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PubMed2003

Soluble branched beta-(1,4)glucans from Acetobacter species show strong activities to induce interleukin-12 in vitro and inhibit T-helper 2 cellular response with immunoglobulin E production in vivo.

An extracellular polysaccharide, AC-1, produced by Acetobacter polysaccharogenes is composed of beta-(1,4)glucan with branches of glucosyl residues. We found that AC-1 showed a strong activity to induce production of interleukin-12 P40 and tumor necrosis factor-alpha by macrophage cell lines in vitro. Cellulase treatment completely abolished the activity of AC-1 to induce tumor necrosis factor-alpha production by macrophages, whereas treatment of AC-1 with polymyxin B or proteinase did not affect the activity. Results of experiments using toll-like receptor (TLR) 4-deficient mice and TLR4-transfected human cell line indicated that TLR4 is involved in pattern recognition of AC-1. In vivo administration of AC-1 significantly reduced the serum levels of ovalbumin (OVA)-specific IgE and interleukin-4 production by T cells in response to OVA in mice immunized with OVA. AC-1, a soluble branched beta-(1,4)glucan may be useful in prevention and treatment of allergic disorders With IgE production.

Acetobacter↗
PubMed2005

Acetobacter turbidans alpha-amino acid ester hydrolase: how a single mutation improves an antibiotic-producing enzyme.

The alpha-amino acid ester hydrolase (AEH) from Acetobacter turbidans is a bacterial enzyme catalyzing the hydrolysis and synthesis of beta-lactam antibiotics. The crystal structures of the native enzyme, both unliganded and in complex with the hydrolysis product D-phenylglycine are reported, as well as the structures of an inactive mutant (S205A) complexed with the substrate ampicillin, and an active site mutant (Y206A) with an increased tendency to catalyze antibiotic production rather than hydrolysis. The structure of the native enzyme shows an acyl binding pocket, in which D-phenylglycine binds, and an additional space that is large enough to accommodate the beta-lactam moiety of an antibiotic. In the S205A mutant, ampicillin binds in this pocket in a non-productive manner, making extensive contacts with the side chain of Tyr(112), which also participates in oxyanion hole formation. In the Y206A mutant, the Tyr(112) side chain has moved with its hydroxyl group toward the catalytic serine. Because this changes the properties of the beta-lactam binding site, this could explain the increased beta-lactam transferase activity of this mutant.

Acetobacter↗
PubMed1962

Synthesis of cellulose by Acetobacter xylinum. V. Ultrastructure of polymer.

Appearance of cellulose microfibrils in the medium of a suspension of cells of Acetobacter xylinum in buffered glucose solution was preceded by a stage during which the cellulose in the medium was amorphous within the available resolution. The size of the vertical axis of the microfibrils of the bacterial cellulose was found on the basis of measurement of shadow length to be only about 16 A. In good agreement with findings of earlier workers, the size of the lateral axis ("width") of the image of the metal-shadowed cellulose microfibrils was found to be 11 mmicro. After correcting for a large part probably contributed by deposited metal in the observed width of the microfibrils, the real width is estimated roughly to be in the neighborhood of 3 mmicro. To account for the occurrence of diverse morphological elements in the fields and for the fact that the cellulose fibrils are free entities rather than physical appendages of the cell, it is suggested that individual cellulose molecules are released at the cell surface and diffuse into the medium, wherein they finally enter into crystal-line patterns.

Acetobacter↗
PubMed1982

New restriction endonucleases from Acetobacter aceti and Bacillus aneurinolyticus.

Two restriction endonucleases with new sequence specificities have been isolated from Acetobacter aceti IFO 3281 and Bacillus aneurinolyticus IAM 1077 and named AatII and BanII, respectively. Based on analysis of the sequences around the restriction sites, the recognition sequences and cleavage sites of these endonucleases were deduced as below: (formula; see text)

Acetobacter↗
PubMed1983

A new restriction endonuclease from Acetobacter pasteurianus.

A restriction endonuclease, ApaI, has been partially purified from Acetobacter pasteurianus. This enzyme cleaves bacteriophage lambda DNA and Simian virus 40 DNA at one site, adenovirus-2 DNA at more than nine sites, but it does not cleave phi X174 DNA nor plasmid pBR322 DNA. This enzyme recognizes the sequence (formula; see text) and cuts at the sites indicated by the arrows.

