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PubMed1997

Cloning and expression of AatII restriction-modification system in Escherichia coli.

The genes encoding the AatII restriction endonuclease and methylase from Acetobacter aceti have been cloned and expressed in Escherichia coli. The nucleotide sequences of aatIIM and aatIIR genes were determined. The aatIIM and aatIIR genes are 996 bp and 1038 bp, respectively, encoding the 331-aa methylase with a predicted molecular mass of 36.9 kDa, and the 345-aa AatII restriction endonuclease with a predicted molecular mass of 38.9 kDa. The two genes overlap by 4 base pairs and are transcribed in the same orientation. The aatIIRM genes are located next to a putative gene for plasmid mobilization. A stable overproducing strain was constructed, in which the aatIIM gene was expressed from a pSC101-derived plasmid. The aatIIR gene was inserted into a modified T7 expression vector that carries transcription terminators upstream from the T7 promoter. The recombinant AatII restriction endonuclease was purified to near homogeneity by chromatography through DEAE Sepharose, Heparin Sepharose, and phosphocellulose columns.

Acetobacter↗
PubMed1998

Phylogenetic identification of two major nitrogen-fixing bacteria associated with sugarcane.

Acetobacter diazotrophicus and Herbaspirillum seropedicae were identified by genetic methods based on 16S rRNA sequences. A specific PCR method in combination with probing was developed for A. diazotrophicus. The PCR system includes four primers, of which the primers named AC (CTGTTTCCCGCAAGGGAC) and DI (GCGCCCCATTGCTGGGTT) generated an 445 bp amplicon in all of the 11 A. diazotrophicus strains tested. The phylogenetic position of H. seropedicae was determined. H. seropedicae forms with Oxalobacter formigenes a separate lineage in the beta-subclass of Proteobacteria.

Acetobacter↗
PubMed1998

Life in grasses: diazotrophic endophytes.

N2-fixing bacteria such as Azoarcus spp., Herbaspirillum spp, and Acetobacter diazotrophicus can infect the interior of gramineous plants without causing symptoms of plant disease but do not survive in soil. Like phytopathogens, they can penetrate into central tissues and spread systemically. There is no evidence for an endosymbiosis in living plant cells; however, the bacteria are physiologically active in the plant apoplast.

Acetobacter↗
PubMed2001

Chemical and microbiological characterisation of kefir grains.

Chemical and microbiological composition of four Argentinean kefir grains from different sources as well as characteristics of the corresponding fermented milk were studied. Kefir grains CIDCA AGK1, AGK2 and AGK4 did not show significant differences in their chemical and microbiological composition. In contrast, protein and yeast content of AGK3 was higher than in the other grains. Although grain microflora comprised lactobacilli, lactococcus, acetic acid bacteria and yeast, we found an important difference regarding species. Lactococcus lactis subsp. lactis, Lactobacillus kefir, Lactobacillus plantarum, Acetobacter and Saccharomyces were present in all types of kefir grain. While Leuconostoc mesenteroides was only isolated from grains CIDCA AGK1 and Lactococcus lactis subsp. lactis biovar diacetylactis, Lactobacillus parakefir and Kluyveromyces marxianus were only isolated from CIDCA AGK2 grains. All grains produced acid products with pH between 3.5 and 4.0. The apparent viscosity of AGK1 fermented milk was greater than the product obtained with AGK4. All fermented milks had inhibitory power towards Escherichia coli but AGK1 and AGK2 supernatants were able to halt the bacterial growth for at least 25 h. Grain weight increment in AGK1, AGK2 and AGK3 during growth in milk did not show significant differences. Despite their fermenting activity, AGK4 grains did not increase their weight.

Acetobacter↗
PubMed2026

Metagenomic Insights into Microbial Assembly and Key Metabolic Genes Driving Flavor Formation in Spontaneously Fermented Zhejiang Rosy Vinegar.

