Role of Directional Mutation Pressure in the Evolution of the Eubacterial Genetic Code (original) (raw)

  1. S. Osawa*,
  2. T.H. Jukes†,
  3. A. Muto*,
  4. F. Yamao*,
  5. T. Ohama*, and
  6. Y. Andachi*
  7. *Laboratory of Molecular Genetics, Department of Biology, Nagoya University, Nagoya 464, Japan; †Space Sciences Laboratory, University of California, Berkeley, California 94720

Excerpt

GC Contents of Eubacterial Genomes

Among eubacteria, the mean guanine and cytosine (GC) contents of genomic DNA vary approximately from 25% to 75% (Sueoka 1962). The phylogenetic tree to eubacterial 5S rRNA has indicated that bacterial genome GC contents are to some extent related to phylogeny (Hori and Osawa 1986). According to this tree, the gram-negative and the gram-positive bacteria diverged first. Among the gram-positive bacteria, those with low genomic GC content such as Bacillus subtilis (genomic GC: 43%), Lactobacillus viridescens (40%), Staphylococcus aureus (33%), Clostridium perfringens (38%), and Mycoplasma capricolum (25%) are phylogenetically close, whereas those with high genomic GC, such as Micrococcus luteus (74%), Streptomyces griseus (73%), and Mycobacterium tuberculosis (67%) comprise another phylogenetic group. These two groups separated long ago. The gram-negative bacteria with intermediate GC, such as Escherichia coli (50%), Serratia marcescens (58%), Salmonella typhimurium (51%), and Pseudomonas fluorescens (60%) belong to the common gram-negative branch...