Acetobacter↗
PubMed1989

Nucleotide sequence of the membrane-bound aldehyde dehydrogenase gene from Acetobacter polyoxogenes.

The nucleotide sequence of the membrane-bound aldehyde dehydrogenase (ALDH) gene from an industrial vinegar producer, Acetobacter polyoxogenes, was determined. Comparison of the sequence with the NH2-terminal amino acid sequence of the mature ALDH and determination of the actual translational initiation codon by means of in vitro manipulation of the upstream and proximal regions of the cloned gene showed that ALDH was primarily translated as a 773-amino-acid protein and that the 44-amino-acid sequence at the NH2-terminus, which probably serves as a signal peptide, was processed during maturation and localization in the membrane. When ALDH was expressed in a large quantity in Escherichia coli cells after the coding region had been placed downstream of the lac promoter, the ALDH protein, which still contained the signal peptide and had no ALDH activity, was localized in the membrane fraction.

Acetobacter↗
PubMed1992

Methanol and ethanol oxidase respiratory chains of the methylotrophic acetic acid bacterium, Acetobacter methanolicus.

Acetobacter methanolicus is a unique acetic acid bacterium which has a methanol oxidase respiratory chain, as seen in methylotrophs, in addition to its ethanol oxidase respiratory chain. In this study, the relationship between methanol and ethanol oxidase respiratory chains was investigated. The organism is able to grow by oxidizing several carbon sources, including methanol, glycerol, and glucose. Cells grown on methanol exhibited a high methanol-oxidizing activity and contained large amounts of methanol dehydrogenase and soluble cytochromes c. Cells grown on glycerol showed higher oxygen uptake rate and dehydrogenase activity with ethanol but little methanol-oxidizing activity. Furthermore, two different terminal oxidases, cytochrome c and ubiquinol oxidases, have been shown to be involved in the respiratory chain; cytochrome c oxidase predominates in cells grown on methanol while ubiquinol oxidase predominates in cells grown on glycerol. Both terminal oxidases could be solubilized from the membranes and separated from each other. The cytochrome c oxidase and the ubiquinol oxidase have been shown to be a cytochrome co and a cytochrome bo, respectively. Methanol-oxidizing activity was diminished by several treatments that disrupt the integrity of the cells. The activity of the intact cells was inhibited with NaCl and/or EDTA, which disturbed the interaction between methanol dehydrogenase and cytochrome c. Ethanol-oxidizing activity in the membranes was inhibited with 2-heptyl-4-hydroxyquinoline N-oxide, which inhibited ubiquinol oxidase but not cytochrome c oxidase. Alcohol dehydrogenase has been purified from the membranes of glycerol-grown cells and shown to reduce ubiquinone-10 as well as a short side-chain homologue in detergent solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetobacter↗
PubMed2001

Comparison of benefit to sugarcane plant growth and 15N2 incorporation following inoculation of sterile plants with Acetobacter diazotrophicus wild-type and Nif- mutants strains.

The ability of the nitrogen-fixing bacterial endophyte Acetobacter diazotrophicus strain PAl5 to enhance the growth of sugarcane SP70-1143 was evaluated in the growth chamber, greenhouse, and field by comparing plants inoculated with wild-type and Nif mutant MAd3A in two independent experiments. The wild-type and Nif mutant strains colonized sugarcane plants equally and persisted in mature plants. In N-deficient conditions, sugarcane plants inoculated with A. diazotrophicus PAl5 generally grew better and had a higher total N content 60 days after planting than did plants inoculated with mutant MAd3A or uninoculated plants. These results indicate that the transfer of fixed N from A. diazotrophicus to sugarcane might be a significant mechanism for plant growth promotion in this association. When N was not limiting, growth enhancement was observed in plants inoculated with either wild-type or Nif- mutants, suggesting the additional effect of a plant growth promoting factor provided by A. diazotrophicus. A 15N2 incorporation experiment demonstrated that A. diazotrophicus wild-type strains actively fixed N2 inside sugarcane plants, whereas the Nif- mutants did not.

