Intracolonial differences in gut bacterial community between worker and soldier castes of Coptotermes formosanus

Abstract The establishment of symbiotic relationships with intestinal microorganisms enables termites to thrive on recalcitrant substrates such as cellulose and wood. A termite colony is composed of several different castes which have distinct feeding habits. The soldiers, for example, cannot feed by themselves and depend on workers, who feed them with digested or semi‐digested foods. To investigate the influence of feeding habits on the bacterial symbionts, a comparative study of gut bacteria between worker and soldier castes of the termite Coptotermes formosanus was conducted. The bacterial communities of both castes were investigated using denaturing gradient gel electrophoresis (DGGE) and clonal analysis of 16S ribosomal DNA (rDNA). Both methods indicated Bacteroidetes was the common predominant group; the common dominant phylotype was affiliated with a reported uncultured Bacteroidetes phylotype (BCf1–03). There were significant differences in Bacteroidetes and Spirochaetes between two castes. Compared to the gut bacteria of workers, those of soldiers were lower in abundance and diversity of Bacteroidetes and slightly higher in Spirochaetes. Two phylotypes (W8, W11) affiliated to Bacteroidetes and two (W26, W29) affiliated to Spirochaetes were exclusively found in the DGGE profile of the worker caste. Bacteroidetes are assumed to be involved in fermentation of sugars and nitrogenous compounds as well as degradation of uric acid. Spirochaetes are supposed to aid in the functions of acetogenesis and N₂‐fixation. The different feeding habits between workers and soldiers of C. formosanus may explain the observed differences in the gut bacterial community.     

Colour variation and polyethism of the soldier caste in the termite Macrotermes bellicosus

Based on abdominal colour three categories of major soldiers were found in Macrotermes bellicosus (Smeathman) (Isoptera: Termitidae). The three main colour types, yellow, red and brown are due to the colour of the defence-secretion stored in the labial gland's reservoirs. The order of these categories correlates with the uric acid titres of the whole individuals. It is concluded that colour could be used as a label for the relative age of a soldier. Age dependent polyethism was observed in soldiers: the individuals of the highest age class were the only ones leaving the nest to accompany the foraging workers, whereas all age categories were found inside the nest. After a significant loss of old individuals younger individuals show flexibility by replacing the missing outgoing nestmates. Caste regulation takes place by an increased rate of soldier development.     

Intestinal microbiota in fishes: what's known and what's not

High‐throughput sequencing approaches have enabled characterizations of the community composition of numerous gut microbial communities, which in turn has enhanced interest in their diversity and functional relationships in different groups of vertebrates. Although fishes represent the greatest taxonomic and ecological diversity of vertebrates, our understanding of their gut microbiota and its functional significance has lagged well behind that of terrestrial vertebrates. In order to highlight emerging issues, we provide an overview of research on fish gut microbiotas and the biology of their hosts. We conclude that microbial community composition must be viewed within an informed context of host ecology and physiology, and that this is of particular importance with respect to research planning and sampling design.     

Presumptive horizontal symbiont transmission in the fungus-growing termite Macrotermes natalensis

All colonies of the fungus-growing termite Macrotermes natalensis studied so far are associated with a single genetically variable lineage of Termitomyces symbionts. Such limited genetic variation of symbionts and the absence of sexual fruiting bodies (mushrooms) on M. natalensis mounds would be compatible with clonal vertical transmission, as is known to occur in Macrotermes bellicosus. We investigated this hypothesis by analysing DNA sequence polymorphisms as codominant SNP markers of four single-copy gene fragments of Termitomyces isolates from 31 colonies of M. natalensis. A signature of free recombination was found, indicative of frequent sexual horizontal transmission. First, all 31 strains had unique multilocus genotypes. Second, SNP markers (n = 55) were largely in Hardy-Weinberg equilibrium (90.9%) and almost all possible pairs of SNPs between genetically unlinked loci were in linkage equilibrium (96.7%). Finally, extensive intragenic recombination was found, especially in the EF1alpha fragment. Substantial genetic variation and a freely recombining population structure can only be explained by frequent horizontal and sexual transmission of Termitomyces. The apparent variation in symbiont transmission mode among Macrotermes species implies that vertical symbiont transmission can evolve rapidly. The unexpected finding of horizontal transmission makes the apparent absence of Termitomyces mushrooms on M. natalensis mounds puzzling. To our knowledge, this is the first detailed study of the genetic population structure of a single lineage of Termitomyces.     

