Prokaryotic taxa play keystone roles in the soil microbiome associated with woody perennial plants in the genus Buxus

The microbiome associated with ornamental plants has largely been neglected, despite its potential for impacting plant health. This work characterized the composition, diversity, and microbial co‐associations in the soil microbiome associated with species and cultivars of plant in the genus Buxus (common name boxwood), a group of woody perennial shrubs commonly used in residential landscapes and found in native ecosystems. Soil was collected from 82 individual curated boxwood accessions at the U.S. National Arboretum National Boxwood Collection. Amplicon libraries targeting archaea, bacteria, and fungi were generated and sequenced using the Illumina MiSeq platform. Identification of individual sequence variants resulted in 275 archaeal, 15,580 bacterial, and 7,525 fungal taxa. Neither spatial distance among samples nor association with different types of boxwood were significant predictors of soil microbiome composition. However, archaeal and bacterial diversity was significantly different in soil from distinct types of boxwood. Co‐association networks indicated that archaea and bacteria show greater evidence of being keystone taxa than fungi. Overall, this work demonstrates the potential for targeting specific keystone taxa to shift the soil microbiome associated with these boxwood accessions and that planting different species or cultivars in the landscape may shift the diversity of prokaryotic microorganisms.     

Age‐related changes in the marmoset gut microbiome

The gut microbiome is known to play a significant role in human health but its role in aging remains unclear. The objective of this study was to compare the gut microbiome composition between young adult and geriatric non‐human primates (marmosets) as a model of human health and disease. Stool samples were collected from geriatric (8+ years) and young adult males (2–5 years). Stool 16S ribosomal RNA V4 sequences were amplified and sequenced on the Illumina MiSeq platform. Sequences were clustered into operational taxonomic units and classified via Mothur's Bayesian classifier referenced against the Greengenes database. A total of 10 young adult and 10 geriatric marmosets were included. Geriatric marmosets had a lower mean Shannon diversity compared with young marmosets (3.15 vs. 3.46; p = 0.0191). Geriatric marmosets had a significantly higher mean abundance of Proteobacteria (0.22 vs. 0.09; p = 0.0233) and lower abundance of Firmicutes (0.15 vs. 0.19; p = 0.0032) compared with young marmosets. Geriatric marmosets had a significantly higher abundance of Succinivibrionaceae (0.16 vs. 0.01; p = 0.0191) and lower abundance of Porphyromonadaceae (0.07 vs. 0.11; p = 0.0494). In summary, geriatric marmosets had significantly altered microbiome diversity and composition compared with young adult marmosets. Further studies are needed to test microbiome‐targeted therapies to improve healthspan and lifespan.     

Dual inoculation of dark septate endophytes and Trichoderma viride drives plant performance and rhizosphere microbiome adaptations of Astragalus mongholicus to drought

Rhizosphere microbiome adapts their structural compositions to water scarcity and have the potential to mitigate drought stress of plants. To unlock this potential, it is crucial to understand community responses to drought in the interplay between soil properties, water management and exogenous microbes interference. Inoculation with dark septate endophytes (DSE) (Acrocalymma vagum, Paraboeremia putaminum) and Trichoderma viride on Astragalus mongholicus grown in the non-sterile soil was exposed to drought. Rhizosphere microbiome were assessed by Illumina MiSeq sequencing of the 16S and ITS2 rRNA genes. Inoculation positively affected plant growth depending on DSE species and water regime. Ascomycota, Proteobacteria, Actinobacteria, Chloroflexi and Firmicutes were the dominant phyla. The effects of dual inoculation on bacterial community were greater than those on fungal community, and combination of P. putaminum and T. viride exerted a stronger impact on the microbiome under drought stress. The observed changes in soil factors caused by inoculation could be explained by the variations in microbiome composition. Rhizosphere microbiome mediated by inoculation exhibited distinct preferences for various growth parameters. These findings suggest that dual inoculation of DSE and T. viride enriched beneficial microbiota, altered soil nutrient status and might contribute to enhance the cultivation of medicinal plants in dryland agriculture.     

