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.
Kojic
Milan
M
Institute of Molecular Genetics and Genetic Engineering, Belgrade, Serbia and Montenegro. mkojics@eunet.yu
Strahinic
Ivana
I
Fira
Djordje
D
Jovcic
Branko
B
Topisirovic
Ljubisa
L
D001430:Bacteriocins / Q000096:biosynthesis* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002611:Cheese / Q000382:microbiology*; D005516:Food Microbiology; D013294:Lactococcus lactis / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D010957:Plasmids / Q000235:genetics* / Q000302:isolation & purification
D001430:Bacteriocins; C075150:lactococcin B