Effects of ultra-strong static magnetic field on the gut microbiota of humans and mice

To explore the effect of ultra-strong static magnetic field on gut microbiota, 16 T static magnetic field was used to study the changes in the structure and composition of human and mouse gut microbiota in this environment. In the mouse gut microbiota, at the genus level, the magnetic field significantly decreased the relative abundances of Escherichia-Shigella, Lactobacillus, Enterococcus, Burkholderia-Caballeronia-Paraburkholderia, Parasutterella, and Ralstonia and significantly increased those of Parabacteroides, Alloprevotella, Alistipes, Odoribacter, Bacteroides, Mucispirillum, Sutterella, and Prevotellaceae_UCG-001. Similarly, at the genus level, the relative abundances of Bacteroides, Parabacteroides, Romboutsia, and Streptococcus significantly decreased in the human gut microbiota. Contrary to the changing trend of the abundance in the mouse gut, the abundances of Bacteroides and Parabacteroides in the human gut were significantly reduced under magnetic field. The BugBase phenotypic prediction analysis showed that the relative abundances of five phenotypes, including anaerobism, mobile elements, potential pathogenicity, stress-tolerant, and biofilm formation, changed significantly in the mouse gut microbiota, while the relative abundances of two phenotypes, including Gram-positive and Gram-negative phenotypes, changed significantly in the human gut microbiota. The 16 T magnetic field could differently affect the composition, structure, and phenotypes of gut microbiota in human and mice, suggesting the importance of model selection in studying the biological effects of magnetic field.     

Spatial distribution of bacterial phylotypes in the gut of the termite Reticulitermes speratus and the bacterial community colonizing the gut epithelium

The bacterial community colonizing the gut wall of the termite Reticulitermes speratus was characterized without cultivation. Analysis of 16S rRNA genes after fractionation of the gut revealed that the bacterial composition on the gut wall was diverse and significantly different from that able to move unconfined in the gut fluid or physically associated with the gut protists. Actinobacteria, Firmicutes and Bacteroidetes were dominant on the gut wall, but Spirochaetes and the Termite group 1 phylum, abundant in the gut lumen, were relatively rare. A sequence-specific probe enabled the in situ detection of a rod-shaped Actinobacteria member, abundantly colonizing the gut paunch epithelium.     

Associations of physical activity with gut microbiota in pre-adolescent children

[Purpose] To determine whether physical activity (PA), primarily the recommended 60 minutes of moderate-to-vigorous PA, is associated with gut bacterial microbiota in 10-year-old children.[Methods] The Block Physical Activity Screener, which provides minutes/day PA variables, was used to determine whether the child met the PA recommendations. 16S rRNA sequencing was performed on stool samples from the children to profile the composition of their gut bacterial microbiota. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac) relationships were assessed using PERMANOVA. Taxon relative abundance differentials were determined using DESeq2.[Results] The analytic sample included 321 children with both PA and 16S rRNA sequencing data (mean age [SD] =10.2 [0.8] years; 54.2% male; 62.9% African American), where 189 (58.9%) met the PA recommendations. After adjusting for covariates, meeting the PA recommendations as well as minutes/day PA variables were not significantly associated with gut richness, evenness, or diversity (p ≥ 0.19). However, meeting the PA recommendations (weighted UniFrac R² = 0.014, p = 0.001) was significantly associated with distinct gut bacterial composition. These compositional differences were partly characterized by increased abundance of Megamonas and Anaerovorax as well as specific Christensenellaceae_R-7_group taxa in children with higher PA.[Conclusion] Children who met the recommendations of PA had altered gut microbiota compositions. Whether this translates to a reduced risk of obesity or associated metabolic diseases is still unclear.     

Phylogenetic Analysis of the Gut Bacterial Microflora of the Fungus-Growing Termite Odontotermes formosanus

We constructed a bacterial 16S rRNA gene clone library from the gut microbial community of O. formosanus and phylogenetically analyzed it in order to contribute to the evolutional study of digestive symbiosis and method development for termite control. After screening by restriction fragment length polymorphism (RFLP) analysis, 56 out of 280 clones with unique RFLP patterns were sequenced and phylogenetically analyzed. The representative phylotypes were affiliated to four phylogenetic groups, Firmicutes, the Bacteroidetes/Chlorobi group, Proteobacteria, and Actinobacteria of the domain Bacteira. No one clone affiliated with the phylum Spirochaetes was identified, in contrast to the case of wood-feeding termites. The phylogenetic analysis revealed that nearly half of the representative clones (25 phylotypes) formed monophyletic clusters with clones obtained from other termite species, especially with the sequences retrieved from fungus-growing termites. These results indicate that the presence of termite-specific bacterial lineages implies a coevolutional relationship of gut microbes and host termites.     

