Gut Bacterial Diversity in Different Life Cycle Stages of Adelphocoris suturalis (Hemiptera: Miridae)

Substantially altered bacterial diversity associated with developmental stages of litchi stink bug, Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae)

The mutualistic symbiotic relationship between insects and bacteria greatly influences the growth and development of host insects. Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae), also referred to as the litchi stink bug, has recently been established as an important insect pest of Litchi chinensis Sonn. and causes substantial yield loss in India. To design effective and environmentally safe management strategies, an understanding of the diversity and functions of microbiota harbored across the development stages is very important. The assessment of the diversity of development-associated bacteria in T. javanica and their predicted functions was conducted using 16S rRNA gene sequences obtained by the Illumina MiSeq technology. The result showed that taxonomic analysis of associated bacteria in different developmental stages includes a total of 46 phyla, encompassing 139 classes, 271 orders, 474 families, and 893 genera of bacteria. All developmental stages of T. javanica shared a total of 42.82 percent of operational taxonomic units (OTUs), with a 97 % similarity threshold. Alpha diversity indices showed maximum species richness in the egg and adult stages. The phyla Proteobacteria followed by Firmicutes, Bacteriodetes, and Actinobacteria, exhibited the highest levels of abundance across all the developmental stages of T. javanica. Microbiota were most different between the egg and the 4th nymphal stage (χ2 = 711.67) and least different between the 2nd and 4th nymphal instars (χ2 = 44.45). The predicted functions of the microbiota associated with T. javanica are mainly involved in amino acid metabolism, cell motility, cellular processes and signaling, glycan biosynthesis and metabolism, lipid metabolism, and membrane transport. The present study documentation and information on symbiotic bacteria across T. javanica life stages will prompt the development of novel biological management strategies.

The role of insect gut microbiota in host fitness, detoxification and nutrient supplementation

Insects are incredibly diverse, ubiquitous and have successfully flourished out of the dynamic and often unpredictable nature of evolutionary processes. The resident microbiome has accompanied the physical and biological adaptations that enable their continued survival and proliferation in a wide array of environments. The host insect and microbiome's bidirectional relationship exhibits their capability to influence each other's physiology, behavior and characteristics. Insects are reported to rely directly on the microbial community to break down complex food, adapt to nutrient-deficit environments, protect themselves from natural adversaries and control the expression of social behavior. High-throughput metagenomic approaches have enhanced the potential for determining the abundance, composition, diversity and functional activities of microbial fauna associated with insect hosts, enabling in-depth investigation into insect-microbe interactions. We undertook a review of some of the major advances in the field of metagenomics, focusing on insect-microbe interaction, diversity and composition of resident microbiota, the functional capability of endosymbionts and discussions on different symbiotic relationships. The review aims to be a valuable resource on insect gut symbiotic microbiota by providing a comprehensive understanding of how insect gut symbionts systematically perform a range of functions, viz., insecticide degradation, nutritional support and immune fitness. A thorough understanding of manipulating specific gut symbionts may aid in developing advanced insect-associated research to attain health and design strategies for pest management.

Integrated Omics Analysis Reveals Key Pathways in Cotton Defense against Mirid Bug (Adelphocoris suturalis Jakovlev) Feeding

The recent dominance of Adelphocoris suturalis Jakovlev as the primary cotton field pest in Bt-cotton-cultivated areas has generated significant interest in cotton pest control research. This study addresses the limited understanding of cotton defense mechanisms triggered by A. suturalis feeding. Utilizing LC-QTOF-MS, we analyzed cotton metabolomic changes induced by A. suturalis, and identified 496 differential positive ions (374 upregulated, 122 downregulated) across 11 categories, such as terpenoids, alkaloids, phenylpropanoids, flavonoids, isoflavones, etc. Subsequent iTRAQ-LC-MS/MS analysis of the cotton proteome revealed 1569 differential proteins enriched in 35 metabolic pathways. Integrated metabolome and proteome analysis highlighted significant upregulation of 17 (89%) proteases in the α-linolenic acid (ALA) metabolism pathway, concomitant with a significant increase in 14 (88%) associated metabolites. Conversely, 19 (73%) proteases in the fructose and mannose biosynthesis pathway were downregulated, with 7 (27%) upregulated proteases corresponding to the downregulation of 8 pathway-associated metabolites. Expression analysis of key regulators in the ALA pathway, including allene oxidase synthase (AOS), phospholipase A (PLA), allene oxidative cyclase (AOC), and 12-oxophytodienoate reductase3 (OPR3), demonstrated significant responses to A. suturalis feeding. Finally, this study pioneers the exploration of molecular mechanisms in the plant-insect relationship, thereby offering insights into potential novel control strategies against this cotton pest.

