FACTORS AFFECTING THE BACTERIOCIN PRODUCTION OF THE RUMINAL BACTERIUM, STREPTOCOCCUS BOVIS HC5

Authors: MANTOVANI, H - CORNELL UNIVERSITY; Russell, James

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2002
Publication Date: 1/5/2003
Citation: MANTOVANI, H.C., RUSSELL, J.B. FACTORS AFFECTING THE BACTERIOCIN PRODUCTION OF THE RUMINAL BACTERIUM, STREPTOCOCCUS BOVIS HC5. CURRENT MICROBIOLOGY. 2003.

Interpretive Summary: Cattle in the U.S. are often fed antibiotics, but the widespread use of antibiotics in animal feed has been criticized. Antibiotics are primarily targeted against gram-positive gut bacteria. Gram-positive ruminal bacteria produce large amounts of hydrogen, a precursor of methane ammonia, a wasteful end-product of amino acid degradation, and lactic acid, an acid that causes ruminal acidosis, ruminal ulcers, founder and even death of the animal. Some gram-positive bacteria produce peptides (bacteriocins) that can inhibit other gram-positive bacteria, and bacteriocins have been proposed an alternative to antibiotics. We isolated a bacterium with a very active and heat stable bacteriocin, and we have defined factors that affect its production. Research on bacteriocins has the potential to decrease the need for antibiotic in animal feed and lessen the risk of antibiotic resistance in human medicine.

Technical Abstract: Nisin-sensitive Streptococcus bovis JB1 cells were inhibited by bovicin 255, bacteriocin a produced by Streptococcus gallolyticus LRC0255, but nisin-resistant cells were bovicin 255-resistant. Ruminal fluid had bacteria that could inhibit nisin-resistant S. bovis JB1 cells, and 16S rDNA sequencing indicated that the most active strain (HC5) was closely related to other S. bovis. The inhibitory activity of S. bovis HC5 was no due to a bacteriophage, and the inhibition could be reversed pronase E and trypsin. Batch cultures of S. bovis HC5 did not produce bacteriocin until glucose was depleted and cells entered stationary phase, but slow dilution rate continuous cultures had as much bacteriocin activity as stationary phase cultures. Because the activity of continuous cultures was inversely related to the glucose consumption rate, it appeared that bacteriocin production was being catabolite repressed by glucose, but very slow continuous cultures had a little activity. When the pH of continuous cultures was decreased from 6.7 to 5.4, bacteriocin activity increase 1-fold, but bacteriocin production declined at pH values less than 5.0. Continuous cultures that had only ammonia as a nitrogen source produced some bacteriocin, but Trypticase addition caused a 1.5-fold in cell protein and 2.0 fold decline in the amount of HC5 protein that was to prevent S. bovis JB1 growth. Because S. bovis JB1 cultures that had been transferred with sub-lethal doses of S. bovis HC5 bacteriocin never became resistant, it is conceivable that S. bovis HC5 could have a significant impact on S. bovis ecology in vivo.