Submitted to: Conference on Gastrointestinal Function
Publication Type: Abstract Only
Publication Acceptance Date: 1/27/2005
Publication Date: 4/11/2005
Citation: Russell, J.B., Mantovani, H.C., Houlihan, A.J., Flythe, M.D., Xavier, B.M. 2005. Bovicin hc5, a novel bacteriocin from streptococcus bovis. Conference on Gastrointestinal Function. p. 15.
Technical Abstract: Many gram-positive bacteria produce small peptides that have antimicrobial activity, and bacteriocins have been used for a variety of applications. Several species of ruminal bacteria are known to produce bacteriocins. Because the bacteriocin, nisin, and monensin have similar effects on ruminal fermentation, bacteriocins have been proposed as an alternative to this antibiotic. However, the quest for suitable bacteriocins has been stymied by at least 3 factors: 1) some bacteriocins are highly specific and only a narrow spectrum of activity, 2) many bacteria can become bacteriocin-resistant and 3) some bacteriocins are highly unstable or difficult to purify. Streptococcus bovis HC5 produces a bacteriocin (bovicin HC5) that circumvents all of these problems. Bovicin HC5 is a pore forming lantibiotic that has only 23 amino acids, is stable at high temperatures (121 C) and is not degraded some proteinases. Bacteria repeatedly exposed to sub-lethal doses did not become significantly more resistant. Bovicin HC5 has maximal activity at acidic pH values, but bacterial competition experiments indicated that it could have significant effect at pH values typical of the rumen. Bovicin HC5 is a cell-associated bacteriocin, but it can be liberated from the cell by acidic NaCl. This treatment does not cause significant cell lysis and gives a nearly purified product. Bovicin HC5 appears to be chromosomally encoded. Mutants in bovicin HC5 were obtained with the insertion sequence ISS1, but the antibiotic markers didn't remain in the chromosome and this approach could not be used to locate the gene. The amino acid sequence of bovicin HC5 is similar to a bacteriocin produced by S. pyogenes, and primers to a S. pyogenes immunity protein amplified an immunity protein from S. bovis HC5. Because immunity proteins and bacteriocin structural genes are typically contiguous, we are confident that the structural gene of bovicin HC5 will be identified.