

The endoparasitoid Asecodes hispinarum (Bouček) (Hymenoptera: Eulophidae) serves as an effective biological control agent against Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), a notorious palm pest. Endosymbionts found in parasitoids and their hosts have attracted significant attention due to their substantial influence on biocontrol efficacy. In this study, we employed 16S rRNA sequencing, polymerase chain reaction, and fluorescence in situ hybridization to assess the symbiotic bacteria composition, diversity, phylogeny, and localization in A. hispinarum and its host B. longissima. Our findings showed significant differences in the richness, diversity, and composition of symbiotic bacteria among different life stages of B. longissima. Notably, the bacterial richness, diversity, and composition of A. hispinarum was similar to that of B. longissima. Firmicutes and Proteobacteria were the dominant phyla, while Wolbachia was the dominant genera across the parasitoid and host. It was discovered for the first time that Wolbachia was present in A. hispinarum with a high infection rate at ≥ 96.67%. Notably, the Wolbachia strain in A. hispinarum was placed in supergroup A, whereas it was categorized under supergroup B in B. longissima. Furthermore, Wolbachia is concentrated in the abdomen of A. hispinarum, with particularly high levels observed in the ovipositors of female adults. These findings highlight the composition and diversity of symbiotic bacteria in both A. hispinarum and its host B. longissima, providing a foundation for the development of population regulation strategies targeting B. longissima.

Characterization of larval gut microbiota of two endoparasitoid wasps associated with their common host, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae)

Insect gut microbes play important roles in digestion, metabolism, development, and environmental adaptation. Parasitoid wasps are one of the most important biological control agents in pest control, while the gut microbial species compositions and the associated functions have been poorly investigated. Two endoparasitoid wasps, Cotesia vestalis and Diadromus collaris, parasitize the larval stage and pupal stage of the diamondback moth, Plutella xylostella, respectively. Using whole-genome shotgun metagenomic sequencing, we characterized the gut microbial composition, diversity, and potential functional roles associated with the two parasitoid wasp larvae. The results reveal that Proteobacteria and Firmicutes are the dominant phyla in the gut of C. vestalis and D. collaris larvae, with Rhizobium and Enterococcus being the dominant genera. The putative microbial functions associated with the two parasitoid wasps might play a virtual role in assisting in consuming the host's nutritional composition. The enriched CAZymes family genes are primarily involved in the degradation and synthesis of chitin. Despite the richness of microbial species and communities, the microbes species and the microbial community structure exhibit significant similarity between the two parasitoid wasps and between the parasitoid wasp and the host P. xylostella. Notably, the prevalence of the genus Enterococcus shared among them suggests a possible link of gut microbes between the host and their associated parasitoids. Our study offers insights into the gut microbe-based interactions between the host and parasitoid wasps for the first time, potentially paving the way for the development of an ecologically friendly biocontrol strategy against the pest P. xylostella.IMPORTANCEEndoparasitoid wasps spend the majority of their lifespan within their host and heavily rely on the host's nutrition for survival. There is limited understanding regarding the composition and physiological impacts of gut microbial communities in parasitoid wasps, particularly during the larval stage, which is directly linked to the host. Based on a thorough characterization of the gut microbe and comprehensive comparative analysis, we found the microbial species of the larval parasitoid wasp Cotesia vestalis and the pupal parasitoid wasp Diadromus collaris were similar, sharing 159 genera and 277 species, as were the microbial community structure. Certain of the dominant microbial strains of the two parasitoid wasps were similar to that of their host Plutella xylostella larvae, revealing host insect may affect the microbial community of the parasitoid wasps. The putative microbial functions associated with the parasitoid wasp larvae play an important role in dietary consumption.