The spontaneous fermentation of Zhejiang rosy vinegar (ZRV) is driven by environmental microbiota, but the processes underlying its flavor formation remain poorly understood. Using metagenomic sequencing, we investigated microbial community assembly, environmental drivers, and metabolic networks during industrial-scale ZRV fermentation. Acetic acid dominated the final organic acids. Community assembly shifted toward deterministic selection with rising acidity, with a slight rebound of stochastic processes in the late stage (R2 values of 0.442 and 0.346 for bacteria and fungi, respectively). Mantel tests confirmed that environmental factors significantly regulated microbial assembly. Co-occurrence networks grew more complex, with positive interactions accounting for 85.24% (bacteria) and 90.10% (fungi) in the late stage. Key genes (ldh, gapA, pgk) from Acetobacter pasteurianus and Lactobacillus acetotolerans dominated late-stage fermentation, while genes (adhP, SDH) from Aspergillus oryzae and Saccharomyces cerevisiae supported early- and mid-stage fermentation. These findings elucidate microbiota-driven metabolic pathways in ZRV, supporting the fermentation window optimization and industrial vinegar quality standardization.

Acetic Acid↗
PubMed2002

A comparative resonance Raman analysis of heme-binding PAS domains: heme iron coordination structures of the BjFixL, AxPDEA1, EcDos, and MtDos proteins.

The heme-PAS is a specialized domain with which a broad class of signal-transducing heme proteins detect physiological heme ligands. Such domains exhibit a wide range of ligand binding parameters, yet they are all expected to feature an alpha-beta heme binding fold and a predominantly hydrophobic heme distal pocket without a distal histidine. We have compared, for the first time, the resonance Raman spectra of several heme-PASs: the heme-binding domains of Bradyrhizobium japonicum FixL, Escherichia coli Dos, Acetobacter xylinum PDEA1, and Methanobacterium thermoautotrophicum Dos. In all cases, the nu(Fe)-(CO) and nu(C-O) values of the carbonmonoxy forms were consistent with coordination of the heme iron to histidine on the proximal side and binding of the CO without electrostatic interaction with the heme distal pocket. EcDos was unusual in having predominantly hexacoordinate heme iron in the deoxy and met forms. Despite an evident lack of CO interaction with the EcDos heme pocket, relatively low Fe-O(2) (562 cm(-1)) and N-O (1576 cm(-1)) stretching frequencies indicated that strong polar interactions with that heme distal pocket are possible for highly bent ligands such as O(2) or NO. None of the newly studied NO adducts exhibited evidence of the Fe-His rupture and pentacoordination previously noted for Sinorhizobium meliloti FixL. A low Fe-His stretching frequency, formerly interpreted as a strained Fe-His bond, and the slow association of O(2) with S. meliloti FixL failed to correlate with the newly studied proteins having low association rate or low equilibrium association constants for binding of O(2). We conclude that although heme-PASs share some features, they represent distinct signal transduction mechanisms.

Acetobacter↗
PubMed2006

Structure of a NADH-insensitive hexameric citrate synthase that resists acid inactivation.

Acetobacter aceti converts ethanol to acetic acid, and strains highly resistant to both are used to make vinegar. A. aceti survives acetic acid exposure by tolerating cytoplasmic acidification, which implies an unusual adaptation of cytoplasmic components to acidic conditions. A. aceti citrate synthase (AaCS), a hexameric type II citrate synthase, is required for acetic acid resistance and, therefore, would be expected to function at low pH. Recombinant AaCS has intrinsic acid stability that may be a consequence of strong selective pressure to function at low pH, and unexpectedly high thermal stability for a protein that has evolved to function at approximately 30 degrees C. The crystal structure of AaCS, complexed with oxaloacetate (OAA) and the inhibitor carboxymethyldethia-coenzyme A (CMX), was determined to 1.85 A resolution using protein purified by a tandem affinity purification procedure. This is the first crystal structure of a "closed" type II CS, and its active site residues interact with OAA and CMX in the same manner observed in the corresponding type I chicken CS.OAA.CMX complex. While AaCS is not regulated by NADH, it retains many of the residues used by Escherichia coli CS (EcCS) for NADH binding. The surface of AaCS is abundantly decorated with basic side chains and has many fewer uncompensated acidic charges than EcCS; this constellation of charged residues is stable in varied pH environments and may be advantageous in the A. aceti cytoplasm.

