Abstract
BackgroundLactobacillus fermentum is economically important in the production and preservation of fermented foods. A repeatable and discriminative typing method was devised to characterize L. fermentum at the molecular level. The multilocus sequence typing (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).ResultsMLST analysis of 203 isolates of L. fermentum from Mongolia and seven provinces/ autonomous regions in China identified 57 sequence types (ST), 27 of which were represented by only a single isolate, indicating high genetic diversity. Phylogenetic analyses based on the sequence of the 11 housekeeping gene fragments indicated that the L. fermentum isolates analyzed belonged to two major groups. A standardized index of association (IAS) indicated a weak clonal population structure in L. fermentum. Split decomposition analysis indicated that recombination played an important role in generating the genetic diversity observed in L. fermentum. The results from the minimum spanning tree strongly suggested that evolution of L. fermentum STs was not correlated with geography or food-type.ConclusionsThe MLST scheme developed will be valuable for further studies on the evolution and population structure of L. fermentum isolates used in food products.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0447-z) contains supplementary material, which is available to authorized users.
Highlights
Lactobacillus fermentum is economically important in the production and preservation of fermented foods
The numbers of alleles, polymorphic sites, guanine-cytosine content, nucleotide diversity per site (Pi) and rate of Non-synonymous Substitutions (dN)/Synonymous Substitutions (dS) value were all determined (Table 2)
Fragment sizes of the 11 housekeeping gene fragments, which ranged from 589 bp to 748 bp, were used for multilocus sequence typing (MLST) analysis
Summary
Lactobacillus fermentum is economically important in the production and preservation of fermented foods. A repeatable and discriminative typing method was devised to characterize L. fermentum at the molecular level. Lactobacillus fermentum is an economically important species of lactic acid bacterium (LAB) used in the production and preservation of fermented food as an acidproducing starter culture [1, 2]. Lactobacillus fermentum was first described by Beijerink (1901), as an obligate heterofermentative bacterium associated with the fermentation of hexoses to lactic acid [9, 10]. Molecular typing approaches have been used to characterize L. fermentum and the subspecies within it. L. fermentum isolates could be differentiated from other Lactobacillus species using randomly amplified polymorphic DNA(RAPD-PCR) methods [14, 15]. RAPD-PCR has been used in combination with amplified 16S rDNA restriction analysis (16SARDRA), pulsed-field gel electrophoresis with restriction
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