Cockroaches as a model for understanding gut microbiome stability and dynamics in omnivores

The gut microbiome plays a key role in shaping host health and nutrition, serving (among many other functions) as a flexible accessory genome that allows access to dietary resources that the host cannot access alone. However, maintenance of gut homeostasis is dependent on a complex web of host:microbe and microbe:microbe interactions, and omnivorous animals in particular face a key challenge in maintaining their gut microbiome despite a highly diverse and changing diet. Cockroaches represent an exciting new model for understanding how diet shapes host:gut microbiome interactions. We have found that the omnivorous cockroach Periplaneta americana exhibits remarkable stability in its gut microbiota, even when challenged with highly biased dietary compositions. We are exploring the underpinnings of this stability via genomic, metagenomic, and metatransriptomic analyses. When fed whole food diets with highly biased compositions, P. americana gut microbiome composition and microbial transcriptional activity shows remarkable stability. Individual microbes showed limited change in relative abundance, but did exhibit some alteration of transcriptional activity to respond to differences in substrate availability. In contrast, we were able to induce shifts in gut microbiota composition through synthetic diets dominated by specific high molecular weight polysaccharides, with the largest difference observed between xylan-based and microcrystalline-based diets. These shifts were not replicated in cockroaches fed xylose and glucose monomers. Together, these findings are shedding new light on host and microbial interactions underlying gut microbiome stability and resilience in the presence of complex and changing omnivorous diets.