The hemolymph of Biomphalaria snail vectors of schistosomiasis supports a diverse microbiome

The microbiome - the microorganism community that is found on or within an organism's body - is increasingly recognized to shape many aspects of its host biology and is a key determinant of health and disease. Microbiomes modulate the capacity of insect disease vectors (mosquitoes, tsetse flies, sandflies) to transmit parasites and disease. We investigate the diversity and abundance of microorganisms within the hemolymph (i.e. blood) of Biomphalaria snails, the intermediate host for Schistosoma mansoni, using Illumina MiSeq sequencing of the bacterial 16S V4 rDNA. We sampled hemolymph from five snails from six different laboratory populations of B. glabrata and one population of B. alexandrina. We observed 279.84 ± 0.79 amplicon sequence variants per snail. There were significant differences in microbiome composition at the level of individual snails, snail populations and species. Snail microbiomes were dominated by Proteobacteria and Bacteroidetes while water microbiomes from snail tank were dominated by Actinobacteria. We investigated the absolute bacterial load using qPCR: hemolymph samples contained 2784 ± 339 bacteria/μl. We speculate that the microbiome may represent a critical, but unexplored intermediary in the snail–schistosome interaction as hemolymph is in very close contact with the parasite at each step of its development.     

Interspecific comparison of the fecal microbiota structure in three Arctic migratory bird species

The gut microbiota of birds is known to be characterized for different species, although it may change with feeding items. In this study, we compared the gut microbiota of birds with different feeding behaviors in the same habitat. We collected fecal samples from three Arctic species, snow buntings Plectrophenax nivalis, sanderlings Calidris alba, and pink‐footed geese Anser brachyrhynchus that are phylogenetically quite distant in different families to evaluate effects of diet on gut microbiota. Also, we characterized the prevalence of fecal bacteria using the Illumina MiSeq platform to sequence bacterial 16S rRNA genes. Our NMDS results showed that fecal bacteria of snow buntings and sanderlings were significantly distant from those of pink‐footed geese. Although all three birds were occupied by three bacterial phyla, Proteobacteria, Firmicutes, and Bacteroidetes, dominant taxa still varied among the species. Our bacterial sequences showed that snow buntings and sanderlings were dominated by Firmicutes and Bacteroidetes, while pink‐footed geese were dominated by Proteobacteria. In addition, the bacterial diversity in snow buntings and sanderlings was significantly higher than that in pink‐footed geese. Our results suggest that insectivorous feeding diet of snow buntings and sanderlings could be responsible for the similar bacterial communities between the two species despite the distant phylogenetic relationship. The distinctive bacterial community in pink‐footed geese was discussed to be related with their herbivorous diet.     

High-throughput sequencing-based analysis of bacterial communities associated with Barbour's seahorses (Hippocampus barbouri) from Surigao del Norte,Philippines

This study identified the bacterial community composition associated with Barbour's seahorses (Hippocampus barbouri). Seahorses and samples from the surrounding environment (sediment and water) were collected from Cantiasay Island in Surigao del Norte, Philippines. Genomic DNA was isolated from these samples, and the V1–V3 region of the 16S rRNA gene was amplified and sequenced on the Illumina MiSeq platform. There were 929 803 sequence reads corresponding to 859 operational taxonomic units (OTUs), which were obtained from the six genomic libraries. The results showed that the most abundant OTUs were affiliated to the phylum Proteobacteria, particularly those belonging to the genera Shewanella, Pseudomonas, Acinetobacter and Aeromonas, which were found to be dominant in seahorse gut samples. The only exception was for the skin of male seahorses, which was dominated by members belonging to the genus Bacillus (phylum Firmicutes). These findings on bacterial community structure and composition may shed light on therapeutic claims of Barbour's seahorses and help in the conservation of this species.     

