Summary auto-generated
This study describes the discovery and characterization of Lactobacillus durianis, a novel lactic acid bacterium species isolated from tempoyak, a Malaysian acid-fermented condiment made from durian fruit. Three similar strains could not be identified using conventional methods, so researchers conducted a comprehensive polyphasic taxonomic analysis. Using 16S rDNA sequencing, the representative strain clustered within Lactobacillus and showed closest relationship to the L. reuteri phylogenetic group, with only 93-94% similarity to known species. DNA-DNA hybridization between two strains yielded 82% homology, confirming they represent a single genomic species with 43.2-43.3 mol% G+C content. The three isolates were differentiated at the strain level using plasmid profiling and pulsed-field gel electrophoresis. All strains are obligately heterofermentative lactobacilli producing both lactic acid isomers and acetic acid from glucose and xylose, with limited growth on glucose alone. The species exhibits distinctive characteristics including acid production from arabinose and xylose but not cellobiose or sucrose, inability to produce ammonia from arginine, and resistance to vancomycin. Based on these findings, the authors propose Lactobacillus durianis sp. nov. as the official species name, with strain LMG 19193T designated as the type strain.
Key findings
- L. durianis is a novel obligately heterofermentative Lactobacillus species isolated from Malaysian tempoyak, distinguished by 16S rDNA sequence analysis showing only 93-94% similarity to known species
- The three strains represent a single genomic species based on 82% DNA-DNA hybridization homology and 43.2-43.3 mol% G+C content
- The species produces both lactic acid isomers and acetic acid from glucose and xylose, with enhanced growth on xylose compared to glucose
- L. durianis can be differentiated from related heterofermentative bacteria by its inability to produce ammonia from arginine, resistance to vancomycin, and specific carbohydrate utilization patterns
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Abstract
Lactic acid bacteria (LAB) are the predominant micro-organisms in tempoyak, a Malaysian acid-fermented condiment. In a study on the diversity of LAB in this product, three isolates could not be identified using SDS-PAGE of whole-cell proteins or API 50 CH. The taxonomic position of the three isolates was clarified in the present study. 16S rDNA sequencing classified a representative strain in the genus Lactobacillus, clearly separated from all known species, and most closely related to the Lactobacillus reuteri phylogenetic group. DNA--DNA hybridization experiments and an extensive phenotypic description confirm that the strains represent a single and separate novel species among the obligately heterofermentative lactobacilli. The three isolates are distinguished at the intra-species level by plasmid profiling, pulsed-field gel electrophoresis of macro-restriction fragments and biochemical features. The name Lactobacillus durianis sp. nov. is proposed for the novel taxon and the type strain is LMG 19193(T) (=CCUG 45405(T)).