Phylogenetic analysis of gram-positive bacteria based on grpE, encoded by the dnaK operon.

The dnaK operon in gram-positive bacteria includes grpE, dnaJ and, in some members, hrcA as well. Both DnaK and DnaJ have been utilized for constructing phylogenetic relationships among various organisms. Multiple copies exist for dnaK and dnaJ genes in some bacterial genera, as opposed to a single gene copy for grpE and for hrcA, according to the currently available data. Here, we present a partial protein-based phylogenetic tree for gram-positive bacteria, derived by using the amino acid sequence identity of GrpE; the results are compared with the phylogenetic trees generated from 5S rRNA, 16S rRNA, dnaK and dnaJ sequences. Our results indicate three main groupings: two are within low-G+C DNA gram-positive bacteria comprising Bacillus species and Staphylococcus aureus on the one hand and Streptococcus species/Lactococcus lactis/Enterococcus faecalis/Lactobacillus sakei on the other hand; the Mycobacterium species and Streptomyces coelicolor, belonging to the high-G+C DNA gram-positive bacteria, form the third cluster. This hierarchical arrangement is in close agreement with that obtained with 16S rRNA and DnaK sequences but not DnaJ-based phylogeny.