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Sphere-rod morphogenesis in Arthrobacter crystallopoietes. I. Cell wall composition and polysaccharides of the peptidoglycan.

Cell walls of Arthrobacter crystallopoietes were prepared from cells grown as spheres and from peptone- and succinate-induced rod stage cells. Undegraded polysaccharide backbones of the peptidoglycans were isolated from myxobacter AL-1 protease digests by ECTEOLA cellulose and Sephadex G-50 chromatography. The polysaccharide backbones of the sphere cell wall peptidoglycan are heterogeneous in their size, and average less than 40 hexosamines per chain. Those of the rod cell walls are homogeneous in size and average 114 to 135 hexosamines per chain.

Amino Acids↗

Sphere-rod morphogenesis in Arthrobacter crystallopoietes. II. Peptides of the cell wall peptidoglycan.

Cell walls of Arthrobacter crystallopoietes grown as spheres and as rods were solubilized by treatment with the B enzyme from Chalaropsis, an N-acetylmuramidase. The neutral glycopeptides were then isolated by chromatography on ECTEOLA cellulose. The glycopeptides, consisting of disaccharide-peptide units interlinked by peptide cross-bridges, were fractionated by gel filtration on Sephadex columns into oligomers of various sizes. The size distribution ranged from monomers with no cross-bridges to polymers with a high degree of polymerization, but did not differ significantly between cell walls from cells grown as spheres or rods. Some small differences in the distribution of C- and N-terminal amino acids were found. Analyses revealed that all the peptide bridges in the glycopeptide fractions from rod cell walls were formed by one l-alanine residue. In sphere cell walls, l-alanine was also found, but, in addition, higher oligomers of the glycopeptide contained glycine in their cross-bridges. These results were confirmed by determinations of C- and N-terminal amino acids released after lysostaphin and AL-1 enzyme digestions and by Edman degradations. Models representing the structures of the sphere and rod cell walls are presented. These structures indicate that the sphere cell wall is probably a more loosely knit macromolecule than is the rod cell wall.

Alanine↗

PrairieDogTown and Kinny: lytic environmental bacteriophages of Arthrobacter globiformis.

Two bacteriophages, PrairieDogTown and Kinny, were isolated from topsoil using Arthrobacter globiformis as a host. PrairieDogTown has a 36.2-kb genome encoding 52 genes, whereas Kinny has a 56.4-kb genome with 93 genes. Comparative genomic analysis places PrairieDogTown in Cluster FO and Kinny in Cluster AU in the Actinobacteriophage database.

Arthrobacter spp.↗

The catabolism of L-tyrosine by an Arthrobacter sp.

An Arthrobacter sp. metabolizes L-tyrosine by a pathway involving 3,4-dihydroxyphenylacetate as a key intermediate. p-Hydroxyphenylpyruvate is formed from tyrosine by an amino-transferase specifically requiring alpha-ketoglutarate for activity, and is then converted to p-hydroxyphenylacetate by an oxidative decarboxylation. p-Hydroxyphenylacetaldehyde is not an intermediate in the formation of p-hydroxyphenylacetate. Extracts of the bacterium oxidize 3,4-dihydroxyphenylacetate to delta-carboxymethyl-alpha-hydroxymuconic acid which, when supplemented with 2 mol of diphosphopyridine dinucleotide, results in the production of stoichiometric amounts of succinate and pyruvate.

3,4-Dihydroxyphenylacetic Acid↗

Morphogenetic expression of Arthrobacter globiformis 425 in continuous culture with carbon or biotin limitation.

When deprived of biotin, Arthrobacter globiformis 425 exhibits abnormal morphology (large, branched forms of variable size) and a retardation of its normal growth rate. In chemostat cultures, when cells were grown under glucose limitation, the morphology was normal (coccoids or rods) at specific growth rates between 0.05 and 0.125 h-1 (doubling times between 14 and 5.5 h, respectively) at 25 degrees C. The coccoid-to-rod morphogenesis occurs at a specific growth rate of 0.11 h-1. At the same specific growth rates and temperature, but under biotin limitation, abnormal morphology was observed.

Arthrobacter↗

Plasmid-determined 2-hydroxypyridine utilization by Arthrobacter crystallopoietes.

