Influence of spxB gene on competence in Streptococcus pneumoniae

Institute for Infectious Diseases, University of Bern, Bern, Switzerland; University Hospital, Bern, Switzerland

^* To whom correspondence should be addressed. Email: kathrin.muehlemann{at}ifik.unibe.ch.

	Abstract

In Streptococcus pneumoniae expression of pyruvate oxidase (SpxB) peaks during the early growth phase coincident with the time of natural competence. This study investigated, whether SpxB influences parameters of competence, such as spontaneous transformation frequency, expression of competence genes and DNA release. Knock-out of spxB gene in strain D39 abolished spontaneous transformation frequency (as compared to 6.3x10^-6 in the parent strain, p<0.01). It also reduced expression levels of comC and recA as well as DNA release from bacterial cells significantly during the early growth phase coincident with the time of spontaneous competence in the parent strain. In the spxB mutant supplementation with competence stimulating peptide-1 (CSP-1) restored transformation frequency (rate 1.8x10^-2). This speaks against the role of SpxB as a necessary source of energy for competence. Neither supplementation with CSP-1, nor with the SpxB products H₂O₂ and acetate altered DNA release. Supplementation of the parent strain with catalase did not reduce DNA release significantly

In conclusion, the pneumococcal spxB gene influences competence, however, the mechanism remains elusive.