CHARACTERISTICS OF A NITROPROPANOL-METABOLIZING BACTERIUM ISOLATED FROM THE RUMEN

We report some characteristics of a ruminal bacterium (strain NPOH1) t hat metabolizes 3-nitropropanol, the toxic principle of various milk v etchs that are distributed worldwide. The gram-positive bacterium was nonmotile and did not produce spores. Growth of strain NPOH1 occurred under anaerobic conditions and was supported by the electron accepters 3-nitropropanol, 3-nitropropionate, nitrate, 2-nitropropanol, nitroet hane, nitroethanol, or 3-nitro-1-propyl-beta-D-glucopyranoside (misero toxin). Other potential electron accepters, namely sulfate, sulfite, a zide, chlorate, perchlorate, nitrite, fumarate, 2-nitrobutane, or nitr obenzene, did not support growth. Formate, lactate, and H-2 stimulated growth of strain NPOH1 in the presence of the appropriate nitrocompou nd. whereas a variety of other potential H-2 donors did not. When grow n in medium containing both nitrate and either 3-nitropropanol or 3-ni tropropionate, nitrate was the preferred acceptor. Strain NPOH1 reduce d nitrate to nitrite and, when grown with excess reductant, nitrite wa s further reduced to ammonia. The products formed during the metabolis m of 3-nitropropanol and 3-nitropropionate by mixed ruminal population s, 3-aminopropanol and beta-alanine, were not found in culture fluids of strain NPOH1. Analysis of total cellular fatty acid profiles and of the mole percent guanine plus cytosine suggests that strain NPOH1 is a novel bacterium. The capacity of strain NPOH1 to metabolize 3-nitrop ropanol suggests that this organism may play an important role in deto xification of 3-nitropropanol in the rumen.