Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 8, 1997
Publication Date: N/A
Technical Abstract: Rumen microbial metabolism is an important factor for adaptation of ruminants to dietary selenium. Microbial reduction of selenium has nutritional, toxicological, and environmental implications because of reduced bioavailability to the host animal. The general mechanism of selenium reduction in the rumen has been described, but the microbes responsible are poorly characterized. To address this question, inocula of rumen contents were enriched in media containing rumen fluid, basal salts, bicarbonate, cysteine, 10 mM selenate, and an energy source of either hydrogen (80%/20%, H2CO2 headspace gas), lactate (10 mM), or a solution of carbohydrates (.05% each of glucose, cellobiose, starch, and xylose). Single, red colonies, indicating elemental selenium reduction, were isolated and characterized. Selenium-reducing bacteria were present in rumen contents up to a concentration of 10 exp 5/ml. These isolates could be grouped into three categories: 1) common rumen species such as Selenomonas ruminantium ad Wolinella succinogenes; 2) facultative anaerobes such as Escherichia coli; and 3) specific, selenium-respiring bacteria including Desulfovibrio sp. and other novel, motile rods. In enrichment media containing carbohydrates, the isolates were predominately facultative anaerobes.