Co-transfer of two plasmids determining bacteriocin production and sucrose utilization in Streptococcus faecium

Abstract Streptococcus faecium strain 25 produced a bacteriocin (enterococcin Sf25), metabolized sucrose and contained three plasmids of 2.4, 4.7 and 13.0 MDa. Plasmids Sfp2.4 and Sfp4.7 were cotransferred in a filter mating procedure to sucrose negative and bacteriocin negative S. faecium strain M16. Strain M16 harboured a nonselftransferable plasmid Sfp 19.1 MDa, which was responsible for erythromycin resistance. Transcipient cells of S. faecium M16 contained the 19.1-MDa plasmid and plasmids Sfp2.4 and Sfp4.7, produced the enterococcin Sf25 and gained the ability to degrade sucrose.     

Protoplast-induced curing of bacteriocin plasmid in Lactococcus lactis subsp. lactis 484

Plasmid-specified traits like lactose metabolism and bacteriocin production could be eliminated from Lactococcus lactis subsp. lactis 484 culture during production and regeneration of protoplasts with lysozyme at the concentration of 300 μg/ml after 3 h treatment. Plasmid-free strains and cured derivatives harbouring only a single plasmid (2 MDa) were also obtained. Loss of high molecular weight (65 MDa) low copy number Lac plasmid occurred more frequently compared with low molecular weight (2 MDa) high copy number plasmid. Treatment of L. lactis subsp. lactis 484 cells with lysozyme at concentrations of 1000 μg/ml could produce a large number of Lac⁻ Bac⁻ variants at a very high frequency (94%). The curing data confirmed the linkage of Lac and Bac phenotypes to 65 and 2 MDa plasmids, respectively.     

Mobilization and expression of bacteriocin plasmids from Carnobacterium piscicola isolated from meat

Mobilization and expression of bacteriocin plasmids from Carnobacterium piscicola isolated from meat. The nonconjugative plasmids pCP40 and pCP49 associated with bacteriocin production in Carnobacterium piscicola LV17, a lactic acid bacterium isolated from meat, were mobilized by the wide host range conjugative plasmid pAMβ1 by two stage conjugation. At the first stage, pAMβ1 was conjugally transferred into C. piscicola LV17 containing the two plasmids associated with bacteriocin production and a cryptic plasmid. Mobilization of the two bacteriocin plasmids by pAMβ1 was done by the second stage conjugation between the pAMβ1-containing C. piscicola LV17 and chloramphenicol (Cm)-resistant Bac^- mutant of C. piscicola LV17. The transconjugants had either partial bacteriocin activity associated with acquisition of pCP40 or pCP49, or complete bacteriocin activity associated with acquisition of all three of the resident plasmids from C. piscicola LV17 or an 89 MDa cointegrated plasmid derived from pCP40 and pCP49. Further manipulation of the transconjugants and a mutant strain of C. piscicola LV17 resulted in separate strains with only pCP40 or pCP49 which produce different bacteriocins. The bacteriocin gene from pCP49 was cloned into pCaT, a chloramphenicol resistance-encoding vector, and electrotransformed into another bacteriocin-producing strain of C. piscicola , enhancing the antagonistic spectrum of the recipient strain.     

Self-transferable plasmids determining the hemolysin and bacteriocin of Streptococcus faecalis var. zymogenes.