Discussion: Harnessing microbiome-mediated adaptations in insect pollinators to mitigate climate change impact on crop pollination

Insect pollinators, vital for agriculture and biodiversity, face escalating threats from climate change. We argue and explore the pivotal role of the microbiomes in shaping adaptations of insect pollinator resilience amid climate-induced challenges (climate change and habitat alteration). Examining diverse taxonomic groups, we unravel the interplay between insect physiology, microbiomes, and adaptive mechanisms. Climate-driven alterations in microbiomes impact insect health, behavior, and plant interactions, posing significant effects on agricultural ecosystems. We propose harnessing microbiome-mediated adaptations as a strategic approach to mitigate climate change impacts on crop pollination. Insights into insect-pollinator microbiomes offer transformative avenues for sustainable agriculture, including probiotic interventions (use of EM PROBIOTIC) and microbiome engineering (such as engineering gut bacteria) to induce immune responses and enhanced pollination services. Integrating microbiome insights into conservation practices elucidates strategies for preserving pollinator habitats, optimizing agricultural landscapes, and developing policies to safeguard pollinator health in the face of environmental changes. Finally, we stress interdisciplinary collaboration and the urgency of understanding pollinator microbiome dynamics under climate change in future research.

Episyrphus balteatus symbiont variation across developmental stages, living states, two sexes, and potential horizontal transmission from prey or environment

Introduction

Episyrphus balteatus is one representative Syrphidae insect which can provide extensive pollination and pest control services. To date, the symbiont composition and potential acquisition approaches in Syrphidae remain unclear.

Methods

Herein, we investigated microbiota dynamics across developmental stages, different living states, and two sexes in E. balteatus via full-length 16S rRNA genes sequencing, followed by an attempt to explore the possibility of symbiont transmission from prey Megoura crassicauda to the hoverfly.

Results

Overall, Proteobacteria and Firmicutes were the dominant bacteria phyla with fluctuating relative abundances across the life stage. Cosenzaea myxofaciens is dominant in adulthood, while Enterococcus silesiacus and Morganella morganii dominate in larvae and pupae of E. balteatus, respectively. Unexpectedly, Serratia symbiotica, one facultative endosymbiont commonly harbored in aphids, was one of the predominant bacteria in larvae of E. balteatus, just behind Enterococcus silesiacus. In addition, S. symbiotica was also surprisingly most dominated in M. crassicauda aphids (92.1% relative abundance), which are significantly higher than Buchnera aphidicola (4.7% relative abundance), the primary obligate symbiont of most aphid species. Approximately 25% mortality was observed among newly emerged adults, of which microbiota was also disordered, similar to normally dying individuals. Sexually biased symbionts and 41 bacteria species with pairwise co-occurrence in E. balteatus and 23 biomarker species for each group were identified eventually. Functional prediction showed symbionts of hoverflies and aphids, both mainly focusing on metabolic pathways. In brief, we comprehensively explored the microbiome in one Syrphidae hoverfly using E. balteatus reared indoors on M. morganii as the model, revealed its dominated symbiont species, identified sexually biased symbionts, and found an aphid facultative endosymbiont inhabited in the hoverfly. We also found that the dominated symbiotic bacteria in M. crassicauda are S. symbiotica other than Buchnera aphidicola.

