A new staphylococcal sigma factor in the conserved gene cassette: functional significance and implication for the evolutionary processes.
BACKGROUND
Staphylococcus aureus is a major human pathogen and causes a serious hospital infection due to the acquired multidrug resistance. Unlike the well-studied bacteria such as Escherichia coli and Bacillus subtilis, which have seven and 18 sigma factors, respectively, only two sigma factors have been known for S. aureus. We searched for possible sigma factor genes by examining the S. aureus genome with a special attention to the gene arrangement around the sigma factor genes of a close relative, B. subtilis.


RESULTS
A new sigma factor gene was identified in Staphylococcus. The gene constituted a conserved gene cluster with other genes including translation- and transcription-related genes. Phylogenetic analysis and comparison of the gene sequences among species indicated that the staphylococcal sigma factor originated from a common ancestor of B. subtilis SigH. An over-expression of this sigma factor in S. aureus resulted in a drastic induction of the expression of the com operons that encode proteins required for the natural genetic competence.


CONCLUSIONS
We demonstrated that the newly identified staphylococcal sigma factor participated in a regulatory network of transcription that controlled the genetic competence genes. In our phylogenetic tree, the factor was classified as a single group with a common function.
Morikawa
Kazuya
K
Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, 305-8577 Japan.
Inose
Yumiko
Y
Okamura
Hideyuki
H
Maruyama
Atsushi
A
Hayashi
Hideo
H
Takeyasu
Kunio
K
Ohta
Toshiko
T
D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology; D017124:Conserved Sequence; D019143:Evolution, Molecular; D023061:Gene Order; D005810:Multigene Family; D010802:Phylogeny; D012808:Sigma Factor / Q000502:physiology*; D013211:Staphylococcus aureus / Q000235:genetics*
D001426:Bacterial Proteins; D012808:Sigma Factor