Strains of Streptococcus faecalis var. zymogenes, designated JH1 and JH3, produced a hemolysin and a bacteriocin. Hemolytic activity was lost from a low percentage of cells grown in broth at either 37 or 45 C. All nonhemolytic (Hly-) variants had lost bacteriocin activity (Ben-), and those from strain JH3 had also lost resistance to the bacteriocin (Bnr-). The majority of Hly-, Ben- variants from JH1 retained bacteriocin resistance (Bnrplus). Strains JH1 and JH3 contained a plasmid deoxyribonucleic acid species of molecular weight 38 times 10-6 (plasmids pJH2 and pJH3, respectively), and strain JH1 also contained a 50 times 10-6 molecular weight plasmid (pJH1) which has previously been shown to carry the genes determining resistance to the antibiotics kanamycin, neomycin, streptomycin, erythromycin, and tetracycline. Hly-, Bcn-, Bnr- variants of strain JH3 had completely lost plasmid pJH3. Hly-, Bcn-, Bnr- variants of strain JH1 had completely lost plasmid pJH2 and retained plasmid pJH1, but Hly-, Bcn-, Bnrplus variants had retained both plasmids pJH2 and pJH1. The Hlyplus, Bcnplus, Bnrplus traits from both parental strains were transferable to nonhemolytic S. faecalis strains during mixed incubation in broth at 37 C, and hemolytic recipient strains were found to have received plasmid pJH2 from strain JH1 and pJH3 from JH3. We conclude that the Hlyplus, Bnrplus traits are borne on plasmid pJH2 in strain JH1 and pJH3 in strain JH3 and that, in Hly-, Bcn-, Bnrplus variants of strain JH1, plasmic pJH2 has suffered a mutation affecting hemolysin and bacteriocin expression. We infer that the plasmids transfer by conjugation. Beta-hemolytic activity is the only property distinguishing the zymogenes variety from S. faecalis. Since we have shown that this activity is plasmid borne in strains JH1 and JH3, we endorse the view that the varietal status of zymogenes should be dropped.     

Purification of bacteriocin AS-48 from an Enterococcus faecium strain and analysis of the gene cluster involved in its production

The cyclic bacteriocin AS-48 has previously been shown to be produced by Enterococcus faecalis strains. A bacteriocin has been purified from an E. faecium strain (E. faecium 7C5), and it has been found to possess molecular mass, cyclization and amino acid sequence typical of bacteriocin AS-48. In addition to the structural gene as-48A, the sequence analysis of the AS-48 gene cluster present in E. faecium 7C5 has revealed the presence of several putative coding regions presumably involved in bacteriocin production and immunity. The results of DNA hybridization assays have indicated that the AS-48 gene cluster and the gene pd78 are present on the same plasmid, possibly the pPD1 plasmid, in E. faecium 7C5.     

Purification and N-terminal amino acid sequence of Enterocin CRL 35, a 'pediocin-like' bacteriocin produced by Enterococcus faecium CRL 35

M.E. FARÍAS, R.N. FARÍAS, A.P. DE RUIZ HOLGADO AND F. SESMA. 1996. Enterocin CRL 35, a bacteriocin produced by Enterococcus faecium CRL 35 that inhibits food-borne pathogens, was purified by precipitation with (NH₄)₂SO₄, gel filtration, ion exchange and reverse phase chromatography. The partial N-terminal amino acid sequence indicated a strong homology with other 'pediocin-like bacteriocins' previously described.     

Genetic analysis of bacteriocin 43 of vancomycin-resistant Enterococcus faecium

A total of 636 vancomycin-resistant Enterococcus faecium (VRE) isolates obtained between 1994 and 1999 from the Medical School Hospital of the University of Michigan were tested for bacteriocin production. Of the 277 (44%) bacteriocinogenic strains, 21 were active against E. faecalis, E. faecium, E. hirae, E. durans, and Listeria monocytogenes. Of those 21 strains, a representative bacteriocin of strain VRE82, designated bacteriocin 43, was found to be encoded on mobilizable plasmid pDT1 (6.2 kbp). Nine open reading frames (ORFs), ORF1 to ORF9, were presented on pDT1 and were oriented in the same direction. The bacteriocin 43 locus (bac43) consists of the bacteriocin gene bacA (ORF1) and the immunity gene bacB (ORF2). The deduced bacA product is 74 amino acids in length with a putative signal peptide of 30 amino acids at the N terminus. The bacB gene encodes a deduced 95-amino-acid protein without a signal sequence. The predicted mature BacA protein (44 amino acids) showed sequence homology with the membrane-active class IIa bacteriocins of lactic acid bacteria and showed 86% homology with bacteriocin 31 from E. faecalis YI717 and 98% homology with bacteriocin RC714. Southern analysis with a bac43 probe of each plasmid DNA from the 21 strains showed hybridization to a specific fragment corresponding to the 6.2-kbp EcoRI fragment, suggesting that the strains harbored the pDT1-like plasmid (6.2 kb) which encoded the bacteriocin 43-type bacteriocin. The bac43 determinant was not identified among non-VRE clinical isolates.     