Diversity of fungal isolates from fungus-growing termite Macrotermes barneyi and characterization of bioactive compound from Xylaria escharoidea

Owing to their potential applications,as well as their structural diversity,the discovery of novel secondary metabolites from insect-associated fungi has been of interest to researchers in recent years.The aim of this study was therefore to estimate the diversity of fungi associated with fungus-growing termites and bioprospecting these for potential secondary metabolites.In total,18 fungal species were isolated and described from the gut and comb of Macrotermes barneyi based on 18S ribosomal DNA gene sequence analysis.Antimicrobial activity assays were carried out on all the known fungi,and nine isolates were recorded as active against pathogenic fungi.Xylaria escharoidea,the best performing isolate,was grown at laboratory scale and 4,8-dihydroxy-3,4-dihydronaphthalen-l(2H)was isolated and characterized.The minimum inhibitory concentration of this isolated compound against tested pathogenic organisms was found to be 6.25 fig.In addition,molecular docking studies have revealed that 4,8-dihydroxy-3,4-dihydronaphthalen-l(2H)is a prominent antibacterial agent with a marked interaction with key residues on protein A(agrAc)that regulates the accessory gene.The findings of this study support the drug discovery of antimicrobial properties in insect-associated fungi,which may lead to novel secondary metabolites.     

Seasonal variation in structure and function of gut microbiota in Pomacea canaliculata

Gut microbiota is associated with host health and its environmental adaption, influenced by seasonal variation. Pomacea canaliculata is one of the world''s 100 worst invasive alien species. Here, we used high‐throughput sequencing of the 16S rRNA gene to analyze the seasonal variation of gut microbiota of P. canaliculata. The results suggested that the predominant gut microbial phyla of P. canaliculata included Firmicutes and Proteobacteria, which helped digest plant food and accumulate energy. The gut microbiota of P. canaliculata in summer group showed the highest diversity, whereas the winter group possessed the lowest, probably due to the shortage of food resources of P. canaliculata in winter. Principal coordinate analysis analysis based on unweighted unifrac and weighted unifrac indicated that the composition of gut microbiota of P. canaliculata significantly varied across seasons. Bacteroidetes tended to be enriched in summer by linear discriminant analysis effect size analysis. Actinobacteria and Cyanobacteria were extremely abundant in autumn, while Fusobacteria and Cetobacterium enriched in winter. In conclusion, the structure of the gut microbiota of P. canaliculata was significantly different among seasons, which was beneficial to the environment adaptation and the digestion and metabolism of food during different periods.     

Intranuclear verrucomicrobial symbionts and evidence of lateral gene transfer to the host protist in the termite gut

In 1944, Harold Kirby described microorganisms living within nuclei of the protists Trichonympha in guts of termites; however, their taxonomic assignment remains to be accomplished. Here, we identified intranuclear symbionts of Trichonympha agilis in the gut of the termite Reticulitermes speratus. We isolated single nuclei of T. agilis, performed whole-genome amplification, and obtained bacterial 16S rRNA genes by PCR. Unexpectedly, however, all of the analyzed clones were from pseudogenes of 16S rRNA with large deletions and numerous sequence variations even within a single-nucleus sample. Authentic 16S rRNA gene sequences were finally recovered by digesting the nuclear DNA; these pseudogenes were present on the host Trichonympha genome. The authentic sequences represented two distinct bacterial species belonging to the phylum Verrucomicrobia, and the pseudogenes have originated from each of the two species. Fluorescence in situ hybridization confirmed that both species are specifically localized, and occasionally co-localized, within nuclei of T. agilis. Transmission electron microscopy revealed that they are distorted cocci with characteristic electron-dense and lucent regions, which resemble the intranuclear symbionts illustrated by Kirby. For these symbionts, we propose a novel genus and species, ‘Candidatus Nucleococcus trichonymphae'' and ‘Candidatus Nucleococcus kirbyi''. These formed a termite-specific cluster with database sequences, other members of which were also detected within nuclei of various gut protists, including both parabasalids and oxymonads. We suggest that this group is widely distributed as intranuclear symbionts of diverse protists in termite guts and that they might have affected the evolution of the host genome through lateral gene transfer.     

慢性乙型肝炎患者肠道菌群与肝脏生化指标的相关性

乙型肝炎病毒感染引起的慢性乙型肝炎(Chronic hepatitis B,CHB)是一种全球性流行疾病,严重时可引起肝功能衰竭,甚至发展成肝硬化和肝癌.也已发现CHB的发生和发展与肠道菌群的组成和结构的变化密切相关.为进一步探究肠道菌群结构与肝脏生化指标之间的联系,文中随机纳入14名CHB患者和11名健康对照者(Co...     

