Acetoin production by wild-type strains and a lactate dehydrogenase-deficient mutant of Streptococcus mutans.
Eleven different laboratory strains of Streptococcus mutans representing the various serogroups were found to produce an average of 6.0 +/- 4.8 mM acetoin when grown in glucose-containing medium under aerobic conditions. None of the strains produced detectable acetoin when grown anaerobically. A lactate dehydrogenase-deficient mutant produced acetoin both aerobically and anaerobically and in substantially greater amounts than the wild-type strains did. Substitution of mannitol for glucose resulted in decreased acetoin production by wild-type strains and the lactate dehydrogenase-deficient mutant, indicating a role for NADH2 in the regulation of the acetoin pathway. Pyruvate incorporated into the growth medium of a wild-type strain caused acetoin to be produced anaerobically and stimulated acetoin production aerobically. Cell extracts of a wild-type S. mutans strain were capable of producing acetoin from pyruvate and were (partly) dependent on thiamine PPi. Extracts prepared from aerobically grown cells had approximately twice the acetoin-producing activity as did extracts prepared from anaerobically grown cells. The results indicate that acetoin production by S. mutans may represent an auxiliary reaction of pyruvate dehydrogenase in this organism.
D000093:Acetoin / Q000096:biosynthesis*; D002074:Butanones / Q000096:biosynthesis*; D000431:Ethanol / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000172:deficiency*; D009154:Mutation; D013295:Streptococcus mutans / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
D002074:Butanones; D000431:Ethanol; D000093:Acetoin; D007770:L-Lactate Dehydrogenase