Influence of dietary aconitine and nicotine on the gut microbiota of two lepidopteran herbivores

The gut microbiota plays an important role in pheromone production, pesticide degradation, vitamin synthesis, and pathogen prevention in the host animal. Therefore, similar to gut morphology and digestive enzyme activity, the gut microbiota may also get altered under plant defensive compound-induced stress. To test this hypothesis, Dendrolimus superans larvae were fed either aconitine- or nicotine-treated fresh leaves of Larix gmelinii, and Lymantria dispar larvae were fed either aconitine- or nicotine-treated fresh leaves of Salix matsudana. Subsequently, the larvae were sampled 72hr after diet administration and DNA extracted from larval enteric canals were employed for gut microbial 16S ribosomal RNA gene sequencing (338 F and 806 R primers). The sequence analysis revealed that dietary nicotine and aconitine influenced the dominant bacteria in the larval gut and determined their abundance. Moreover, the effect of either aconitine or nicotine on D. superans and L. dispar larvae had a greater dependence on insect species than on secondary plant metabolites. These findings further our understanding of the interaction between herbivores and host plants and the coevolution of plants and insects.     

Endophyte roles in nutrient acquisition,root system architecture development and oxidative stress tolerance

Plants associate with communities of microbes (bacteria and fungi) that play critical roles in plant development, nutrient acquisition and oxidative stress tolerance. The major share of plant microbiota is endophytes which inhabit plant tissues and help them in various capacities. In this article, we have reviewed what is presently known with regard to how endophytic microbes interact with plants to modulate root development, branching, root hair formation and their implications in overall plant development. Endophytic microbes link the interactions of plants, rhizospheric microbes and soil to promote nutrient solubilization and further vectoring these nutrients to the plant roots making the soil-plant-microbe continuum. Further, plant roots internalize microbes and oxidatively extract nutrients from microbes in the rhizophagy cycle. The oxidative interactions between endophytes and plants result in the acquisition of nutrients by plants and are also instrumental in oxidative stress tolerance of plants. It is evident that plants actively cultivate microbes internally, on surfaces and in soils to acquire nutrients, modulate development and improve health. Understanding this continuum could be of greater significance in connecting endophytes with the hidden half of the plant that can also be harnessed in applied terms to enhance nutrient acquisition through the development of favourable root system architecture for sustainable production under stress conditions.     

Characterization of the gut microbiota of migratory passerines during stopover along the northern coast of the Gulf of Mexico

Although the gut microbiota is known to provide many beneficial functions to animal hosts, such as aiding in digestion, fat metabolism, and immune function, relatively little is known about the gut microbiota of passerines. Gut microbes may have both beneficial and detrimental impacts on the fitness of migratory passerines; however physiological and morphological changes associated with prolonged migratory flight may cause disruptions of the stable microbiota and potentially a loss of function. Fecal samples were collected from Swainson's thrushes Catharus ustulatus and gray catbirds Dumetella carolinensis immediately after crossing the Gulf of Mexico during spring migration and before crossing during fall, and microbiota communities were analyzed using next‐generation sequencing. Microbiota communities were generally dominated by Firmicutes and Proteobacteria, with potential pathogens as well as potentially beneficial bacteria identified in all birds. Energetic condition of migrants was not significantly related to overall microbiota community structure though it cannot be conclusively stated that migratory flight does not impact the microbiota. Spring and fall migrants showed clear differences in microbiota communities, indicating that environmental factors influence the gut microbiota of these species more than host genetics.     

Are you what you eat? A highly transient and prey‐influenced gut microbiome in the grey house spider Badumna longinqua

Stable core microbial communities have been described in numerous animal species and are commonly associated with fitness benefits for their hosts. Recent research, however, highlights examples of species whose microbiota are transient and environmentally derived. Here, we test the effect of diet on gut microbial community assembly in the spider Badumna longinqua. Using 16S rRNA gene amplicon sequencing combined with quantitative PCR, we analyzed diversity and abundance of the spider's gut microbes, and simultaneously characterized its prey communities using nuclear rRNA markers. We found a clear correlation between community similarity of the spider's insect prey and gut microbial DNA, suggesting that microbiome assembly is primarily diet‐driven. This assumption is supported by a feeding experiment, in which two types of prey—crickets and fruit flies—both substantially altered microbial diversity and community similarity between spiders, but did so in different ways. After cricket consumption, numerous cricket‐derived microbes appeared in the spider's gut, resulting in a rapid homogenization of microbial communities among spiders. In contrast, few prey‐associated bacteria were detected after consumption of fruit flies; instead, the microbial community was remodelled by environmentally sourced microbes, or abundance shifts of rare taxa in the spider's gut. The reshaping of the microbiota by both prey taxa mimicked a stable core microbiome in the spiders for several weeks post feeding. Our results suggest that the spider's gut microbiome undergoes pronounced temporal fluctuations, that its assembly is dictated by the consumed prey, and that different prey taxa may remodel the microbiota in drastically different ways.     

