Abstract
Motivation: The three corynebacterial complete genomes have been sequenced. Comparative genome sequence analysis will highlight the evolutional history responsible for their functional differentiation.
Results: Corynebacterium efficiens but not Corynebacterium glutamicum can grow above, 40 degrees C. The genome GC contents of C. efficiens was 63.1 % and about 10 % higher than that of C glutamicum or Corynebacierium diphtheriae. This difference was reflected in codon usage and nucleotide substitutions. By analyzing orthologous gene pairs with 60-95 % amino acid sequence identity between C efficiens and C glutamicum, we observed tremendous bias in amino acid substitutions. Especially, three asymmetrical amino acid substitutions: from lysine to arginine, serine to alanine and serine to threonine, were important for protein thermostability in C efficiens. The accumulations of these amino acid substitutions were responsible. for thermostability in C efficiens and greater GC contents.