Recovery of Streptococcus mutans after amino acid deprivation

The recovery of Streptococcus mutans FA-1 in a complete, chemically defined medium was examined after 1, 3, and 6 h of essential amino acid deprivation. Amino acids could be divided into two groups based on their effect on the relative rates of recovery: those amino acids (leucine and cystine) that are precursors of protein only, and amino acids (glutamate/glutamine or lysine) that are incorporated into both protein and cell wall peptidoglycan. Culture turbidity, deoxyribonucleic acid, ribonucleic acid, protein and cell wall peptidoglycan measurements indicated rapid recovery after leucine/cystine starvation periods. However, a 6-h leucine/cystine deprivation resulted in a slower exponential rate of growth (180-min doubling time compared to the normal doubling time of 85 to 90 min) after recovery. Glutamate/glutamine starvation, on the contrary, resulted in greatly extended recovery periods, especially after 3- and 6-h amino acid deprivations. Macromolecular synthesis was most severely affected by 6-h glutamate/glutamine starvation and required 6 to 10 h for recovery of an exponential rate. A delay in the recovery of deoxyribonucleic acid and cell wall peptidoglycan synthesis beyond that of the other macromolecules was observed after 1 and 3 h of deprivation with either leucine/cystine or glutamate/glutamine. However, after a 6-h amino acid deprivation, deoxyribonucleic acid synthesis recovered more rapidly than that of the other macromolecules studied. The results are discussed in terms of the nutritional environment of the oral cavity and its effect on the growth and survival of S. mutans.