In vitro investigations on microbial incorporation of nitrogen from [15N2]urea and [15N2]ammonium chloride by the human intestinal flora

6 typical bacteria species of the human intestinal flora (E. coli, Klebsiella pneumoniae, Proteus vulgaris, Streptococcus faecalis, Bacteroides fragilis, Bifidobacterium sp.) were incubated in a liquid medium for 48 h with [15N2]urea and [15N]ammonium chloride. The rates of 15N incorporation were calculated. They depend reproducibly on the species examined, on the kind of the offered NPN substance and on the amount of NPN substance in the medium. With [15N2]urea the minimal rate of incorporation was 3.8% (E. coli) and the maximal one 95.6% (Bifidobacterium sp.). With [15N]ammonium chloride the corresponding figures were 31.0 (Proteus vulg.) and 98.0% (Bifidobacterium sp.). The findings are discussed with regard to a possible enteral detoxification in uremic patients by bacterial utilization and elimination of urea and ammonia. (author)