Host Species Affects Gut Microbial Community and Offspring Developmental Performances in the Pupal Parasitoid Chouioia cunea Yang (Hymenoptera: Eulophidae)

Chouioia cunea are known to exploit in varying degrees a wide range of lepidopteran species and its offspring development may vary with host species. This study examined its preimaginal development and larval gut microbiota in parasitizing five folivorous lepidopteran hosts including Hyphantria cunea (referred to thereafter as CcHc), Antherea pernyi (CcAp), Helicoverpa armigera (CcHa), Spodoptera exigua (CcSe), and Spodoptera frugiperda (CcSf). Though rates of parasitism and offspring eclosion did not change with host species, the development period and number of offspring eclosed varied with hosts, with the shortest period in CcSf and the highest number from CcAp. For offspring larval gut microbiota, though phylum Proteobacteria was dominant for attacking CcAp, Firmicutes was so for the other hosts. All microbial genera except Enterococcus were less abundant for CcSf than the other hosts. The database-based predictions indicate a significant positive correlation between Cutibacterium and Aureimonas with the relative number of wasp emergence, while Blastomonas exhibits a strong positive association with the developmental period. Our results imply the potential relevance of the gut microbial community in offspring larvae to host species attacked by C. cunea.

Faecal Microbiota Transplantation Alleviates Ferroptosis after Ischaemic Stroke

Ischaemic stroke can induce changes in the abundance of gut microbiota constituents, and the outcome of stroke may also be influenced by the gut microbiota. This study aimed to determine whether gut microbiota transplantation could rescue changes in the gut microbiota and reduce ferroptosis after stroke in rats. Male Sprague-Dawley rats (6 weeks of age) were subjected to ischaemic stroke by middle cerebral artery occlusion (MCAO). Fecal samples were collected for 16S ribosomal RNA (rRNA) sequencing to analyze the effects of FMT on the gut microbiota. Neurological deficits were evaluated using the Longa score. triphenyl tetrazolium chloride (TTC) staining was performed in the brain, and kits were used to measure malondialdehyde (MDA), iron, and glutathione (GSH) levels in the ipsilateral brain of rats. Western blotting was used to detect the protein expression levels of glutathione peroxidase 4 (GPX4), solute carrier family 7 member 11 (SLC7A11), and the transferrin receptor 2 (TFR2) in the ipsilateral brain of rats. Stroke induced significant changes in the gut microbiota, and FMT ameliorated these changes. TTC staining results showed that FMT reduced cerebral infarct volume. In addition, FMT diminished MDA and iron levels and elevated GSH levels in the ipsilateral brain. Western blot analysis showed that FMT increased GPX4 and SLC7A11 protein expression and decreased TFR2 protein expression in the ipsilateral brain after stroke. FMT can reverse gut microbiota dysbiosis, reduce cerebellar infarct volume, and decrease ferroptosis after stroke.

The endosymbiotic bacterium Wolbachia (Rickettsiales) alters larval metabolism of the parasitoid Habrobracon hebetor (Hymenoptera: Braconidae)

Infection of intestinal tissues with Wolbachia has been found in Habrobracon hebetor. There are not many studies on the relationship between Habrobracon and Wolbachia, and they focus predominantly on the sex index of an infected parasitoid, its fertility, and behavior. The actual role of Wolbachia in the biology of Habrobracon is not yet clear. The method of complete eradication of Wolbachia in the parasitoid was developed here, and effects of the endosymbiont on the host's digestive metabolism were compared between two lines of the parasitoid (Wolbachia-positive and Wolbachia-negative). In the gut of Wolbachia+ larvae, lipases' activity was higher almost twofold, and activities of acid proteases, esterases, and trehalase were 1.5-fold greater than those in the Wolbachia- line. Analyses of larval homogenates revealed that Wolbachia+ larvae accumulate significantly more lipids and have a lower amount of pyruvate as compared to Wolbachia- larvae. The presented results indicate significant effects of the intracellular symbiotic bacterium Wolbachia on the metabolism of H. hebetor larvae and on the activity of its digestive enzymes.

