Technical University of Munich, Germany
Title: Competence development and natural transformation in Micrococcus luteus
Biography: Antoni Lichev
Natural genetic transformation has been documented in more than 80 bacterial species, including members of nearly all major taxonomic groups. Being one of the main routes for horizontal gene transfer, this process incorporates the internalization and the chromosomal integration of exogenous DNA during a genetically preprogrammed differentiated state called competence. In spite of the longstanding investigation of this phenomenon, so far only little is known about the regulatory mechanisms involved in genetic transformation and notably so in the case of representatives of the Actinobacteria phylum (high GC Gram-positive bacteria). In this report we focus on the competence development in the Actinobacteria member Micrococcus luteus. We provide evidence that nutritional limitation, provoked by the absence of amino acids in the growth medium, induces natural transformation in this species. Paradoxically, we also show that amino acid auxotrophy strongly inhibits competence development. We demonstrate the negative impact of a deletion of a RelA/SpoT-like homologue (Mlut_12840) and a putative novel (p)ppGpp synthetase (Mlut_22200) on natural transformation and we therefore speculate the involvement of the stringent response in the complex regulation of the competent state of Micrococcus luteus. Furthermore we investigate the specific regulatory function of branched-chain amino acids (BCAAs) and signify them as modulators of competence that alter expression of transformation-related genes. To our knowledge our data provides the first general insights into the regulation of natural transformation in a member of the Actinobacteria phylum and may also prove to be pertinent to a number of important pathogens belonging to the same taxonomic group.