Isolation and identification of ruminal methanogens from grazing cattle

To obtain information on the diversity of ruminal methanogens in grazing an imals, three ruminal methanogens from grazing cattle were characterized and identified. Two of the isolates were rod-shaped, with one staining Gram-po sitive and being non-motile (BRM9), and the other (BRM16) staining Gram-neg ative and being motile. These isolates grew only on H-2/CO2 and formate, an d optimally at 38 degrees C and pH 6.5-7.0. The third isolate (CM1) was non -motile, pseudosarcina-shaped, and grew on H-2/CO2, acetate, and methyl-con taining compounds, with optimal growth at 40 degrees C and pH 6.5. DNA was prepared from the three isolates, and their 16S rRNA genes were sequenced. Phenotypic data and comparisons of nearly complete 16S rDNA sequences showe d that BRM9, BRM16, and CM1 are strains of Methanobacterium formicicum, Met hanomicrobium mobile, and Methanosarcina barkeri respectively. To the best of our knowledge, this is the first information on ruminal methanogens in c attle maintained under grazing management.