1. Genetic diversity of exopolysaccharides from acetic acid bacteria isolates originating from apple cider vinegarsTadeja Vajdič, 2022, izvirni znanstveni članek Opis: Acetic acid bacteria (AAB) produce acetic acid but are also gaining importance as safe microorganisms for producing extracellular polysaccharides (EPSs). The best-known homopolysaccharides among them are cellulose and levan. In addition, acetic acid bacteria also produce heteropolysaccharides, water-soluble acetans. Isolates from the broth of organic and conventional
apple cider vinegar production were screened for biofilm production. Phenotypic and genomic
diversity of EPS-producing isolates was assessed. The diversity of phenotypically different EPSs
of apple cider vinegar isolates was investigated at the gene level for the following novel strains:
Komagataeibacter (K.) melomenusus SI3083, K. oboediens SI3053, K. pomaceti SI3133, and
Gluconacetobacter (Ga.) entanii SI2084. Strain K. melomenusus SI3083 possesses cellulose
operons bcs1, bcs2, and bcs4 together with the type I acetan cluster in the absence of the levan
operon, strain K. oboediens SI3053 has the operons bcs1, bcs2, bcs3, and bcs4, the levan operon,
and the acetan cluster (type I), and the strains K. pomaceti SI3133 and Ga. entanii SI2084
both contain recently described novel ace-type II cluster in addition to the incomplete operon
bcs1. A comparison of the genetic diversity of these EPSs to those of the reference strains suggests that the studied EPSs are not species-descriptive. The results of this study deepen our
understanding of the genetic variability of the EPS genes in AAB, thereby enabling us to better
characterize and exploit the various insoluble and soluble exopolysaccharides produced by AAB
for biotechnological applications in the future.
Ključne besede: acetic acid bacteria genomes, apple cider vinegar microbiota, biofilm production, bacterial cellulose, acetan, Acetobacter, Komagataeibacter
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2. Comparative genomics and phenotypic characterization of Gluconacetobacter entanii, a highly acetic acid-tolerant bacterium from vinegarsKarin Jelenko, Eva Cepec, Francisco X. Nascimento, Janja Trček, 2023, izvirni znanstveni članek Opis: The bacterial species Gluconacetobacter entanii belongs to a group of acetic acid bacteria. In 2000, it was described as a primary species of submerged spirit vinegar-producing bioreactors with a strict requirement of acetic acid, ethanol, and glucose for growth. Over the years, the type-strain of G. entanii deposited in international culture collections has lost the ability for revitalization and is thus not available any more in a culturable form. Here, we have systematically characterized phenotypic features and genomes of recently isolated G. entanii strains and compared them with characteristics of the type-strain available from published data. Using the functional annotation, genes gmhB and psp were identified as unique for G. entanii genomes among species in the clade Novacetimonas. The genome stability of G. entanii was assessed after 28 and 43 months of preculturing the strain Gluconacetobacter entanii AV429 twice a week. The strain G. entanii AV429 did not accumulate giant insertions or deletions but a few gene mutations. To unify further research into acetic acid bacteria systematics and taxonomy, we propose G. entanii AV429 as the neotype strain.