Restriction enzyme analysis of lactose and bacteriocin plasmids from Streptococcus lactis subsp. diacetylactis WM4 and cloning of BclI fragments coding for bacteriocin production

The 131.1-kilobase (kb) bacteriocin production (Bac) plasmid pNP2 and the 63.6-kb lactose metabolism (Lac) plasmid pCS26, from Streptococcus lactis subsp. diacetylactis WM4, as well as pWN8, a 116.7-kb recombinant plasmid from a Lac+ transconjugant, were analyzed with restriction enzymes to determine the origin of pWN8. Plasmid pWN8 conferred a Lac+ Bac- phenotype, contained DNA derived from pCS26 and pNP2, and, like pNP2, exhibited self-transmissibility (Tra+). In cloning attempts, Bac+ transformant S. lactis KSH1 was isolated. The recombinant plasmid, pKSH1, contained three BclI fragments from pNP2. Bac- transformants which individually contained each of the three fragments were also identified. Comparison of restriction maps of pKSH1 and pNP2 revealed an 18.4-kb region common to both plasmids, involving two of the three BclI fragments. S. lactis KSH1 also exhibited greater inhibitory activity against the indicator strain S. diacetylactis 18-16 than did a strain containing the 131.1-kb Bac plasmid.     

Purification and some characteristics of enterocin ON-157, a bacteriocin produced by Enterococcus faecium NIAI 157

Bacteriocin-like activity (BLA) was screened in 690 strains of lactic acid bacteria isolated from plant materials such as silages and fermented vegetables. Among them, a strain identified as Enterococcus faecium NIAI 157 showed a clear BLA against the indicator strain, Ent. faecium IFO 13712. The proteinaceous nature and antimicrobial activity against closely related species strongly indicated that this BLA was a bacteriocin and was designated enterocin ON-157. The bacteriocin activity of this strain was extracellularly produced in the logarithmic growth phase in MRS broth and purified by ultrafiltration, ammonium sulphate precipitation and cation-exchange chromatography. Purified enterocin ON-157 had a molecular weight of approximately 2500 Da in SDS-PAGE analysis and was easily inhibited by treatment with alpha-amylase and proteolytic enzymes. Enterocin ON-157 had a bactericidal mode of action and inhibited the growth of the enterococci, Lactobacillus sake and Listeria monocytogenes. Enterococcus faecium NIAI 157 harboured two plasmids, 49.0 kb and 43.7 kb, and a variant missing a larger plasmid by curing with novobiocin lost the bactriocin activity.     

Restriction enzyme analysis of lactose and bacteriocin plasmids from Streptococcus lactis subsp. diacetylactis WM4 and cloning of BclI fragments coding for bacteriocin production.

The 131.1-kilobase (kb) bacteriocin production (Bac) plasmid pNP2 and the 63.6-kb lactose metabolism (Lac) plasmid pCS26, from Streptococcus lactis subsp. diacetylactis WM4, as well as pWN8, a 116.7-kb recombinant plasmid from a Lac+ transconjugant, were analyzed with restriction enzymes to determine the origin of pWN8. Plasmid pWN8 conferred a Lac+ Bac- phenotype, contained DNA derived from pCS26 and pNP2, and, like pNP2, exhibited self-transmissibility (Tra+). In cloning attempts, Bac+ transformant S. lactis KSH1 was isolated. The recombinant plasmid, pKSH1, contained three BclI fragments from pNP2. Bac- transformants which individually contained each of the three fragments were also identified. Comparison of restriction maps of pKSH1 and pNP2 revealed an 18.4-kb region common to both plasmids, involving two of the three BclI fragments. S. lactis KSH1 also exhibited greater inhibitory activity against the indicator strain S. diacetylactis 18-16 than did a strain containing the 131.1-kb Bac plasmid.     

