Understanding the development of the gut microbiome in pigs: an overview

Living organisms continuously and intimately interact with commensal microbial communities referred to as microbiota and microbiomes. These complex ecosystems provide their hosts with vital services. The gut microbiome develops and diversifies after birth in pigs, as in all mammals. The diversification dynamics follows the host development early in life, reaches an initial level of richness and stabilization before 60 days of age, and continues to mature but at a much lower rate while ageing and adapting to environmental changes. There is a wide variation in microbiome composition at individual and group levels, due to a combination of many factors including host genetics, environmental factors, feed and feed additives, and farm practices. Although the gut microbiome displays region-specific composition along the digestive tract, with likely sequential, complementary biological functionalities, the fecal microbiome is often considered as a good surrogate and provides many of the associations identified with host phenotypes.

Overexpression of an Osa-miR162a Derivative in Rice Confers Cross-Kingdom RNA Interference-Mediated Brown Planthopper Resistance without Perturbing Host Development

Rice is a main food crop for more than half of the global population. The brown planthopper (BPH, Nilaparvata lugens) is one of the most destructive insect pests of rice. Currently, repeated overuse of chemical insecticides represents a common practice in agriculture for BPH control, which can induce insect tolerance and provoke environmental concerns. This situation calls for innovative and widely applicable strategies for rice protection against BPH. Here we report that the rice osa-miR162a can mediate cross-kingdom RNA interference (RNAi) by targeting the NlTOR (Target of rapamycin) gene of BPH that regulates the reproduction process. Through artificial diet or injection, osa-miR162a mimics repressed the NlTOR expression and impaired the oviposition of BPH adults. Consistently, overproduced osa-miR162a in transgenic rice plants compromised the fecundity of BPH adults fed with these plants, but meanwhile perturbed root and grain development. To circumvent this issue, we generated osa-miR162a-m1, a sequence-optimized osa-miR162a, by decreasing base complementarity to rice endogenous target genes while increasing base complementarity to NlTOR. Transgenic overexpression of osa-miR162a-m1 conferred rice resistance to BPH without detectable developmental penalty. This work reveals the first cross-kingdom RNAi mechanism in rice-BPH interactions and inspires a potentially useful approach for improving rice resistance to BPH. We also introduce an effective strategy to uncouple unwanted host developmental perturbation from desirable cross-kingdom RNAi benefits for overexpressed plant miRNAs.

Microbiota-Dependent and -Independent Production of l- Dopa in the Gut of Daphnia magna

Neurotransmitters are commonly implicated in host-microbiome communication, yet the molecular mechanisms of this communication remain largely elusive. We present novel evidence linking the gut microbiome to host development and growth via neurotransmitter l- Dopa in Daphnia , the established model species in ecology and evolution.

Molting Alters the Microbiome, Immune Response, and Digestive Enzyme Activity in Mud Crab ( Scylla paramamosain )

Molting is crucial for crustaceans. In mud crab, its exoskeleton is renewed periodically during molting, and this process is an ideal model to study the effects of host development on its microbiota.

Global composition of the bacteriophage community in honeybees

The microbial communities in animal digestive systems are critical to host development and health. These assemblages of primarily viruses, bacteria, and fungi stimulate the immune system during development, synthesize important chemical compounds like hormones, aid in digestion, competitively exclude pathogens, etc. The bacteriophages in animal microbiomes are harder to characterize than the bacterial or fungal components of the microbiome and thus we know comparatively little about the temporal and spatial dynamics of bacteriophage communities in animal digestive systems. Recently, the bacteriophages of the honeybee gut were characterized in two European bee populations. Most of the bacteriophages described in these two reports were novel, encoded many metabolic genes in their genomes, and had a community structure that suggests coevolution with their bacterial hosts. To describe the conservation of bacteriophages in bees and begin to understand their role in the bee microbiome, we sequenced the virome of Apis mellifera from Austin, Texas and compared bacteriophage composition between three locations around the world. We found that most bacteriophages from Austin are novel, sharing no sequence similarity to anything in public repositories. However, many bacteriophages are shared among the three bee viromes, indicating specialization of bacteriophages in the bee gut. Our study along with the two previous bee virome studies shows that the bee gut bacteriophage community is simple compared to that of many animals, consisting of several hundred types of bacteriophages that primarily infect four of the dominant bacterial phylotypes in the bee gut.

