Development of a lactococcal integration vector by using IS981 and a temperature-sensitive lactococcal replication region

Article Abstract:

Gene stability in milk fermentation prevents plasmid loss and consequently, lactococcus starter failure. Vectors are constructed from plasmids.However, they do not replicate in lactococci. Developing a lactococcalintegration vector is done by constructing it in such a way that it would be able to integrate genes into the lactococcal chromosome by Campbell-like integration. pKMP10, the lactococcal integration vector constructed in this study, consists of three components: the replication and temperature-sensitive maintenance regions from pSK11 which is a lactose plasmid; an internal fragmentof IS981 which is a lactococcal insertion sequence as the region for homologousrecombination; and the erythromycin resistance and Escherichia coli replicationregion from pVA891, an encoding erthromycin.

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Molecular characterization of the integration of the lactose plasmid from Lactococcus lactis subsp. cremoris SK11 into the chromosome of L. lactis subsp. lactis

Article Abstract:

XbaI-XhoI fragment of a Lac plasmid pSK11L was subcloned for used as probe in Southern hybridization analyses of the natural lactococcal integration of pSK11L into the chromosome of Lactococcus lactis subspecies lactis LMO230. The two junction fragments followed a Campbell-like, single-cross over mechanism. In addition, the presence of the 1.6-kb fragment in a recombinant vector allowed the Rec-dependent, single-crossover integration of the plasmid into the lactoccal chromosome.

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Characterization of the highly autolytic Lactococcus lactis subsp. cremoris strains CO and 2250

Article Abstract:

The autolytic properties of the Lactococcus lactis subsp cremoris strains 2250 and CO were characterized. Maximum lysis were observed when the strains were grown in M17 broth with 0.4%-0.5% glucose concentration. Autolysis was avoided when the strains were grown in M17 with 1% glucose and rapid lysis of CO occurred when sodium fluoride was introduced in the broth. Results indicate the existence of at least two autolytic enzymes in the strains.

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