Diversity and evolution of Lactobacillus casei group isolated from fermented dairy products in Tibet
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ORIGINAL PAPER
Diversity and evolution of Lactobacillus casei group isolated from fermented dairy products in Tibet Jing Feng1 · Yujun Jiang1,2 · Mingyu Li1 · Siyu Zhao1 · Yanming Zhang3 · Xuesong Li1 · Hui Wang1 · Guangen Lin1 · Hao Wang4 · Tiejing Li1 · Chaoxin Man1 Received: 31 August 2017 / Revised: 30 November 2017 / Accepted: 18 May 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018
Abstract Bacteria in Lactobacillus casei group, including Lactobacillus casei (L. casei), Lactobacillus paracasei (L. paracasei), and Lactobacillus rhamnosus (L. rhamnosus) are important lactic acid bacteria in the production of fermented dairy products and are faced with the controversial nomenclatural status due to their close phylogenetic similarity. To probe the evolution and phylogeny of L. casei group, 100 isolates of lactic acid bacteria originated from naturally fermented dairy products in Tibet of China were subjected to multilocus sequence typing (MLST). The MLST scheme, based on analysis of the housekeeping genes fusA, ileS, lepA, leuS, pyrG, recA and recG, revealed that all the isolates belonged to a group containing the L. paracasei reference strains and were clearly different from the strains of L. casei and L. rhamnosus. Although nucleotide diversity (π) was low for the seven genes (ranging from 0.00341 for fusA to 0.01307 for recG), high genetic diversity represented by 83 sequence types (STs) with a discriminatory index of 0.98 was detected. A network-like structure based on split decomposition analysis, and the high values of the relative effect of recombination and mutation in the diversification of the lineages (r/m = 4.76) and the relative frequency of occurrence of recombination and mutation (ρ/θ = 2.62) indicated that intra-species recombination occurred frequently and homologous recombination played a key role in generating genotypic diversity amongst L. paracasei strains in Tibet. The discovery of 51 new STs and the results of STRUCTURE analysis suggested that the L. casei group in Tibet had an individual and particular population structure in comparison to European isolates. Overall, this research might be the first report about genetic diversity and population structure of Lactobacillus populations isolated from naturally fermented dairy products in Tibet based on MLST scheme. Keywords Multilocus sequence typing · Lactobacillus casei group · Genetic diversity · Homologous recombination
Introduction Communicated by Erko Stackebrandt. Jing Feng and Yujun Jiang contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00203-018-1528-9) contains supplementary material, which is available to authorized users. * Chaoxin Man [email protected] 1
Key Laboratory of Dairy Science, Ministry of Education, College of Food Science and Engineering, Northeast Agricultural University, Harbin 150030, People’s Republic of China
National Research Center of Dairy Engineering and Technology, Northeast Agricultural University,
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