Diversification during cross-kingdom microbial experimental evolution

Abstract

Experimental evolution in a laboratory helps researchers to understand the genetic and phenotypic background of adaptation under a particular condition. Simultaneously, the simplified environment that represents certain aspects of a complex natural niche permits the dissection of relevant parameters behind the selection, including temperature, oxygen availability, nutrients, and biotic factors. The presence of other microorganisms or a host has a major influence on microbial evolution that often differs from the adaptation paths observed in response to abiotic conditions. In the current issue of the ISME Journal, Cosetta and colleagues reveal how cross-kingdom interaction representing the cheese microbiome succession promotes distinct evolution of the food- and animal-associated bacterium, Staphylococcus xylosus. The authors also identified a global regulator-dependent adaption that leads to evolved derivatives exhibiting reduced pigment production and colony morphologies in addition to altered differentiation phenotypes that potentially contribute to increased fitness.

Fig. 1. Natural succession and laboratory evolution of microbial interactions on cheese rind.

Panel A depicts the cheese rind microbiome, including the early colonizer Staphylococcus xylosus and Debaryomyces hansenii, and the late successive Brevibacterium aurantiacum and Penicillium solitum. S. xylosus isolates display variable colony morphologies (morphotypes), including reduced structure and pigmentation. Panel B presents a laboratory experimental evolution with S. xylosus cultivated for 15 consecutive cycles alone or in co-culture with either Debaryomyces, Brevibacterium, or Penicillium on cheese curd agar medium. Co-evolution with the yeast, Debaryomyces was accompanied by S. xylosus morphotypes that displayed reduced colony architecture and carotenoid staphyloxanthin production. The evolved strains harbored mutations in one or several genes encoding a global transcriptional regulator, including the sigB, agr, and walKR loci. Created with BioRender.com.