Discussion

Taken together, this study provides new valuable resources about symbionts in hoverflies and prey aphids jointly, which will benefit further exploring the potential roles of microbiota in E. balteatus.

Dynamic Gut Microbiota of Apolygus lucorum Across Different Life Stages Reveals Potential Pathogenic Bacteria for Facilitating the Pest Management

Insect's gut microbiota has diverse effects on their fitness, and a comprehensive understanding of gut microbiota functions requires analyzing its diversity. Apolygus lucorum is a highly destructive pest that threatens many economically important crops in China. This study investigated the gut microbiota of A. lucorum across its life cycle using both culture-dependent and culture-independent methods. A total of 87 gut bacterial isolates were identified, belonging to 4 phyla, 27 families, and 45 genera, while Miseq sequencing detected 91 amplicon sequence variants (ASVs) assigned to 5 phyla, 28 families, and 39 genera. Proteobacteria and Firmicutes were the predominant phyla, with Staphylococcus and Serratia as the major genera. There were significant differences in the relative abundance of these genera between the nymph and adult stages. Staphylococcus was significantly more abundant in nymphs than it in adults, while Serratia was significantly more abundant in sexually mature adults than in other developmental stages. Notably, Serratia is a common opportunistic pathogen in many insects. Injecting the gut-dominant isolate Serratia marcescens verified its high pathogenicity. Additionally, immune indicators of the bug at different developmental stages supported the hypothesis that Serratia is a pathogen of A. lucorum. This study provides a foundation for understanding the role of gut bacteria in the life history of A. lucorum and developing new pest control strategies based on microbes.

The comparison of gut gene expression and bacterial community in Diaphorina citri (Hemiptera: Liviidae) adults fed on Murraya exotica and 'Shatangju' mandarin (Citrus reticulate cv. Shatangju)

BACKGROUND

Diaphorina citri Kuwayama is an important citrus pest. It serves as the vector for the transmission of Candidatus Liberibacter asiaticus (CLas), which induced a destructive disease, Huanglongbing, and caused huge economic losses. During the interaction between insects and plants, insects have evolved a series of mechanisms to adapt to various host plants. Murraya exotica and 'Shatangju' mandarin (Citrus reticulate cv. Shatangju) are the Rutaceae species from different genera that have been discovered as suitable hosts for D. citri adults. While the adaptation mechanism of this pest to these two host plants is unclear.

RESULTS

In this study, RNA-seq and 16 S rDNA amplification sequencing were performed on the gut of D. citri adults reared on M. exotica and 'Shatangju' mandarin. RNA-seq results showed that a total of 964 differentially expressed genes were found in different gut groups with two host plant treatments. The impacted genes include those that encode ribosomal proteins, cathepsins, and mitochondrial respiratory chain complexes. According to 16 S rDNA sequencing, the compositions of the gut bacterial communities were altered by different treatments. The α and β diversity analyses confirmed that the host plant changes influenced the gut microbial diversity. The functional classification analysis by Tax4Fun revealed that 27 KEGG pathways, mostly those related to metabolism, including those for nucleotide metabolism, energy metabolism, metabolism of cofactors and vitamins, amino acid metabolism, carbohydrate metabolism, xenbiotics biodegradation and metabolism, lipid metabolism, and biosynthesis of other secondary metabolites, were significantly altered.

CONCLUSION

Our preliminary findings shed light on the connection between D. citri and host plants by showing that host plants alter the gene expression profiles and bacterial community composition of D. citri adults.