Kinship,inbreeding and fine‐scale spatial structure influence gut microbiota in a hindgut‐fermenting tortoise

Herbivorous vertebrates rely on complex communities of mutualistic gut bacteria to facilitate the digestion of celluloses and hemicelluloses. Gut microbes are often convergent based on diet and gut morphology across a phylogenetically diverse group of mammals. However, little is known about microbial communities of herbivorous hindgut‐fermenting reptiles. Here, we investigate how factors at the individual level might constrain the composition of gut microbes in an obligate herbivorous reptile. Using multiplexed 16S rRNA gene sequencing, we characterized the faecal microbial community of a population of gopher tortoises (Gopherus polyphemus) and examined how age, genetic diversity, spatial structure and kinship influence differences among individuals. We recovered phylotypes associated with known cellulolytic function, including candidate phylum Termite Group 3, suggesting their importance for gopher tortoise digestion. Although host genetic structure did not explain variation in microbial composition and community structure, we found that fine‐scale spatial structure, inbreeding, degree of relatedness and possibly ontogeny shaped patterns of diversity in faecal microbiomes of gopher tortoises. Our findings corroborate widespread convergence of faecal‐associated microbes based on gut morphology and diet and demonstrate the role of spatial and demographic structure in driving differentiation of gut microbiota in natural populations.     

肠道菌群多糖利用及代谢

宿主与肠道共生菌之间存在一种互利共生的关系.肠道共生菌可以代谢宿主自身不能消化的多糖.进入肠道内的多糖是影响肠道共生菌生理状态和组成的重要因素,这些多糖主要来自饮食和宿主的粘膜分泌物.人类饮食中含有几十种不同的膳食多糖,其中大多数不能被人类基因组中编码的酶降解,并进入大肠,供肠道共生菌利用.肠道共生菌将这些不易消化的多...     

Gut microbes of mammalian herbivores facilitate intake of plant toxins

The foraging ecology of mammalian herbivores is strongly shaped by plant secondary compounds (PSCs) that defend plants against herbivory. Conventional wisdom holds that gut microbes facilitate the ingestion of toxic plants; however, this notion lacks empirical evidence. We investigated the gut microbiota of desert woodrats (Neotoma lepida), some populations of which specialise on highly toxic creosote bush (Larrea tridentata). Here, we demonstrate that gut microbes are crucial in allowing herbivores to consume toxic plants. Creosote toxins altered the population structure of the gut microbiome to facilitate an increase in abundance of genes that metabolise toxic compounds. In addition, woodrats were unable to consume creosote toxins after the microbiota was disrupted with antibiotics. Last, ingestion of toxins by naïve hosts was increased through microbial transplants from experienced donors. These results demonstrate that microbes can enhance the ability of hosts to consume PSCs and therefore expand the dietary niche breadth of mammalian herbivores.     

Herbicide residues in soil decrease microbe-mediated plant protection

• The residues of glyphosate are found to remain in soils longer than previously reported, affecting rhizosphere microbes. This may adversely affect crop and other non-target plants because the plant's resilience and resistance largely rely on plant-associated microbes. Ubiquitous glyphosate residues in soil and how they impact mutualistic microbes inhabiting the aboveground plant parts are largely unexplored.
• We studied the effects of herbicide residues in soil on Epichloë sp., which are common endophytic symbionts inhabiting aerial parts of cool-season grasses. In this symbiosis, the obligate symbiont subsists entirely on its host plant, and in exchange, it provides alkaloids conferring resistance to herbivores for the host grass that invests little in its own chemical defence.
• We first show decreased growth of Epichloë endophytes in vitro when directly exposed to two concentrations of glyphosate or glyphosate-based herbicides. Second, we provide evidence for a reduction of Epichloë-derived, insect-toxic loline alkaloids in endophyte-symbiotic meadow fescue (F. pratensis) plants growing in soil with a glyphosate history. Plants were grown for 2 years in an open field site, and natural herbivore infestation was correlated with the glyphosate-mediated reduction of loline alkaloid concentrations.
• Our findings indicate that herbicides residing in soil not only affect rhizosphere microbiota but also aerial plant endophyte functionality, which emphasizes the destructive effects of glyphosate on plant symbiotic microbes, here with cascading effects on plant–pest insect interactions.

