Variable correlation of genome GC% with transfer RNA number as well as with transfer RNA diversity among bacterial groups: alpha-proteobacteria and tenericutes exhibit strong positive correlation.

Mainly two selective forces are thought to affect transfer RNA (tRNA) gene numbers in cells: firstly, transfer RNA genes have coevolved with codon usage to optimize the translation rate in organisms; and secondly, tRNA gene number is positively correlated with growth rate of organisms. Since a codon ending with 'G' is recognized with lower efficiency than the synonymous codon ending with 'A' by a tRNA, organisms with high genome GC% are expected to possess tRNA molecules with 'C' at the first anticodon position to decode efficiently the former codon. This is in concordance with the observation of higher tRNA diversity in several bacteria with higher genome GC%. In addition to this, tRNA gene redundancy has been reported to be correlated with genome size. In this paper we have carried out a comprehensive correlation analysis of tRNA gene diversity, total tRNA number, genome GC% and genome size, in 626 bacterial strains (belonging to 433 species). A common positive trend of correlation in bacteria of GC% with tRNA diversity, of GC% with genome size and of genome size with total tRNA number, is observed, even within individual bacterial groups. Comparison of organisms' growth rate data with their genome GC% indicated that organisms with higher growth rate are most likely with <50% GC. This work extends the list of features in organisms that relate to genome GC%.