Gut microbiomes of free‐ranging and captive Namibian cheetahs: Diversity,putative functions and occurrence of potential pathogens

Although the significance of the gut microbiome for host health is well acknowledged, the impact of host traits and environmental factors on the interindividual variation of gut microbiomes of wildlife species is not well understood. Such information is essential; however, as changes in the composition of these microbial communities beyond the natural range might cause dysbiosis leading to increased susceptibility to infections. We examined the potential influence of sex, age, genetic relatedness, spatial tactics and the environment on the natural range of the gut microbiome diversity in free‐ranging Namibian cheetahs (Acinonyx jubatus). We further explored the impact of an altered diet and frequent contact with roaming dogs and cats on the occurrence of potential bacterial pathogens by comparing free‐ranging and captive individuals living under the same climatic conditions. Abundance patterns of particular bacterial genera differed between the sexes, and bacterial diversity and richness were higher in older (>3.5 years) than in younger individuals. In contrast, male spatial tactics, which probably influence host exposure to environmental bacteria, had no discernible effect on the gut microbiome. The profound resemblance of the gut microbiome of kin in contrast to nonkin suggests a predominant role of genetics in shaping bacterial community characteristics and functional similarities. We also detected various Operational Taxonomic Units (OTUs) assigned to potential pathogenic bacteria known to cause diseases in humans and wildlife species, such as Helicobacter spp., and Clostridium perfringens. Captive individuals did not differ in their microbial alpha diversity but exhibited higher abundances of OTUs related to potential pathogenic bacteria and shifts in disease‐associated functional pathways. Our study emphasizes the need to integrate ecological, genetic and pathogenic aspects to improve our comprehension of the main drivers of natural variation and shifts in gut microbial communities possibly affecting host health. This knowledge is essential for in situ and ex situ conservation management.     

Diversity of gut microbiota increases with aging and starvation in the desert locust

Here we report the effects of starvation and insect age on the diversity of gut microbiota of adult desert locusts, Schistocerca gregaria, using denaturing gradient gel electrophoretic (DGGE) analysis of bacterial 16S rRNA genes. Sequencing of excised DGGE bands revealed the presence of only one potentially novel uncultured member of the Gammaproteobacteria in the guts of fed, starved, young or old locusts. Most of the 16S rRNA gene sequences were closely related to known cultured bacterial species. DGGE profiles suggested that bacterial diversity increased with insect age and did not provide evidence for a characteristic locust gut bacterial community. Starved insects are often more prone to disease, probably because they compromise on immune defence. However, the increased diversity of Gammaproteobacteria in starved locusts shown here may improve defence against enteric threats because of the role of gut bacteria in colonization resistance.     

The development and ecology of the Japanese macaque gut microbiome from weaning to early adolescence in association with diet

Previously we have shown that the Japanese macaque gut microbiome differs not by obesity per se, but rather in association with high‐fat diet (HFD) feeding. This held true for both pregnant dams, as well as their 1‐year‐old offspring, even when weaned onto a control diet. Here we aimed to examine the stability of the gut microbiome over time and in response to maternal and postweaning HFD feeding from 6 months of age, and at 1 and 3 years of age. In both cross‐sectional and longitudinal specimens, we performed analysis of the V4 hypervariable region of the 16S rRNA gene on anus swabs collected from pregnant dams and their juveniles at age 6 months to 3 years (n = 55). Extracted microbial DNA was subjected to 16S‐amplicon‐based metagenomic sequencing on the Illumina MiSeq platform. We initially identified 272 unique bacterial genera, and multidimensional scaling revealed samples to cluster by age and diet exposures. Dirichlet multinomial mixture modeling of microbiota abundances enabled identification of two predominant enterotypes to which samples sorted, characterized primarily by Treponema abundance, or lack thereof. Approximating the time of initial weaning (6 months), the Japanese macaque offspring microbiome underwent a significant state type transition which stabilized from 1 to 3 years of age. However, we also found the low abundance Treponema enterotype to be strongly associated with HFD exposure, be it during gestation/lactation or in the postweaning interval. Examination of taxonomic co‐occurrences revealed samples within the low Treponema cluster were relatively permissive (allowing for increased interactions between microbiota) whereas samples within the high Treponema cluster were relatively exclusionary (suggesting decreased interactions amongst microbiota). Taken together, these findings suggest that Treponemes are keystone species in the developing gut microbiome of the gut, and susceptible to HFD feeding in their relative abundance.     

