Open AccessIdentification and characterization of the loci encoding the competence‐associated alternative σ factor of Streptococcus gordonii
Author(s) -
Heng Nicholas C.K.,
Tagg John R.,
Tompkins Geoffrey R.
Publication year - 2006
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2006.00238.x
Subject(s) - streptococcus gordonii , biology , genetics , complementation , gene , mutant , operon , regulatory sequence , streptococcus pneumoniae , regulation of gene expression , bacteria , streptococcus
In naturally‐competent streptococci such as Streptococcus pneumoniae , expression of the late competence operons is regulated by ComX (σ X ), the competence‐specific alternative σ factor. In this study, duplicate genes ( comR1 and comR2 ) encoding the putative ComX homologue of the oral bacterium Streptococcus gordonii were identified. Like the identical twin comX loci of S. pneumoniae , both comR determinants are independently functional as well as responsive to the ComDE signal transduction system activated by competence‐stimulating peptide. However, in contrast to the comX system, nucleotide sequence analyses in combination with in trans complementation studies with a comR null mutant demonstrate that the identical 83 bp tracts (Region I) located immediately upstream of the comR structural genes are insufficient to confer wild‐type competence levels. Wild‐type transformation levels required additional distal nonhomologous DNA segments (Region II). Our findings suggest that alternative regulatory elements, under overall control of the ComDE pathway, may influence expression of the comR loci.