Response of the Pardosa astrigera bacterial community to Cry1B protein

While genetically modified (GM) crops bring economic benefits to human beings, their impact on non-target organisms has become an important part of environmental safety assessments. Symbiotic bacteria play an important role in eukaryotic biological functions and can adjust host communities to adapt to new environments. Therefore, this study examined the effects of Cry1B protein on the growth and development of non-target natural enemies of Pardosa astrigera (L. Koch) from the perspective of symbiotic bacteria. Cry1B protein had no significant effect on the health indicators of P. astrigera (adults and 2nd instar spiderlings). 16S rRNA sequencing results revealed that Cry1B protein did not change the symbiotic bacteria species composition of P. astrigera, but did reduce the number of OTU and species diversity. In 2nd instar spiderlings, neither the dominant phylum (Proteobacteria) nor the dominant genus (Acinetobacter) changed, but the relative abundance of Corynebacterium-1 decreased significantly; in adult spiders, the dominant bacteria genera of females and males were different. The dominant bacterial genera were Brevibacterium in females and Corynebacterium-1 in males, but Corynebacterium-1 was the dominant bacteria in both females and males feeding on Cry1B. The relative abundance of Wolbachia also increased significantly. In addition, bacteria in other genera varied significantly by sex. KEGG results showed that Cry1B protein only altered the significant enrichment of metabolic pathways in female spiders. In conclusion, the effects of Cry1B protein on symbiotic bacteria vary by growth and development stage and sex.

Dynamic changes in species richness and community diversity of symbiotic bacteria in five reproductive morphs of cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae)

Introduction

Reproductive polymorphism and symbiotic bacteria are commonly observed in aphids, but their interaction remains largely unclear. In polymorphic aphid species (Aphis gossypii), offspring of parthenogenetic females (PFs) develops into sexuparae which produces gynoparae and males successively. Gynoparae further produces sexual females (SFs), and these sexual females mate with males to produce offspring.

Methods

In this study, we investigated the dynamic changes of symbiotic bacteria during the above-mentioned five reproductive morph switch in A. gossypii via 16S rRNA sequencing technology.

Results

The results showed that species richness and community diversity of symbiotic bacteria in males were the highest. Proteobacteria was absolutely dominant bacterial phylum (with relative abundance of more than 90%) in the five reproductive morphs of A. gossypii, and Buchnera was absolutely dominant genus (with relative abundance of >90%), followed by Rhodococcus, Pseudomonas, and Pantoea. Male-killing symbiont Arsenophonus presented the highest relative abundance in gynoparae, a specific morph whose offsprings were exclusively sexual females. Both principal component analysis (PCA) and clustering analysis showed trans-generation similarity in microbial community structure between sexuparae and sexual females, between PFs and gynoparae. PICRUSt 2 analysis showed that symbiotic bacteria in the five reproductive morphs were mainly enriched in metabolic pathways.

Discussion

Reproductive morph switch induced by environmental changes might be associated with bacterial community variation and sexual polymorphism of aphids. This study provides a new perspective for further deciphering the interactions between microbes and reproductive polymorphism in host aphids.

High Prevalence of Pantoea spp. in Microbiota Associated with the Sorghum Plant Bug Stenotus rubrovittatus (Heteroptera: Miridae)

The sorghum plant bug, Stenotus rubrovittatus (order Heteroptera: family Miridae), is a notorious insect pest in Japan that causes pecky rice. In the present study, we sampled this insect pest in the northern part of Honshu Island in Japan and investigated its associated microbiota. The results obtained showed that Pantoea dominated the associated microbiota and was the sole genus detected in all samples. The dominant Pantoea were phylogenetically close to rice pathogens. The present results suggest that the sorghum plant bug needs to be regarded and controlled not only as a notorious insect pest, but also as a potential vector of rice pathogenic Pantoea spp.

Diversity of endosymbionts in camellia spiny whitefly, Aleurocanthus camelliae (Hemiptera: Aleyrodidae), estimated by 16S rRNA analysis and their biological implications

