The sigH gene sequence can subspeciate staphylococci.

In an evolutionarily conserved gene organization (syntenic region), the sigH gene shares exceptionally low homology among staphylococcal species. We analyzed the "positionally cloned" sigH sequences of 39 staphylococcal species. The topology of the SigH phylogenetic tree was consistent with that of 16S rRNA. Certain clinical isolates were successfully differentiated at the species level with the sigH sequence data set. We propose that the sigH gene is a promising molecular target in genotypic identification because it is highly discriminative in differentiating closely related staphylococcal species.