Development of the cockroach as a human gut microbiome model

The human gut microbiome is a noteworthy area of interest due to the potential beneficial functions involving human health, fitness, and immunity. Cockroaches are omnivorous insects with a diverse microbial population that could be suggested as an alternate model for investigating the effect of the microbiome on the human gut. The aim of this project was to explore whether broader knowledge and understanding of the human gut microbiota could be achieved by studying cockroaches as a model. The microbiota of a total of 693 publicly accessible samples (345 humans, 86 mice, and 262 cockroaches) were analysed. Firmicutes, Bacteroidota, and Proteobacteria are predominant phyla across all samples, which led us to pursue further analyses of the cockroach microbiome, as a potential model. Colonization of a commensal Escherichia coli (E. coli), and response to antibiotics were studied in the adult female American cockroaches (Periplaneta americana). Kanamycin treatment on the cockroach gut microbiome showed similarities with the control group but lower community abundance. In contrast, bacterial communities fed ampicillin exhibited significant shifts and were less abundant than those fed kanamycin or control. In the following experiment with E. coli inoculation, the findings demonstrated that despite our application of antibiotics for ten days prior to the introduction of E. coli, the invading bacterium could not be established in the cockroach's digestive organ. By treating cockroaches with increased concentrations of 0.1% and 0.2% sulfate, the impact of a sulfate diet was investigated. According to the study, there were no significant variations in the abundance of Desulfovibrio and bacterial communities between the diet groups. Additionally, the dissimilatory sulfate reduction genes, including dsrA and aprA genes, did not significantly alter expression between treatments, but they did appear to be expressed slightly higher than the control.