Camellia spiny whitefly, Aleurocanthus camelliae (Hemiptera: Aleyrodidae), is a major pest in tea, which poses a serious threat to tea production. Similar to many insects, various bacterial symbioses inside A. camelliae may participate in the reproduction, metabolism, and detoxification of the host. However, few reports included research on the microbial composition and influence on A. camelliae growth. We first applied high-throughput sequencing of the V4 region in the 16S rRNA of symbiotic bacteria to study its component and effect on the biological trait of A. camelliae by comparing it with the antibiotic treatment group. The population parameters, survival rate, and fecundity rate of A. camelliae were also analyzed using the age-stage two-sex life table. Our results demonstrated that phylum Proteobacteria (higher than 96.15%) dominated the whole life cycle of A. camelliae. It unveiled the presence of Candidatus Portiera (primary endosymbiont) (67.15-73.33%), Arsenophonus (5.58-22.89%), Wolbachia (4.53-11.58%), Rickettsia (0.75-2.59%), and Pseudomonas (0.99-1.88%) genus. Antibiotic treatment caused a significant decrease in the endosymbiont, which negatively affected the host's biological properties and life process. For example, 1.5% rifampicin treatment caused a longer preadult stage in the offspring generation (55.92 d) compared to the control (49.75d) and a lower survival rate (0.36) than the control (0.60). The decreased intrinsic rate of increase (r), net reproductive rate (R ₀), and prolonged mean generation time (T) were signs of all disadvantageous effects associated with symbiotic reduction. Our findings confirmed the composition and richness of symbiotic bacteria in larva and adult of A. camelliae by an Illumina NovaSeq 6000 analysis and their influence on the development of the host by demographic research. Together, the results suggested that symbiotic bacteria play an important role in manipulating the biological development of their hosts, which might help us for developing new pest control agents and technologies for better management of A. camelliae.

Dynamic changes of gut bacterial communities present in larvae of Anoplophora glabripennies collected at different developmental stages

The Asian long-horned beetle, Anoplophora glabripennies (Motschulsky), is a destructive wood-boring pest that is capable of killing healthy trees. Gut bacteria in the larvae of the wood-boring pest is essential for the fitness of hosts. However, little is known about the structure of the intestinal microbiome of A. glabripennies during larval development. Here, we used Illumina MiSeq high-throughput sequencing technology to analyze the larval intestinal bacterial communities of A. glabripennies at the stages of newly hatched larvae, 1st instar larvae and 4th instar larvae. Significant differences were found in larval gut microbial community structure at different larvae developmental stages. Different dominant genus was detected during larval development. Acinetobacter were dominant in the newly hatched larvae, Enterobacter and Raoultella in the 1st instar larvae, and Enterococcus and Gibbsiella in the 4th instar larvae. The microbial richness in the newly hatched larvae was higher than those in the 1st and 4th instar larvae. Many important functions of the intestinal microbiome were predicted, for example, fermentation and chemoheterotrophy functions that may play an important role in insect growth and development was detected in the bacteria at all tested stages. However, some specific functions are found to be associated with different development stages. Our study provides a theoretical basis for investigating the function of the intestinal symbiosis bacteria of A. glabripennies.

Specific Enriched Acinetobacter in Camellia Weevil Gut Facilitate the Degradation of Tea Saponin: Inferred from Bacterial Genomic and Transcriptomic Analyses

Beneficial gut bacteria can enhance herbivorous arthropod adaptation to plant secondary compounds (PSMs), and specialist herbivores provide excellent examples of this. Tea saponin (TS) of Camellia oleifera is triterpenoids toxic to seed-feeding weevil pest, Curculio chinensis (CW). Previous studies disclosed that Acinetobacter, which was specific enriched in the CW's gut, was involved in helping CW evade TS toxicity of C. oleifera. However, it is still not clear whether Acinetobacter is associated with other anti-insect compounds, and the molecular mechanism of Acinetobacter degradation of TS has not been clarified. To address these questions, we explored the relationship between host plant toxin content and Acinetobacter of CW gut bacteria. Results demonstrated that TS content significantly affected the CW gut microbiome structure and enriched bacteria functional for TS degradation. We further isolated Acinetobacter strain and conducted its genome and transcriptome analyses for bacterial characterization and investigation on its role in TS degradation. Biological tests were carried out to verify the ability of the functional bacterium within CW larvae to detoxify TS. Our results showed that TS-degrading bacteria strain (Acinetobacter sp. AS23) genome contains 47 genes relating to triterpenoids degradation. The AS23 strain improved the survival rate of CW larvae, and the steroid degradation pathway could be the key one for AS23 to degrade TS. This study provides the direct evidence that gut bacteria mediate adaptation of herbivorous insects to phytochemical resistance. IMPORTANCE Microorganism is directly exposed to the plant toxin environment and play a crucial third party in herbivores gut. Although previous studies have proved the existence of gut bacteria that help CWs degrade TS, the specific core flora and its function have not been explored. In this study, we investigated the correlation between the larva gut microbiome and plant secondary metabolites. Acinetobacter genus was the target flora related to TS degradation. There were many terpenoids genes in Acinetobacter sp. AS23 genome. Results of transcriptome analysis and biological tests suggested that steroid degradation pathway be the key pathway of AS23 to degrade TS. This study not only provides direct evidence that gut microbes mediate the rapid adaptation of herbivorous insects to phytochemical resistance, but also provides a theoretical basis for further research on the molecular mechanism of intestinal bacteria cooperating with pests to adapt to plant toxins.

