Coordinated bacteriocin expression and competence in

Streptococcus pneumoniae contributes to genetic adaptation through neighbor predation

Wei-Yun Wholey, Travis J. Kochan, David N. Storck, Suzanne Dawid

 PLoS Pathog. (2016) 12(2): e1005413

Speaker: Hsiang-Ning Chang (張翔甯)                    Time: 14:00~15:00, Sep. 27, 2017

Commentator: Dr. Ching-Hao Teng (鄧景浩老師)      Place: Room 601

Abstract:

Streptococcus pneumoniae (S. pneumoniae) is gram-positive, facultative anaerobic bacteria. S. pneumoniae has the ability to take up and recombine exogenous genetic material from the surrounding microbial community through a phenomena called competence. S. pneumonaie is also known to produce anti-bacterial proteins called bacteriocins capable of lysing neighboring bacteria. The blp locus, which encodes for components involved in the production and secretion of a peptide pheromone BlpC, is responsible for the production of these bacteriocin. In S. pneumonaie, competence is activated by extracellular accumulation of another pheromone called competence stimulating peptide (CSP) which binds to and activate a transcriptional regulator ComE. Previous studies suggested there might be a regulatory connection between the competence regulon and bacteriocin systems (1). In this study, the authors demonstrated that the expression and secretion of a bacteriocin pheromone, BlpC, can be induced via CSP in a ComE dependent process. Moreover, they found that CSP stimulation of the blpABC operon is mediated by ComE-cross recognition of a BlpR (a response regulator encoded by the blp locus) binding site. In addition, the authors determined that the BlpC can also be secreted by the competence associated transporter protein ComA following CSP stimulation resulting in further activation of the entire blp locus. In nature, gene exchange between streptococci takes place in biofilms, not in liquid cultures. (2) Therefore, the authors used biofilm as a model to and determined that the cooperation between competence and bacteriocin system would enhance DNA exchange. This result implied that co-stimulation of bacteriocins and competence provided an advantage for adaptation. In conclusion, the authors discovered that the regulation of competence and bacteriocin production are linked to promote DNA exchange o exchange adequate DNA for survival and adaptation.

References:

1.      Peterson SN, Sung CK, Cline R, Desai BV, Snesrud EC, et al. (2004) Identification of competence pheromone responsive genes in Streptococcus pneumoniae by use of DNA microarrays. Mol Microbiol 51: 1051–1070.

2.     Hua Wei and Leiv Sigve Håvarstein. (2012) Fratricide Is Essential for Efficient Gene Transfer between Pneumococci in Biofilms. Appl Environ Microbiol. 78(16): 5897–5905.