Comparative growth of Bacteroides species in various anaerobic culture media.

The growth of five species of Bacteroides in four anaerobic culture media was continuously monitored turbidimetrically. Interspecies differences were observed in the growth of Bacteroides spp. in the various media, but growth in Brain Heart Infusion broth supplemented with yeast extract, haemin and menadione, was consistently better than in Wilkins-Chalgren, Thioglycollate or Schaedler broths. Microscopy of cultures grown overnight in Brain Heart Infusion broth showed that the bacteria exhibited normal morphology but most species grown in the other media displayed filamentation or chain formation. Four of the five species grown in Schaedler broth also exhibited spheroplast formation. This morphological change occurred in the stationary phase of growth, was reduced by inclusion of NaCl in the medium and was abolished in Schaedler broth prepared at double the recommended strength.