健康藏族与汉族大学生肠道细菌多样性研究

【目的】探究生活在相同环境下,同年龄段健康藏族人群和汉族人群肠道细菌组成的多样性特征及其可能的成因。【方法】入选同专业的20–24岁男性健康藏族学生和汉族学生各20名,同一时间段收集新鲜粪便,提取新鲜粪便细菌总DNA,通过高通量测序和生物信息学分析,结合对饮食习惯的问卷调查,研究健康藏族学生与汉族学生肠道细菌多样性与饮食习惯之间的关系。【结果】从40份样本中,测序共得到2880个OTU,alpha和beta多样性分析表明,生活在相同环境下,不同民族男性学生的肠道细菌组成有明显差异。Prevotella 9、Bacteroides和Lachnoclostridium等18个属为两民族学生共有,同时,Prevotella 9、Faecalibacterium和Succinivibrio等10个属细菌为对两民族学生肠道细菌组成差异具有显著性影响的标志性菌属。进一步聚类分析表明,所有学生样本分为ET F型、ET P型、ET F和ET B混合型3种不同肠型,随访调查结果显示不同类型分别对应以脂肪为主和以淀粉为主的不同饮食习惯。【结论】生活在相同环境下,健康藏族和汉族学生的肠道细菌组成特征及其差异可能与遗传因素及饮食习惯密切相关。     

不同生长季节黑果枸杞的根际细菌群落结构

【目的】黑果枸杞是一种耐盐植物,是我国西北干旱区盐渍土改良的优良植物物种,其根际土壤细菌群落结构在不同生长时期的变化特征尚不清楚。【方法】本研究采用Illumina MiSeq高通量测序研究了黑果枸杞3个生长阶段的根际土壤细菌群落结构的动态变化。【结果】所有样品中共获得317467条序列,对应于7028个细菌/古细菌OTUs。根际土壤细菌群落的α多样性显著高于非根际土壤。衰老期根际细菌的多样性和丰富度明显低于营养生长期和花/果期。变形菌门和酸杆菌门的相对丰度随生长时期的演变而逐渐降低,而蓝细菌门则相反。厚壁菌门的丰度在衰老期明显高于营养生长期和花/果期。优势属的组成也随生长期的演变而改变,营养生长期、花/果期、衰老期的优势属数量分别为17、16、4,且组成也具有差异。相似性分析表明营养生长期和花/果期的根际细菌群落具有很高的相似性,衰老期根际细菌群落组成与生长期和花/果期具有很高差异,然而与非根际土壤的群落结构具有较高的相似性。【结论】根际土壤细菌群落多样性和组成随生长期的改变而表现出明显的动态变异性,表明黑果枸杞生长时期对根际土壤细菌群落结构具有重要的影响。     

Diversity and composition of the bacterial community of Poyang Lake (China) as determined by 16S rRNA gene sequence analysis

Poyang Lake is the largest fresh water lake in China. In this study, the objective was to examine the diversity of bacterial community in this environment. The phylogenetic composition of bacterioplankton communities from two sites and two dates (northern and southern sub-basins in October 2006 and in May 2007, respectively) in the water column of Poyang Lake were investigated by partially sequencing cloned 16SrRNA genes. Moreover, restriction fragment length polymorphism (RFLP) was applied in the 16SrRNA gene clones. In total, four clone libraries were constructed and 347 clones were screened by RFLP, yielding 153 operational taxonomic units, which mainly belonged to the proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Verrucomicrobia and Planctomycetes. Our results showed that Beta-proteobacteria was the most significant lineage, with dominant numbers of operational taxonomic units in the northern October 2006, southern October 2006 and May 2007 libraries. The highest bacterial diversity occurred in the library from the southern sub-basin in May 2007 and the lowest in the library from the northern sub-basin in May 2007. Horizontal and temporal differences associated with the concentration of total phosphorus, water temperature and pH suggested that the trophic state and the physicochemical properties of lake play key roles in sustaining bacterial community composition structure.     

