COMPARATIVE-EVALUATION OF PLASMID PROFILING AND RIBOTYPING IN THE ANALYSIS OF LACTOBACILLUS-PLANTARUM STRAIN HETEROGENEITY IN SILAGE

Seventy-two Lactobacillus plantarum isolates were recovered from six u ninoculated grass silages for the purposes of firstly evaluating the u sefulness of(1) restriction endonuclease digestion of total genomic DN A, (2) plasmid profiling and (3) ribotyping in Lact. plantarum strain differentiation and secondly, examining the strain heterogeneity in we ll preserved silage. The three methods for differentiation were applie d to 72 of the isolates and allowed at least 32 different strains to b e identified. Twenty-five different plasmid profiles were detected (26 if the absence of plasmids is included as a profile). Ribotyping with EcoRI identified only 1 1 patterns among the silage isolates. A varie ty of restriction enzymes was screened to increase the sensitivity of ribotyping to detect strain differences and BamHI was used successfull y for this purpose, differentiating all of the strains tested. Two dom inant strains (I and II) were identified in one particular silage, com prising 47% and 17% respectively of the isolates, while strains III an d V comprised 37% and 25% of the Lact. plantarum population isolated f rom another of the silages.