Authors: Kenro Oshima Hiromi Nishida
Publish Date: 2008/04/15
Volume: 66, Issue: 5, Pages: 529-532
Abstract
Mycoplasmas are parasitic bacteria with small genomes Since parasitic bacteria need to adapt themselves to their hosts there is a possibility that some genes evolved under speciesspecific constraint We assume that Ureaplasma parvum has candidate genes that evolved in a speciesspecific manner in its genome Here we examined synonymoustononsynonymous substitution ratios ω of the 143 mycoplasmaorthologous genes of Ureaplasma and other mycoplasmas using branch models As a result the model allowing for Ureaplasma branchspecific ω in addition to ω of other mycoplasmas was significantly supported in 16 genes First the Ureaplasmaspecific model was significantly supported in the genes encoding a transcription elongation factor and a transcription terminator factor suggesting that transcriptionrelated genes of Ureaplasma have evolved in a unique manner compared to those of other mycoplasmas Second the Ureaplasmaspecific model was significantly supported in the gene encoding uracilDNA glycosylase In addition the ω value of the gene in the Ureaplasma lineage was approximately 30fold lower than those of other lineages suggesting that uracilDNA glycosylase of Ureaplasma evolved under stronger functional constraint than those of other mycoplasmas Finally three glycolytic genes of Ureaplasma were suggested to have evolved under relaxed selection Among mycoplasmas only Ureaplasma has urease and synthesizes ATPs via hydrolysis of urea This raises the possibility that Ureaplasma does not need a glycolysis pathway for ATP synthesis This unique energyproducing system may be related to the Ureaplasmaspecific evolution of the glycolytic genes
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