Submitted to: Current Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/8/2005
Publication Date: 12/15/2006
Citation: Houlihan, A.J., Russell, J.B. 2006. The effect of calcium and magnesium on the activity of bovicin hc5 and nisin. Current Microbiology. 53:365-369. 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: Nisin is a cationic peptide (lantibiotic) that inhibits bacteria by inserting into cell membranes to form pores that dissipate ion gradients. Nisin resistance has been correlated with alterations in the cell surface of previously sensitive bacteria. Nisin-resistant bacteria have more lipoteichoic acids and a greater positive (less negative) surface charge. Bovicin HC5 is a lantibiotic produced by Streptococcus bovis HC5, and it has the ability to inhibit nisin-resistant bacteria. S. bovis JB1 is a non-bacteriocin producing bacterium that can be inhibited by either bovicin HC5 or nisin. However, this strain becomes rapidly nisin-resistant when exposed to sub-lethal doses. S. bovis JB1 cells treated or washed with the divalent cations calcium or magnesium bound more Congo red, an anionic dye, and became more resistant to nisin and bovicin HC5. However, bovicin HC5 was affected to a greater degree by magnesium than calcium and the reverse was observed with nisin. These results indicated that nisin and bovicin HC5 have different properties, and Kyte-Doolittle hydropathy plots showed that the C-terminus of bovicin HC5 was more hydrophobic than nisin. Because the C-terminus of lantibiotics makes initial cell contact and passes through the membrane to form pores, increased hydrophobicity may make bovicin HC5 resistance less likely.