Acetobacter↗
PubMed1993

Phage Acm1-mediated transduction in the facultatively methanol-utilizing Acetobacter methanolicus MB 58/4.

Phage Acm1, generally virulent for the acidophilic facultatively methanol-utilizing strain of Acetobacter methanolicus MB 58/4, is also capable of lysogenizing its host strain at a low rate. Using amino acid-auxotrophic mutants of A. methanolicus MB 58/4 as recipient strains, transduction of His, Leu and Tyr markers could be demonstrated in this system. The ability to prepare transducing lysates by propagation of phage Acm1 on the prototrophic donor strain A. methanolicus MB 58/4, the transduction of three different markers as well as the efficiency of transduction, and the occurrence of permutations in the phage genome indicate that phage Acm1 mediates generalized transduction. Phage Acm1 might be a useful tool in genetic studies of methylotrophic A. methanolicus.

Acetobacter↗
PubMed1996

Molecular characterization of the levansucrase gene from the endophytic sugarcane bacterium Acetobacter diazotrophicus SRT4.

The Acetobacter diazotrophicus SRT4 gene encoding levansucrase (EC 2.4.1.10) (IsdA) was isolated from a genomic library. The nucleotide sequence of a 2.3 kb DNA fragment sufficient for complementation of a levansucrase-deficient mutant (obtained by EMS treatment) was determined. The IsdA gene (1751 bp) coded for a polypeptide of molecular mass 64.9 kDa with an isoelectric point of 5.2. The N-terminal amino acid sequence of the extracellular levansucrase indicated the presence of a precursor protein with a putative signal sequence of 51 residues which is possibly cleaved in two successive steps. Expression of the IsdA gene from the lac promoter in Escherichia coli resulted in the production of a protein with levansucrase activity. The deduced amino acid sequence of the IsdA gene was 48% and 46% identical with the levansucrases from the Gram-negative bacteria Zymomonas mobilis and Erwinia amylovora, respectively, but only 28-31% identical with levansucrases from Gram-positive bacteria. Multiple alignments of published levansucrase sequences from Gram-negative and Gram-positive bacteria revealed eight conserved motifs. A comparison of the catalytic properties and the sequence of the A. diazotrophicus levansucrase with those of the Bacillus subtilis levansucrase suggested that one of these motifs may be involved in the specificity of the synthetized product. Disruption of the IsdA gene in the genome of A. diazotrophicus resulted in a mutant lacking both levansucrase activity and the ability to utilize sucrose as a carbon source, suggesting that levansucrase is the key enzyme in sucrose metabolism of A. diazotrophicus.

Acetobacter↗
PubMed2005

Characterization and spontaneous mutation of a novel gene, polE, involved in pellicle formation in Acetobacter tropicalis SKU1100.

Acetobacter tropicalis SKU1100 produces a pellicle polysaccharide, consisting of galactose, glucose and rhamnose, which attaches to the cell surface. This strain forms two types of colony on agar plates: a rough-surfaced colony (R strain) and a mucoid smooth-surfaced colony (S strain). The R strain forms a pellicle, allowing it to float on the medium surface in static culture, while the S strain does not. The pellicle is an assemblage of cells which are tightly associated with capsular polysaccharides (CPS) on the cell surface. In this study, a gene required for pellicle formation by the R strain was investigated by transposon mutagenesis using Tn10. The resulting mutant, designated Pel-, has a smooth-surfaced colony and a defect in pellicle formation, as for the S strain. The mutant produced polysaccharide which was instead secreted into the culture medium as extracellular polysaccharide (EPS). An ORF was identified at the Tn10 insertion site, designated polE, upstream of which polABCD genes were also found. The deduced amino acid sequences of polABCD showed a high level of homology to those of rfbBACD which are involved in dTDP-rhamnose synthesis, whereas polE had a relatively low level of homology to glycosyltransferase. In this study a polB (rfbA) disruptant was also prepared, which lacked both CPS and EPS production. A plasmid harbouring the polE or polB genes could restore pellicle formation in the Pel(-) mutant and S strains, and in the DeltapolB mutant, respectively. Thus both polE and polB are evidently involved in pellicle formation, most likely by anchoring polysaccharide to the cell surface and through the production of dTDP-rhamnose, respectively. The Pel- and DeltapolB mutants were unable to grow in static culture and became more sensitive to acetic acid due to the loss of pellicle formation. Additionally, this study identified the mutation sites of several S strains which were spontaneously isolated from the original culture and found them to be concentrated in a sequence of 7 C residues in the coding sequence of polE, with the deletion or addition of a single C nucleotide.

