Invited Speaker: Ran Wenqi

  Among bacteria, species that are capable of rapid growth have stronger selection on codon usage than slow growing species, and possess higher numbers of rRNA and tRNA genes. This suggests that fast-growers are adapted for fast protein synthesis. There is also evidence that codon usage is influenced by accuracy of translation. We compare the strength of the two effects by studying codon usages with our statistical method that can be used to assess the significance and the strength of the two types of bias in diversified sequences. We also compare our statistical measure of codon bias to the common used codon adaptation index (CAI), and show that the new measure is preferable for the purposes of this analysis.
  Genes with related functions often cluster as operons in genomes of bacteria and archaea. Such an organization allows for co-regulation of gene expression, generally resulting in equimolar amounts of gene products. In terms of efficiency, an operonic organization is important for subunits of protein complexes with even stoichiometries.  On the other hand, protein complexes with an uneven stoichiometry do require an additional level of control. We used comparative genomics combined with molecular genetics to show that codon bias is the key determinant of differential production of proteins encoded by genes within the same operon.