Influence of heme and vitamin B12 on growth and fermentations of Bacteroides species.

We examined the effects of heme on the growth and fermentations of Bacteroides species. Bacteroides fragilis ATCC 25285 required heme for growth and produced malate and lactate as major products of glucose fermentation when the concentration of heme was 1 ng/ml. With 1 microgram of heme per ml, malate was not formed, lactate production decreased, and succinate and acetate were the major fermentation products. B. eggerthii ATCC 27754 grew without heme, with the production of mainly malate and lactate from glucose. Its fermentation with 1 microgram of heme per ml was similar to that of B. fragilis grown with the same concentration of heme. B. splanchicus VPI 6842 grew without heme, with the production of mainly malate, acetate, and H2 from glucose. With 1 microgram of heme per ml, malate disappeared, H2 decreased significantly, and succinate, acetate, and butyrate were the major products. The addition of vitamin B12 to media containing 1 microgram of heme per ml caused all species to produce propionate at the expense of succinate and, with B. splanchnicus, also at the expense of butyrate. Thus, the concentration of heme and the presence of vitamin B12 significantly influenced the course of glucose fermentation by these bacteria.