Acetobacter↗
PubMed2000

Multifunctional epoxy supports: a new tool to improve the covalent immobilization of proteins. The promotion of physical adsorptions of proteins on the supports before their covalent linkage.

Multifunctional supports containing epoxy groups are here proposed as a second generation of activated supports for covalent immobilization of enzymes following the epoxy chemistry on any type of support (hydrophobic or hydrophilic ones) under very mild experimental conditions (e.g., low ionic strength, neutral pH values, and low temperatures). These multifunctional supports have been easily prepared by modifying a small fraction (10-20%) of the epoxy groups contained in commercial epoxy supports. In this way, additional groups that were able to physically adsorb proteins (e.g., cationic or anionic groups, metal chelate, phenyl boronate) are generated on the support surface. The covalent immobilization of proteins on these supports proceeds via their initial physical adsorption on the supports (via different structural features). Then, "intramolecular" covalent linkages between some nucleophilic groups of the adsorbed enzyme (e.g., amino, thiol, or hydroxy groups) and the dense layer of nearby epoxy groups on the support are established. This two-step covalent immobilization dramatically improves the very low reactivity of epoxy groups toward nonadsorbed proteins. In this way, all other relevant practical advantages of epoxy groups for protein immobilization (their high stability and their ability to form very strong linkages with several nucleophilic enzyme residues with minimal chemical modification) can be an object of universal exploitation. The use of these new multifunctional supports exhibits important advantages regarding immobilization of enzymes previously adsorbed on hydrophobic homofunctional epoxy supports: (i) hydrophilic supports can also be used for immobilization of industrial enzymes; (ii) immobilization can also be carried out at low ionic strength; (iii) every protein contained in crude extracts from Escherichia coli and Acetobacter turbidans can be immobilized by sequentially using a set of different supports; (iv) in most cases, each enzyme has been immobilized on different supports, orientated through different structural features and very likely involving different areas of its surface. For example, three industrial enzymes (penicillin G acylase, lipase, and beta-galactosidase) could be immobilized through different strategies yielding immobilized derivatives with very different activities. The best derivatives preserved 75-100% of activity corresponding to the soluble enzymes used for immobilization, while in some cases a particular immobilization protocol promoted the full inactivation of the enzyme.

Acetobacter↗
PubMed2001

Biotransformations catalyzed by multimeric enzymes: stabilization of tetrameric ampicillin acylase permits the optimization of ampicillin synthesis under dissociation conditions.

The importance of the stabilization of the quaternary structure of multimeric enzymes has been illustrated using a model reaction with great industrial relevance: the enzymatic synthesis of ampicillin from 6-amino penicillanic acid (6APA) and phenylglycine methyl ester (PGM) catalyzed by the tetrameric enzyme alpha-amino acid ester hydrolase from Acetobacter turbidans. The stabilization of the multimeric structure of the enzyme was achieved by multi-subunit immobilization of the enzyme followed by its further solid-phase chemical intersubunit cross-linking with polyfunctional macromolecules (dextran-aldehyde). This stabilized derivative has permitted the study of the reaction under conditions where nonstabilized enzyme molecules tended to dissociate (e.g., absence of phosphate ions). Synthetic yields improved from around 65%, under conditions where the nonstabilized derivative was stable, to around 85% in conditions where only the stabilized derivative could be utilized (40% methanol and absence of phosphate ions). When using high concentrations of PGM, a significant worsening of the reaction performance was detected with a significant decrease in the yields (below 55%, using 50 mM 6APA and PGM). This problem has been sorted out by using a fed-batch reaction system. By addition of PGM continuously to the reaction mixture (to maintain the concentration between 0.5 and 3 mM), 95% of 6-APA could be transformed to antibiotic (47.5 mM) by only using a 20% excess of acylating ester.