Construction of a synthetic microbial community based on multiomics linkage technology and analysis of the mechanism of lignocellulose degradation

The efficient degradation of lignocellulose is a bottleneck for its integrated utilization. This research performed species analysis and made functional predictions in various ecosystems using multiomics coupling to construct a core synthetic microbial community with efficient lignocellulose degradation function. The synthetic microbial community was employed to degrade corn straw via solid-state fermentation. The degradation mechanisms were resolved using proteomics. The optimum culture conditions included 10% inoculum level (w/v), 4% nitrogen source ratio and a fermentation time of 23 d. Under these conditions, the degradation rates of cellulose, hemicellulose, and lignin were 34.91%, 45.94%, and 23.34%, respectively. Proteomic analysis revealed that lignin 1,4-β-xylanase, β-xylosidase and endo-1,4-β-xylanase were closely related to lignocellulose degradation. The metabolic pathways involved in lignocellulose degradation and the functional roles of eight strains were obtained. The synthesis of a microbial community via multiomics linkage technology can effectively decompose lignocellulose, which is useful for their further utilization.

Construction of a Banker Plant System via the Host Switch Trait of a Natural Enemy Aenasius bambawalei

Understanding the most effective host switch patterns in parasitic wasps, specifically Aenasius bambawalei (AB), is crucial for effectively controlling pests like Penacoccus solenopsis (PSS). This study aims to elucidate AB's ideal host switch pattern and assess its utility in maintaining synchronization between AB and PSS, thereby aiding in PSS control. We examined various host switch patterns and cycles to evaluate their impact on AB's offspring's parasitism rates and fitness in laboratory conditions. Concurrently, we assessed the fitness of both PSS and AB on tomato plants using different banker plant systems to maintain field synchronization. Results indicate that the three-repeat T1 host switch pattern of PSS-Penacoccus solani (PSI)-PSS was the most effective. Additionally, a specific banker plant system, "System B", which provided succulent plants hosting PSI, was optimal for synchronizing AB and PSS in a summer greenhouse setting. Our findings underscore the importance of employing specific host switch patterns and banker plant systems to effectively control PSS in the field. This research offers foundational data for incorporating a banker plant system into integrated pest management strategies for enhanced PSS control.

Effect of Different Host Plants on the Diversity of Gut Bacterial Communities of Spodoptera frugiperda (J. E. Smith, 1797)

Intestinal symbiotic bacteria have formed an interdependent symbiotic relationship with many insect species after long-term coevolution, which plays a critical role in host growth and adaptation. Spodoptera frugiperda (J. E. Smith) is a worldwide significant migratory invasive pest. As a polyphagous pest, S. frugiperda can harm more than 350 plants and poses a severe threat to food security and agricultural production. In this study, 16S rRNA high-throughput sequencing technology was used to analyze the diversity and structure of the gut bacteria of this pest feeding on six diets (maize, wheat, rice, honeysuckle flowers, honeysuckle leaves, and Chinese yam). The results showed that the S. frugiperda fed on rice had the highest bacterial richness and diversity, whereas the larvae fed on honeysuckle flowers had the lowest abundance and diversity of gut bacterial communities. Firmicutes, Actinobacteriota, and Proteobacteria were the most dominant bacterial phyla. PICRUSt2 analysis indicated that most of the functional prediction categories were concentrated in metabolic bacteria. Our results confirmed that the gut bacterial diversity and community composition of S. frugiperda were affected significantly by host diets. This study provided a theoretical basis for clarifying the host adaptation mechanism of S. frugiperda, which also provided a new direction to improve polyphagous pest management strategies.

Intestinal Bacterial Diversity and Functional Analysis of Three Lepidopteran Corn Ear Worm Larvae

Insects, as the most abundant animal group on earth, and their symbionts help their hosts to adapt to various environments. Conogethes punctiferalis, Ostrinia furnacalis and Helicoverpa armigera are three main pests co-occurring in the ear stage of corn, which significantly affect the yield and quality of corn. The purpose of this study was to compare the diversity and function of the intestinal bacteria of the three co-occurring lepidopteran pests, C. punctiferalis, O. furnacalis and H. armigera, and to explore the reason of their prevalence from the microbiota's view. Our results showed the difference of diversity and abundance of the gut bacteria of three co-occurring lepidopteran pests at the ear stage. Proteobacteria and Firmicutes were the dominant phyla, and the Enterobacteriaceae and Enterococcaceae were the dominant families in the three pests. Compared with the other two pests, Bacteroidetes was found much more in C. punctiferalis. In addition, C. punctiferalis showed more correlation and similarity in bacteria composition with corn endophytic bacteria, as well as had obvious advantages in metabolic, environmental information processing, cellular processes and organic systems function pathways. Our findings may provide insight into the prevalence of corn earworm larvae from the perspective of gut microbiota and function prediction.

