Synthesis of cDNA were performed from 150 ng of total RNA confirmed free of DNA after an additional DNase treatment, 6 μg hexamers, 10 mM of dNTP with Superscript III and supplied reagents as described above. The primers used in real-time quantitative PCR are listed in Table 1. Real-time PCR was performed with a cDNA dilution in triplicates, representing 0.75 ng RNA, 0.1 μM of each primer with FastStart SYBR Green master included ROX (Roche Applied Science) on an ABI Prism 7700 Sequence Detection System (Applied Biosystems).

After denaturation at 95°C the program was 40 KU55933 mouse cycles, including 95°C for 15 seconds, 30 seconds at 62°C and 72°C for 30 seconds. Standard curves were made for each primer pair to calculate amplification efficiency of the target genes and the endogenous control gene (EF0013). Differential expression was determined by calculating the change in threshold cycles for each gene with the ΔΔCt-method, with RNA isolated from resistant mutants and wild type bacteria. DNA manipulations and sequencing Isolation of DNA from E. faecalis V583 buy EPZ-6438 and mutants was done using Advamax-beads (Advanced Genetic Technologies Corp.). PCR products were generated with Phusion DNA polymerase (Finnzymes). Other enzymes for DNA manipulation were from New England Biolabs. DNA fragments were purified by use of agarose gel electrophoresis and Qiaquick PCR purification columns (Qiagen).

Plasmids were isolated using Qiagen miniprep columns. Standard procedures [32] were used for restriction cutting of DNA, ligation and cloning in E. coli. DNA was sequenced using the ABI Prism BigDye terminator sequencing ready reaction kit version 3.1 and analyzed with the ABI Prism 3100 genetic analyzer according to the supplier’s procedures (Applied Biosystems). Results Isolation and characterization of bacteriocin resistant mutants Four class IIa bacteriocin resistant mutants of E. faecalis V583 were obtained. Mutants MOP1 and MOP5 were isolated after exposure to two different

concentrations of pediocin PA-1. A third spontaneous mutant (MOP2) was obtained by selecting colonies resistant to 2-DG. The MOP2 mutant was also resistant to pediocin (Table 2). Pediocin PA-1 resistant mutants were Histamine H2 receptor isolated at a frequency of 3 10-4, consistent with reported resistance frequency in Enterococcus and Listeria [6, 7]. Previous studies have shown that pediocin resistance can be obtained by mutations in the mannose PTS operon, mpt [33, 34], therefore we GSI-IX supplier constructed a resistant E. faecalis V583 (MOM1) disrupted in mptD. Mutants MOM1 and MOP5 were highly resistant to pediocin PA-1, while MOP1 and MOP2 were less resistant (Table 2). The pediocin resistance phenotype was stably maintained in all mutants in the absence of bacteriocin. All mutants were resistant to 2-DG (results not shown). In exponential phase up to an optical density of 0.