Diet, gut bacteria and the metabolism of hissing cockroaches

The gut microbiome plays a role in shaping the metabolic phenotype of animals.  While the core microbiota remains stable in adulthood, certain parts of the microbiome can be influenced by environmental stressors like diet.  Research has revealed the relationship between diet, microbiome and metabolism in many organisms. However, there is much to learn about these relationships in invertebrates and insects.  In this study, the effects of diet on the metabolic rate and microbiota of the hissing cockroach, Gromphadorhina portentosa, were measured after cockroaches were placed under different diet treatments. The microbiota of forty male cockroaches were normalized by placing them on a control diet for two weeks prior to experimentation. Ten roaches were then placed in one of three different diet treatments: high carbohydrate, high lipid or high protein diet. Metabolic rates for individual cockroaches were recorded every two weeks for a total of 8 weeks. Fecal samples were collected at the beginning and end of the experimental period to determine changes in the gut microbiota due to diet.  We saw that metabolic rates were significantly higher in roaches placed in the high protein diet, in comparison to the rest of the diet treatments. Furthermore, we saw a difference in the populations of bacteria in cockroaches placed under different diet treatments. Ultimately, we see that there is an intricate relationship between diet, metabolism and gut microbiota in this insect.