Characterization of brevicin 27, a bacteriocin synthetized byLactobacillus brevis SB27

Lactobacillus brevis SB27, isolated from sausages, produced an antimicrobial substance active against numerous strains of heterofermentative lactobacilli and against some strains of pediococci andBacillus. The antibacterial agent was shown to be heat stable, resistant over a wide pH range, and sensitive to proteolytic enzymes. It was identified as a bacteriocin and termed brevicin 27. Dialysis and ultrafiltration suggested an apparent molecular weight between 10 and 30 kDa for the crude inhibitory molecule. Brevicin 27 exhibited a hydrophobic character. A partially purified preparation, resulting from ammonium sulfate precipitation and cation exchange chromatography, permitted confirmation of some characteristics of the bacteriocin, previously established with the crude extract. After treatment of the original brevicin 27-producing strain with novobiocin, a nonproducing mutant was obtained. This mutant was sensitive to brevicin 27, and its plasmid profile revealed the loss of a plasmid of about 3 MDa.     

Conjugal transfer of a plasmid encoding bacteriocin production and immunity in Pediococcus acidilactici H

Previous investigations indicated that curing of a 7.4-Md plasmid (pSMB74) resulted in concomitant loss of bacteriocin activity and immunity in Pediococcus acidilactici H. Transfer of pSMB74 to a gentamicin-neomycin resistant (Gm^rNm^r) derivative of P. acidilactici LB42, which was devoid of any plasmid DNA, required cell-to-cell contact on a solid mating surface and converted the strain to Bac⁺Bac^r phenotype. Gene transfer processes such as transduction and transformation were ruled out from the experiment. Treatment of donor cells with chloroform did not allow the appearance of recombinant clones, confirming that viable cells were essential for this particular mechanism of genetic transfer. Transconjugants obtained from selective agar surface were subjected to plasmid isolation and agarose gel electrophoresis. Each of them exhibited plasmid size corresponding to pSMB74 of donor strain. All results suggested this genetic transfer similar to conjugation, and provided presumptive evidence for plasmid-encoded bacteriocin activity and immunity in P. acidilactici H.     

Selection of strains cured of the Rhizobium leguminosarum Sym-plasmid pRL1JI by using small bacteriocin

Abstract Fast growing Rhizobia are usually insensitive to a low M _r (small) bacteriocin. Introduction of the Sym-plasmid pRL1JI into these strains results in sensitivity towards small bacteriocin. Of such strains, small bacteriocin insensitive mutants (Sbs⁻) were selected.
A high percentage of these Sbs⁻ mutants appeared to be cured of pRL1JI. This selection of cured strains was feasible as well for the wild-type plasmid pRL1JI, as for a variety of transposon marked derivatives in several bacterial backgrounds.     

Purification, partial characterization and plasmid-linkage of pediocin SJ-1, a bacteriocin produced by Pediococcus acidilactici

