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.
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.
Authors: Yong Jun Goh; M Andrea Azcárate-Peril; Sarah O'Flaherty; Evelyn Durmaz; Florence Valence; Julien Jardin; Sylvie Lortal; Todd R Klaenhammer Journal: Appl Environ Microbiol Date: 2009-03-20 Impact factor: 4.792
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