Unleashing Natural Competence in Lactococcus lactis by Induction of the Competence Regulator ComX.

In biotechnological workhorses like and , natural competence can be induced, which facilitates genetic manipulation of these microbes. However, in strains of the important dairy starter , natural competence has not been established to date. However, analysis of the complete genome sequences of 43 strains revealed complete late competence gene sets in 2 subsp. strains (KW2 and KW10) and at least 10 subsp. strains, including the model strain IL1403 and the plant-derived strain KF147. The remainder of the strains, including all dairy isolates, displayed genomic decay in one or more of the late competence genes. Nisin-controlled expression of the competence regulator in subsp. KF147 resulted in the induction of expression of the canonical competence regulon and elicited a state of natural competence in this strain. In contrast, expression in NZ9000, which was predicted to encode an incomplete competence gene set, failed to induce natural competence. Moreover, mutagenesis of the operon in strain KF147 abolished the -driven natural competence, underlining the involvement of the competence machinery. Finally, introduction of nisin-inducible expression into -harboring derivatives of strains IL1403 and KW2 allowed the induction of natural competence in these strains also, expanding this phenotype to other strains of both subspecies. Specific bacterial species are able to enter a state of natural competence in which DNA is taken up from the environment, allowing the introduction of novel traits. Strains of the species are very important starter cultures for the fermentation of milk in the cheese production process, where these bacteria contribute to the flavor and texture of the end product. The activation of natural competence in this industrially relevant organism can accelerate research aiming to understand industrially relevant traits of these bacteria and can facilitate engineering strategies to harness the natural biodiversity of the species in optimized starter strains.