Arthrobacter crystallopoietes has the ability to utilize 2-hydroxypyridine (2-HP) as a source of carbon and nitrogen and forms a blue extracellular pigment when grown in the presence of 2-HP. Ultracentrifugal analyses of pigment producing (Pig+) and pigment nonproducing (Pig-) strains of A. crystallopoietes revealed the presence of plasmid material in both strains. Recovery of plasmid DNA from Pig+ strains is two or three times greater than from Pig- strains. The molecular weight of plasmid DNA recovered from Pig+ strains (62 Mdaltons) is slightly higher than the molecular weight of plasmid DNA from Pig- strains. Consistent with the characterization of plasmid DNA from the two strains is that Pig+ strains contain a 63-Mdalton plasmid encoding 2-HP utilization as well as a cryptic plasmid of very nearly equal molecular weight. Pig- strains contain only the cryptic plasmid.

Arthrobacter↗

Effect of oxygen on batch and continuous cultures of a nitrogen-fixing Arthrobacter sp.

Growth, acetylene reduction, and respiration rate were studied in batch and continuous cultures of Arthrobacter fluorescents at different oxygen partial pressures. The optimum pO2 values for growth and acetylene reduction were 0.05 and 0.025 atm, respectively, but microorganisms can tolerate higher pO2 values. The growth of cultures provided with combined nitrogen was dependent on oxygen availability, and strict anaerobic conditions did not support growth. Acetylene reduction of a population grown in continuous culture and adapted to low pO2 (0.02 atm) was much more sensitive to oxygenation than that of a population adapted to high pO2 (0.4 atm). Their maximum nitrogenase activity, at their optimal pO2 values, were quite different. The respiratory activity of nitrogen-fixing cultures increased with increasing oxygen tensions until a pO2 of 0.2 atm. At higher pO2 values, the respiration rate began to decrease.

Acetylene↗

Thiocyanate utilization by an Arthrobacter.

An Arthrobacter species, which utilized thiocyanate (SCN-) as a nitrogen source, was isolated from soil by the enrichment culture method. The organism tolerated SCN- concentrations up to 0.1 M. On addition of nitrate or ammonium ion to cultures of the isolate growing in the presence of SCN-, the organism continued to degrade SCN-. Degradation could be followed by release of 14CO2 from SCN-(14C). The SCN- -degrading activity diminished to low levels as the stationary phase of growth was appraoched.

Arthrobacter↗

Low temperature reduction of hexavalent chromium by a microbial enrichment consortium and a novel strain of Arthrobacter aurescens.

BACKGROUND: Chromium is a transition metal most commonly found in the environment in its trivalent [Cr(III)] and hexavalent [Cr(VI)] forms. The EPA maximum total chromium contaminant level for drinking water is 0.1 mg/l (0.1 ppm). Many water sources, especially underground sources, are at low temperatures (less than or equal to 15 Centigrade) year round. It is important to evaluate the possibility of microbial remediation of Cr(VI) contamination using microorganisms adapted to these low temperatures (psychrophiles). RESULTS: Core samples obtained from a Cr(VI) contaminated aquifer at the Hanford facility in Washington were enriched in Vogel Bonner medium at 10 Centigrade with 0, 25, 50, 100, 200, 400 and 1000 mg/l Cr(VI). The extent of Cr(VI) reduction was evaluated using the diphenyl carbazide assay. Resistance to Cr(VI) up to and including 1000 mg/l Cr(VI) was observed in the consortium experiments. Reduction was slow or not observed at and above 100 mg/l Cr(VI) using the enrichment consortium. Average time to complete reduction of Cr(VI) in the 30 and 60 mg/l Cr(VI) cultures of the consortium was 8 and 17 days, respectively at 10 Centigrade. Lyophilized consortium cells did not demonstrate adsorption of Cr(VI) over a 24 hour period. Successful isolation of a Cr(VI) reducing organism (designated P4) from the consortium was confirmed by 16S rDNA amplification and sequencing. Average time to complete reduction of Cr(VI) at 10 Centigrade in the 25 and 50 mg/l Cr(VI) cultures of the isolate P4 was 3 and 5 days, respectively. The 16S rDNA sequence from isolate P4 identified this organism as a strain of Arthrobacter aurescens, a species that has not previously been shown to be capable of low temperature Cr(VI) reduction. CONCLUSION: A. aurescens, indigenous to the subsurface, has the potential to be a predominant metal reducer in enhanced, in situ subsurface bioremediation efforts involving Cr(VI) and possibly other heavy metals and radionuclides.

Arthrobacter↗

Cloning and nucleotide sequence of carbaryl hydrolase gene (cahA) from Arthrobacter sp. RC100.

