Conjugative Plasmid fromLactobacillus gasseriLA39 That Carries Genes for Production of and Immunity to the Circular Bacteriocin Gassericin A

Abstract

Gassericin A is a circular bacteriocin produced by Lactobacillus gasseri strain LA39. We found a 33,333-bp plasmid, designated pLgLA39, in this strain. pLgLA39 contained 44 open reading frames, including seven genes related to gassericin A production/immunity (gaa), as well as genes for replication, plasmid maintenance, and conjugative transfer. pLgLA39 was transferred from LA39 to the type strain of L. gasseri (JCM 1131) by filter mating. The transconjugant exhibited >30-fold-higher more resistance to gassericin A and produced antibacterial activity. Lactobacillus reuteri LA6, the producer of reutericin 6, was proved to harbor a plasmid indistinguishable from pLgLA39 and carrying seven genes 100% identical to gaa. This suggests that pLgLA39 might have been transferred naturally between L. gasseri LA39 and L. reuteri LA6. The seven gaa genes of pLgLA39 were cloned into a plasmid vector to construct pGAA. JCM 1131 T transformed with pGAA expressed antibacterial activity and resistance to gassericin A. pGAA was segregationally more stable than a pGAA derivative plasmid from which gaaA was deleted and even was more stable than the vector. This suggests the occurrence of postsegregational host killing by the gaa genes. pLgLA39 carried a pemIK homolog, and segregational stabilization of a plasmid by the pLgLA39-type pemIK genes was also confirmed. Thus, pLgLA39 was proved to carry the genes for at least two plasmid maintenance mechanisms, i.e., gaa and pemIK. Plasmids containing a repA gene similar to pLgLA39 repA were distributed in several L. gasseri strains.

Solution Structure of Acidocin B, a Circular Bacteriocin Produced by Lactobacillus acidophilus M46

“…However, the smaller size observed previously for this ORF was likely the result of a sequence error. Based on sequence homology, AciI is likely involved in immunity and AciTE may form the secretion apparatus for acidocin B (41,43). The amino acid sequences of AciBCADITE show that these proteins are highly similar, and sometimes 100% identical, to their homologs in the gassericin A gene cluster ( Table 1).…”

“…The amino acid sequence of acidocin B is highly similar to that of gassericin A, a circular bacteriocin that is encoded by a gene cluster of approximately 3.3 kb (Fig. 1A) (41). Previously, a nucleotide sequence of 2.2 kb around the structural acidocin B gene on plasmid pCV461 was determined (22).…”

Discovering the Bacterial Circular Proteins: Bacteriocins, Cyanobactins, and Pilins

“…1, panel 1). These gene clusters are chromosomally encoded, except those of gassericin A/reutericin 6 and acidocin B (21,27,34), garvicin ML (28), and AS-48 (1), which are plasmid-located. As an exception, the AS-48RJ variant is encoded on the chromosome (35).…”

Isolation of the Bacillus thuringiensis plasmid carrying Bacthuricin F4 coding genes and evidence of its conjugative transfer

“…In fact, several reports have described the association between the bacteriocin genes and those involved in plasmid transfer [20,21]. The 33.333 bp plasmid from Lactobacillus gasseri LA39 was described to carry genes for production of and immunity to the circular bacteriocin gassericin, as well as genes for replication, plasmid maintenance, and conjugative transfer [22]. More investigations are also needed to determine the entire machinery involved in BF4 synthesis and production.…”