Enumeration of H 2-utilizing methanogenic archaea, acetogenic and sulfate-reducing bacteria from human feces

Abstract

Fecal specimens from 19 healthy humans were used to enumerate H 2-utilizing microbial populations of methanogenic archaea (MA), acetogenic bacteria (AB) and sulfate-reducing bacteria (SRB). Eight subjects were methane (CH 4) excretors (CH 4 +) and 11 non CH 4-excretors (CH 4 −), based on breath methane concentrations. The mean ± S.E. of the logarithm of MA per gram wet weight feces were 8.8 ± 0.21 and 2.6 ± 0.39 for CH 4+ and CH 4−, respectively ( P < 0.001). SRB counts were 7.1 ± 0.43 and 7.3 ± 0.39, respectively (NS), while counts of AB were 4.6 ± 0.75 and 6.6 ± 0.38, respectively ( P < 0.02). Counts of AB were negatively correlated with counts of MA (r = −0.53; P < 0.05). These results confirm the potential importance of AB in the human colon, especially for CH 4 — subjects, and suggest that a much greater competitive interrelation occurs in the human colon between MA and AB than between the former and SRB. We further report on the isolation of representatives of the dominant H 2 CO 2 acetogenic population. Three strains from two CH 4 — subjects were characterized from 10 −5-10 −7 dilutions. They all consumed H 2 CO 2 and several carbohydrates to produce acetate as the sole metabolite. Phenotypically related to the species Peptostreptococcus productus, the strains used H 2 CO 2 via the acetyl-CoA pathway.