Acetobacter↗
PubMedDate not supplied

A multiphasic hollow fiber reactor for the whole-cell bioconversion of 2-methyl-1,3-propanediol to (r)-beta-hydroxyisobutyric acid.

This paper describes the bioconversion of 2-methyl-1,3-propanediol to (R)-beta-hydoxyisobutyric acid (HIBA) by Acetobacter ALEI in a hollow fiber membrane bioreaction system arrangement that allows the integration of three liquid phases: the aqueous bioconversion phase, the organic phase consisting of a solution of trioctyl phosphine oxide (TOPO) in isooctane, and the third phase consisting of a basic stripping solution that allows reextraction of HIBA from the organic phase. A comparison of HIBA mass transfer experiments was carried out in the membrane reactor with two and three phases for different pH and TOPO concentrations. The use of the three-phase arrangement allows the extraction of high quantities of HIBA from the aqueous medium (higher than 85%) independently of the pH, whereas in the two-phase system the percentage of HIBA extracted from the aqueous medium was lower, 42% in the best case, and strongly influenced by the pH. The percentage of the extractive agent TOPO in the organic phase influenced on the mass transfer rate in both bi- and triphasic arrangements. By simply integrating the re-extraction phase in the system it was possible to increase the extraction yield by 2-fold, reduce the amount of TOPO by 4-fold, and operate at the more favorable pH 4. A bioconversion experiment was done in these conditions (pH = 4, TOPO = 5%) to confirm the advantages of including the third stripping solution. Fed-batch operation of the triphasic membrane reactor was maintained for more than 20 h, reaching an HIBA concentration in the stripping solution of 29 g L(-)(1).

Acetobacter↗
PubMedDate not supplied

Effect of addition of water-soluble polysaccharides on bacterial cellulose production in a 50-L airlift reactor.

Bacterial cellulose (BC) production was carried out in a batch cultivation of Acetobacter xylinum in a 50-L internal loop airlift reactor by addition of water-soluble polysaccharides into the medium. When 0.1% (w/w) agar was added, BC production reached 8.7 g/L compared with 6.3 g/L in the control, and duration of the cultivation period to reach the maximum concentration of BC was almost half of that without addition of polysaccharides. During cultivation, BC was formed into pellets whose size was smaller when the productivity of BC was higher, indicating that increase in the relative viscosity by addition of polysaccharides hindered formation of large clumps of BC and increase in the volumetric oxygen transfer coefficient at high flow rate led to increase in BC productivity.

Acetobacter↗
PubMedDate not supplied

Acetate-specific stress response in acetate-resistant bacteria: an analysis of protein patterns.

Many metabolic byproducts have toxic effects on bacteria, and acetic acid is an excellent model for such molecules. The negative effects of acetate, which include decreased growth rates and specific productivities, appear for Escherichia coli at acetate concentrations lower than 5 g/L. Acetic acid bacteria, however, are naturally resistant to the detrimental effects of acetate in their surroundings; they remain active at acetate levels well over 40 g/L. This study investigated the response to acetate challenges by the naturally acetate-resistant bacteria Acetobacter aceti and Gluconobacter suboxydans to learn more about possible mechanisms of tolerance to otherwise toxic low molecular weight metabolites. Growth studies showed that the resistant bacteria grow more slowly in the presence of acetate but are not slowed nearly so much as is E. coli. In addition, two-dimensional gel electrophoresis (2DE) was applied to study the relative protein patterns of acetate-resistant bacteria during growth in the presence and absence of acetate. In each organism, growth in acetate-containing medium led to elevated levels of many stress response proteins. 2DE analysis of heat-shocked cultures was used to determine which were nonspecific. Elimination of those proteins that were also amplified following heat shock left only eight proteins, here designated acetate-specific stress proteins (Asps), which are overexpressed specifically in response to acetate. Three of these, AspA, AspB, and AspC, appear to be analogous in the two bacterial strains studied, based on their apparent pIs and molecular weights.