Ključne besede: acetic acid bacteria, vinegar, acetic acid tolerant bacteria, Gluconacetobacter, Novacetimonas, Gluconacetobacter entanii, Komagataeibacter
Objavljeno v DKUM: 14.02.2024; Ogledov: 348; Prenosov: 18
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3. Description of Komagataeibacter melaceti sp. nov. and Komagataeibacter melomenusus sp. nov. isolated from apple cider vinegarLeon Marič, Ilse Cleenwerck, Tomaž Accetto, Peter Vandamme, Janja Trček, 2020, izvirni znanstveni članek Opis: Two novel strains AV382 and AV436 were isolated from a submerged industrial bioreactor for production of apple cider vinegar in Kopivnik (Slovenia). Both strains showed very high (≥98.2%) 16S rRNA gene sequence similarities with Komagataeibacter species, but lower 16S–23S rRNA gene internal transcribed spacer (ITS). The highest similarity of the 16S–23S rRNA gene ITS of AV382 was to Komagataeibacter kakiaceti LMG 26206$^T$ (91.6%), of AV436 to Komagataeibacter xylinus LMG 1515$^T$ (93.9%). The analysis of genome sequences confirmed that AV382 is the most closely related to K. kakiaceti (ANIb 88.2%) and AV436 to K. xylinus (ANIb 91.6%). Genome to genome distance calculations exhibit for both strains ≤47.3% similarity to all type strains of the genus Komagataeibacter. The strain AV382 can be differentiated from its closest relatives K. kakiaceti and Komagataeibacter saccharivorans by its ability to form 2-keto and 5-keto-D-gluconic acids from glucose, incapability to grow in the presence of 30% glucose, formation of C$_{19:0}$ cyclo ω8c fatty acid and tolerance of up to 5% acetic acid in the presence of ethanol. The strain AV436 can be differentiated from its closest relatives K. xylinus, Komagataeibacter sucrofermentans, and Komagataeibacter nataicola by its ability to form 5-keto-D-gluconic acid, growth on 1-propanol, efficient synthesis of cellulose, and tolerance to up to 5% acetic acid in the presence ethanol. The major fatty acid of both strains is C$_{18:1}$ ω7c. Based on a combination of phenotypic, chemotaxonomic and phylogenetic features, the strains AV382$^T$ and AV436$^T$ represent novel species of the genus Komagataeibacter, for which the names Komagataeibacter melaceti sp. nov. and Komagataeibacter melomenusus are proposed, respectively. The type strain of Komagataeibacter melaceti is AV382$^T$ (= ZIM B1054$^T$ = LMG 31303$^T$ = CCM 8958$^T$) and of Komagataeibacter melomenusus AV436$^T$ (= ZIM B1056$^T$ = LMG 31304$^T$ = CCM 8959$^T$).
Ključne besede: Acetic acid bacteria, Acetobacteraceae, Komagataeibacter, Komagataeibacter melaceti, Komagataeibacter melomenusus, vinegar
Objavljeno v DKUM: 02.09.2022; Ogledov: 498; Prenosov: 16
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4. Comparison of cultivable acetic acid bacterial microbiota in organic and conventional apple cider vinegarAleksandra Mori Štornik, Barbara Skok, Janja Trček, 2016, izvirni znanstveni članek Opis: Organic apple cider vinegar is produced from apples that go through very restricted treatment in orchard. During the first stage of the process, the sugars from apples are fermented by yeasts to cider. The produced ethanol is used as a substrate by acetic acid bacteria in a second separated bioprocess. In both, the organic and conventional apple cider vinegars the ethanol oxidation to acetic acid is initiated by native microbiota that survived alcohol fermentation. We compared the cultivable acetic acid bacterial microbiota in the production of organic and conventional apple cider vinegars from a smoothly running oxidation cycle of a submerged industrial process. In this way we isolated and characterized 96 bacteria from organic and 72 bacteria from conventional apple cider vinegar. Using the restriction analysis of the PCR-amplified 16S-23S rRNA gene ITS regions, we identified four different HaeIII and five different HpaII restriction profiles for bacterial isolates from organic apple cider vinegar. Each type of restriction profile was further analyzed by sequence analysis of the 16S-23S rRNA gene ITS regions, resulting in identification of the following species: Acetobacter pasteurianus (71.90 %), Acetobacter ghanensis (12.50 %), Komagataeibacter oboediens (9.35 %) and Komagataeibacter saccharivorans (6.25 %). Using the same analytical approach in conventional apple cider vinegar, we identified only two different HaeIII and two different HpaII restriction profiles of the 16S‒23S rRNA gene ITS regions, which belong to the species Acetobacter pasteurianus (66.70 %) and Komagataeibacter oboediens (33.30 %). Yeasts that are able to resist 30 g/L of acetic acid were isolated from the acetic acid production phase and further identified by sequence analysis of the ITS1-5.8S rDNA‒ITS2 region as Candida ethanolica, Pichia membranifaciens and Saccharomycodes ludwigii. This study has shown for the first time that the bacterial microbiota for the industrial production of organic apple cider vinegar is clearly more heterogeneous than the bacterial microbiota for the industrial production of conventional apple cider vinegar. Further chemical analysis should reveal if a difference in microbiota composition influences the quality of different types of apple cider vinegar.
Ključne besede: microbiology, acetic acid bacteria, apple cider vinegar
Objavljeno v DKUM: 24.07.2017; Ogledov: 11297; Prenosov: 239
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