Summary auto-generated
This study describes the isolation and characterization of a novel bacteriocin-producing lactic acid bacterium (strain MT-1077T) from kimchi, a Korean fermented vegetable food. The researchers employed a polyphasic taxonomic approach combining phenotypic characterization, 16S rDNA phylogenetic analysis, and DNA-DNA hybridization studies. Morphologically, the organism is a Gram-positive, non-spore-forming rod. Physiologically, it is catalase-negative, facultatively heterofermentative, and produces both D- and L-lactic acid. Phylogenetic analysis based on 16S rDNA sequences confirmed its membership in the genus Lactobacillus, with closest relatives being L. alimentarius (98.4% similarity) and L. farciminis (98.2% similarity). However, DNA-DNA relatedness values between MT-1077T and these reference strains were only 6.3-10.9%, well below the 70% threshold for species identity. The organism also showed phenotypic differences from both reference species in sugar fermentation patterns and fatty acid profiles. Based on these combined genetic and phenotypic differences, the authors propose this isolate as a new species: Lactobacillus kimchii sp. nov., with type strain MT-1077T.
Key findings
- Strain MT-1077T, isolated from kimchi, represents a new Lactobacillus species designated L. kimchii sp. nov.
- Despite high 16S rDNA similarity (98.2-98.4%) to L. alimentarius and L. farciminis, DNA-DNA hybridization values (6.3-10.9%) confirm genetic distinctiveness as a separate species.
- L. kimchii exhibits facultative heterofermentation, produces both D- and L-lactic acid, and shows phenotypic differences from closely related species in sugar fermentation patterns.
- The bacteriocin-producing strain grows optimally at 30°C and pH 6.0-7.0, with a genomic G-C content of 35 mol%.
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Abstract
A bacteriocin-producing lactic acid bacterium, which was isolated from the Korean fermented-vegetable food kimchi, was subjected to a polyphasic taxonomic study using phenotypic characterization and phylogenetic and genetic methods. This organism (MT-1077(T)) has phenotypic properties that are consistent with the description characterizing the genus Lactobacillus. Phylogenetic analysis based on 16S rDNA sequences showed clearly that strain MT-1077(T) is a member of the genus Lactobacillus. The closest phylogenetic relatives are Lactobacillus alimentarius KCTC 3593(T) and Lactobacillus farciminis LMG 9200(T), with levels of 16S rDNA similarity of 98.4 and 98.2%, respectively. Levels of 16S rDNA similarity between strain MT-1077(T) and other Lactobacillus species were less than 93.0%. Differences in some phenotypic characteristics and DNA--DNA relatedness data indicated that strain MT-1077(T) should be distinguished from L. alimentarius KCTC 3593(T) and L. farciminis LMG 9200(T). On the basis of the data presented, it is proposed that strain MT-1077(T) should be placed in the genus Lactobacillus as a new species, Lactobacillus kimchii sp. nov. The type strain of the new species is strain MT-1077(T) (=KCTC 8903P(T) =JCM 10707(T)).