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


CONCLUSIONS
A three-component regulatory system common to class II bacteriocins regulates the production of this bacteriocin by Lact. acidophilus.
Dobson
A E
AE
Department of Food Science, North Carolina State University, Raleigh, NC, USA.
Sanozky-Dawes
R B
RB
Klaenhammer
T R
TR
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000032:analysis / Q000096:biosynthesis*; D001431:Bacteriological Techniques; D001483:Base Sequence; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D047908:Intracellular Signaling Peptides and Proteins; D007779:Lactobacillus acidophilus / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D010455:Peptides / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
D018528:ATP-Binding Cassette Transporters; D001430:Bacteriocins; D047908:Intracellular Signaling Peptides and Proteins; D010455:Peptides; C098845:inducing factor, Lactobacillus; C035728:lactocin