Two TOBAMOVIRUS MULTIPLICATION 2A homologs in tobacco determine asymptomatic response to tobacco mosaic virus

The most common response of a host to pathogens is arguably the asymptomatic response. However, the genetic and molecular mechanisms responsible for asymptomatic responses to pathogens are poorly understood. Here we report on the genetic cloning of two genes controlling the asymptomatic response to Tobacco mosaic virus (TMV) in cultivated tobacco (Nicotiana tabacum). These two genes are homologous to tobamovirus multiplication 2A (TOM2A) from Arabidopsis, which was shown to be critical for the accumulation of TMV. Expression analysis indicates that the TOM2A genes might play fundamental roles in plant development or in responses to stresses. Consistent with this hypothesis, a null allele of the TOM2A ortholog in tomato (Solanum lycopersicum) led to the development of bent branches and a high tolerance to both TMV and ToMV. However, the TOM2A ortholog in Nicotiana glauca did not account for the asymptomatic response to TMV in N. glauca. We showed that TOM2A family is plant-specific and originated from Chlorophyte, and the biological functions of TOM2A orthologs to promote TMV accumulation are highly conserved in the plant kingdom—in both TMV host and non-host species. In addition, we showed that the interaction between tobacco TOM1 and TOM2A orthologs in plant species is conserved, suggesting a conserved nature of TOM1-TOM2A module in promoting TMV multiplication in plants. The tradeoff between host development, the resistance of hosts to pathogens and their influence on gene evolution are discussed. Our results shed light on mechanisms that contribute to asymptomatic responses to viruses in plants and provide approaches for developing TMV/ToMV resistant crops.

In their sister’s footsteps: Taxonomic divergence obscures substantial functional overlap among the metabolically diverse symbiotic gut communities of adult and larval turtle ants

Gut bacterial symbionts can support animal nutrition by facilitating digestion and providing valuable metabolites. While the composition of gut symbiont communities shifts with host development in holometabolous insects, changes in symbiotic roles between immature and adult stages are not well documented, especially in ants. Here, we explored the metabolic capabilities of microbiomes sampled from herbivorous turtle ant (Cephalotes sp.) larvae and adult workers through genomic and metagenomic screenings and targeted in vitro metabolic assays. We reveal that larval guts harbor bacterial symbionts from the Enterobacteriales, Lactobacillales and Rhizobiales orders, with impressive metabolic capabilities, including catabolism of plant and fungal recalcitrant fibers common in turtle ant diets, and energy-generating fermentation. Additionally, several members of the specialized turtle ant adult gut microbiome, sampled downstream of an anatomical barrier that dams large food particles, show a conserved potential to depolymerize many dietary fibers and other carbohydrates. Symbionts from both life stages have the genomic capacity to recycle nitrogen, synthesize amino acids and B-vitamins, and perform several key aspects of sulfur metabolism. We also document, for the first time in ants, an adult-associated Campylobacterales symbiont with an apparent capacity to anaerobically oxidize sulfide, reduce nitrate, and fix carbon dioxide. With help of their gut symbionts, including several bacteria likely acquired from the environment, turtle ant larvae appear as an important component of turtle ant colony digestion and nutrition. In addition, the conserved nature of the digestive, energy-generating, and nutritive capacities among adult-enriched symbionts suggests that nutritional ecology of turtle ant colonies has long been shaped by specialized, behaviorally-transferred gut bacteria with over 46 million years of residency.