Acetobacter↗
PubMed2003

Acetobacter turbidans alpha-amino acid ester hydrolase: merohedral twinning in P21 obscured by pseudo-translational NCS.

The structure elucidation of the alpha-amino acid ester hydrolase from Acetobacter turbidans by molecular replacement is described. In the monoclinic crystal, the molecules are related by both rotational and pseudo-crystallographic translational NCS (non-crystallographic symmetry). Refinement of the structure converged at unacceptably high R factors. After re-evaluation of the data, it was found that the crystal was merohedrally twinned, with a high twinning fraction. It is shown that the pseudo-crystallographic NCS causes aberrant behaviour of conventional twinning indicators, which explains why the twinning was only realized at the refinement stage.

Acetobacter↗
PubMed2004

Acidophilic adaptations in the structure of Acetobacter aceti N5-carboxyaminoimidazole ribonucleotide mutase (PurE).

The crystal structure of Acetobacter aceti PurE was determined to a resolution of 1.55 A and is compared with the known structures of the class I PurEs from a mesophile, Escherichia coli, and a thermophile, Thermotoga maritima. Analyses of the general factors that increase protein stability are examined as potential explanations for the acid stability of A. aceti PurE. Increased inter-subunit hydrogen bonding and an increased number of arginine-containing salt bridges appear to account for the bulk of the increased acid stability. A chain of histidines linking two active sites is discussed in the context of the proton transfers catalyzed by the enzyme.

Acetobacter↗
PubMed2007

Atomic-resolution crystal structure of thioredoxin from the acidophilic bacterium Acetobacter aceti.

The crystal structure of thioredoxin (AaTrx) from the acetic acid bacterium Acetobacter aceti was determined at 1 A resolution. This is currently the highest resolution crystal structure available for any thioredoxin. Thioredoxins facilitate thiol-disulfide exchange, a process that is expected to be slow at the low pH values encountered in the A. aceti cytoplasm. Despite the apparent need to function at low pH, neither the active site nor the surface charge distribution of AaTrx is notably different from that of Escherichia coli thioredoxin. Apparently the ancestral thioredoxin was sufficiently stable for use in A. aceti or the need to interact with multiple targets constrained the variation of surface residues. The AaTrx structure presented here provides a clear view of all ionizable protein moieties and waters, a first step in understanding how thiol-disulfide exchange might occur in a low pH cytoplasm, and is a basis for biophysical studies of the mechanism of acid-mediated unfolding. The high resolution of this structure should be useful for computational studies of thioredoxin function, protein structure and dynamics, and side-chain ionization.

Acetobacter↗
PubMed1995

Differentiation of capsular polysaccharides from Acetobacter diazotrophicus strains isolated from sugarcane.

Capsular polysaccharides (CPSs) from six representative strains of Acetobacter diazotrophicus were isolated and fractionated by gel filtration and anion-exchange chromatography. Purified CPSs obtained in the non-adsorbed fraction of a DEAE-Sephadex A-25 column were qualitatively and quantitatively analyzed for sugar composition. Uronic acid and amino sugars were not detected in all purified CPSs. Basically the CPSs of A. diazotrophicus are composed of rhamnose, mannose, galactose and glucose. The presence of fucose was only observed in the CPS of strains PR2 and PAL3. Based on these results, the six strains of A. diazotrophicus could be divided into four groups according to the sugar content of their capsules: (i) fucose-containing capsules (PR2 and PAL3, localized in roots), (ii) mannose-rich capsule (PAL5, localized in root), (iii) capsules with a high ratio of hexose to rhamnose (PR4 and PR20, localized in stems) and (iv) capsules with a low ratio of hexose to rhamnose (PR14, localized in rhizosphere). For all CPSs, sodium dodecy sulfate-polyacrylamide gel electrophoresis showed diffuse bands of slow mobility in silver-stained gels. The different CPS migration patterns could not be correlated with sugar composition. The purified CPS of strain PAL3 was found to be immunogenic and immunochemically similar to the CPS of strain PR2. The serological specificity to CPS of strains PAL3 and PR2 correlated well with the presence of focuse, indicating that this deoxyhexose is immunodominant.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetobacter↗
PubMed1995

Repression of lipopolysaccharide biosynthesis in Escherichia coli by an antisense RNA of Acetobacter methanolicus phage Acm1.