Diet strongly influences the gut microbiota of surgeonfishes

Intestinal tracts are among the most densely populated microbial ecosystems. Gut microbiota and their influence on the host have been well characterized in terrestrial vertebrates but much less so in fish. This is especially true for coral reef fishes, which are among the most abundant groups of vertebrates on earth. Surgeonfishes (family: Acanthuridae) are part of a large and diverse family of reef fish that display a wide range of feeding behaviours, which in turn has a strong impact on the reef ecology. Here, we studied the composition of the gut microbiota of nine surgeonfish and three nonsurgeonfish species from the Red Sea. High‐throughput pyrosequencing results showed that members of the phylum Firmicutes, especially of the genus Epulopiscium, were dominant in the gut microbiota of seven surgeonfishes. Even so, there were large inter‐ and intraspecies differences in the diversity of surgeonfish microbiota. Replicates of the same host species shared only a small number of operational taxonomic units (OTUs), although these accounted for most of the sequences. There was a statistically significant correlation between the phylogeny of the host and their gut microbiota, but the two were not completely congruent. Notably, the gut microbiota of three nonsurgeonfish species clustered with some surgeonfish species. The microbiota of the macro‐ and microalgavores was distinct, while the microbiota of the others (carnivores, omnivores and detritivores) seemed to be transient and dynamic. Despite some anomalies, both host phylogeny and diet were important drivers for the intestinal microbial community structure of surgeonfishes from the Red Sea.     

Identifying the core microbial community in the gut of fungus‐growing termites

Gut microbes play a crucial role in decomposing lignocellulose to fuel termite societies, with protists in the lower termites and prokaryotes in the higher termites providing these services. However, a single basal subfamily of the higher termites, the Macrotermitinae, also domesticated a plant biomass‐degrading fungus (Termitomyces), and how this symbiont acquisition has affected the fungus‐growing termite gut microbiota has remained unclear. The objective of our study was to compare the intestinal bacterial communities of five genera (nine species) of fungus‐growing termites to establish whether or not an ancestral core microbiota has been maintained and characterizes extant lineages. Using 454‐pyrosequencing of the 16S rRNA gene, we show that gut communities have representatives of 26 bacterial phyla and are dominated by Firmicutes, Bacteroidetes, Spirochaetes, Proteobacteria and Synergistetes. A set of 42 genus‐level taxa was present in all termite species and accounted for 56–68% of the species‐specific reads. Gut communities of termites from the same genus were more similar than distantly related species, suggesting that phylogenetic ancestry matters, possibly in connection with specific termite genus‐level ecological niches. Finally, we show that gut communities of fungus‐growing termites are similar to cockroaches, both at the bacterial phylum level and in a comparison of the core Macrotermitinae taxa abundances with representative cockroach, lower termite and higher nonfungus‐growing termites. These results suggest that the obligate association with Termitomyces has forced the bacterial gut communities of the fungus‐growing termites towards a relatively uniform composition with higher similarity to their omnivorous relatives than to more closely related termites.     

Bacterial microbiota associated with ants of the genus Tetraponera

Tropical arboreal ants mainly feed as 'secondary herbivores', relying mostly on nitrogen-poor homopteran exudates as food. It has been speculated that this nitrogen-limitation of their diet may be overcome by nutritional upgrading with the help of symbiotic bacteria. We examined the bacterial diversity associated with several representatives of three species groups of the arboreal ant genus Tetraponera based on genes encoding 16S rRNA, citrate synthase and a structural protein of the dinitrogenase complex ( nifH ). The bacterial microflora showed group-specificity, suggesting long-term association between ants and bacteria. In all specimens of four species of the nigra group, we detected bacteria closely related to Bartonella (order Rhizobiales). Ants of the allaborans group harboured bacteria belonging to the enterobacteria. In Tetraponera pilosa of the third species group, we found the enterobacterium Pantoea agglomerans . In spite of the different phylogenetic affiliation of the bacteria identified in the three species groups, the presence of nifH in most species suggests a role in nitrogen metabolism of the bacterial microbiota. We also detected a high infection rate with the intracellular bacterium Wolbachia in all Tetraponera species groups. Besides the widespread bacteria found in Tetraponera , we discovered a diverse group of bacteria represented by single sequences. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90 , 399–412.     

