Plasmid content and bacteriocin production by five strains ofLactococcus lactisisolated from semi-hard homemade cheese

2006 ◽  
Vol 52 (11) ◽  
pp. 1110-1120 ◽  
Author(s):  
Milan Kojic ◽  
Ivana Strahinic ◽  
Djordje Fira ◽  
Branko Jovcic ◽  
Ljubisa Topisirovic
Keyword(s):  
Lactococcus Lactis ◽  
Bacteriocin Production ◽  
Plasmid Curing ◽  
Structural Genes ◽  
Rolling Circle ◽  
Plasmid Content ◽  
Plasmid Maintenance ◽  
Lactococcus Lactis Subsp ◽  
Natural Isolates ◽  
Large Plasmids

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.Key words: lactococci, natural isolates, bacteriocin, plasmid curing.

A Bacteriocin Production on Soya Nutri Nuggets Extract Medium by Lactococcus lactis Subsp. Lactis CCSUB202

2007 ◽  
Vol 3 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Archana Kumari ◽  
Amar P. Garg ◽  
Kousar Makeen ◽  
Mohan Lal ◽  
Charu Gupta ◽  
...  
Keyword(s):  
Lactococcus Lactis ◽  
Bacteriocin Production ◽  
Lactococcus Lactis Subsp ◽  
Extract Medium

scholarly journals Detection and characterization of bacteriocin-producing Lactococcus lactis strains

1999 ◽  
Vol 30 (2) ◽  
pp. 130-136 ◽  
Author(s):  
Izildinha Moreno ◽  
Alda L.S. Lerayer ◽  
Mauro F. de Freitas Leitão
Keyword(s):  
Hydrogen Peroxide ◽  
Antimicrobial Activity ◽  
Lactococcus Lactis ◽  
Antimicrobial Activities ◽  
Bacteriocin Production ◽  
The Other ◽  
Plasmid Content ◽  
Molecular Weights ◽  
Diffusion Assay

One hundred sixty seven strains of Lactococcus lactis were screened for bacteriocin production by well diffusion assay of GM17 agar. Fourteen (8.4%) produced antimicrobial activity other than organic acids, bacteriophages or hydrogen peroxide. The frequency of bacteriocin production ranged from 2% in L. lactis subsp. cremoris up to 12% in L. lactis subsp. lactis. Antimicrobial activities were not observed in any strain of L. lactis subsp. lactis var. diacetylactis. Among thirteen bacteriocin-producing strains and two nisin-producing strains (L. lactis subsp. lactis ATCC 11454 and L. lactis subsp. lactis CNRZ 150), eight (53%) were characterized as lactose-positive (Lac+) and proteinase-negative (Prt-). The bacteriocin-producing cultures were also characterized on the basis of plasmid content. All strains had 2 to 7 plasmids with molecular weights varying from 0.5 to 28.1 Mdal. Four strains (ITAL 435, ITAL 436, ITAL 437 and ITAL 438) showed identical profiles and the other were quite distinct.

scholarly journals Lactococcus lactis subsp. lactis LTM 32, a new bacteriocin-producing strain isolated from Vietnamese fermented milk

2013 ◽  
Vol 19 (No. 5) ◽  
pp. 171-176 ◽  
Author(s):  
T.M. Do ◽  
M. Plocková ◽  
J. Chumchalová
Keyword(s):  
Lactococcus Lactis ◽  
Proteolytic Enzymes ◽  
Optimal Growth ◽  
Fermented Milk ◽  
Culture Collection ◽  
Fermented Food ◽  
Bacteriocin Production ◽  
Proteinase K ◽  
Lactococcus Lactis Subsp ◽  
Initial Ph

Screening for bacteriocin production of 60 strains of lactic acid bacteria (LAB) both isolated from various Vietnamese fermented food and obtained from the culture collection resulted in the detection of a bacteriocin-producing strain, Lactococcus lactis subsp. lactis LTM 32 isolated from Vietnamese fermented milk. This strain was identified and partly characterized. This bacteriocin inhibited not only closely relative strains of LAB but also strains of Listeria monocytogenes, Bacillus sp. including B. cereus, B. stearothermophilus, B. subtilis, B. pumilus and Staphylococcus aureus. It was heat stable at 121°C for 15 min, at 100°C for 120 min and stable during storage at –20°C and 4°C for 3 months. The bacteriocin was inactivated by some proteolytic enzymes, namely by proteinase K and pronase E in concentrations up to 0.5 mg/ml but not by  α-amylase and pepsin. The optimal growth and bacteriocin production were achieved in M17L broth at 30°C and initial pH 6.8. The characteristics of bacteriocin-producing strain Lactococcus lactis subsp. lactis LTM 32 are of interest for food safety.

Proteinase PI and lactococcin A genes are located on the largest plasmid inLactococcus lactissubsp.lactisbv. diacetylactis S50

2005 ◽  
Vol 51 (4) ◽  
pp. 305-314 ◽  
Author(s):  
Milan Kojic ◽  
Ivana Strahinic ◽  
Ljubisa Topisirovic
Keyword(s):  
Dna Hybridization ◽  
Cell Envelope ◽  
Bacteriocin Production ◽  
Conjugative Plasmid ◽  
Enzyme Analysis ◽  
Restriction Enzyme Analysis ◽  
Plasmid Curing ◽  
Test Frequency ◽  
Genes Encoding ◽  
Large Plasmids

Lactococcus lactis subsp. lactis bv. diacetylactis S50 produces a lactococcin A-like bacteriocin named bacteriocin S50, and cell envelope-associated PI-type proteinase activity. This strain harbours 3 small size plasmids: pS6 (6.3 kb), pS7a (7.31 kb), and pS7b (7.27 kb). Plasmid curing using a combination of novobiocin treatment (10 µg·mL–1) and sublethal temperature (40 °C) resulted in a very low yield (0.17%) of Prt–, Bac–, Bacsderivatives, which retained all 3 small size resident plasmids. Pulsed-field gel electrophoresis of DNA isolated from the strain S50 and cured derivatives in combination with restriction enzyme analysis and DNA–DNA hybridization revealed that S50 contains 2 additional large plasmids: pS140 (140 kb) and pS80 (80 kb). Conjugation experiments using strain S50 as a donor and various lactococcal recipients resulted in Prt+, Bac+, Bacrtransconjugants. Analysis of these transconjugants strongly indicated that plasmid pS140 harbours the prt and bac genes encoding proteinase and bacteriocin production, and immunity to bacteriocin, since each Prt+, Bac+, Bacrtranconjugant contained pS140. Accordingly, none of the Prt–, Bac–, Bacstransconjugants contained this plasmid. pS140 was a self-transmissible conjugative plasmid regardless of the host lactococcal recipient used in the test. Frequency of conjugation of plasmid pS140 did not depend on either the donor or recipient strain.Key words: Lactococcus, plasmids, conjugation, bacteriocin, proteinase.

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