Rickettsia species are important emerging pathogens causing rickettsial diseases, which are important cause death worldwide. The number of recombinant proteins used for diagnostic and therapeutic applications has increased dramatically, which is important in determination of protein function, structure and antigensity. Although E. coli is widely used expression system, the codon bias can hamper protein expression due to the presence of rare codons in gene sequence coding protein of interest. Using bioinformatics tools, rare codon analysis of rickettsial genes was performed and compared to not expressed proteins in both R. prowazekii and R. rickettsii. A negative correlation between frequencies of rare codons in Rickettsia and success of rickettsial protein expression was observed. This study suggested a useful tool to improve rickettsial recombinant protein expression in E. coli.
