Codon Usage in the A/T-Rich Bacterium Campylobacter Jejuni

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Abstract
Campylobacter jejuni is a Gram negative, microaerophilic pathogen that causes gastroenteritis in humans. The genome of C. jejuni is AT-rich, with a mol% G + C. of 30.4. This high AT content was hypothesized to result in unique codon usage. In the present study, we analyzed the codon usage of sixty-seven C. jejuni genes and generated a codon frequency table. As predicted, the codon usage of C. jejuni revealed a strong bias towards codons ending in A or U. In addition to determining codon usage frequencies, the relative synonymous codon usage values were calculated to identify rare and optimal codons. Seventeen codons were identified as optimal and twelve codons as rare. Thirty-two codons exhibited little or no bias. A plot of the effective number of codons versus the third position %G + C. values for the sixty-seven genes revealed that C. jejuni uses an average of 39 of the 61 codons to encode proteins. These data will be useful for various molecular analyses including selection of degenerate primers to screen C. jejuni-genomic DNA libraries.