Streptococcus mutans appears to possess no fewer than 65 transfer RNA genes as determined by the tRNAscan-SE 1.1 algorithm of T.M. Lowe and S.R. Eddy (Nucl. Acids Res. 25: 955-964,1997). These tRNAs are potentially modified by a minimum of 14 enzymes and charged by at least 25 aminoacyl-tRNA synthetases. In contrast to Porphyromonas gingivalis, most of the tRNA genes are clustered (see accompanying map).