Niacin Saturation Constants for Lactobacillus plantarum and Treponema bryantii

Lactobacillus plantarum 17-5 and Treponema bryantii RUS-1 were grown in batch culture with niacin as the growthlimiting nutrient.Growth rates determined from linear portions of plots of natural log optical density versus time were used to estimate the saturation constants for niacin.These were .00066/ag/ml (5.36 nM) for Treponema bryantii and .0012/ag/ml (9.75 nM) for Lactobacillus plantarum.These saturation constants suggest that .012 to .022pg/ml, respectively, would provide for 95% of their maximum specific growth rates.Niacin concentrations usually present in rumen fluid of animals not receiving supplemental dietary niacin are sufficient to support maximum growth rates of these two bacterial species that require niacin.