Acetates↗
PubMed2002

CP/MAS (13)C NMR study of cellulose and cellulose derivatives. 1. Complete assignment of the CP/MAS (13)C NMR spectrum of the native cellulose.

The precise assignments of cross polarization/magic angle spinning (CP/MAS) (13)C NMR spectra of cellulose I(alpha) and I(beta) were performed by using (13)C labeled cellulose biosynthesized by Acetobacter xylinum (A. xylinum) ATCC10245 strain from culture medium containing D-[1,3-(13)C]glycerol or D-[2-(13)C]glucose as a carbon source. On the CP/MAS (13)C NMR spectrum of cellulose from D-[1,3-(13)C]glycerol, the introduced (13)C labeling were observed at C1, C3, C4, and C6 of the biosynthesized cellulose. In the case of cellulose biosynthesized from D-[2-(13)C]glucose, the transitions of (13)C labeling to C1, C3, and C5 from C2 were observed. With the quantitative analysis of the (13)C transition ratio and comparing the CP/MAS (13)C NMR spectrum of the Cladophora cellulose with those of the (13)C labeled celluloses, the assignments of the cluster of resonances which belong to C2, C3, and C5 of cellulose, which have not been assigned before, were performed. As a result, all carbons of cellulose I(alpha) and I(beta) except for C1 and C6 of cellulose I(alpha) and C2 of cellulose I(beta) were shown in equal intensity of doublet in the CP/MAS spectrum of the native cellulose, which suggests that two inequivalent glucopyranose residues were contained in the unit cells of both cellulose I(alpha) and I(beta) allomorphs.

Acetobacter↗
PubMed2002

CP/MAS (13)C NMR study of cellulose and cellulose derivatives. 2. Complete assignment of the (13)C resonance for the ring carbons of cellulose triacetate polymorphs.

Complex ring (13)C resonance lines of the cross-polarization/magic angle spinning (CP/MAS) (13)C NMR spectra of cellulose triacetate (CTA) I and CTA II were completely assigned, for the first time, by (13)C-enriched CTA allomorphs. The (13)C-enriched CTA I was prepared by heterogeneous acetylation of bacterial cellulose which was biosynthesized by Acetobacter xylinum (A. xylinum) ATCC10245 from culture medium containing D-(2-(13)C)-, D-(3-(13)C)-, or D-(5-(13)C)glucose as a carbon source, while CTA II samples were obtained by solution acetylation of the (13)C-enriched bacterial celluloses. From comparison of the spectra of normal CTA prepared from ramie with those of the enriched CTA samples, it was revealed that all carbons composed of CTA I appeared as a singlet, while those of CTA II except for C1 were shown as equal-intensity doublets in the CP/MAS (13)C NMR spectrum. This finding suggests that CTA I is made up of one kind of glucopyranose residue while there are two magnetically inequivalent sites in the unit cell of CTA II in the same population.

Acetobacter↗
PubMed2002

Fermentability of grape must after inhibition with dimethyl dicarbonate (DMDC).

