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PubMed1997

Isolation and characterization of D-threonine aldolase, a pyridoxal-5'-phosphate-dependent enzyme from Arthrobacter sp. DK-38.

D-Threonine aldolase is an enzyme that catalyzes the cleavage of D-threonine into glycine and acetaldehyde. Its activity was found in several genera of bacteria such as Arthrobacter, Alcaligenes, Xanthomonas, and Pseudomonas, but not in yeasts or fungi. The enzyme was purified to homogeneity from one strain, Arthrobacter sp. DK-38. The enzyme appeared to consist of a single polypeptide chain with an apparent molecular mass of 51 kDa. This enzyme, as well as L-threonine aldolase, requires pyridoxal 5'-phosphate (pyridoxal-P) as a coenzyme. Unlike other pyridoxal-P enzymes, D-threonine aldolase also requires a divalent cation such as Co2+, Ni2+, Mn2+, or Mg2+ for its catalytic activity. The enzyme completely lost its activity in the absence of either pyridoxal-P or a divalent cation. A divalent cation was also essential for the thermal stability of the enzyme. The metal-free enzyme tends to become thermally unstable, resulting in the irreversible loss of its catalytic activity. The enzyme is strictly D-specific for the alpha-position, whereas it cannot distinguish between threo and erythro forms at the beta-position. Thus, D-threonine and D-allothreonine act as substrates of the enzyme, but their kinetic parameters are different; the Km and Vmax values are 3.81 mM and 38.8 micromol x min(-1) x mg(-1) toward D-threonine, and 14.0 mM and 102 micromol x min(-1) x mg(-1) toward D-allothreonine. respectively. The aldolase reaction is reversible, and the enzyme is therefore able to produce nearly equimolar amounts of D-threonine and D-allothreonine through C-C bond formation between glycine and acetaldehyde. The enzyme also acts, in the same manner, on several other D-beta-hydroxy-alpha-amino acids, including D-beta-phenylserine, D-beta-hydroxy-alpha-aminovaleric acid, D-beta-3,4-dihydroxyphenylserine, and D-beta-3,4-methylenedioxyphenylserine.

Acetaldehyde↗
PubMed1999

Purification and characterization of two extracellular proteinases from Arthrobacter nicotianae 9458.

Two extracellular serine proteinases with molecular masses of about 53-55 and 70-72 kDa, were purified from Arthrobacter nicotianae 9458 and characterized. The enzymes differed with respect to temperature optimum, 55-60 and 37 degrees C, respectively, tolerance to low values of pH and temperature, heat stability, sensitivity to EDTA and sulfhydryl blocking agents, and hydrophobicity. Both proteinases were optimally active in the pH range of 9.0 and 9.5, had considerable activity at pH 6.0 on alpha s1- and beta-caseins, and tolerated NaCl over 5%. Specificity on casein fractions was generally similar and beta-casein was more susceptible to hydrolysis than alpha s1-casein. The proteinases of Arthrobacter spp. may play a significant role in ripening of the smear surface-ripened cheeses.

Arthrobacter↗
PubMed2007

Adaptation of the psychrotroph Arthrobacter chlorophenolicus A6 to growth temperature and the presence of phenols by changes in the anteiso/iso ratio of branched fatty acids.

Arthrobacter chlorophenolicus is a previously described Gram-positive bacterium capable of degrading high concentrations of several phenolic compounds under optimal mesophilic (28 degrees C) as well as psychrophilic (5 degrees C) conditions. However, the exact mechanisms by which this organism is able to tolerate such extremes in temperature and high levels of toxic compounds are currently not known. In this study, we monitored changes in the fatty acid composition of the cell membrane under different extreme growth conditions. Arthrobacter chlorophenolicus adapts to differences in temperature and phenol concentrations by altering the anteiso/iso ratio of fatty acids in the cell membrane to different extents. According to the different physico-chemical properties of those two species of branched fatty acids, the bacteria showed an increased amount of anteiso fatty acids when grown under psychrophilic conditions to decrease the viscosity of their membranes. On the other hand, at higher growth temperatures as well as in the presence of toxic concentrations of phenol, 4-chlorophenol and 4-nitrophenol, the cells adapted their membrane by a dose-dependent decrease in the anteiso/iso ratio, leading to a more rigid membrane and counteracting the fluidity increase caused by the higher temperature and the organic solvents.

Adaptation, Physiological↗
PubMed1992

Cloning and sequence analysis of genes for dehalogenation of 4-chlorobenzoate from Arthrobacter sp. strain SU.