Diversity and composition of the microbiome associated with eggs of the Southern green stinkbug, Nezara viridula (Hemiptera: Pentatomidae)

Although microbial communities of insects from larval to adult stage have been increasingly investigated in recent years, little is still known about the diversity and composition of egg-associated microbiomes. In this study, we used high-throughput amplicon sequencing and quantitative PCR to get a better understanding of the microbiome of insect eggs and how they are established using the Southern green stinkbug Nezara viridula (L.) (Hemiptera: Pentatomidae) as a study object. First, to determine the bacterial community composition, egg masses from two natural populations in Belgium and Italy were examined. Subsequently, microbial community establishment was assessed by studying stinkbug eggs of different ages obtained from laboratory strains (unlaid eggs collected from the ovaries, eggs less than 24 h old, and eggs collected 4 days after oviposition). Both the external and internal egg-associated microbiomes were analyzed by investigating egg washes and surface-sterilized washed eggs, respectively. Eggs from the ovaries were completely devoid of bacteria, indicating that egg-associated bacteria were deposited on the eggs during or after oviposition. The bacterial diversity of deposited eggs was very low, with on average 6.1 zero-radius operational taxonomic units (zOTUs) in the external microbiome and 1.2 zOTUs in internal samples of egg masses collected from the field. Bacterial community composition and density did not change significantly over time, suggesting limited bacterial growth. A Pantoea-like symbiont previously found in the midgut of N. viridula was found in every sample and generally occurred at high relative and absolute densities, especially in the internal egg samples. Additionally, some eggs harbored a Sodalis symbiont, which has previously been found in the abdomen of several insects, but so far not in N. viridula populations. We conclude that the egg-associated bacterial microbiome of N. viridula is species-poor and dominated by a few symbionts, particularly the species-specific obligate Pantoea-like symbiont.

Dynamics of symbiotic bacterial community in whole life stage of Harmonia axyridis (Coleoptera: Coccinellidae)

INTRODUCTION

Bacteria play critical roles in the reproduction, metabolism, physiology, and detoxification of their insect hosts. The ladybird beetle (Harmonia axyridis) harbors a myriad of endosymbiotic microbes. However, to date, little is known about how the microbial composition of H. axyridis varies throughout its life cycle.

METHODS

In this study, 16S rRNA amplicon sequencing and quantitative PCR were employed to investigate the diversity and dynamics of bacterial symbionts across the egg, larval, pupae, and adults stages of H. axyridis.

RESULTS

Higher bacterial community richness and diversity were observed in eggs, followed by those in adults and pupae. The community richness index differed significantly between second-instar larvae and other developmental stages. Proteobacteria, Firmicutes, and Actinobacteria were the dominant phyla. Staphylococcus, Enterobacter, Glutamicibacter, and Acinetobacter were the dominant bacteria genera; however, their relative abundances fluctuated across host developmental stages. Interestingly, the larval stage harbored high proportions of Firmicutes, whereas the adult microbial community largely consisted of Proteobacteria.

DISCUSSION

This study is the first to determine the symbiotic bacterial composition across key life stages of H. axyridis. These outcomes can foster the development of environmental risk assessments and novel biological control strategies.

