Estimation of growth parameters for some oral bacteria grown in continuous culture under glucose-limiting conditions

Abstract

The coexistence of bacteria in natural environments can often be explained in terms of competition for a growth-limiting substrate(s), and the outcome of such competition depends upon relevant growth parameters such as substrate affinity and yield. Dental plaque bacteria are frequently carbon and energy limited. Growth parameters for seven oral Sreptococcus species and one Actinomyces viscosus strain were estimated under glucose-limited conditions in continuous culture. In all strains, mixed-acid fermentation occurred at low growth rates, while amounts of lactate increased at higher growth rates. Two important growth parameters, ulmax and Ygi,cose, were very similar in the two serotype c Streptococcus mutans strains (T8 and Ingbritt), one of the serotype d/g Streptococcus mutans strains (OMZ65), and the two Streptococcus milledi strains (699B3 and B448). Two other serotype d/g S. mutans strains (KIR and B13) were divergent from this group and had lower ILmax values and a lower YglU,O,e. The maintenance energy coefficients were lower in the S. mutans serotype c

Fermentation products, amino acid utilization, maintenance energies and growth yields for the fibrillar Streptococcus salivarius HB and a non‐fibrillar mutant HB‐B grown in continuous culture under glucose limitation

“…The maximum specific growth rates of the two strains are high when compared with those found for Strep. mutans strains (Rogers et al 1986). Streptococcus mutans Ingbritt had a maximum specific growth rate of 1.10/h when grown under similar conditions.…”

“…This is very different from the fermentation profile found in Strep. mutans strains found by Rogers et al (1986), where the amount of lactate recovered increased with increasing growth rate, until at the highest growth rate lactate was the major end product. Although the amount of lactate was higher in strain HB-B it did not become the major product of fermentation.…”

“…The fall in the yield for Strep. mutans at the highest growth rates found by Rogers et al 1986, was explained by the shift from the mixed acid fermentation at low growth rates (3 mol ATP/mol glucose) to a homolactic fermentation (2 mol ATP/mol glucose) at the high growth rates. The slight fall in the yield for strains HB and HB-B is reflected in the same way as there is not such a large increase in the lactate concentration.…”

“…salivarius HB has never been published., however fermentation balances for a number of strains of Strep. mutans (van der Hoeven et al 1985;Rogers et al 1986) have been produced. These show that lactate production increases with increasing growth rate, achieving a maximum at just below the maximum specific growth rate.…”

“…Values have also been calculated for the maintenance energy coefficient, the energy required by the organism for processes that do not contribute to the biomass of the cell; and the maximum growth yield, the maximum possible value of the growth yield from the energy source (Pirt 1975). Values for the maintenance energy coefficient and maximum growth yield of oral streptococci (Rogers et al 1986) show relatively little difference between the strains investigated.…”