Factors Influencing Pulmonary Methane Excretion in Man

Abstract

It is becoming increasingly apparent that the metabolic activity of the normal intestinal flora may exert a profound influence on the physiology of their host (1). There is, however, only limited information concerning the metabolism of these bacteria, and this information has been derived primarily from studies carried out with isolated species in culture media. The results of such studies may not accurately reflect the in situ behavior of these organisms within the complex environment of the bowel.In the present investigation, we studied the production of a bacterial metabolite, methane (CH4), in man. Measurement of the pulmonary excretion rate of methane appeared to offer a unique opportunity to study the in situ metabolism of a group of intestinal organisms since it is commonly assumed that (a) all CH4 excreted by man is derived from the metabolism of intestinal bacteria, and (b) there is no appreciable utilization of CH4 by man; thus, all CH4 absorbed from the colon will be quantitatively eliminated by the lungs.In this investigation we first attempted to demonstrate that pulmonary CH4 excretion can serve as an accurate indicator of CH4 production by intestinal bacteria. Subsequent studies were then directed towards elucidating the factors which influence the rate of production of this bacterial metabolite in the human colon. Materials and MethodsSubjects and Experimental Animals.~he pulmonary excretion rate of CH4 was studied in 20 infants ranging in age from 2 hr to 5 months and in 22 normal adults. The CH4 concentration of end-expiratory air was measured in 280 adults and 40 children. The adults consisted of 180 normal subjects and 100 patients hospitalized on a general medical ward. The children consisted of 25 healthy subjects and 15 children hospitalized with various cardiac defects.

Abundance and diversity of mucosa-associated hydrogenotrophic microbes in the healthy human colon

“…Although breath methane reliably reflects the abundance of colonic methanogens, non-methanogenic subjects, as thereby defined, often harbor a relatively lower number of stool MA (El Oufir et al, 1996). One study, based on a fortuitous measurement of colonic gases, suggested that methane was predominantly produced in the left colon (Bond et al, 1971). Culture-based data consistent with the abundance of MA increasing in a proximal to distal gradient have also been reported (Macfarlane et al, 1992).…”

Pan-genome of the dominant human gut-associated archaeon, Methanobrevibacter smithii , studied in twins

“…Thirty to fifty percent of humans are positive for methanogens in the gut as measured either by breath tests (10,11) or PCR assays targeting mcrA (methyl coenzyme M reductase subunit A, conserved in the methanogenesis pathway) (12). However, whether and how host physiologic factors, such as gastrointestinal transit time (13,14) and BMI (15,16), influence interpersonal variation in the representation of methanogens remains unclear.…”

Association of Fecal Indicator Bacteria with Human Viruses and Microbial Source Tracking Markers at Coastal Beaches Impacted by Nonpoint Source Pollution

“…Methanobrevibacter smithii is the most prominent methanogen in the human gastrointestinal tract and has been found at concentrations of 10 7 to 10 10 organisms · g Ϫ1 in feces (12,35). The use of the nifH gene of M. smithii to identify human-associated fecal pollution has been limited but successful in MST studies conducted to date (23,55), as it is relatively host specific compared to some other MST markers (3,23,31).…”