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Abstract:Microbes, the ubiquitous organisms in nature, usually live in the "microbial community". A microbial community usually contains tens to thousands of different microorganisms, where they cooperate with each other to adapt to changes in the environment to complete the evolution of life, while their life activities also have a long and profound impact on the environment. With a better understanding of microorganisms, basic research on microbial community and its application in the field of health and the environment is increasingly important. There are a large number and a wide variety of microbes in the intestine of insects. On the one hand, the diversity of these intestinal microbial populations is closely related to insect species, age, digestive tract form, food source and environment. On the other hand, these microflora also have some effect on the host's physiological activities. With the development of high-throughput sequencing technology and omics technology, the use of molecular biology technology to quickly, qualitatively and quantitatively study insect intestinal microbes has become a popular filed. Data mining and application on insect intestine metagenome will greatly promote our ability to use microbial resources. This paper summarizes the development of metagenomics of insect intestinal, especially the excavation tools and applications of large data of intestinal genome and the research progress, application, advantages, as well as bottlenecks of metagenomics in insect intestine. The future research direction of insect microbial population is also forecasted.

Abstract:Insects are the most diverse and abundant group of animals in nature. They are highly adaptive and play important roles in various ecological environments. As a special microbial niche, the intestinal tracts of insects offer habitats for diverse symbiotic microorganisms, many of which are different from those originated from the other environments. Studies based on pure cultures show that the symbiotic microbes are associated with insect nutrition, development and immunity, etc. Therefore, isolation pure cultures are the basis for the discovery of new microorganisms, new genes and new functions. However, up to now, only about 1% of microorganisms in nature are cultivable. To solve this problem, microbiologists have put great efforts to develop many new culture techniques and strategies during the past two decades. With the use of these new strategies, many uncultured microbes have been successfully isolated, which greatly enriched our understanding of the physiological functions of symbiotic microorganisms. In this paper we reviewed the latest advances of the novel strategies used for the cultivation of symbiotic microorganisms in insect guts, as well as the future perspective of this field.

Abstract:[Objective] The bacteria of the genus Dysgonomonas are the second dominant microbes in the hindgut of Macrotermes barney. In the previous work, we isolated a novel bacterium from the hindgut of M. barneyi and designated it as Dysgonomonas macrotermitis. To further understand the roles of the bacteria in termite, it is necessary to obtain the genome sequence of D. macrotermitis. [Methods] The whole genome was sequenced by Illumina MiSeq. The protein sequences from the whole genome were annotated and compared with those in the Cluster of Orthologous Groups of proteins (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases by BLASTp. Several potential lignocellulose-degrading enzymes were identified. [Results] The genome sequence is composed of 4655756 bp with G+C content of 38.54%. This whole genome sequencing has been deposited in DDBJ under the accession numbers BBXL01000001 to BBXL01000078. Bioinformatic analysis shows that strain harbored genes encoding important enzymes with potential to degrade lignocellulose. Also, it had a complete cellulose degradation pathway where acetate and lactate were end-products. Genes possibly involved in nitrogen metabolism and defending against pathogens were also identified. [Conclusion] Our findings provide basis for the understanding the roles of hindgut bacteria contributing to termite host lignocellulose degradation.

Abstract:The capability to degrade lignocellulose in a variety of termite species is important for global carbon recycling on lignocellulosic biomass. This unique capability from termites relies on their special "gut digestome" such as bacterial, archaeal, yeast, or other eukaryotic symbionts. However, to date, their highly specialized gut systems of such insects are not yet fully understood regarding their unique symbiont functions and their potential values applied in biotechnology or other relevant fields, particularly for the group of various yeast symbionts. In recent years, there is a growing evidence to demonstrate the symbiotic yeast importance and their widespread distributions in various termite digestive systems, as well as their unique functions played in termite-symbiont interactions. Along with more yeast species to be identified from insect gut systems in the past two decades, their potential functions and relevant mechanisms interacted with host insects and other gut symbionts have been reported, which may be related to host nutrition, essential enzymes for biomass processing, intermediate chemical compounds, suppressing external pathogens, even colony outbreeding, etc. This review paper would mainly focus on the recent research work on yeast symbionts identified from termite gut and their potential values and functions applied in different fields.

