Skin Microbial Endocrinology: When host neurohormones control bacterial homeostasis

Skin harbours the second microbiote of the human body and is the largest neuroendocrine organ. As skin neurohormes diffuse in sweet and epidermis, skin bacteria are exposed to these host factors. Since the pioneering works of M. Lyte who established the basis of Microbial Endocrinology it is known that bacteria can sense a multitude of hormones. The mechanism of action of skin neuropeptides, such as Substance P and CGRP, was investigated on representative cutaneous bacteria leading to the identification of moonlighting (multifunctional) proteins acting as bacterial sensors and the demonstration that host factors are key regulators of skin microbiote homeostasis.