ANALYSIS OF THE BETA' SUBUNIT OF DNA-DEPENDENT RNA-POLYMERASE DOES NOT SUPPORT THE HYPOTHESIS INFERRED FROM 16S RIBOSOMAL-RNA ANALYSIS THATOENOCOCCUS-OENI (FORMERLY LEUCONOSTOC-OENOS) IS A TACHYTELIC (FAST-EVOLVING) BACTERIUM

rRNA sequencing has shown that leuconostocs comprise three distinct ph ylogenetic lineages which have been designated separate genera (viz,, the genera Leuconostoc sensu stricto, Oenococcus, and Weissella). In a ddition, the 16S rRNA line formed by Oenococus oeni (formerly Leuconos toc oenos) is exceptionally long; this fact, together with variations in the compositions of conserved positions in the 16S rRNA, has led to the hypothesis (D. Yang and C. R. Woese, Syst, Appl, Microbiol. 12:11 5-149, 1989) that this organism is a fast-evolving bacterium, Previous evidence that the leuconostocs should be divided into three genera an d that O. oeni Is an example of tachytelic evolution has come solely f rom rRNA analyses, In this study we sequenced tile rpoC gene encoding the beta' subunit of DNA-dependent RNA polymerase of leuconostocs and performed a comparative phylogenetic analysis, The subdivision of the leuconostocs into three distinct lineages was confirmed by the rpoC ge ne data, but no evidence that indicated that O. oeni is evolving at an extraordinary rate was found, If O. oeni is truly tachytelic, then fa st-evolving phenomena would be expected to occur throughout the whole genome, including this independent molecular chronometer.