Disturbing epithelial homeostasis in the metazoan Hydra leads to drastic changes in associated microbiota.

Microbes have profound influence on the biology of host tissue. Imbalances in host-microbe interaction underlie many human diseases. Little, however, is known about how epithelial homeostasis affects associated microbial community structure. In Hydra, the epithelium actively shapes its microbial community indicating distinct selective pressures imposed on the epithelium. Here, using a mutant strain of Hydra magnipapillata we eliminated all derivatives of the interstitial stem cell lineage while leaving both epithelial cell lineages intact. By bacterial 16S rRNA gene analysis we observed that removing gland cells and neurones from the epithelium causes significant changes in hydra's microbial community. Absence of interstitial stem cells and nematocytes had no affect on the microbiota. When compared with controls, animals lacking neurones and gland cells showed reduced abundance of beta-Proteobacteria accompanied by a significantly increased abundance of a Bacteroidetes bacterium. This previously unrecognized link between cellular tissue composition and microbiota may be applicable to understanding mechanisms controlling host-microbe interaction in other epithelial systems.