不同身体质量指数人群肠道菌群结构及共存网络解析

[背景] 人体能量稳态失衡表现为体重过轻、超重和肥胖,肠道菌群与人体能量稳态的维持有关,但不同身体质量指数（Body Mass Index,BMI）人群的肠道菌群特征仍需进一步探究。[目的] 基于美国肠道计划公开数据库,解析4类BMI人群肠道菌群的特征,并探究4类BMI人群肠道菌群共存网络特征及差异,为基于肠道菌群来干预肥胖及体重过轻等不健康状态提供新的理论依据。[方法] 从美国肠道计划数据集中筛选具有BMI信息的肠道菌群样本,并根据世界卫生组织规定的BMI划分标准将筛选后的样本分为4类：体重过轻（BMI<18.5 kg/m²）,正常体重（18.5 kg/m²2）,超重（25 kg/m²2）,肥胖（BMI>30 kg/m²）;通过计算和比较肠道菌群的α多样性和β多样性探究4类BMI人群肠道菌群的整体结构特征及差异;通过多元线性回归模型对不同BMI分类与肠道菌群进行相关性分析,并且将地域、年龄、性别因素作为混杂因素加入到模型中进行校正;采用SparCC分别计算4类BMI人群肠道菌群中菌属相关性,并分别构建肠道菌群共存网络。[结果] 经过Wilcoxon秩和检验,发现体重过轻、超重、肥胖人群的肠道菌群α多样性都显著低于正常体重人群;β多样性分析结果表明4类BMI人群肠道菌群的整体结构存在显著差异;4类BMI人群肠道中厚壁菌门（Firmicutes）和拟杆菌门（Bacteroidetes）的相对含量无显著差异;通过MaAsLin分析,并且将地域、年龄、性别因素作为混杂因素加入到模型中进行校正,共得到49个与BMI类型显著相关的物种;4类BMI人群肠道菌群共存网络的拓扑结构具有一定差异,体重过轻和正常体重人群肠道菌群共存网络的复杂度较高,超重和肥胖人群肠道菌群共存网络的复杂度较低。[结论] 4类BMI人群肠道菌群的多样性、整体结构和共存网络间均存在差异。     

孕晚期肠道菌群与孕妇血糖血脂的临床相关性

[背景]孕期体重增长不当与孕妇血糖血脂水平紊乱密切相关,而血糖血脂水平与母胎代谢性疾病的发生密切相关.肠道菌群协调肠道细胞吸收营养物质,可能与母婴糖脂代谢疾病的发生具有密切关系.[目的]观察孕期增重不同的孕妇肠道菌群生物多样性、丰富度与功能间差异,探讨孕晚期肠道菌群与孕妇血糖血脂的相关性.[方法]收集34例孕晚期孕妇粪...     

用于蜜蜂和熊蜂肠道微生物分类的细菌16S rRNA数据库优化

蜜蜂和熊蜂是重要的传粉昆虫, 对农业生产及生态平衡的维持具有重要作用。近年来, 研究发现蜜蜂及熊蜂肠道内含有大量微生物, 其组成简单、特异。正常的肠道微生物群落对蜜蜂的生长、激素调节、致病菌抵抗等具有重要作用。随着高通量测序的发展, 研究者们也可快速获得传粉蜂肠道微生物组成, 这给生物多样性和物种保护及蜂类健康等的研究带来了便捷。但是由于蜜蜂和熊蜂肠道微生物群落均由特殊菌种组成, 目前的细菌16S rRNA数据库无法对其进行准确的分类, 并且部分东方蜜蜂(Apis cerana)特有的肠道微生物菌种缺乏16S rRNA序列信息。本文从来源于5个不同省份的东方蜜蜂肠道中分离得到在东方蜜蜂中普遍含有的Apibacter菌属纯菌, 获取其全长16S rRNA序列, 并对目前蜜蜂和熊蜂肠道的5个核心菌种的分类进行了综述, 对其分类和命名进行了修正。根据蜜蜂肠道微生物的明确分类, 在目前常用的SILVA细菌分类数据库基础之上对其进行了命名及分类优化, 并加入东方蜜蜂中普遍含有的Apibacter序列, 从而获得了优化数据库Bee Gut Microbiota-Database (BGM-Db)。通过1组东方蜜峰及1组西方蜜蜂(Apis mellifera)的肠道菌群高通量测序结果, 分析不同数据库的表现, 我们发现相比于SILVA和Ribosomal Database Project (RDP), BGM-Db对蜜蜂肠道16S rRNA高通量测序短序列实现了菌种级别的分类, 分辨率更高。