Lysogenic Acetobacter methanolicus strains carrying the prophage Acm1 were found to be unable to synthesize both the capsular polysaccharide (CPS) and the O-specific side-chain of lipopolysaccharide (LPS) and to represent rough variants of the host bacterium. A 262 bp DNA fragment of phage Acm1, obviously required for interference with LPS biosynthesis, was cloned and expressed in Escherichia coli. Independently of the O-type, transformation of various E. coli strains with the recombinant DNA resulted in a suppression of biosynthesis of the O-specific chains. The DNA fragment of phage Acm1 contained three very short open reading frames of 21, 24, and 36 bp. However, attempts to express phage-encoded peptides were not successful. Instead, the Acm1-derived DNA fragment was shown to code for the synthesis of a trans-acting RNA molecule of 97 nucleotides, designated lbi (LPS biosynthesis-interfering) RNA. This RNA contains sequence complementarity to E. coli target RNA sequences and appears to have the ability to form intracellularly RNA hybrid duplexes with mRNA. The data presented in this study support the hypothesis that the phenotypic effect of conversion to rough-type LPS is accompanied by the expression of an antisense RNA of phage Acm1.

Acetobacter↗
PubMed1980

Non-specific biosynthesis of hopane triterpenes by a cell-free system from Acetobacter pasteurianum.

1. A cell-free system from the bacterium Acetobacter pasteurianum was incubated with [12-3H]squalene; diploptene and diplopterol, hopanoids normally present in the bacterium, were labelled. Their radioactivity was confirmed by purification using thin-layer chromatography, synthesis of derivatives and recrystallization to constant specific activity. This demonstrates the direct cyclization of squalene into diploptene and diplopterol, catalysed by a squalene cyclase activity in A. pasteurianum. 2. The same cell-free system transformed (RS)-2,3-epoxy-2,3-dihydro-[12,13-3H]squalene into labelled 3 alpha-hydroxyhop-22(29)-ene, 3 beta-hydroxyhop-22(29)-ene, hopane-3 alpha,22-diol and hopane-3 beta,22-diol. Their radioactivity was similarly confirmed. This bacterial homogenate is thus capable of cyclizing an unnatural substrate, 2,3-epoxy-squalene, into 3-hydroxyhopanoids normally absent in the bacterium. 3. The 3 alpha-hydroxy and 3 beta-hydroxyhopanoids could have been enzymatically interconverted via the 3-oxo compound. Synthetic racemic (RS)-2,3-epoxy-2,3-dihydro-[3-3H]squalene was incubated and gave rise to 3-3H-labelled 3 alpha and 3 beta-hydroxyhopanoids. This excludes an isomerization via a 3-oxo compound which would give unlabelled 3-hydroxyhopanoids. 4. In conclusion, the cyclase of A. pasteurianum accepts the replacement of the normal substrate, squalene, by the corresponding epoxide. Furthermore it is not selective in the stereochemistry of the epoxide and cyclizes both enantiomers, contrary to the epoxysqualene cyclase of eukaryotes.

Acetobacter↗
PubMed1985

Prokaryotic triterpenoids. 1. 3 beta-Methylhopanoids from Acetobacter species and Methylococcus capsulatus.

3 beta-Methylbacteriohopanepolyol derivatives were isolated from three bacteria, Acetobacter pasteurianus ssp. pasteurianus, Methylococcus capsulatus and Nostoc muscorum, and identified by spectroscopic methods and direct comparison with 3 beta-methyldiplopterol and 3 beta-methylhopan-29-ol synthesized from 22-hydroxyhopan-3-one. The 3 beta-methylhopanoid content of A. pasteurianus ssp. pasteurianus could be dramatically increased (up to 60% of the total hopanoid content) by addition of L-methionine, the actual methyl donor, to the culture medium.

Acetobacter↗