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Identification of an operon and inducing peptide involved in the production of lactacin B by Lactobacillus acidophilus

Dobson, A.E., Sanozky‐Dawes, R.B., Klaenhammer, T.R.
Journal of applied microbiology 2007 v.103 no.5 pp. 1766-1778
ABC transporters, Lactobacillus acidophilus, bacteriocins, culture media, microbiology, open reading frames, operon, peptides, signal transduction, transcription (genetics)
Aim: To determine if a 9·5‐kb region on the Lactobacillus acidophilus NCFM genome, encoded the genetic determinants for regulation and production of lactacin B, a class II bacteriocin. Methods: Transcriptional analysis was used to identify a 9·5‐kb polycistronic region suspected of encoding the lab operon. The 12 putative open reading frames (LBA1803–LBA1791) were organized into three clusters: a production and regulation cluster encoding a putative two‐component signal transduction system; an export cluster encoding a putative ABC transporter and a final cluster composed of three unknown proteins. Seven genes were typical of bacteriocins, encoding small, cationic peptides, each with an N‐terminal double‐glycine leader motif. Inactivation of a predicted ABC transporter completely abolished bacteriocin activity. When cloned and expressed together, LBA1803–LBA1800 resulted in markedly higher levels of lactacin B activity. The four peptides were chemically synthesized but exhibited no bacteriocin activity, alone or in combination. Only LBA1800 induced lactacin B production in broth cultures. Conclusions: Lactacin B production is encoded within the 9·5‐kb lab operon of 12 genes that are transcribed in a single transcript. LBA1800 is an inducing peptide of bacteriocin production. Significance and Impact of the Study: A three‐component regulatory system common to class II bacteriocins regulates the production of this bacteriocin by Lact. acidophilus.