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Bac 32, a novel bacteriocin widely disseminated among clinical isolates of Enterococcus faecium.

ABSTRACT: A total of 636 vancomycin-resistant Enterococcus faecium (VRE) isolates that had been obtained between 1994 and 1999 from the Medical School Hospital of the University of Michigan, Ann Arbor, were tested for bacteriocin production. Two hundred seventy-seven (44%) of the strains were bacteriocinogenic; and 193 of these exhibited activity against Enterococcus faecium, Enterococcus hirae, and Enterococcus durans. Strain VRE200 harbors the highly efficient conjugative gentamicin resistance plasmid pG200 (70 kb) and bacteriocin plasmid pTI1 (12.5 kb). The bacteriocin encoded on pTI1 was designated bacteriocin 32 (Bac 32). Bacteriocin 32 was active against E. faecium, E. hirae, and E. durans but showed no activity against Listeria monocytogenes. The Bac 32 genetic locus consists of a bacteriocin gene (bacA) and an immunity gene (bacB). Neither of these genes showed significant homology to any known bacteriocin determinants. The deduced bacA product is 89 amino acids in length, with a putative signal peptide of 19 amino acids at the N terminus. The bacB gene encodes a deduced 55-amino-acid protein without a signal sequence. One hundred eighty-nine strains (97.9%) of the 193 strains with activity against the 3 test enterococcal strains gave rise to the expected specific PCR product with a primer specific for bacA, indicating that there is a high incidence of Bac 32 production among VRE clinical isolates. Data from Southern analyses of plasmid DNA from 189 of the Bac 32-producing strains with a plasmid pTI1-specific probe suggested that 137 (72.5%) of the strains harbored a pTI1-type plasmid. Bac 32 or Bac 32-type bacteriocin activity and the determinant genes were also identified in 22 (39.3%) of a total of 56 vancomycin-sensitive E. faecium clinical isolates, which suggests that this bacteriocin is widely disseminated among E. faecium strains.

SUBMITTER: Inoue T

PROVIDER: S-EPMC1426941 | biostudies-literature | 2006 Apr

REPOSITORIES: biostudies-literature

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Bac 32, a novel bacteriocin widely disseminated among clinical isolates of Enterococcus faecium.

Inoue Takako T Tomita Haruyoshi H Ike Yasuyoshi Y

Antimicrobial agents and chemotherapy 20060401 4

A total of 636 vancomycin-resistant Enterococcus faecium (VRE) isolates that had been obtained between 1994 and 1999 from the Medical School Hospital of the University of Michigan, Ann Arbor, were tested for bacteriocin production. Two hundred seventy-seven (44%) of the strains were bacteriocinogenic; and 193 of these exhibited activity against Enterococcus faecium, Enterococcus hirae, and Enterococcus durans. Strain VRE200 harbors the highly efficient conjugative gentamicin resistance plasmid p ...[more]

PMID: 16569830

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Project description:Bacteriocin 51 (Bac 51) is encoded on the mobile plasmid pHY (6,037 bp), which was isolated from vancomycin-resistant Enterococcus faecium VRE38. Bacteriocin 51 is active against E. faecium, E. hirae, and E. durans. Sequence analysis of pHY showed that it encodes nine open reading frames (ORFs) from ORF1 to ORF9 (in that order). Genetic analysis suggested that ORF1 and ORF2, which were designated bacA and bacB, respectively, are the bacteriocin and immunity genes. bacA encodes a 144-amino-acid protein. The deduced BacA protein has a typical signal sequence at its amino terminus, and a potential signal peptidase-processing site corresponding to the V-E-A sequence is located between the 37th and 39th amino acids. The predicted mature BacA protein consists of 105 amino acids. A potential promoter sequence was identified upstream of the start codon. bacB encodes a 55-amino-acid protein. No obvious promoter or terminator sequence was identified between bacA and bacB. Northern blot analysis of bacA and bacB with a bacA RNA probe produced a transcript of approximately 700 nucleotides, which corresponded to the combined nucleotide sizes of bacA and bacB, indicating that transcription was initiated from the promoter upstream of bacA, continued through bacB, and was terminated at the terminator downstream of bacB. The transcription start site was determined to be the T nucleotide located 6 nucleotides downstream from the -10 promoter sequence. These results indicate that bacA and bacB constitute an operon and that bacA is the bacteriocin structural gene while bacB is the immunity gene. The purified C-terminally His tagged BacA protein of Bac 51 showed bacteriostatic activity against the indicator strain. The purified C-terminally His tagged BacA protein of Bac 32 (whose mature BacA protein has 54 amino acids) and the culture filtrates of the Bac 31- and Bac 43-producing E. faecalis strain FA2-2 showed bactericidal activity. Bac 31 and Bac 43 are pore-forming bacteriocins, unlike the newly characterized bacteriocin Bac 51.

Dataset Information

Bac 32, a novel bacteriocin widely disseminated among clinical isolates of Enterococcus faecium.

Publications

Bac 32, a novel bacteriocin widely disseminated among clinical isolates of Enterococcus faecium.

Similar Datasets

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