Multilocus Sequence Typing Of Lactobacillus Fermentum From Home-made Fermented Foods

Lactobacillus ferrmentum is an economically important in the production and preservation of fermented foods,which giving the product good taste and extending shelf-life.Rapid and accurate bacterial typing of Lactobacillus fermentum for its application is of greatest importance.In present stuty,the 202 L.fermentum isolates,isolated from fermented dairy products(65 isolates)in Mongolia,fermented dairy products(73 isolates)and acid gruel(60 isolates)in seven provinces/autonomous regions of China,combining with the reference isolates L.fermentum IFO 3956 that was obtained from the NCBI genome data base were analyzed.MLST scheme developed was based on analysis of the internal sequence of 11 housekeeping gene fragments(clpX,dnaA,dnaK,groEL,murC,murE,pepX,pyrG,recA,rpoB and uvrC),then the genetic relationship and evolutionary process among all of isolates were deduced.This study,provided a reference for the selection of starter culture and accurate identification of L.fermentum at gene level by developing a MLST scheme.the following conclusions:(1)203 L.fermentum isolates were divided into 57 sequence types(ST),27 STs were each represented by a single isolate.(2)By eBURST analzing,57 STs that were distributed amongst five clonal complexes(CCs),respectively named CC1,CC2,CC3,CC4,CC5 and 34 unique STs.Within CC1,ST-4 had the largest number of isolates(46 isolates)and was identified as the anscestral genotype.(3)LIAN-Linkage analysis indicated that linkage disequilibrium was present in the population structure in L.fermentum(IAS =0.2142).Split decomposition analysis indicated that recombination was the main reason for the genetic diversity of L.fermentum.(4)Phylogenetic analyses based on the sequence of the 11 housekeeping gene fragments indicated that the L.fermentum isolates analyzed belonged to two major groups.The group A of 33 STs contain 78,73%isolates from acid gruel;There were 24 STs.(125 isolates)within group B and 95%isolates were isolated from fermented dairy products.L.fermentum isolates that were included in the same group shared similarities in genome organization.(5)The results from the minimum spanning tree strongly suggested that evolution of L.fermentum STs was correlated with food-type,and confirmed that isolates from fermented dairy products and acidic gruel have a common recent ancestor.