Pediococcus acidilactici SJ-1, isolated from a naturally-fermented meat product, produced an antibacterial agent active against selected strains of Lactobacillus spp., Clostridium perfringens and Listeria monocytogenes. The agent was bactericidal against sensitive indicators, and sensitive to proteolytic enzymes; it was identified as a bacteriocin, and was designated as pediocin SJ-1. It was stable over a wide pH range (3–9), and apparently most stable in the lower part of that range. At pH 3.6, pediocin SJ-1 was stable at heat-processing temperatures within the range 65–121°C; its activity decreased significantly, however, when it was heated at pH 7.0. The activity of pediocin SJ-1 on sensitive indicator cells was lost in the presence of α-amylase, suggesting that it contains a glyco moiety, necessary for its antibacterial action.
Native pediocin SJ-1 exists in the form of monomers and aggregates (with molecular weights in the range 80–150 kDa). Pediocin SJ-1 was purified 262-fold by direct application of cell-free supernatant fluids to a cation-exchange chromatography column, and was resolved by SDS-PAGE as a single peptide band with a MW of ca 4 kDa. The original pediocin SJ-1-producing strain (bac⁺) harbours three plasmids of 4.6, 23.5, and 45.7 MDa. Production of pediocin SJ-1, but not immunity to SJ-1, is associated with the 4.6 MDa plasmid.     

In vitro study on bacteriocin production of Enterococci associated with chickens

In recent years, the approach of using innovative strategies such as probiotics or bacteriocins for the prevention or treatment of bacterial infections has come into focus. The present study was undertaken to check in vitro ability of Enterococci-isolated from the gastrointestinal tract of chickens-to produce a bacteriocin-like substance and to describe some further probiotic properties in five selected Enterococcus faecium strains. All strains (n=17) were found to produce bacteriocin-like substances against 14 out of 20 indicator bacteria of animal, food or environmental origin. Selected E. faecium strains expressed sufficient survival by pH 3.0 after 3h, in the presence of 1% bile after 24h and they were sensitive to most of antimicrobials tested. All tested strains adhere to the human, canine and porcine intestinal mucus (between 1.5% and 9.2%). However, better adhesion ability was observed for the canine mucus. PCR detection of enterocin structural genes determined presence of enterocins A and P genes in all selected strains. Characterization of bacteriocin substance in detail was performed in E. faecium EF55. The EF55 strain produced a bacteriocin-like substance (during the late logarithmic and early stationary growth phase) with inhibitory activity mostly against Gram-positive bacteria (100-51,200 AU/mL) including Listeria monocytogenes. Proteinaceous character of the bacteriocin substance was confirmed (its inhibitory activity was lost after its treatment with proteases), it was found to be stable after heating (100 degrees C 10 min) and during 12 months storage at -20 degrees C. The highest inhibitory activity of bacteriocin produced by EF55 strain (growing in MRS) broth was achieved between pH 7.0 and 9.0.     

Plasmid content and bacteriocin production by five strains of Lactococcus lactis isolated from semi-hard homemade cheese

In this study, the plasmid content and bacteriocin production of natural isolates of lactococci were investigated. Five bacteriocin producing lactococcal strains (Lactococcus lactis subsp. lactis BGMN1-2, BGMN1-3, BGMN1-5, BGMN1-6, and BGMN2-7) were isolated as nonstarter microflora of semi-hard homemade cheese and characterized. All isolates contained a number of plasmids. It was shown that lcnB structural genes for bacteriocin lactococcin B were located on large plasmids in all isolates. In the strains BGMN1-3 and BGMN1-5 proteinase prtP genes collocated with lcnB. Furthermore, these strains produced two additional bacteriocins (LsbA and LsbB) with genes responsible for their production and immunity located on the small rolling circle-replicating plasmid pMN5. Using deletion experiments of pMN5, minimal replicon of the plasmid and involvement of a bacteriocin locus in plasmid maintenance were identified. In addition, plasmid curing experiments showed that genes for catabolism or transport of 10 carbohydrates in the strain BGMN1-5 were plasmid located.     

