Grouping of Lactobacillus brevis strains using the gyrB gene

Genotypic characterization, based on the analysis of the restriction fragment length polymorphism (RFLP) of the gyrB gene fragment polymerase chain reaction (PCR) product (gyrB-RFLP), was performed on Lactobacillus brevis strains. PCR primers allowed the amplification of approximately 540-base pair DNA fragments from each of 16 strains with different levels of isohumulone resistance. Amplified gyrB gene fragments were compared by using RFLP analysis with three restriction enzymes (HinII, ApaLI, and HaeIII), allowing the detection of the characteristic patterns of RFLP products. As a result, the strains of L. brevis were divided into four groups (groups I, IIa, IIb, and III) on the basis of the RFLP product patterns. A relationship was observed between isohumulone resistance and the RFLP groups, and all the isohumulone (40 ppm)-resistant strains were classified into group IIb. Moreover, all of the isohumulone-resistant strains, except one, could grow in beer (pH 4.5, 30 ppm of isohumulones). Thus, it seemed that the isohumulone-resistant strains of L. brevis form one group in the phylogenetic tree based on the gyrB gene. In addition, this gyrB-RFLP analysis would be useful for discriminating the L. brevis strains with respect to beer-spoilage ability.