Abstract:Bees are essential pollinators for most crops and play an invaluable role in sustaining our planet's ecosystems. In the past decades, dramatic reductions of bee colonies caused significant economic losses all through the world. Recently, it was found that social bees (genus Apis and Bombus) harbor simple and highly specific gut microbiota. Thus, there is tremendous interest in understanding the role of the gut symbionts in shaping physiology, behavior, and fitness traits of the host. Moreover, the social bee microbiota shows similarity to those of human and other animals, such as the transmission through social interactions. This review focuses on the most recent studies on the function of the bee gut microbiota in food digestion, nutrition provision, and defense against pathogens. We finally propose the opportunity of bee gut as a new model system for research on human nutrition and health.

Abstract:[Objective] Diamondback moth (DBM) Plutella xylostella (L.) is the most important pest of cruciferous crops worldwide. The purpose of this study was to find the effect of gut bacteria and antibiotics on the fitness of DBM. [Methods] The radish DBM strain and the germ-free artificial diet DBM strain were reared under antibiotic, and then the effect of gut bacteria and antibiotics on the fitness of DBM was evaluated. [Results] The antibiotic-treatment on the radish DBM strain has reduced hosts' fitness, reflected as retarded development, reduced weights, declined pupation rates, descended fecundity and shorted adult life-span. The antibiotic-treatment on the germ-free artificial diet DBM strain decreased pupation rate and fecundity. [Conclusion] Negative effects on the host fitness after antibiotic treatment was partly caused by the toxic effect of antibiotic and partly by the deficiency of gut bacteria. The gut bacteria may play a promote role in the fitness of DBM.

Abstract:In the long-term evolution process, insects have formed a unique intestinal defense system. The combination of physical barrier and the immune system resists invasive microbes. Alike most metazoans, the guts of insects are in permanent contact with the microbial realm that includes beneficial symbionts, food-borne microbes and life-threatening pathogens. Thus, gut epithelium can tolerate a certain amount of commensal microbes proliferation for the beneficial gut-microbe interactions, accompanied by the proficient elimination of detrimental microbes. Based on the function of Duox-ROS system and immune deficiency pathway in the intestinal immune response, these immune systems are involved in the regulation of gut microbiota homeostasis. In this article, we reviewed recent advances in insect intestinal defense mechanisms, combined with the intestinal immune signaling pathways and the regulation mechanism of intestinal immune system on the gut microbiota homeostasis.

Abstract:Entomopathogens are an important factor to regulate dynamics of insect population, and widely applied for biological control of pest insects. Entomopathogens increase their fitness by modifying the host behavior; some modifications of host behavior are immune response for infection of pathogens. Behavioral fever could suppress pathogen reproduction and extend the death time of host. The changes of feeding behavior affect the fitness of both host and pathogen. Reproductive behavior changes contain the modification from the fecundity, sexual attractiveness and sex pheromones. The alterations of social behavior are effective on the fitness of social crowd and transmission of pathogens. The weakness of defensive and aggregation behavior of infected host is unbeneficial to the transmission of pathogens; but the responses of phototropism and geotropism of host manipulated by pathogen are helpful for the spread and transmission of the pathogen. It is meaningful to find new methods controlling insect pests by discovering the strategy and mechanism of the pathogen regulating host behaviors.

Abstract:As an important pathogenic microorganism, microsporidia are widely found in Lepidopteran insects. Microsporidia diseases not only affect the natural balance of wild insect populations, but also are detrimental to the economic and resource insects such as Bombyx mori and Antheraea pernyi. The molecular biology of microsporidia is relatively less studied and the microsporidian spore wall is fairly rigid. These disadvantages make the study of microsporidia more difficult. With the rapid development of the sequencing technique and the preparation method of nucleinic acid, protein and other biomacromolecules, various microsporidia researches based on Omicsare now reported, which have significantly contributed to this field. Our review focouses on interactions between microsporidian parasites and their Lepidopteran hosts, and recent progress in microsporidia genome, transcriptome and proteome studies. The further research of insect microsporidia will provide new insights on the biocontrol of lepidopteran pests and improve the diagnosis, prevention and treatment of the microsporidia diseases of economic insects as well.

