Determination of chromosome size and number of rrn loci in Lactobacillus plantarum by pulsed‐field gel electrophoresis

The size of the Lactobacillus plantarum CCM 1904 chromosome was determined by pulse‐field gel electrophoresis. It was found to be 3.3–3.4 Mb using SfiI or AscI restriction endonucleases, compared to 3–4 Mb found for the other L. plantarum strains tested. L. plantarum CCM 1904 5S rDNA was cloned by polymerase chain reaction, sequenced, and used as a probe to characterize strains. At least five rrn loci were found. The pulsed‐field gel electrophoresis macrorestriction patterns were strain‐specific, while the rDNA restriction hybridization patterns were species‐specific.