Analysis of Different Lactobacillus rhamnosus by Random Amplified Polymorphic DNA

Abstract:

[Objective] We developed a molecular method to mark and differentiate Lactobacillus rhamnosus strains and to analyze genetic diversity among isolates from different sources. [Methods] Ten strains of Lactobacillus spp. were isolated from 56 feces samples of elderly people above 90 years of age in regions of Hetian, Xinjiang and Bama, Guangxi, China. We used API 50CHL test chip for strain identification. These isolates belonged to Lactobacillus rhamnosus with 98.6%~99.9% satisfactory. Ten L. rhamnosus isolates and one reference strain ATCC7496 were analyzed by random amplified polymorphic DNA (RAPD) technique to differentiate L. rhamnosus strains at molecular level. We screened 5 random primers named P14, OPG28, OPG25, P7 and P4 and developed optimum RAPD amplifying system. [Results] The clear and stable DNA fingerprints of each strain were obtained; the amplicon size ranged from 100 to 2000 bp, and the band patterns showed polymorphism among different L. rhamnosus strains. Genetic similarity coefficients based on RAPD patterns varied from 0.581 to 0.935, which suggested genetic diversity and different genetic relationship among these strains. Eleven strains of Lr could be clustered into 5 groups (group A to E) at the level of 80% similarity. Seven L. rhamnosus strains isolated from Hetian, Xinjiang, were grouped in group B and C, 3 isolates from Bama, Guangxi, were grouped in group D and E. [Conclusion] RAPD method is feasible for molecular mark and differentiation of L. rhamnosus strains and high level of genetic diversity and different relationship are found among L. rhamnosus isolates.