Strains of Arthrobacter catalyze a hydrolytic dehalogenation of 4-chlorobenzoate (4-CBA) to p-hydroxybenzoate. The reaction requires ATP and coenzyme A (CoA), indicating activation of the substrate via a thioester, like that reported for Pseudomonas sp. strain CBS3 (J. D. Scholten, K.-H. Chang, P. C. Babbit, H. Charest, M. Sylvestre, and D. Dunaway-Mariano, Science 253:182-185, 1991). The dehalogenase genes of Arthrobacter sp. strain SU were cloned and expressed in Escherichia coli. Analyses of deletions indicate that dehalogenation depends on three open reading frames (ORFs) which are organized in an operon. There is extensive sequence homology to corresponding gene products in Pseudomonas sp. strain CBS3, suggesting that ORF1 and ORF2 encode a 4-CBA-CoA-ligase and a 4-CBA-CoA dehalogenase, respectively. ORF3 possibly represents a thioesterase, although no homology to the enzyme from Pseudomonas sp. strain CBS3 exists.

Amino Acid Sequence↗
PubMed1993

Degradation of a sodium acrylate oligomer by an Arthrobacter sp.

Arthrobacter sp. strain NO-18 was first isolated from soil as a bacterium which could degrade the sodium acrylate oligomer and utilize it as the sole source of carbon. When 0.2% (wt/wt) oligomer was added to the culture medium, the acrylate oligomer was found to be degraded by 70 to 80% in 2 weeks, using gel permeation chromatography. To determine the maximum molecular weight for biodegradation, the degradation test was done with the hexamer, heptamer, and octamer, which were separated from the oligomer mixture by fractional gel permeation chromatography. The hexamer and heptamer were consumed to the extents of 58 and 36%, respectively, in 2 weeks, but the octamer was not degraded. Oligomers with three different terminal groups were synthesized to examine the effect of the different terminal groups on biodegradation, but few differences were found. Arthrobacter sp. NO-18 assimilated acrylic acid, propionic acid, glutaric acid, 2-methylglutaric acid, and 1,3,5-pentanetricarboxylic acid. Degradation of the acrylic unit structure by this strain is discussed.

Acrylates↗
PubMed1994

Characterization of a psychrotrophic Arthrobacter gene and its cold-active beta-galactosidase.

Enzymes with high specific activities at low temperatures have potential uses for chemical conversions when low temperatures are required, as in the food industry. Psychrotrophic microorganisms which grow at low temperatures may be a valuable source of cold-active enzymes that have higher activities at low temperatures than enzymes found for mesophilic microorganisms. To find cold-active beta-galactosidases, we isolated and characterized several psychrotrophic microorganisms. One isolate, B7, is an Arthrobacter strain which produces beta-galactosidase when grown in lactose minimal media. Extracts have a specific activity at 30 degrees C of 2 U/mg with o-nitrophenyl-beta-D-galactopyranoside as a substrate. Two isozymes were detected when extracts were subjected to electrophoresis in a nondenaturing polyacrylamide gel and stained for activity with 5-bromo-4-chloro-indolyl-beta-D-galactopyranoside (X-Gal). When chromosomal DNA was prepared and transformed into Escherichia coli, three different genes encoding beta-galactosidase activity were obtained. We have subcloned and sequenced one of these beta-galactosidase genes from the Arthrobacter isolate B7. On the basis of amino acid sequence alignment, the gene was found to have probable catalytic sites homologous to those from the E. coli lacZ gene. The gene encoded a protein of 1,016 amino acids with a predicted molecular mass of 111 kDa. The enzyme was purified and characterized. The beta-galactosidase from isolate B7 has kinetic properties similar to those of the E. coli lacZ beta-galactosidase but has a temperature optimum 20 degrees C lower than that of the E. coli enzyme.

Amino Acid Sequence↗
PubMed1997

New metabolites in the degradation of fluorene by Arthrobacter sp. strain F101.

