Summary auto-generated
Researchers isolated and characterized four strains of acetic acid bacteria from high-acid spirit vinegar fermentations in Southern Germany. These strains—LTH 4560T, LTH 4341, LTH 4551, and LTH 4637—shared distinctive characteristics including a requirement for acetic acid, ethanol, and glucose for growth, and inability to over-oxidize acetate. The bacteria only grew when total concentrations of acetic acid plus ethanol exceeded 6%. Comparative analysis of 16S rRNA sequences showed 99% similarity to Gluconacetobacter hansenii, but DNA-DNA hybridization studies revealed only 41% DNA relatedness. The strains could be differentiated by distribution patterns of insertion element 1031C in their chromosomes. Based on these findings, the researchers proposed a new species, Gluconacetobacter entanii, with LTH 4560T designated as the type strain. A species-specific oligonucleotide probe was developed for identification, and the bacterium's phylogenetic position within acetic acid bacteria was established through 16S rRNA analysis.
Key findings
- Gluconacetobacter entanii is a new species of acetic acid bacteria isolated from high-acid spirit vinegar fermentations, requiring acetic acid, ethanol, and glucose for growth at total concentrations exceeding 6%.
- Despite 99% 16S rRNA sequence similarity to G. hansenii, DNA-DNA hybridization showed only 41% relatedness, confirming G. entanii as a distinct species.
- The four isolates displayed nearly identical plasmid profiles but could be differentiated by unique distribution patterns of insertion element 1031C, suggesting adaptation through random mutations during industrial fermentation.
- G. entanii strains do not over-oxidize acetic acid and cannot utilize gluconate, glycerol, or lactate, distinguishing them from G. europaeus and other related species.
- A preservation method using calcium carbonate treatment followed by lyophilization successfully maintained viable cells for at least 2 months at -18°C.
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Abstract
Acetic acid bacteria have been isolated from submerged high-acid spirit vinegar fermentations in the Southern part of Germany. Four strains (LTH 4560(T), LTH 4341, LTH 4551 and LTH 4637) were characterized in more detail and it was revealed that they have in common certain properties such as requirement of acetic acid, ethanol and glucose for growth, and no over-oxidation of acetate. Growth occurs only at total concentrations (sum of acetic acid and ethanol) exceeding 6.0%. A method for their preservation was developed. Comparative analysis of the 16S rRNA revealed sequence similarities of 99% between strain LTH 4560(T) and the type strains of the related species Gluconacetobacter hansenii. However, low levels of DNA relatedness (41%) were determined in DNA--DNA similarity studies. In addition, specific physiological characteristics permitted a clear identification of the strains within established species of acetic acid bacteria. The strains could also be differentiated on the basis of the distribution of IS element 1031 C within the chromosome. Based on these results, the new species Gluconacetobacter entanii sp. nov. is proposed for strain LTH 4560(T) (=DSM 13536(T)). A 16S-rRNA-targeted oligonucleotide probe was constructed that was specific for G. entanii, and the phylogenetic position of the new species was derived from a 16S-rRNA-based tree.