RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM OF LACTOBACILLUS-REUTERI ANDLACTOBACILLUS-FERMENTUM, ORIGINATING FROM INTESTINAL-MUCOSA, BASED ON16S RIBOSOMAL-RNA GENES

Restriction Fragment Length Polymorphisms (RFLPs) of the 16S rRNA gene were determined for fourteen field strains originally labelled Lactob acillus reuteri, four Lactobacillus fermentum strains, and eight type and reference strains of Lactobacillus. The strains were mainly origin ating from intestinal mucosa. The probe was a 420 bp internal fragment of a Lactobacillus reuteri 16S rRNA gene, amplified by Polymerase Cha in Reaction (PCR). The patterns were obtained by cleavage of the chrom osomal DNAs by the restriction endonucleases EcoRI and HindIII separat ely. Unweighted Pair Group Method, using arithmetic Averages (UPGMA) b ased on Jaccard coefficients (S(J)) of the ribopatterns resolved five clusters at the 30% similarity level. The L. reuteri field strains for med two clusters according to their source of isolation; strains origi nating from rat formed one cluster while those from pig and human stra ins formed the other cluster. These strains could not be affiliated to the type strain of L. reuteri. However, two field strains, classified by phenotypically means as L. fermentum, clustered together with the type strain of this species. The numbers of 16S rRNA genes of the L. r euteri strains were, depending on the strain, determined to be at leas t five through seven. The ribopatterns were compared to the results of DNA:DNA hybridization and partial sequencing of the 16S rDNA genes. A ll but one of the L. reuteri field strains bad more than 70% DNA simil arity and identical 16S rDNA sequence to the type strain L. reuteri DS M 20016T. Two of the L. fermentum field strains had identical 16S rDNA sequence and more than 70% DNA similarity to L. fermentum ATCC 14931T . Ribotyping appears not to be a means to identify L. reuteri at the s pecies level but eventually this is possible with L. fermentum.