Contribution of insect gut microbiota and their associated enzymes in insect physiology and biodegradation of pesticides

Synthetic pesticides are extensively and injudiciously applied to control agriculture and household pests worldwide. Due to their high use, their toxic residues have enormously increased in the agroecosystem in the past several years. They have caused many severe threats to non-target organisms, including humans. Therefore, the complete removal of toxic compounds is gaining wide attention to protect the ecosystem and the diversity of living organisms. Several methods, such as physical, chemical and biological, are applied to degrade compounds, but as compared to other methods, biological methods are considered more efficient, fast, eco-friendly and less expensive. In particular, employing microbial species and their purified enzymes makes the degradation of toxic pollutants more accessible and converts them into non-toxic products by several metabolic pathways. The digestive tract of insects is usually known as a superior organ that provides a nutrient-rich environment to hundreds of microbial species that perform a pivotal role in various physiological and ecological functions. There is a direct relationship between pesticides and insect pests: pesticides reduce the growth of insect species and alter the phyla located in the gut microbiome. In comparison, the insect gut microbiota tries to degrade toxic compounds by changing their toxicity, increasing the production and regulation of a diverse range of enzymes. These enzymes breakdown into their derivatives, and microbial species utilize them as a sole source of carbon, sulfur and energy. The resistance of pesticides (carbamates, pyrethroids, organophosphates, organochlorines, and neonicotinoids) in insect species is developed by metabolic mechanisms, regulation of enzymes and the expression of various microbial detoxifying genes in insect guts. This review summarizes the toxic effects of agrochemicals on humans, animals, birds and beneficial arthropods. It explores the preferential role of insect gut microbial species in the degradation process and the resistance mechanism of several pesticides in insect species. Additionally, various metabolic pathways have been systematically discussed to better understand the degradation of xenobiotics by insect gut microbial species.

Tardigrade Community Microbiomes in North American Orchards Include Putative Endosymbionts and Plant Pathogens

The microbiome of tardigrades, a phylum of microscopic animals best known for their ability to survive extreme conditions, is poorly studied worldwide and completely unknown in North America. An improved understanding of tardigrade-associated bacteria is particularly important because tardigrades have been shown to act as vectors of the plant pathogen Xanthomonas campestris in the laboratory. However, the potential role of tardigrades as reservoirs and vectors of phytopathogens has not been investigated further. This study analyzed the microbiota of tardigrades from six apple orchards in central Iowa, United States, and is the first analysis of the microbiota of North American tardigrades. It is also the first ever study of the tardigrade microbiome in an agricultural setting. We utilized 16S rRNA gene amplicon sequencing to characterize the tardigrade community microbiome across four contrasts: location, substrate type (moss or lichen), collection year, and tardigrades vs. their substrate. Alpha diversity of the tardigrade community microbiome differed significantly by location and year of collection but not by substrate type. Our work also corroborated earlier findings, demonstrating that tardigrades harbor a distinct microbiota from their environment. We also identified tardigrade-associated taxa that belong to genera known to contain phytopathogens (Pseudomonas, Ralstonia, and the Pantoea/Erwinia complex). Finally, we observed members of the genera Rickettsia and Wolbachia in the tardigrade microbiome; because these are obligate intracellular genera, we consider these taxa to be putative endosymbionts of tardigrades. These results suggest the presence of putative endosymbionts and phytopathogens in the microbiota of wild tardigrades in North America.

Composition and Diversity of Gut Bacterial Community in Different Life Stages of a Leaf Beetle Gastrolina depressa