Laboratory rearing of huhu,Prionoplus reticularis (Cerambycidae): insights into the gut microbiome

We developed a laboratory rearing method for huhu grubs, Prionoplus reticularis White (Coleoptera: Cerambycidae), on defined cellulose (cotton) and lignocellulose (pine) diets. Huhu grubs were shown to both gain weight and eventually undergo metamorphosis on these diets, two indications of successful use of the substrates for healthy growth. Since insects typically rely on their gut microbiome to assist in nutrient assimilation this rearing method was used to study the gut microbiome of P. reticularis, using the frass produced as a proxy for the gut contents. In this preliminary study patterns of fungal community diversity in frass suggest that their composition is significantly influenced by diet; however, the influence of diet on bacterial community diversity was less clear. Results do demonstrate the potential of the experimental model for studying shifts in the gut microbiome induced by diet change. This approach could prove essential in identifying microorganisms, or consortia, involved in the breakdown of lignocellulose.     

Biocontrol of strawberry fruit infected by Botrytis cinerea: Effects on the microbial communities on fruit assessed by next‐generation sequencing

Fruit grey mould, caused by the fungus Botrytis cinerea, is known to be a harmful disease of strawberry at postharvest stage. However, effects of an application of biological control agents (BCAs) on strawberry fruit in terms of shift in the microbial community are still unknown. The present research aimed to investigate the effects of an application of BCAs on postharvest microbial populations present on strawberry fruits. Strawberry plants were sprayed with three kinds of BCA, RhizoVital 42 fl. (Bacillus amyloliquefaciens FZB42), Trianum‐P (Trichoderma harzianum T22) and Naturalis (Beauveria bassiana ATCC 74040), targeting Botrytis cinerea fungus. Control plots were composed of water and fungicide treatments. Microbial communities (bacteria and fungi) were analysed via next‐generation sequencing on an Illumina MiSeq. Analysis of 16S RNA and ITS rRNA sequences indicated that the BCAs application modified both bacterial and fungal community compositions and diversity. An application of two BCAs together had more effects on microbial community composition than a single application. These results suggest that BCAs can modify bacterial and fungal community composition and diversity on strawberry fruits, which may consequently improve the efficiency and establishment of these products on control of postharvest diseases of fruits, such as grey mould.     

Spatiotemporal variation of bacterial and archaeal communities in sediments of a drinking reservoir,Beijing, China

Bacterial and archaeal assemblages are one of the most important contributors to the recycling of nutrients and the decomposition of organic matter in aquatic sediments. However, their spatiotemporal variation and its driving factors remain unclear, especially for drinking reservoirs, which are strongly affected by human consumption. Using quantitative PCR and Illumina MiSeq sequencing, we investigated the bacterial and archaeal communities in the sediments of a drinking reservoir, the Miyun Reservoir, one of the most important drinking sources for Beijing City. The abundance of bacteria and archaea presented no spatiotemporal variation. With respect to community diversity, visible spatial and temporal differences were observed in archaea, whereas the bacterial community showed minor variation. The bacterial communities in the reservoir sediment mainly included Proteobacteria, Bacteroidetes, Nitrospirae, Acidobacteria, and Verrucomicrobia. The bacterial community structure showed obvious spatial variation. The composition of the bacterial operational taxonomic units (OTUs) and main phyla were dam-specific; the composition of samples in front of the dam were significantly different from the composition of the other samples. The archaeal communities were mainly represented by Woesearchaeota and Euryarchaeota. Distinctly spatial and seasonal variation was observed in the archaeal community structure. The sediment NH₄ ⁺–N, pH, and water depth were identified as the key driving factors of changes in the composition of the bacterial and archaeal communities. Water depth might have the greatest influence on the microbial community structure. The dam-specific community structure may be related to the greater water depth in front of the dam. This finding indicates that water depth might be the greatest contributor to the microbial community structure in the Miyun Reservoir.