Characterization of a bacteriocin produced by Enterococcus faecium GM-1 isolated from an infant

AIM: To partially characterize the bacteriocin produced by the GM-1 strain of Enterococcus faecium, isolated from the faeces of a newborn human infant. METHODS AND RESULTS: The bacteriocin produced by E. faecium GM-1 showed a broad spectrum of activity against indicator strains of Escherichia coli, Staphylococcus aureus, Vibrio spp., Salmonella typhimurium, Listeria monocytogenes, Lactobacillus acidophilus, and Streptococcus thermophilus. Treatment of the GM-1 bacteriocin with proteolytic enzymes reduced its inhibitory activities. The bacteriocin was stable at 100 degrees C for 20 min and displayed inhibitory activity at neutral pH. The optimal production of bacteriocin from E. faecium GM-1 was obtained when the culture conditions were pH 6.0-6.5 and 35-40 degrees C. The inhibitory activity of the bacteriocin was not substantially changed by the use of different carbon sources in the media, except when galactose was substituted for glucose. The use of a sole nitrogen source caused a decrease in inhibitory activity. A bacteriocin gene similar to enterocin P was identified from the total DNA of E. faecium GM-1 by PCR and direct sequencing methods. CONCLUSION: E. faecium GM-1, which was isolated from the faeces of a newborn baby, produces an enterocin P-like bacteriocin with inhibitory activity against Gram-positive and Gram-negative bacteria, including food-borne pathogens. SIGNIFICANCE AND IMPACT OF THE STUDY: E. faecium GM-1, isolated from infant faeces, produces a new bacteriocin that is similar to enterocin P. This bacteriocin is heat stable and has a broad antibacterial spectrum that includes both Gram-positive and Gram-negative bacteria.     

Bacteriocin production by Enterococcus faecium NA01 from 'wara'—a fermented skimmed cow milk product from West Africa

An Enterococcus faecium strain from Nigerian fermented skimmed cow milk ('wara') produced bacteriocin inhibitory towards Lactobacillus, Enterococcus and Listeria strains. The bacteriocin (designated enterocin 01) was inactivated by proteases, heat-stable at 100°C and active at pH 2.0–6.0. The Ent. faecium isolate harboured plasmids of ca 36.3 and 23.1 kb. Curing experiments with ethidium bromide resulted in a bacteriocin-negative mutant which had not lost immunity to the bacteriocin. Slight differences in plasmid profiles between wild-type and mutant indicated a possible plasmid-coded bacteriocin production.     

C55 bacteriocin produced by ETB‐plasmid positive Staphylococcus aureus strains is a key factor for competition with S. aureus strains

Exfoliative toxin (ET) produced by Staphylococcus aureus is closely associated with the onset of bullous impetigo. To date, three ETs (ETA, ETB and ETD) have been identified. The gene encoding ETB is located in a plasmid designated pETB. Bacteriocin synthesis genes are also located in this plasmid and pETB‐positive strains reportedly produce the C55 bacteriocin. In this study, the antibacterial activity against S. aureus strains of the bacteriocin produced by the pETB‐positive strain TY4 was investigated. This bacteriocin demonstrated antibacterial activity against all pETB‐negative but not pETB‐positive strains, including TY4. Additionally, a TY4? strain from which the pETB plasmid had been deleted exhibited susceptibility to the bacteriocin. Further experiments revealed that two immunity factors (orf 46‐47 and orf 48) downstream of the bacteriocin synthesis genes in the pETB plasmid are associated with immunity against the bacteriocin produced by TY4. The TY4? with orf46‐47 strain exhibited complete resistance to bacteriocin, whereas the TY4? with orf48 strain exhibited partial resistance. Whether bacteriocin affects the proportion of each strain when co‐cultured with S. aureus strains was also investigated. When TY4 or TY4? was co‐cultured with 209P strain, which is susceptible to the bacteriocin, the proportion of 209P co‐cultured with TY4 was significantly less than when 209P was co‐cultured with TY4?, whereas the proportion of TY4? with orf46‐48 co‐cultured with TY4 was greater than with TY4?. These results suggest that the C55 bacteriocin produced by pETB‐positive strains affects the proportion of each strain when pETB‐positive and ‐negative strains co‐exist.