Insect gut bacteria have a significant impact on host biology, which has a favorable or negative impact on insect fitness. The walnut leaf beetle (Gastrolina depressa) is a notorious pest in China, causing severe damage to Juglandaceae trees including Juglans regia and Pterocarya rhoifolia. To date, however, we know surprisingly little about the gut microbiota of G. depressa. This study used a high-throughput sequencing platform to investigate the gut bacterial community of G. depressa throughout its life cycle, including the 1st, 2nd, and 3rd instar larvae, as well as male, female, and pre-pregnant female adults. Our results showed that the diversity of the gut bacterial community in larvae was generally higher than that in adults, and young larvae (1st and 2nd larvae) possessed the most diversified and abundant community. Principal coordinate analysis results showed that the gut microbiota of adults cluster together, which is independent of the 1st and 2nd instar larvae. The main phyla were Proteobacteria and Firmicutes in the microbial community of G. depressa, while the dominant genera were Enterobacter, Rosenbergiella, Erwinia, Pseudomonas, and Lactococcus. The gut bacteria of G. depressa were mostly enriched in metabolic pathways (carbohydrate metabolism and amino acid metabolism) as revealed by functional prediction. This study contributes to a better knowledge of G. depressa's gut microbiota and its potential interactions with the host insect, facilitating the development of a microbial-based pest management strategy.

Bacterial Communities in the Feces of Laboratory Reared Gampsocleis gratiosa (Orthoptera: Tettigoniidae) across Different Developmental Stages and Sexes

Simple Summary

Many insects host a diverse gut microbial community, ranging from pathogenic to obligate mutualistic organisms. Little is known about the bacteria associated with katydids. Gampsocleis gratiosa (Orthoptera, Tettigoniidae) is an economically important singing pet in China. In the present study, the bacterial communities of the laboratory-reared G. gratiosa feces were characterized using Illumina sequencing of the 16S rDNA V3-V4 region.

Abstract

We used Illumina sequencing of the 16S rDNA V3-V4 region to identify the bacterial community in laboratory-reared G. gratiosa feces across different developmental stages (1st–7th instar nymph day 0, and 0-, 7-, 14-, and 21-day adult) and sexes. In total, 14,480,559 high-quality reads were clustered into 2982 species-level operational taxonomic units (OTUs), with an average of 481.197 (±137.366) OTUs per sample. These OTUs were assigned into 25 phyla, 42 classes, 60 orders, 116 families, 241 genera, and some unclassified groups. Only 21 core OTUs were shared by all samples. The most representative phylum was Proteobacteria, followed by Firmicutes, Bacteroidetes, and Acidobacteria. At the genus level, Kluyvera (387 OTUs), Obesumbacterium (339 OTUs), Buttiauxella (296 OTUs), Lactobacillus (286 OTUs), and Hafnia (152 OTUs) were dominant bacteria. The early-instar nymphs harbored a similar bacterial community with other developmental stages, which contain higher species diversity. Both principal coordinate analysis (PCoA) and non-metric multidimensional scaling analysis (NMDS) failed to provide a clear clustering based on the developmental stages and sexes. Overall, we assume that G. gratiosa transmits bacteria vertically by eating contaminated eggshells, and both developmental stages and sexes had no significant effect on the fecal bacterial community.

Stage correlation of symbiotic bacterial community and function in the development of litchi bugs (Hemiptera: Tessaratomidae)

Bacterial symbionts of insects have been shown to play important roles in host fitness. However, little is known about the bacterial community of Tessaratoma papillosa which is one of the most destructive pests of the well-known fruits Litchi chinensis Sonn and Dimocarpus longan Lour in Oriental Region, especially in South-east Asia and adjacent areas. In this study, we surveyed the bacterial community diversity and dynamics of T. papillosa in all developmental stages with both culture-dependent and culture-independent methods by the third-generation sequencing technology. Five bacterial phyla were identified in seven developmental stages of T. papillosa. Proteobacteria was the dominant phylum and Pantoea was the dominant genus of T. papillosa. The results of alpha and beta diversity analyses showed that egg stage had the most complex bacterial community. Some of different developmental stages showed similarities, which were clustered into three phases: (1) egg stage, (2) early nymph stages (instars 1-3), and (3) late nymph stages (instars 4-5) and adult stage. Functional prediction indicated that the bacterial community played different roles in these three phases. Furthermore, 109 different bacterial strains were isolated and identified from various developmental stages. This study revealed the relationship between the symbiotic bacteria and the development of T. papillosa, and may thus contribute to the biological control techniques of T. papillosa in the future.