Submitted to: Federation of European Microbiological Societies Microbiology Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2003
Publication Date: 2/9/2004
Citation: FLYTHE, M.D., RUSSELL, J.B. THE EFFECT OF PH AND A BACTERIOCIN (BOVICIN HC5) ON CLOSTRIDIUM SPOROGENES MD1, A BACTERIUM THAT HAS THE ABILITY TO DEGRADE AMINO ACIDS IN ENSILED PLANT MATERIALS. FEDERATION OF EUROPEAN MICROBIOLOGICAL SOCIETIES MICROBIOLOGY ECOLOGY. 2004. V. 47. P. 215-222. Interpretive Summary: American cattle consume over 150 million tons of fermented plant materials (silage) each year. However, silages are frequently contaminated with clostridia. Clostridia ferment amino acids, produce ammonia and increase silage pH. If the silage pH increases, molds and other toxic microorganisms proliferate. Amino acid fermenting clostridia were isolated from fresh alfalfa, fresh corn, and silages; and all of them could ferment amino acids at acidic pH values. The isolates were tested for their sensitivity to a previously characterized bacteriocin (bovicin HC5) from Streptococcus bovis HC5. Because all of the isolates were sensitive to bovicin HC5, it appears that bacteriocin-producing bacteria could be used to improve silage quality. Research on silage microbiology has the potential to decrease the cost of American cattle production and protect cattle and consumers from potentially toxic bacteria.
Technical Abstract: Fresh plant materials can be fermented and preserved as silage for cattle, but clostridia that deaminate amino acids increase pH. If silage pH rises, other spoilage microorganisms proliferate. Rod-shaped, anaerobic bacteria with spores were isolated from fresh alfalfa, fresh corn, and silages. Strain MD1 had the highest specific activity of amino acid deamination, and it was most closely related to Clostridium botulinum A and B. However, because MD1 did not produce a toxin, it was classified as Clostridium sporogenes. Washed cell suspensions of C. sporogenes MD1 had specific activities as great as 690 nmol ammonia mg protein-1 min-1, and this rate did not decrease until the pH was less than 4.5. Batch cultures of C. sporogenes MD1 did not initiate growth if the initial pH was less than 5.0, but continuous cultures (0.1 h-1 dilution rate) persisted until the pH of culture vessel was 4.6. When C. sporogenes MD1 was co-cultured with a bacteriocin producing Streptococcus bovis strain (HC5), ammonia production was greatly reduced. The ability of S. bovis HC5 to inhibit MD1 was pH-dependent. When the pH was 5.5 or less, MD1 could no longer be detected. These latter results support the idea that bacteriocin-producing bacteria may be used to improve silage quality.