Microbial colonization promotes model cockroach gut tissue growth and development

The gut microbiota confers resistance against Salmonella Typhimurium in cockroaches by modulating innate immunity

Cockroaches exhibit unexplained intra- and interpopulation variation in susceptibility to Salmonella enterica serovar Typhimurium (S. Typhimurium) infection. Here, we show that the gut microbiota has a protective effect against colonization by ingested S. Typhimurium in cockroaches. We further examine two potential mechanisms for this effect, showing that commensal bacteria present in the gut do not compete with S. Typhimurium during growth in cockroach feces, but rather prime expression of host antimicrobial peptide genes that suppress S. Typhimurium infection. Lastly, we determine that neither absolute abundance of the microbiota nor its overall diversity is linked to infection susceptibility. Instead, we identify several minority bacterial taxa that exhibit interindividual variation in abundance as key indicators of infection susceptibility among genetically similar individuals. These findings illuminate the potential of cockroaches as an invertebrate model for interspecies microbial interactions and provide insight into vector-borne Salmonella transmission, suggesting that the microbiota of cockroaches could be targeted to reduce pathogen transmission.

Inter-kingdom communication and the sympoietic way of life

Organisms are now seen as holobionts, consortia of several species that interact metabolically such that they sustain and scaffold each other's existence and propagation. Sympoiesis, the development of the symbiotic relationships that form holobionts, is critical for our understanding the origins and maintenance of biodiversity. Rather than being the read-out of a single genome, development has been found to be sympoietic, based on multigenomic interactions between zygote-derived cells and symbiotic microbes. These symbiotic and sympoietic interactions are predicated on the ability of cells from different kingdoms of life (e.g., bacteria and animals) to communicate with one another and to have their chemical signals interpreted in a manner that facilitates development. Sympoiesis, the creation of an entity by the interactions of other entities, is commonly seen in embryogenesis (e.g., the creation of lenses and retinas through the interaction of brain and epidermal compartments). In holobiont sympoiesis, interactions between partners of different domains of life interact to form organs and biofilms, wherein each of these domains acts as the environment for the other. If evolution is forged by changes in development, and if symbionts are routinely involved in our development, then changes in sympoiesis can constitute an important factor in evolution.

Crosstalk between the microbiota and insect postembryonic development

Insect sequential development evolves from a simple molt towards complete metamorphosis. Like any multicellular host, insects interact with a complex microbiota. In this review, factors driving the microbiota dynamics were pointed out along their development. Special focus was put on tissue renewal, shift in insect ecology, and microbial interactions. Conversely, how the microbiota modulates its host development through nutrient acquisition, hormonal control, and cellular or tissue differentiation was exemplified. Such modifications might have long-term carry-over effects on insect physiology. Finally, remarkable microbe-driven control of insect behaviors along their life cycle was highlighted. Increasing knowledge of those interactions might offer new insights on how insects respond to their environment as well as perspectives on pest- or vector-control strategies.

Cockroaches: a potential source of novel bioactive molecule(s) for the benefit of human health

Cockroaches are one of the hardiest insects that have survived on this planet for millions of years. They thrive in unhygienic environments, are able to survive without food for up to 30 days, without air for around 45 min and being submerged under water for 30 min. Cockroaches are omnivorous and feed on a variety of foods, including cellulose and plastic, to name a few. It is intriguing that cockroaches are able to endure and flourish under conditions that are harmful to Homo sapiens. Given the importance of the gut microbiome on its' host physiology, we postulate that the cockroach gut microbiome and/or its metabolites, may be contributing to their "hardiness", which should be utilized for the discovery of biologically active molecules for the benefit of human health. Herein, we discuss the biology, diet/habitat of cockroaches, composition of gut microbiome, cellular senescence, and resistance to infectious diseases and cancer. Furthermore, current knowledge of the genome and epigenome of these remarkable species is considered. Being one of the most successful and diverse insects, as well as their extensive use in traditional and Chinese medicine, the lysates/extracts and gut microbial metabolites of cockroaches may offer a worthy resource for novel bioactive molecule(s) of therapeutic potential for the benefit of human health and may be potentially used as probiotics.

Genetic drift and host-adaptive features likely underlie cladogenesis of insect-associated Lachnospiraceae

Phylogenetic and functional group analysis of the genomes of anaerobic bacteria isolated from Periplaneta americana digestive tracts suggest that they represent novel Lachnospiraceae genera. PAL113 and PAL227 isolate genomes encoded short-chain fatty acid biosynthetic pathways and plant fiber and chitin catabolism and other carbohydrate utilization genes common in related Lachnospiraceae species, yet the presence of operons containing flagellar assembly pathways were among several distinguishing features. In general, PAL113 and PAL227 isolates encode an array of gene products that would enable them to thrive in the insect gut environment and potentially play a role in host diet processing. We hypothesize that cladogenesis of these isolates could be due to their oxygen sensitivity, reliance upon the host for dispersal and genetic drift and not necessarily as a result of an ongoing mutualism.

Differing Dietary Nutrients and Diet-Associated Bacteria Has Limited Impact on Spider Gut Microbiota Composition

Spiders are a key predator of insects across ecosystems and possess great potential as pest control agents. Unfortunately, it is difficult to artificially cultivate multiple generations of most spider species. Since gut bacterial flora has been shown to significantly alter nutrient availability, it is plausible that the spiders' microbial community plays a key role in their unsuccessful breeding. However, both the gut microbial composition and its influencing factors in many spiders remain a mystery. In this study, the gut microbiota of Campanicola campanulata, specialists who prey on ants and are widely distributed across China, was characterized. After, the impact of diet and diet-associated bacteria on gut bacterial composition was evaluated. First, two species of prey ants (Lasius niger and Tetramorium caespitum) were collected from different locations and fed to C. campanulata. For each diet, we then profiled the nutritional content of the ants, as well as the bacterial communities of both the ants and spiders. Results showed that the protein and carbohydrate content varied between the two prey ant species. We isolated 682 genera from 356 families in the ants (dominant genera including Pseudomonas, Acinetobacter, Paraburkholderia, Staphylococcus, and Novosphingobium), and 456 genera from 258 families in the spiders (dominated by Pseudomonas). However, no significant differences were found in the gut microbiota of spiders that were fed the differing ants. Together, these results indicate that nutritional variation and diet-associated bacterial differences have a limited impact on the microbial composition of spider guts, highlighting that spiders may have a potentially stable internal environment and lay the foundation for future investigations into gut microbiota.