Multilocus Locus Sequence Typing Of Lactococcus Lactis From Traditional Fermented Dairy Products In Different Regions

This study was to investigate the evolutionary relationship of204isolates ofLactococcus lactis collected from Chifeng City, Bayan Nur City, Hulunbeir City, XilinGol League and Ordos Ctiy of Inner Mongolia, and Tibet, Qinghai, YunNan, Szechwan,Gansu and Mongolia by multilocus sequence typing (MLST). The sequences of12housekeeping genes (dnaA, pyrG, rpoB, groEL, recA, clpX, carB, murC, pepN, pepX,murE and pheS) were acquired by Bidirectional sequencing technology, and forward andreverse sequences were trimmed, aligned, and analyzed by BioNumerics v6.0, an allelenumber was given to each distinct combination of alleles of the twelve genes, and eachallele number was assigned a sequence type (ST). The genetic polymorphism andevolution of Lactococcus lactis were analyzed based on STs. The conclusions wereshowed as follows:204isolates were assigned as75STs, the75STs were grouped into13groups byeBURST. Among13groups, there are7clonal complexes (CC), CC26was the major CC,comprised the most strains, and CC26was deemed to founder CC.The realuts of the Minimum-spanning Tree showed that, the genetic relationship ofmost strains from the same regions was close, The most strains from Tibet, Qinghai,Yunnan, Szechwan, Gansu and Mongolia envolved from strains from the Chifeng Ctiy.Moreover, two Lactococcus lactis subsp. lactis identified by16S rDNA wereLactococcus lactis subsp. cremoris by MLST.By phylogenetic analysis, STs of the most strains from the same regions can gatherin the same groups. The population evolution of the srains from Chifeng City was longer.This also proved that the strains of different regions are likely to come from the sameancestor strains, which was from Chifeng City.The research demonstrated the evolutionary relationship of204Lactococcus lactisof different regions by MLST, and established a new classification method ofLactococcus lactis, provided a rich data for Lactococcus lactis of the MLST. Bycomparing the difference of alleles sequences among strains, preliminary realized the theevolutionary relationship of Lactococcus lactis, and analysed the genetic background ofLactococcus lactis from different regions, meanwhile deduced evolution of Lactococcus lactis, which was the foundation of population structure and genetic evolutionworldwide.