A Genome to Chew On

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Science  08 Nov 2002:
Vol. 298, Issue 5596, pp. 1137
DOI: 10.1126/science.298.5596.1137b

As the leading cause of tooth decay, Streptococcus mutans may be held in high esteem by dentists, but to the rest of us the bacterium is an annoying source of pain and expense. The 2-million-base pair genome of S. mutans, recently sequenced by Ajdi_c et al., has shed some light on why this oral pathogen is so successful.

Perhaps not surprisingly, the sequence indicates that S. mutans can metabolize a wider range of carbohydrates than any other Gram-positive organism. Whereas the products of carbohydrate metabolism create an acidic microenvironment that inhibits competing oral bacteria (and causes tooth decay), S. mutans itself appears to survive because it encodes an acid-stable proton-translocating F0F1 ATPase that helps maintain intracellular pH. The sequence also revealed that (i) the bacterium can synthesize all of its required amino acids; (ii) it devotes 15% of its coding potential to transport proteins; and (iii) it encodes many virulence factors, such as adhesins, exoenzymes, and proteases, which likely enable it to escape host defenses and to degrade host tissue. Further analysis of the genes identified in this study may ultimately provide new leads for preventing and treating tooth decay. — PAK

Proc. Natl. Acad. Sci. U.S.A.99, 14434 (2002).

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