     

An integrative bioinformatics pipeline shows that honeybee-associated microbiomes are driven primarily by pollen composition

The microbiomes associated with bee nests influence colony health through various mechanisms, although it is not yet clear how honeybee congeners differ in microbiome assembly processes, in particular the degrees to which floral visitations and the environment contribute to different aspects of diversity. We used DNA metabarcoding to sequence bacterial 16S rRNA from honey and stored pollen from nests of 4 honeybee species (Apis cerana, A. dorsata, A. florea, and A. laboriosa) sampled throughout Yunnan, China, a global biodiversity hotspot. We developed a computational pipeline integrating multiple databases for quantifying key facets of diversity, including compositional, taxonomic, phylogenetic, and functional ones. Further, we assessed candidate drivers of observed microbiome dissimilarity, particularly differences in floral visitations, habitat disturbance, and other key environmental variables. Analyses revealed that microbiome alpha diversity was broadly equivalent across the study sites and between bee species, apart from functional diversity which was very low in nests of the reclusive A. laboriosa. Turnover in microbiome composition across Yunnan was driven predominantly by pollen composition. Human disturbance negatively impacted both compositional and phylogenetic alpha diversity of nest microbiomes, but did not correlate with microbial turnover. We herein make progress in understanding microbiome diversity associated with key pollinators in a biodiversity hotspot, and provide a model for the use of a comprehensive informatics framework in assessing pattern and drivers of diversity, which enables the inclusion of explanatory variables both subtly and fundamentally different and enables elucidation of emergent or unexpected drivers.     

Routes of Acquisition of the Gut Microbiota of the Honey Bee Apis mellifera

Studies of newly emerged Apis mellifera worker bees have demonstrated that their guts are colonized by a consistent core microbiota within several days of eclosure. We conducted experiments aimed at illuminating the transmission routes and spatiotemporal colonization dynamics of this microbiota. Experimental groups of newly emerged workers were maintained in cup cages and exposed to different potential transmission sources. Colonization patterns were evaluated using quantitative real-time PCR (qPCR) to assess community sizes and using deep sequencing of 16S rRNA gene amplicons to assess community composition. In addition, we monitored the establishment of the ileum and rectum communities within workers sampled over time from natural hive conditions. The study verified that workers initially lack gut bacteria and gain large characteristic communities in the ileum and rectum within 4 to 6 days within hives. Typical communities, resembling those of workers within hives, were established in the presence of nurse workers or nurse worker fecal material, and atypical communities of noncore or highly skewed compositions were established when workers were exposed only to oral trophallaxis or hive components (comb, honey, bee bread). The core species of Gram-negative bacteria, Snodgrassella alvi, Gilliamella apicola, and Frischella perrara, were dependent on the presence of nurses or hindgut material, whereas some Gram-positive species were more often transferred through exposure to hive components. These results indicate aspects of the colony life cycle and behavior that are key to the propagation of the characteristic honey bee gut microbiota.     