Abstract:[Objective] In this study, pure culture of A. apis was sequenced using sRNA-seq technology, followed by prediction, identification and analysis of A. apis microRNAs. The microRNAs-mRNAs regulation network was further constructed. [Methods] Illumina Hiseq Xten platform was used to sequence mycelium and spores of A. apis, and corresponding softwares were used to predict and analyze A. apis microRNAs, some of which were identified via Stem-loop PCR. Cytoskype software was used to construct A. apis microRNAs-mRNAs regulation network. [Results] A total of 48268696 clean reads were obtained, and 118 miRNAs of A. apis were predicted, whose length was distributed between 18 nt and 25 nt. The preference of the first base of miRNAs with different length was obviously various. Stem-loop PCR result showed target fragments with expected sizes were amplified from 10 microRNAs, implying most of the predicted microRNAs' true existence. In total, 6529 target genes of A. apis microRNAs were predicted, and among them 5725 could be annotated in Nr, Swissprot, KOG, GO and KEGG databases. Further investigation demonstrated 24 target genes were annotated in MAPK signaling pathway. Cytoskype software analysis suggested complicated regulation networks exist between microRNAs and mRNAs in A. apis, and majority of miRNAs inside the networks bind to several mRNAs. [Conclusion] Our findings enrich the understanding of A. apis microRNAs, provide beneficial supplement for basic biology information of A. apis, and lay some foundation for illustrating the molecular mechanism regulating the pathogenesis of this widespread fungal pathogen.

Abstract:Insect-microbe symbiosis is a common type of interaction in nature. Insects are the most diverse and abundant group of species with a wide range of distribution. The evolutionary success of insects and their diversification into a wide range of ecological niches are partly due to the beneficial interaction with their associated microbiome. With the development and application of omics, numbers of symbionts have been discovered and novel symbiotic relationships were revealed. Symbionts play important roles on insect hosts in many ways, including provision of nutrients, production of bioactive components, modulation of host immune hemeostasis, protection from predators and pathogens. Therefore, symbionts serve as guardian of the insect health and adaptation Considering the important relationship of insect symbionts and hosts, insect symbionts have become promising in the development of novel tools for the biological control of insect pests, and blocking the transmission of insect-borne diseases. In this paper, we provide an overview on diversity of insect symbionts, the latest advance in the understanding of biological functions of insect symbionts, interactions between insect hosts and symbionts, and the novel strategies for the control of insect pest and vetor-borne diseases. Finally, we will discuss the directions for future study.

Abstract:[Objective] The overuse of antibiotics as veterinary feed additives is contributing to a significant reservoir of antibiotic resistance in livestock manure. A housefly larvae (Musca domestica) vermireactor has been increasingly adopted for swine manure value-added bioconversion and pollution control. In order to investigate its efficiency on attenuations of antibiotic and the associated resistome during manure vermicomposting, we implemented dynamic sampling during a typical cycle (6 days). [Methods] High-capacity qPCR, liquid chromatography-electrospray ionization tandem mass spectrometry, the isotope-labeled internal standard method and Illumina Hiseq sequencer were used to explore the effectiveness of antibiotic degradation and microbial mechanisms on dynamics of the associated resistome of full-scale larvae manure vermicomposting. [Results] Nine antibiotics (tetracycline, oxytetracycline, chlortetracycline, doxycycline, sulfadiazine, norfloxacin, ofloxacin, ciprofloxacin and enrofloxacin) were dramatically removed. The cumulative removal of these tested antibiotics reached 34.3%-58.1%, along with the daily reduction percentages ranging from 7.8% to 57.4%. In total, 113 of 158 antibiotic resistance genes (ARGs) were significantly attenuated (by 79.3%), while 23 were significantly enriched (3.48-fold) following vermicomposting. The manure-borne bacterial community showed a decrease in the relative abundance of Bacteroidetes, and an increase in Proteobacteria, specifically Ignatzschineria, following gut transit, while ARG attenuation was significantly correlated with changes in microbial community structure. Bacteria correlated with attenuated ARGs mainly belonged to order Clostridiales and Bacteroidales. Enriched ARGs, were mostly correlated with family Alcaligenaceae,[Weeksellaceae] and order Bacillales. [Conclusion] Housefly larvae vermicomposting is an efficient way to attenuate antibiotics and ARGs in swine manure within the 6-day treatment.