     

The effect of rhizosphere microbes outweighs host plant genetics in reducing insect herbivory

Rhizosphere microbes affect plant performance, including plant resistance against insect herbivores; yet, a direct comparison of the relative influence of rhizosphere microbes versus plant genetics on herbivory levels and on metabolites related to defence is lacking. In the crucifer Boechera stricta, we tested the effects of rhizosphere microbes and plant population on herbivore resistance, the primary metabolome, and select secondary metabolites. Plant populations differed significantly in the concentrations of six glucosinolates (GLS), secondary metabolites known to provide herbivore resistance in the Brassicaceae. The population with lower GLS levels experienced ~60% higher levels of aphid (Myzus persicae) attack; no association was observed between GLS and damage by a second herbivore, flea beetles (Phyllotreta cruciferae). Rhizosphere microbiome (disrupted vs. intact native microbiome) had no effect on plant GLS concentrations. However, aphid number and flea beetle damage were respectively about three‐ and seven‐fold higher among plants grown in the disrupted versus intact native microbiome treatment. These differences may be attributable to shifts in primary metabolic pathways previously implicated in host defence against herbivores, including increases in pentose and glucoronate interconversion among plants grown with an intact microbiome. Furthermore, native microbiomes with distinct community composition (as estimated from 16s rRNA amplicon sequencing) differed two‐fold in their effect on host plant susceptibility to aphids. The findings suggest that rhizosphere microbes, including distinct native microbiomes, can play a greater role than population in defence against insect herbivores, and act through metabolic mechanisms independent of population.     

Influence of dietary fat on intestinal microbes,inflammation, barrier function and metabolic outcomes

Recent studies using germ-free, gnotobiotic microbial transplantation/conventionalization or antibiotic treatment in rodent models have highlighted the critical role of intestinal microbes on gut health and metabolic functions of the host. Genetic and environmental factors influence the abundance and type of mutualistic vs. pathogenic bacteria, each of which has preferred substrates for growth and unique products of fermentation. Whereas some fermentation products or metabolites promote gut function and health, others impair gut function, leading to compromised nutrient digestion and barrier function that adversely impact the host. Such products may also influence food intake, energy harvest and expenditure, and insulin action, thereby influencing adiposity and related metabolic outcomes. Diet composition influences gut microbiota and subsequent fermentation products that impact the host, as demonstrated by prebiotic studies using oligosaccharides or other types of indigestible fiber. Recent studies also show that dietary lipids affect specific populations of gut microbes and their metabolic end products. This review will focus on studies examining the influence of dietary fat amount and type on the gut microbiome, intestinal health and positive and negative metabolic consequences. The protective role of omega-3-rich fatty acids on intestinal inflammation will also be examined.     

Gut microbiota promotes production of aromatic metabolites through degradation of barley leaf fiber

Barley leaf (BL) contains abundant plant fibers, which are important substrates for the metabolism and degradation by the gut microbiota. Here we show that mice fed a diet supplemented with BL exhibited altered gut bacterial composition characterized by the enrichment of fiber-degrading bacteria Lachnospiraceae and Prevotella. Gut microbiota-mediated BL degradation promoted butyrate and propionate production. Metabolomic analysis showed increased aromatic metabolites such as ferulic acid, 3-phenylpropanoic acid, 3-hydroxyphenylacetic acid and 3-hydroxyphenylpropionic acid in feces of mice fed with BL. Finally, antibiotic treatment and anaerobic fermentation confirmed the obligate role of gut microbiota in the production of aromatic metabolites during BL degradation. Together, these findings provide insights into a gut microbiota-mediated degradation process of BL fiber components, which results in the production of microbial-associated metabolites that may exert potential active effects on host physiology.     

