Streptomyces lunaelactis: connecting genetics to metabolite production

Abstract

The group Streptomyces Genetics and Development possess a unique collection of Actinobacteria originating from cave moonmilk deposits of the “Grottes des Collemboles” in Comblain-au-Pont, Belgium. This collection includes new Streptomyces species that produce bioactive compounds of interest for pharmacological and agro-industrial fields. During this master’s thesis, we aimed at connecting the genetic material to molecules produced by the moonmilk-dwelling species S. lunaelactis. In this context, all SARP-family of regulators were identified in the genome of S. lunaelactis and the first experiments at the molecular and genetic level were performed. Although the inactivation by gene disruption of most SARP-encoding gene was not successful, we managed to generate a fevR/bagI null mutant that is situated in the biosynthetic gene cluster (BGC) #12, predicted to be responsible for the production of both bagremycin and ferroverdin metabolites. Combination of gene inactivation, complementation of the fevR/bagI mutant, and overexpression of this SARP-encoding gene - together with the inactivation of the biosynthetic gene fevW/bagE -, allowed us to confirm the hypothesis that production of these two types of compounds depends on a unique BGC. Additionally, this master’s thesis focused on two other types of metabolites that have previously been identified in the metabolome of S. lunaelactis and for which BGCs have been associated. BGC #21c is predicted to produce a xantholipin derivative while BGC #28 is supposed to be responsible for the biosynthesis of three non-ribosomal peptides (NRPs). In order to evaluate their antimicrobial potential, procedures of production, extraction, purification, and disc diffusion assays have been performed revealing promising antibacterial activities for the purified NRPs and antibacterial and antifungal activities for the xantholipin derivative.