Abstract:[Objective] Aimed at studying co-conversion of chicken manure by black soldier fly larvae (BSFL) with non-associated microorganism, we evaluated the influence of larval non-associated microorganism on this conversion. [Methods] Bacteria were determined by plating serial dilutions of chicken manure and pig manure composting on LB agar plates. Each isolated strain was inoculated into sterile chicken manure and converted with BSFL. The conversion effect and the influence to BSFL were evaluated. Bacteria that efficiently promoted the conversion of chicken manure were selected and mixed in different proportions. Different bacteria mixtures were inoculated into fresh chicken manure with BSFL to analyze the efficacy of the mixed inoculation on manure conversion. [Results] Compared with the control, strain R-07, R-09, F-03 and F-06 significantly promoted the growth of BSFL and degradation of chicken manure. Conversion rate of the group inoculated with these four strains increased by 27.21%, 15.00%, 9.93% and 16.29%, respectively. Manure degradation rate increased by 17.94%, 10.42%, 7.84% and 9.27%, respectively. When the proportion of inoculated mixture was R-07:R-09:F-03:F-06=4:1:1:1, the co-conversion efficacy was the best. Compared with the control, the survival rate of BSFL increased by 10.25%, the BSFL weight increased by 28.41%, the conversion rate increased by 30.46%, and the manure degradation rate increased by 7.69%. [Conclusion] Chicken manure co-conversion by BSFL and selected non-associated microorganism could obviously enhance the efficacy of larval conversion. These results will help improve the BSFL conversion system and develop new-type co-conversion of livestock and poultry manure more efficiently.

Abstract:It is a common phenomenon of the symbiosis between microorganisms and insects. There are many different kinds of insects on Earth, and the insect symbionts are also very diverse. In this paper, we summarize and analyze 177 secondary metabolites originated from different insects that have been reported from 2008. The results show that, 61.6% of the compounds produced by insect symbionts are new metabolites, in which the alkaloids are the most abundant. About 75% compounds with unprecedented structure derived from fungi, whereas those from bacteria account for about 25%; the quinones and polyketides are the main structure type accounting for about 23.2% of the compounds produced by insect symbionts; about 47.5% of which displayed significant bioactivities such as antitumor, antimicrobial, herbicidal, antioxidant activity, etc. The main biological type is antibacterial and antitumor properties, in the meantime, the alkaloids possess the widest range of biological activity among all compounds. The results elucidate that the compounds produced by insect symbionts are an important source of leading compounds and have diverse biological types. Based on the structure classification of natural products as the entry points, combined with the sources and bioactivities, the paper aimed to provide important information for fully exerting the insect symbionts' secondary metabolites.

Abstract:[Objective] We identified fungus BYSTW3, from Odontotermes formosanus, and studied its active secondary metabolites. [Methods] BYSTW3 was identified by morphological observation and ITS (Internal Transcribed Spacer) sequence analysis. The antibacterial and antifungal activities of crude extracts were tested by filter paper method and growth rate method respectively. The crude extracts were separated and purified by a variety of chromatographic column separation methods, and the structures of the compounds were analyzed with a variety of spectral data. [Results] Strain BYSTW3 was identified as a potential new species of Pleosporales sp. The crude extract of BYSTW3 inhibited radical growth of Valsa mali and Fusarium oxysporum f. sp. mornordicae with the inhibition rates of 54.5% and 53.4% at the concentration of 100 μg/mL. Bioactivity-guided fractionation lead to the isolation of three fungal metabolites 1−3, including physcion (1), FK-17-p2a (2) and citrinin (3). Both compounds 1 and 3 were firstly isolated from the fungus of Pleosporales sp.. At the concentration of 30 μg/disc, compound 3 showed potent antibacterial activity against Staphyloccocus aureus, Bacillus subtilis and Escherichia coli with the mean halo diameter of 23.0 mm, 24.2 mm and 20.7 mm, respectively. [Conclusion] BYSTW3 is a potential new strain with good prospects as a new antimicrobial agents from microbial resources.