Dimethyl dicarbonate (DMDC) was added to grape must and to synthetic media and results showed that, at 20 degrees C, 150 mg.L(-)(1) DMDC completely inhibited the fermentation of a grape must that was previously inoculated with 10(6) cells.mL(-)(1) Saccharomyces bayanus and Saccharomyces uvarum. Brettanomyces intermedius, Candida guilliermondii, Hansenula jadinii, Hansenula petersonii, Kloeckera apiculata, Pichia membranaefaciens, and Saccharomyces cerevisiae were inhibited by 250 mg.L(-)(1). Candida valida was inhibited in the presence of 350 mg.L(-)(1), whereas Hanseniaspora osmophila, Saccharomycodes ludwigii, Schizosaccharomyces pombe, and Zygosaccharomyces bailii required 400 mg.L(-)(1). Delay of fermentation (but not inhibition) was noted in the presence of 400 mg.L(-)(1) for the following cultures: Brettanomyces anomalus, Hanseniaspora uvarum, Metschnikowia pulcherrima, Schizosaccharomyces japonicus, Torulaspora delbrueckii, and Zygosaccharomyces florentinus. Acetobacter aceti and Lactobacillus sp. were completely inhibited using 1000 and 500 mg.L(-)(1) DMDC, respectively. The fermentation of a grape must inoculated with 10(6) cells.mL(-)(1) of different wine yeasts was delayed for 4 days after the prior addition of 200 mg.L(-)(1) of DMDC; 200 mg.L(-)(1) DMDC did not show any residual inhibitory effect after 12 h, nor did 300 mg.L(-)(1) 24 h after the addition. In cellar experiments, indigenously contaminated grape musts (with and without skins) showed a delay in fermentation of 48 h after the addition of only 50 mg.L(-)(1) DMDC. The possibility of using DMDC (as pure grade as commercially available) in grape must as a disinfectant for the decontamination of musts indigenously contaminated with wild yeast should be considered seriously, despite its apparent low solubility in water.

Acetobacter↗
PubMed2000

Fermentation of a bacterial cellulose/xylan composite by mixed ruminal microflora: implications for the role of polysaccharide matrix interactions in plant cell wall biodegradability.

Growth of the cellulose-synthesizing bacterium Acetobacter xylinum ATCC 53524 in media supplemented with 5% (w/v) glucose and 0.2% (w/v) of a water-soluble, nearly linear xylan from tobacco stalks resulted in the synthesis of a highly crystalline composite having a xylose/glucose ratio ranging from 0.06 to 0.24. The digestion of one composite (88% cellulose/12% xylan) by mixed ruminal microflora displayed kinetics of gas production similar to those of an unassociated mixture of the two components added in a xylan/cellulose ratio similar to that of the composite. The data suggest that intimate association of xylan and cellulose, as is typically found in secondary plant cell walls, does not inhibit the rate of digestion of the component polysaccharides.

Acetobacter↗
PubMed2002

Factors affecting the yield and properties of bacterial cellulose.

Acetobacter xylinum E(25) has been applied in our studies in order to find optimal culture conditions for effective bacterial cellulose (BC) production. The strain displays significantly higher stability in BC production under stationary culture conditions. In contrast, intensive agitation and aeration appear to drastically reduce cellulose synthesis since such conditions induced formation of spontaneous cellulose nonproducing mutants (Cel-), which dominated in the culture. Mutation frequency strictly depends on the medium composition in agitated cultures. Enrichment of the standard SH and Yamanaka media with 1% ethanol significantly enhanced BC production in stationary cultures. Horizontal fermentors equipped with rotating discs or rollers were successfully applied in order to improve culture conditions. Relatively slow rotation velocity (4 rpm) and large surface area enabling effective cell attachment are optimal parameters for cellulose production. Physical properties of BC samples synthesized either in stationary cultures or in a horizontal fermentor revealed that cellulose from stationary cultures demonstrated a much higher value of Young's modulus, but a much lower value of water-holding capacity.

Acetobacter↗
PubMed1999

Acid hydrolysis of bacterial cellulose reveals different modes of synergistic action between cellobiohydrolase I and endoglucanase I.

Intact and partially acid hydrolyzed cellulose from Acetobacter xylinum were used as model substrates for cellulose hydrolysis by 1,4-beta-D-glucan-cellobiohydrolase I (CBH I) and 1,4-beta-D-endoglucanase I (EG I) from Trichoderma reesei. A high synergy between CBH I and EG I in simultaneous action was observed with intact bacterial cellulose (BC), but this synergistic effect was rapidly reduced by acid pretreatment of the cellulose. Moreover, a distinct synergistic effect was observed upon sequential endo-exo action on BC, but not on bacterial microcrystalline cellulose (BMCC). A mechanism for endo-exo synergism on crystalline cellulose is proposed where the simultaneous action of the enzymes counteract the decrease of activity caused by undesirable changes in the cellulose surface microstructure.

Acetobacter↗