THE EFFECT OF CALCIUM AND MAGNESIUM ON THE ACTIVITY OF BOVICIN HC5 AND NISIN

Authors: HOULIHAN, A - CORNELL UNIVERSITY; Russell, James

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2006
Publication Date: 4/15/2006
Citation: Houlihan, A. J. and J. B. Russell. 2006. The effect of calcium and magnesium on the activity of bovicin HC5 and nisin. Curr. Microbiol. 53:365-336.

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 bacteria produce peptides (bacteriocins) that can inhibit gram-positive bacteria, and bacteriocins have been proposed as an alternative to antibiotics. In this paper, we show that the activity of the bacteriocin, bovicin HC5 only inhibited to a small degree by divalent cations. Research on bacteriocins has the potential to decrease the need for antibiotic in animal feed.

Technical Abstract: Some Gram-positive bacteria produce small peptides (bacteriocins) that have antimicrobial activity, but many bacteria can become bacteriocin-resistant. Bovicin HC5, an antibiotic produced by Streptococcus bovis HC5, has the ability to inhibit nisin-resistant bacteria. Because nisin resistance has, in many cases, been correlated with an alteration of lipoteichoic acids or the polar head groups of membrane phospholipids, we decided to examine the effect of divalent cations on nisin and bovicin HC5 activity. Both bacteriocins catalyzed potassium efflux from S. bovis JB1, a non-bacteriocin producing strain. The addition of large amounts (100 mM) of calcium or magnesium increased the ability of S. bovis JB1 to bind Congo red (an anionic dye) counteracted bacteriocin-mediated potassium loss. Calcium was more effective than magnesium in decreasing nisin activity, but reverse was observed with bovicin HC5. Nisin-resistant S. bovis JB1 cells bound 3-times as much Congo red as nisin-sensitive cells, and this result is consistent with the idea that changes in cell surface charge can be a mechanism of bacteriocin resistance. The nisin-resistant cells were less susceptible to bovicin HC5, but bovicin HC5 was still caused a 50% depletion of intracellular potassium. These results indicated that nisin and bovicin HC5 react differently with the cell surfaces of Gram-positive bacteria.