Described are microorganisms which are, in a first aspect, able to stimulate the growth of microorganisms of the resident skin microbial flora and which do not stimulate the growth of microorganisms of the transient pathogenic micro flora. In a second aspect microorganisms are described which are able to inhibit the growth of microorganisms of the transient pathogenic skin micro flora and which do not inhibit the growth of microorganisms of the resident skin micro flora. Also described are compositions comprising such microorganisms as well as the use of such microorganisms in cosmetic, prophylactic or therapeutic applications.