Codon Usage Bias Prefers AT Bases in Coding Sequences Among the Essential Genes of <i>Haemophilus influenzae</i>

The base composition at three different codon positions in relation to codon usagebias and gene expressivity was studied in a sample of twenty five essential genes from Haemophilus influenzae. ENC, CBI and Fop were used to quantify the variation in codon usage bias for the cds. CAI is used to estimate the level of gene expression of the cds selected in the present study. To find out the relationship between the extent of codon bias and nucleotide composition the values of A, T, G, C and GC they were compared with the A3, T3, G3, C3 and GC3 values, respectively. The results showed relatively weak codon usage bias among the coding sequences (cds) of Haemophilus influenzae. This in turn, implies that the essential genes prefer to use a set of restricted codons. However, the base compositional analysis of essential genes in Haemophilus influenzae revealed preference of AT to GC bases within their coding sequences and this preference might affect gene expression as indicated by the relatively high CAI values ofthe coding sequences.