Peptones from diverse sources: pivotal determinants of bacterial growth dynamics

Abstract

In view of the major problems encountered by microbiologists in obtaining reproducible data on growth dynamics in complex media, we studied the effects of different peptones made from different biological sources and produced by numerous manufacturers. Peptones (including casein, gelatin, meat, soy and yeast) were assessed as a constituent of the pre-enrichment broth buffered peptone water (BPW). Generation times (g) and yields of Salmonella serovar Typhimurium were significantly affected by the type of peptone employed with yeast peptones generating yields of 7.04 x 10(9) CFU ml(-1) and gelatin peptones producing 0.81 x 10(9) CFU ml(-1). Medium sterilization was also found to have significant effects (P = 0.000) upon subsequent bacterial growth. Filter sterilization of BPW media produced lower generation times compared with those obtained after sterilization by autoclaving. Finally, it was observed that some peptones which produced good growth when inoculated with healthy organisms, showed relatively poor growth when inocula were sublethally injured by heating. Variation in peptone as a constituent of BPW has a significant effect on growth and enumeration of bacteria. Increased consideration with respect to culture media may significantly improve bacterial growth and experimental reproducibility.