A carbaryl hydrolase gene (cahA) encoded on the plasmid pRC1 in Arthrobacter sp. RC100 was cloned and sequenced. The entire region of the deduced amino acid sequence was found to be homologous to that of an amidase family. Parts of the consensus sequences of the amidase gene have been identified in CahA from strain RC100. CahA was overexpressed in Escherichia coli JM109, and the enzyme was purified to homogeneity by protamine sulfate treatment, ammonium sulfate precipitation, and hydrophobic and anion-exchange chromatographies. The purified enzyme showed hydrolase activity toward 1-naphthylacetamide and isobutyramide but showed no activity toward 1-naphthylacetate. This is the first report of an amidase that is able to hydrolyze N-methylcarbamate pesticides.

Amidohydrolases↗

Molecular cloning and nucleotide sequencing of the Arthrobacter dextranase gene and its expression in Escherichia coli and Streptococcus sanguis.

A bacterial strain, which assimilated dextran and water-insoluble glucan produced by Streptococcus mutans, was isolated from soil. The bacterium produced and secreted potent dextranase activity, which was identified as Arthrobacter sp. and named CB-8. The dextranase was purified and some enzymatic properties were characterized. The enzyme efficiently decomposed the water-insoluble glucan as well as dextran. A gene library from the bacteria was constructed with Escherichia coli, using plasmid pUC19, and clones producing dextranase activity were selected. Based on the result of nucleotide sequencing analysis, it was deduced that the dextranase was synthesized in CB-8 cells as a polypeptide precursor consisting of 640 amino acid residues, including 49 N-terminal amino acid residues which could be regarded as a signal peptide. In the E. coli transformant, the dextranase activity was detected mostly in the periplasmic space. The gene for the dextranase was introduced into Streptococcus sanguis, using an E. coli-S. sanguis shuttle vector that contained the promoter sequence of a gene for glucosyltransferase derived from a strain of S. mutans. The active dextranase was also expressed and accumulated in S. sanguis cells.

Amino Acid Sequence↗

Chemical structures of hetero-oligosaccharides produced by Arthrobacter sp. K-1 beta-fructofuranosidase.

The structures of hetero-oligosaccharides obtained by the action of transglycosylation of Arthrobacter sp. K-1 beta-fructofuranosidase, using sucrose as the fructosyl donor, and several mono- and di-sacchrides as the acceptors were investigated. The main transfer products to most reducing mono- and di-sacchrides were non-reducing oligosaccharides with a fructosyl residue linked to a hemiacetal hydroxyl group. In the presence of L-sorbose, the enzyme produced 2-O-beta-D-fructofuranosyl-alpha-L-sorbopyranoside as the major product. With D-galactose or L-arabinose, the enzyme produced not only non-reducing oligosaccharides, but also reducing oligosaccharides, which were identified as 3-O-beta-D-fructofuranosyl-D-galactopyranose and 4-O-beta-D-fructofuranosyl-L-arabinopyranose, respectively. When a non-reducing sugar such as methyl alpha-glucoside was used as an acceptor, the product formed had a fructosyl residue linked at the C6 hydroxyl group.

Arthrobacter↗

Purification of inulin fructotransferase (DFA I-producing) from Arthrobacter sp. MCI2493 and production of DFA I from inulin by the enzyme.

An extracellular enzyme that produces di-D-fructofuranose-2',1;2,1' dianhydride from inulin was purified from the culture broth of Arthrobacter sp. MCI2493. The molecular weight of the enzyme was 40,000 by gel filtration and SDS polyacrylamide gel electrophoresis. The enzyme had maximum activity at pH 6.0 and 50 degrees C. Using this purified enzyme, 100 g/liter inulin was converted into 60 g/liter of DFA I, nystose, and 1-F-fructofuranosyl-nystose after incubation for 30 h.

Arthrobacter↗

Cloning and nucleotide sequence of the inulin fructotransferase (DFA I-producing) gene of Arthrobacter globiformis S14-3.

A gene encoding an inulin fructotransferase (DFA I-producing) [EC 2.4.1.200] from Arthrobacter globiformis S14-3 was cloned and the nucleotides sequenced, for the first time. The sequence indicated that the native enzyme protein is composed of 392 amino acid residues. The native enzyme is an extracellar enzyme produced in the culture supernatant of A. globiformis S14-3, but the nucleotide sequence of the gene lacks a sequence for signal peptide for secretion. The 1.5-kb DNA fragment encoding the gene was found to produce the active enzyme in the culture supernatant of an E. coli clone, under the control of the lac promoter of pUC119.

Amino Acid Sequence↗

Purification and properties of a novel enzyme, maltooligosyl trehalose synthase, from Arthrobacter sp. Q36.

