5%) and pH tolerance. Further taxonomic classification of BGKP1 involved repPCR with (GTG)5 primer [34], and sequencing of amplified 16S rDNA [35]. A non-aggregating derivative BGKP1-20 (Agg-), L. lactis subsp. lactis BGMN1-596 (9), L. lactis subsp. cremoris MG1363 [36] and Enterococcus faecalis BGZLS10-27 [37] were used for homologous and heterologous expression of the aggregation phenotype. Lactococcal and enterococcal strains were grown at 30°C in M17 medium Rabusertib ic50 [38] supplemented with 0.5% glucose (GM17) and stored in the same medium containing 15% (w/v) glycerol (Sigma Chemie GmbH, Deisenhofen, see more Germany) at -80°C. L. lactis

and E. faecalis electrocompetent cells were prepared and transformed as previously described [39] using an Eppendorf Electroporator (Eppendorf, Hamburg, Germany). E. coli strain DH5α [40] was used for cloning experiments and plasmid propagation. DH5α was grown at 37°C in Luria-Bertani (LB) medium [41]. Agar plates were prepared by addition of agar (1.5% w/v) to the corresponding broth. E. coli competent cells were prepared using chemical treatment and subjected to heat shock transformation. Transformants were selected using the antibiotic erythromycin (5 μg ml-1 for lactococci and enterococci or 250 μg ml-1 for E. coli). Bacteriocin and proteinase activity were determined as described

previously [9]. Growth kinetics Cultures of BGKP1 and BGKP1-20 were grown in 10 ml of GM17 to a density of 109 cells ml-1. Approximately 106 cells of each strain were added to 10 ml of GM17 SRT2104 and cultures were incubated at 30°C. Aliquots from each culture were taken every hour and plated on solid GM17 medium to calculate generation time for each strain. Experiments were done in triplicate. Molecular techniques Molecular cloning techniques like end filling of DNA fragments with the Klenow fragment of DNA polymerase, dephosphorylation, ligation, PCR amplification and agarose gel DNA electrophoresis were carried out essentially as described

previously [41]. The mini-prep method [42] nearly was used for isolation of large plasmids from lactococci. Plasmids from E. coli were isolated using the QIAprep Spin Miniprep kit according to the manufacturer’s recommendations (QIAGEN, Hilden, Germany). The DNA fragments from agarose gels were purified using a QIAqick Gel extraction kit as described by the manufacturer (QIAGEN). Digestion with restriction enzymes was conducted according to the supplier’s instructions (Fermentas, Vilnius, Lithuania). Determination of the effect of ions, pH and proteinase K on aggregation ability of L. lactis subsp. lactis BGKP1 The effect of different ions and pH values on the BGKP1 aggregation phenotype was tested using cells that were three times washed in bi-distilled water until the aggregation phenotype was lost.