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 constructi ng phylogenetic relationships among various organisms, Multiple copies exis t 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 Grampositiv e bacteria, derived by using the amino acid sequence identity of GrpE; the results are compared with the phylogenetic trees generated from 5S rRNA, 16 S rRNA, dnaK and dnaJ sequences. Our results indicate three main groupings: two are within low-G+C DNA Gram-positive bacteria comprising Bacillus spec ies and Staphylococcus aureus on the one hand and Streptococcus species/Lac tococcus lactis/Enterococcus faecalis/Lactobacillus sakei on the other hand ; the Mycobacterium species and Streptomyces coelicolor, belonging to the h igh-G+C DNA Gram-positive bacteria, form the third cluster. This hierarchic al arrangement is in close agreement with that obtained with 16S rRNA and D naK sequences but not DnaJ-based phylogeny.