D3023: Evaluating microbial interactions that determine microbiome composition using a gnotobiotic cockroach model (Periplaneta americana)

The gut microbiome provides a variety of benefits to the host including fermentation of indigestible food, synthesis of nutrients, and proper development of gut tissues.  Observational and experimental studies have linked distinct gut microbial community compositions to host health under a wide variety of conditions.  However, the microbial interactions that drive composition are difficult to test and obscured by microbiome complexity.  Our lab has developed a gnotobiotic cockroach model (Periplaneta americana) that allows us to explore these interactions via generation and inoculation of germ-free nymphs with individual organisms as well as undefined microbial consortia.  Inoculation of germ-free nymphs with mouse fecal microbiota results in two distinct, simple communities dominated by Proteus or Klebsiella, but rarely both.  The relative abundance of one Enterococcus sequence type, Enterococcus_6, tends to be greater in Proteus dominant communities while the relative abundance of another, Enterococcus_3, tends to be greater in Klebsiella dominant communities.  A second fecal inoculation reveals a degree of community plasticity but rarely caused major changes in dominant community member composition.  This is consistent with previous studies showing high stability in cockroach gut communities and suggests of strong priority effects.  Future work will utilize co-culturing/co-inoculation and whole genome sequencing to determine the positive and negative associations between community members, the genomic functions that may contribute to these associations, and the extent to which priority effects play a role in community compositional stability.