Codon usage behavior distinguishes pathogenic Clostridium species from the non-pathogenic species

•Genus Clostridium is comprised of diverse species ranging from human pathogens to nitrogen-fixing bacteria.•Pathogenic species were found to employ a strict codon usage bias as compared to the other clostridial species.•Pathogenic species were found to have a higher genomic AT-content and shorter genomes as compared to other clostridial species.•Amino acid usage revealed an increased usage of amino acids with lower biosynthetic cost by pathogenic clostridium species.•Choices employed by pathogenic Clostridium could help the disease-causing bacteria to improve its survival and replication inside AT-rich human hosts.