Identification of rumen bacteria that anaerobically degrade aliphatic nitrotoxins

Of 33 pure stains of rumen bacteria from the Lethbridge laboratory collection, 5 degraded both 3-nitropropanol (NPOH) and 3-nitropropionic acid (NPA) under anaerobic conditions, and another 5 strains degraded only NPA. The nitroacid was metabolized at a faster rate than the nitroalcohol by both pure cultures of rumen bacteria and mixed rumen microorganisms. Nitrite was detected during incubation of NPOH and of NPA with resting cells but not with growing cultures of active strains of rumen bacteria. Nitrite was metabolized much faster than the nitrotoxins by both pure cultures of rumen bacteria and mixed rumen microorganisms. The results suggest that the nitro moiety of NPA or NPOH is metabolized to inorganic nitrite and nitrite is reduced to ammonia by rumen microorganisms, thereby resulting in its detoxification.