The gut bacterial community affects immunity but not metabolism in a specialist herbivorous butterfly

1. Plant tissues often lack essential nutritive elements and may contain a range of secondary toxic compounds. As nutritional imbalance in food intake may affect the performances of herbivores, the latter have evolved a variety of physiological mechanisms to cope with the challenges of digesting their plant‐based diet. Some of these strategies involve living in association with symbiotic microbes that promote the digestion and detoxification of plant compounds or supply their host with essential nutrients missing from the plant diet. In Lepidoptera, a growing body of evidence has, however, recently challenged the idea that herbivores are nutritionally dependent on their gut microbial community. It is suggested that many of the herbivorous Lepidopteran species may not host a resident microbial community, but rather a transient one, acquired from their environment and diet. Studies directly testing these hypotheses are however scarce and come from an even more limited number of species.
2. By coupling comparative metabarcoding, immune gene expression, and metabolomics analyses with experimental manipulation of the gut microbial community of prediapause larvae of the Glanville fritillary butterfly (Melitaea cinxia, L.), we tested whether the gut microbial community supports early larval growth and survival, or modulates metabolism or immunity during early stages of development.
3. We successfully altered this microbiota through antibiotic treatments and consecutively restored it through fecal transplants from conspecifics. Our study suggests that although the microbiota is involved in the up‐regulation of an antimicrobial peptide, it did not affect the life history traits or the metabolism of early instars larvae.
4. This study confirms the poor impact of the microbiota on diverse life history traits of yet another Lepidoptera species. However, it also suggests that potential eco‐evolutionary host‐symbiont strategies that take place in the gut of herbivorous butterfly hosts might have been disregarded, particularly how the microbiota may affect the host immune system homeostasis.

     

Kin recognition in Drosophila: the importance of ecology and gut microbiota

The animal gut commonly contains a large reservoir of symbiotic microbes. Although these microbes have obvious functions in digestion and immune defence, gut microbes can also affect behaviour. Here, we explore whether gut microbiota has a role in kin recognition. We assessed whether relatedness, familiarity and food eaten during development altered copulation investment in three species of Drosophila with diverse ecologies. We found that a monandrous species exhibited true kin recognition, whereas familiarity determined kin recognition in a species living in dense aggregations. Finally, in a food generalist species, food eaten during development masked kin recognition. The effect of food type on copulation duration, in addition to the removal of this effect via antibiotic treatment, suggests the influence of bacteria associated with the gut. Our results provide the first evidence that varied ecologically determined mechanisms of kin recognition occur in Drosophila, and that gut bacteria are likely to have a key role in these mechanisms.     

The presence,nature, and role of gut microflora in aquatic invertebrates: A synthesis

This review of the literature concerns the gut microbiota of aquatic invertebrates and highlights the questions and processes that merit attention if an understanding of the role of gut microbes in the physiology of host invertebrates and nutrient dynamics of aquatic systems is to be gained. A substantial number of studies report the presence of gut microbes in aquatic invertebrates. Crustacea, Mollusca, and Echinodermata have received the most attention, with few studies involving other invertebrate groups. Different types of associations (e.g., ingestion, contribution of exoenzymes, incubation, parasitism) are reported to occur between gut microbes and aquatic invertebrates, and it is clear that gut bacterial communities cannot be treated as single functional entities, but that individual populations require examination. In addition, gut microbes may be either ingested transients or residents, the presence of which have different implications for the invertebrate. The most commonly reported genera of gut bacteria are Vibrio, Pseudomonas, Flavobacterium, Micrococcus, and Aeromonas. Quite a number of authors report the physiological properties of gut microbes (including enzyme activities and attributes such as nitrogen fixation), while less attention has been given to consideration of the colonization sites within the digestive tract, the density and turnover of gut bacteria, and the factors affecting the presence and nature of gut microflora. In addition, although a few studies have demonstrated a positive relationship between invertebrates and their gut microbiota, particularly with regard to nutrient gain by the invertebrate, very little conclusive evidence exists as to the role of bacteria in the physiology of host invertebrates. This has resulted from a lack of process-oriented studies. The findings for aquatic gut microbes are compared to those of gut bacteria associated with terrestrial invertebrates, where gut microbes contribute significantly to nutrient gain by the host in some environments.     

Two cultivated legume plants reveal the enrichment process of the microbiome in the rhizocompartments

The microbiomes of rhizocompartments (nodule endophytes, root endophytes, rhizosphere and root zone) in soya bean and alfalfa were analysed using high‐throughput sequencing to investigate the interactions among legume species, microorganisms and soil types. A clear hierarchical filtration of microbiota by plants was observed in the four rhizocompartments – the nodule endosphere, root endosphere, rhizosphere and root zone – as demonstrated by significant variations in the composition of the microbial community in the different compartments. The rhizosphere and root zone microbial communities were largely influenced by soil type, and the nodule and root endophytes were primarily determined by plant species. Diverse microbes inhabited the root nodule endosphere, and the corresponding dominant symbiotic rhizobia belonged to Ensifer for alfalfa and Ensifer–Bradyrhizobium for soya bean. The nonsymbiotic nodule endophytes were mainly Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. The variation in root microbial communities was also affected by the plant growth stage. In summary, this study demonstrated that the enrichment process of nodule endophytes follows a hierarchical filtration and that the bacterial communities in nodule endophytes vary according to the plant species.     

