Detection of intraspecific DNA polymorphism in Streptococcus salivarius subsp. thermophilus by a homologous rDNA probe

Abstract

Three ribosomal probes from Streptococcus salivarius subsp. thermophilus were cloned. Sequence data demonstrate that their juxtaposition corresponds to an entire operon. They were used in order to study ribosomal operon number and organization. rRNA genes were shown to be clustered in the order 5'-16S-23S-5S-3' and the number of rrn loci to vary within the subspecies. The smallest of the 3 probes was used for strain characterization. Substantial variability in hybridization patterns was observed among strains, resulting not only from, restriction fragment length polymorphism (RFLP) but also from the variability of ribosomal operon number.

Physical and genetic map of Streptococcus thermophilus A054

“…4B) and resulted in a clone containing only five rm loci instead of the original six. This phenomenon has already been observed in S. themnophilus CNRZ368 (38). Analyses of the restriction patterns of the NST2222 clone revealed two differences from those of the NST2210 clone.…”

“…Several genes have been cloned and analyzed, including genes involved in glucide metabolism (lacZ, lacS, galE, galM, and ldh [5,25,43,44,51]) and DNA recombination (recA [15]), ribosomal sequences (4,23,38), and the aspartate racemase gene (62). A marked restriction polymorphism has been detected between different strains of this species by analysis of hybridization patterns obtained with a species-specific probe (13) and with probes by genes coding for rRNA (38). Despite the availability of gene transfer systems and cloned genes, the structure and organization of the S. thermophilus genome are not well defined.…”

Comparative analysis of the genes encoding 23S-5S rRNA intergenic spacer regions of Lactobacillus casei-related strains.

“…At present, the exact number of rRNA operons for Lactobacillus is still unknown. Lactobacillus lactis has been shown to contain six rrn operons (Tulloch et al, 1991) ; Streptococcus thermophilus, five to six (Pebay et al, 1992) ; Lactobacillus acidophilus, at least four (Roussel et al, 1987) ; and Lactobacillus plantarum, at least five rrn operons (Chevallier et al, 1994). As two ISR amplicons were obtained, we suggest that at least two different sets of rRNA operons are present in this Lactobacillus casei species.…”

Comparison of Streptococcus thermophilus strains by pulse field gel electrophoresis of genomic DNA

“…Intra-strain polymorphism has previously been attributed to DNA rearrangements, deletions due to homologous recombination events between closely linked rRNA loci and to insertions or duplications, some of which in£uence colony morphology [18]. Roussel et al [13] utilised PFGE of genomic double digests to demonstrate genetic alterations in speci¢c morphotypes of strain A054.…”