Mutational drift prevails over translational efficiency in Frankia nif operons

Abstract

Frankia is a Gram-positive actinomycete, fixing atmospheric nitrogen while making associations with a number of dicotyledonous plants. The most important operon of Frankia is the nif operon. Codon usage bias was investigated in three open reading frames and known genes of this organism from three different strains. Genes and ORFs show high biasness due to mutation pressure. Based on our results we conclude that mutational drift is more relevant over translational efficiency. The nif genes showed fairly high expression levels. Analysis of the result of codon indices and BLAST searches revealed that ORF3 might be a good candidate for expression.