Arthrobacter sp. Q36 produces a novel enzyme, maltooligosyl trehalose synthase, which catalyzes the conversion of maltooligosaccharide into the non-reducing saccharide, maltooligosyl trehalose (alpha-maltooligosyl alpha-D-glucoside) by intramolecular transglycosylation. The enzyme was purified from a cell-free extract to an electrophoretically homogeneous state by successive column chromatography on Sepabeads FP-DA13, DEAE-Sephadex A-50, Ultrogel AcA44, and Butyl-Toyopearl 650M. The enzyme was specific for maltooligosaccharides except maltose, and catalyzed the conversion to form maltooligosyl trehalose. The Km of the enzyme for maltotetraose, maltopentaose, maltohexaose, and maltoheptaose were 22.9 mM, 8.7 mM, 1.4 mM, and 0.9 mM, respectively. The enzyme had a molecular mass of 81,000 by SDS-polyacrylamide gel electrophoresis and a pI of 4.1 by gel isoelectrofocusing. The N-terminal and C-terminal amino acids of the enzyme were methionine and serine, respectively. The enzyme showed the highest activity at pH 7.0 and 40 degrees C, and was stable from pH 6.0 to 9.5 and up to 40 degrees C. The enzyme activity was inhibited by Hg2+ and Cu2+.

Amino Acid Sequence↗

Purification and characterization of a novel enzyme, maltooligosyl trehalose trehalohydrolase, from Arthrobacter sp. Q36.

A novel enzyme, maltooligosyl trehalose trehalohydrolase from Arthrobacter sp. Q36 was purified from a cell-free extract to an electrophoretically pure state by successive column chromatography on Sepabeads FP-DA13, Butyl-Toyopearl 650M, DEAE-Toyopearl 650S, and Toyopearl HW-55S. The enzyme specifically catalyzed the hydrolysis of the alpha-1,4-glucosidic linkage that bound the maltooligosyl and trehalose moieties of maltooligosyl trehalose. The Km of the enzyme for maltosyl trehalose, maltotriosyl trehalose, maltotetraosyl trehalose, and maltopentaosyl trehalose was 5.5 mM, 4.6 mM, 7.0 mM, and 4.2 mM, respectively. The enzyme had a molecular mass of 62,000 by SDS-polyacrylamide gel electrophoresis and a pI of 4.1 by gel isoelectrofocusing. The N-terminal amino acid of the enzyme was threonine. The enzyme showed the highest activity at pH 6.5 and 45 degrees C, and was stable from pH 5.0 to 10.0 and up to 45 degrees C. The activity was inhibited by Hg2+, Cu2+, Fe2+, and Zn2+.

Amino Acid Sequence↗

Molecular cloning of levan fructotransferase gene from Arthrobacter nicotinovorans GS-9 and its expression in Escherichia coli.

The gene encoding an extracellular levan fructotransferase, designated the lft gene, was cloned from the genomic DNA of Arthrobacter nicotinovorans GS-9, and expressed in Escherichia coli. It was found that a single open reading frame consisted of 1554 base pairs that encoded a polypeptide composed of a signal peptide of 33 amino acids and a mature protein of 484 amino acids (M(r) 53,152), and it was also found that a putative ribosome-binding site was present in the upstream from the ORF. The primary structure had no significant similarity with those of inulin fructotransferases, but had low similarity to the catalytic regions of other fructosylhydrolases. The expression of the lft gene was increased on a plasmid, pLFT-BB1, in which the lft gene was fused with alpha-peptide of the lacZ gene of pUC18. An E. coli transformant carrying pLFT-BB1 expressed six times as much activity of levan fructotransferase as that of the original strain, A. nicotinovorans GS-9.

Amino Acid Sequence↗

Structural study on a sulfated polysaccharide-peptidoglycan complex produced by Arthrobacter sp.

The structure of a sulfated polysaccharide-peptidoglycan complex (SP-PG) produced by Arthrobacter sp. was analyzed by NMR spectroscopy. In addition, oligosaccharide fragments of the SP-PG-L obtained by HF degradation were analyzed by NMR spectroscopy. These findings indicated that the sulfated polysaccharide (SP) contains a repeating unit composed of two galactofuranosides and a glucopyranoside. The main chain of the trisaccharide is [-->6) beta-D-Galf(1-->6)-beta-D-Galf(1-->ln, with beta-D-Glcp linked to one of the Galfs through a (1-->2) linkage. The sulfated positions of the trisaccharide were identified as C-3 and C-5 of the beta-glucosylated Galf residues, and C-2 or C-3 of the other Galf residue.

Arthrobacter↗