Hydra and the hair follicle – An unconventional comparative biology approach to exploring the human holobiont

Abstract

The microbiome of human hair follicles (HFs) has emerged as an important player in different HF and skin pathologies, yet awaits in-depth exploration. This raises questions regarding the tightly linked interactions between host environment, nutrient dependency of host-associated microbes, microbial metabolism, microbe-microbe interactions and host immunity. The use of simple model systems facilitates addressing generally important questions and testing overarching, therapeutically relevant principles that likely transcend obvious interspecies differences. Here, we evaluate the potential of the freshwater polyp Hydra, to dissect fundamental principles of microbiome regulation by the host, that is the human HF. In particular, we focus on therapeutically targetable host-microbiome interactions, such as nutrient dependency, microbial interactions and host defence. Offering a new lens into the study of HFmicrobiota interactions, we argue that general principles of how Hydra manages its microbiota can inform the development of novel, microbiome-targeting therapeutic interventions in human skin disease.

Beyond Lynn Margulis’ green hydra

“…The simple architecture of the hydra body, the limited number of different bacterial symbionts, and the experimental accessibility of both host tissue and colonizing microbes have made hydra an excellent model organism for studying host-microbe interactions (Klimovich and Bosch 2018;McFall-Ngai and Bosch, 2021;Lousada et al 2022). The microbiome provides colonization resistance and thereby prevents pathobiont invasion (Bosch 2013;Fraune et al 2015;Rathje et al 2020).…”