Diversity and dynamics of bacteria at the Chrysomya megacephala pupal stage revealed by third-generation sequencing

Characterization of the microbial community is essential for understanding the symbiotic relationships between microbes and host insects. Chrysomya megacephala is a vital resource, a forensic insect, a pollinator, and a vector for enteric bacteria, protozoa, helminths, and viruses. However, research on its microbial community is incomprehensive, particularly at the pupal stage, which comprises approximately half of the entire larval development stage and is important entomological evidence in forensic medicine. For the first time, this study investigated the bacterial communities of C. megacephala pupae at different ages using third-generation sequencing technology. The results showed that C. megacephala has a diverse and dynamic bacterial community. Cluster analysis at ≥ 97% similarity produced 154 operational taxonomic units (OTUs) that belonged to 10 different phyla and were distributed into 15 classes, 28 orders, 50 families, 88 genera, and 130 species. Overall, the number of bacterial OTUs increased with the development of pupae, and the relative abundance of Wolbachia in the Day5 group was significantly lower than that in the other groups. Within the pupal stage, Proteobacteria, Firmicutes, and Bacteroidetes were the dominant phyla of bacteria. At the genus level, Wolbachia and Ignatzschineria coexisted, a rarely known feature. In addition, we found Erysipelothrix rhusiopathiae, the etiological agent of swine erysipelas, which is rarely identified in insects. This study enriches the understanding of the microbial community of C. megacephala and provides a reference for better utilization and control of C. megacephala.

Genomic analysis of the nomenclatural type strain of the nematode-associated entomopathogenic bacterium Providencia vermicola

Background

Enterobacteria of the genus Providencia are mainly known as opportunistic human pathogens but have been isolated from highly diverse natural environments. The species Providencia vermicola comprises insect pathogenic bacteria carried by entomoparasitic nematodes and is investigated as a possible insect biocontrol agent. The recent publication of several genome sequences from bacteria assigned to this species has given rise to inconsistent preliminary results.

Results

The genome of the nematode-derived P. vermicola type strain DSM_17385 has been assembled into a 4.2 Mb sequence comprising 5 scaffolds and 13 contigs. A total of 3969 protein-encoding genes were identified. Multilocus sequence typing with different marker sets revealed that none of the previously published presumed P. vermicola genomes represents this taxonomic species. Comparative genomic analysis has confirmed a close phylogenetic relationship of P. vermicola to the P. rettgeri species complex. P. vermicola DSM_17385 carries a type III secretion system (T3SS-1) with probable function in host cell invasion or intracellular survival. Potentially antibiotic resistance-associated genes comprising numerous efflux pumps and point-mutated house-keeping genes, have been identified across the P. vermicola genome. A single small (3.7 kb) plasmid identified, pPVER1, structurally belongs to the qnrD-type family of fluoroquinolone resistance conferring plasmids that is prominent in Providencia and Proteus bacteria, but lacks the qnrD resistance gene.

Conclusions

The sequence reported represents the first well-supported published genome for the taxonomic species P. vermicola to be used as reference in further comparative genomics studies on Providencia bacteria. Due to a striking difference in the type of injectisome encoded by the respective genomes, P. vermicola might operate a fundamentally different mechanism of entomopathogenicity when compared to insect-pathogenic Providencia sneebia or Providencia burhodogranariea. The complete absence of antibiotic resistance gene carrying plasmids or mobile genetic elements as those causing multi drug resistance phenomena in clinical Providencia strains, is consistent with the invertebrate pathogen P. vermicola being in its natural environment efficiently excluded from the propagation routes of multidrug resistance (MDR) carrying genetic elements operating between human pathogens. Susceptibility to MDR plasmid acquisition will likely become a major criterion in the evaluation of P. vermicola for potential applications in biological pest control.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08027-w.