Diversity and temporal dynamics of primate milk microbiomes

Milk is inhabited by a community of bacteria and is one of the first postnatal sources of microbial exposure for mammalian young. Bacteria in breast milk may enhance immune development, improve intestinal health, and stimulate the gut‐brain axis for infants. Variation in milk microbiome structure (e.g., operational taxonomic unit [OTU] diversity, community composition) may lead to different infant developmental outcomes. Milk microbiome structure may depend on evolutionary processes acting at the host species level and ecological processes occurring over lactation time, among others. We quantified milk microbiomes using 16S rRNA high‐throughput sequencing for nine primate species and for six primate mothers sampled over lactation. Our data set included humans (Homo sapiens, Philippines and USA) and eight nonhuman primate species living in captivity (bonobo [Pan paniscus], chimpanzee [Pan troglodytes], western lowland gorilla [Gorilla gorilla gorilla], Bornean orangutan [Pongo pygmaeus], Sumatran orangutan [Pongo abelii], rhesus macaque [Macaca mulatta], owl monkey [Aotus nancymaae]) and in the wild (mantled howler monkey [Alouatta palliata]). For a subset of the data, we paired microbiome data with nutrient and hormone assay results to quantify the effect of milk chemistry on milk microbiomes. We detected a core primate milk microbiome of seven bacterial OTUs indicating a robust relationship between these bacteria and primate species. Milk microbiomes differed among primate species with rhesus macaques, humans and mantled howler monkeys having notably distinct milk microbiomes. Gross energy in milk from protein and fat explained some of the variations in microbiome composition among species. Microbiome composition changed in a predictable manner for three primate mothers over lactation time, suggesting that different bacterial communities may be selected for as the infant ages. Our results contribute to understanding ecological and evolutionary relationships between bacteria and primate hosts, which can have applied benefits for humans and endangered primates in our care.     

Bacterial microbiome of Coptotermes curvignathus (Isoptera: Rhinotermitidae) reflects the coevolution of species and dietary pattern

Coptotermes curvignathus Holmgren is capable of feeding on living trees. This ability is attributed to their effective digestive system that is furnished by the termite's own cellulolytic enzymes and cooperative enzymes produced by their gut microbes. In this study, the identity of an array of diverse microbes residing in the gut of C. curvignathus was revealed by sequencing the near‐full‐length 16S rRNA genes. A total of 154 bacterial phylotypes were found. The Bacteroidetes was the most abundant phylum and accounted for about 65% of the gut microbial profile. This is followed by Firmicutes, Actinobacteria, Spirochetes, Proteobacteria, TM7, Deferribacteres, Planctomycetes, Verrucomicrobia, and Termite Group 1. Based on the phylogenetic study, this symbiosis can be a result of long coevolution of gut enterotypes with the phylogenic distribution, strong selection pressure in the gut, and other speculative pressures that determine bacterial biome to follow. The phylogenetic distribution of cloned rRNA genes in the bacterial domain that was considerably different from other termite reflects the strong selection pressures in the gut where a proportional composition of gut microbiome of C. curvignathus has established. The selection pressures could be linked to the unique diet preference of C. curvignathus that profoundly feeds on living trees. The delicate gut microbiome composition may provide available nutrients to the host as well as potential protection against opportunistic pathogen.     

Gut microbiomes of sympatric Amazonian wood‐eating catfishes (Loricariidae) reflect host identity and little role in wood digestion

Neotropical wood‐eating catfishes (family Loricariidae) can occur in diverse assemblages with multiple genera and species feeding on the same woody detritus. As such, they present an intriguing system in which to examine the influence of host species identity on the vertebrate gut microbiome as well as to determine the potential role of gut bacteria in wood digestion. We characterized the gut microbiome of two co‐occurring catfish genera and four species: Panaqolus albomaculatus, Panaqolus gnomus, Panaqolus nocturnus, and Panaque bathyphilus, as well as that of submerged wood on which they feed. The gut bacterial community did not significantly vary across three gut regions (proximal, mid, distal) for any catfish species, although interspecific variation in the gut microbiome was significant, with magnitude of interspecific difference generally reflecting host phylogenetic proximity. Further, the gut microbiome of each species was significantly different to that present on the submerged wood. Inferring the genomic potential of the gut microbiome revealed that the majority of wood digesting pathways were at best equivalent to and more often depleted or nonexistent within the catfish gut compared to the submerged wood, suggesting a minimal role for the gut microbiome in wood digestion. Rather, these fishes are more likely reliant on fiber degradation performed by microbes in the environment, with their gut microbiome determined more by host identity and phylogenetic history.