空间环境下肠道菌群失调的研究进展

空间环境中的特殊因素会导致航天员肠道菌群及其代谢产物的失调，对机体会产生系统性的生理影响。本文综述了近年来太空飞行/模拟空间环境对肠道菌群及其代谢产物影响的研究进展。太空飞行/模拟空间环境（space flight/simulated space environment，SF/SPE）可导致侵袭性致病菌的增多及有益菌的减少，肠道炎症加剧与通透性增加，也会引起菌群的有益代谢物减少或有害代谢物增加，进而导致机体内代谢的紊乱，或可诱发其他系统的损伤，从而不利于航天员的健康与工作效率。总结太空飞行/模拟空间环境对肠道菌群产生的影响，可为该领域的后续研究与航天员的在轨健康防护提供科学依据。     

Alzheimer’s disease and gut microbiota

Alzheimer’s disease (AD) is a most common neurodegenerative disorder, which associates with impaired cognition. Gut microbiota can modulate host brain function and behavior via microbiota-gut-brain axis, including cognitive behavior. Germ-free animals, antibiotics, probiotics intervention and diet can induce alterations of gut microbiota and gut physiology and also host cognitive behavior, increasing or decreasing risks of AD. The increased permeability of intestine and blood-brain barrier induced by gut microbiota disturbance will increase the incidence of neurodegeneration disorders. Gut microbial metabolites and their effects on host neurochemical changes may increase or decrease the risk of AD. Pathogenic microbes infection will also increase the risk of AD, and meanwhile, the onset of AD support the “hygiene hypothesis”. All the results suggest that AD may begin in the gut, and is closely related to the imbalance of gut microbiota. Modulation of gut microbiota through personalized diet or beneficial microbiota intervention will probably become a new treatment for AD.     

基于代谢组学的植物多酚及其肠道健康效应研究进展

综述了植物多酚的分类和来源、在代谢组学技术的驱动下,新型多酚物质的鉴定、控制植物多酚合成途径的关键因子以及多酚的功能特性的研究进展,阐述了植物多酚在肠道中的代谢以及其作为“益生元”调节肠道微生态并影响机体健康的重要功能。目前的研究表明不同植物多酚在调节肠道微生态方面存在差异,多数有促进肠道有益菌作用,并通过与肠道微生物“互作”发挥促进健康效应。总之,植物多酚作为“益生元”影响人体健康可能离不开肠道微生物的介导。各个植物多酚的益生功能也需要进一步阐析,在此过程中需要考虑宿主,膳食等混杂因素的综合影响,且需要拓展临床应用方面的研究。     

Microbial Community Profiling to Investigate Transmission of Bacteria Between Life Stages of the Wood-Boring Beetle, Anoplophora glabripennis

Many insects harbor specific bacteria in their digestive tract, and these gut microbiota often play important roles in digestion and nutrient provisioning. While it is common for a given insect species to harbor a representative gut microbial community as a population, how this community is acquired and maintained from generation to generation is not known for most xylophagous insects, except termites. In this study, we examined acquisition of gut microbiota by the wood-feeding beetle, Anoplophora glabripennis, by identifying and comparing microbial community members among different life stages of the insect and with microbes it encounters in the environment. Automated ribosomal intergenic spacer analysis was employed to compare bacterial communities present in the egg and larval stages of A. glabripennis as well as with microbes found in the oviposition site and the surrounding woody tissue. Multivariate analyses were used to identify relationships between sample type and specific bacterial types (operational taxonomic units). From this analysis, bacteria that were derived from the environment, the oviposition site, and/or the egg were identified and compared with taxa found in larvae. Results showed that while some larval microbes were derived from environmental sources, other members of the larval microbial community appear to be vertically transmitted. These findings could lead to a better understanding of which microbial species are critical for the survival of this insect and to development of techniques that could be used to alter this community to disrupt the digestive physiology of the host insect as a biological control measure.