Rapid identification and detection of Lactobacillus sanfrancisco in sourdough by species-specific PCR with 16S rRNA-targeted primers.

The application of a species-specific PCR technique to the rapid identification and detection of Lactobacillus sanfrancisco in sourdough was described. Oligonucleotide primers targeted to the L. sanfrancisco 16S rRNA gene sequence provided a means of easily differentiating these lactic acid bacteria from other microorganisms including those naturally occurring in sourdough and closely related species. A 1460 bp region of 16S rRNA gene was specifically amplified when either purified DNA or whole cells of L. sanfrancisco strains were used. The identity of PCR product was confirmed by nested PCR and restriction analysis. PCR assays on DNA extracted from sourdough samples allowed the detection of less than 10 cells within 6 hours. The procedure established is sensitive, specific, simple and rapid, therefore it can be considered a valuable tool for monitoring L. sanfrancisco in mixed microbial populations.