Identification of new metabolites and demonstration of key enzyme activities support and extend the pathways previously reported for fluorene metabolism by Arthrobacter sp. strain F101. Washed-cell suspensions of strain F101 with fluorene accumulated 9-fluorenone, 4-hydroxy-9-fluorenone, 3-hydroxy-1-indanone, 1-indanone, 2-indanone, 3-(2-hydroxyphenyl) propionate, and a compound tentatively identified as a formyl indanone. Incubations with 2-indanone produced 3-isochromanone. The growth yield with fluorene as a sole source of carbon and energy corresponded to an assimilation of about 34% of fluorene carbon. About 7.4% was transformed into 9-fluorenol, 9-fluorenone, and 4-hydroxy-9-fluorenone. Crude extracts from fluorene-induced cells showed 3,4-dihydrocoumarin hydrolase and catechol 2,3-dioxygenase activities. These results and biodegradation experiments with the identified metabolites indicate that metabolism of fluorene by Arthrobacter sp. strain F101 proceeds through three independent pathways. Two productive routes are initiated by dioxygenation at positions 1,2 and 3,4, respectively. meta cleavage followed by an aldolase reaction and loss of C-1 yield the detected indanones. Subsequent biological Baeyer-Villiger reactions produce the aromatic lactones 3,4-dihydrocoumarin and 3-isochromanone. Enzymatic hydrolysis of the former gives 3-(2-hydroxyphenyl) propionate, which could be a substrate for a beta oxidation cycle, to give salicylate. Further oxidation of the latter via catechol and 2-hydroxymuconic semialdehyde connects with the central metabolism, allowing the utilization of all fluorene carbons. Identification of 4-hydroxy-9-fluorenone is consistent with an alternative pathway initiated by monooxygenation at C-9 to give 9-fluorenol and then 9-fluorenone. Although dioxygenation at 3,4 positions of the ketone apparently occurs, this reaction fails to furnish a subsequent productive oxidation of this compound.

Arthrobacter↗
PubMed2000

Genetic diversity among Arthrobacter species collected across a heterogeneous series of terrestrial deep-subsurface sediments as determined on the basis of 16S rRNA and recA gene sequences.

This study was undertaken in an effort to understand how the population structure of bacteria within terrestrial deep-subsurface environments correlates with the physical and chemical structure of their environment. Phylogenetic analysis was performed on strains of Arthrobacter that were collected from various depths, which included a number of different sedimentary units from the Yakima Barricade borehole at the U.S. Department of Energy's Hanford site, Washington, in August 1992. At the same time that bacteria were isolated, detailed information on the physical, chemical, and microbiological characteristics of the sediments was collected. Phylogenetic trees were prepared from the 39 deep-subsurface Arthrobacter isolates (as well as 17 related type strains) based on 16S rRNA and recA gene sequences. Analyses based on each gene independently were in general agreement. These analyses showed that, for all but one of the strata (sedimentary layers characterized by their own unifying lithologic composition), the deep-subsurface isolates from the same stratum are largely monophyletic. Notably, the layers for which this is true were composed of impermeable sediments. This suggests that the populations within each of these strata have remained isolated under constant, uniform conditions, which have selected for a particular dominant genotype in each stratum. Conversely, the few strains isolated from a gravel-rich layer appeared along several lineages. This suggests that the higher-permeability gravel decreases the degree of isolation of this population (through greater groundwater flow), creating fluctuations in environmental conditions or allowing migration, such that a dominant population has not been established. No correlation was seen between the relationship of the strains and any particular chemical or physical characteristics of the sediments. Thus, this work suggests that within sedimentary deep-subsurface environments, permeability of the deposits plays a major role in determining the genetic structure of resident bacterial populations.

Arthrobacter↗
PubMed1969

Role of alcoholic intermediates in formation of isomeric ketones from n-hexadecane by a soil Arthrobacter.

A soil Arthrobacter species isolated from an Oregon soil was capable of transforming n-hexadecane to a series of ketonic products, the 2-,3-, and 4-hexadecanones, with evidence for accumulation of 2- and 3-hexadecanols as oxidative intermediates when yeast extract or peptone was used as a growth substrate. The accumulation and participation of internal alcohols in this type of hydrocarbon transformation has not been previously reported. In the absence of yeast extract or peptone, growth from low-level inocula was not observed when n-hexadecane or two oxidation products, 2-hexadecanol and 3-hexadecanone, were used as substrates. However, washed resting cell suspensions of the organism transformed 2-hexadecanol, or a mixture of 2-,3-, and 4-hexadecanols, to the corresponding ketones without lag, indicating the possible constitutive nature of the alcohol dehydrogenase enzyme(s) carrying out this reaction. The addition of glucose to these resting cells stimulated transformation of n-hexadecane to alcoholic and ketonic oxidation products. Formation of isomeric internal alcohols appears to be a limiting step in ketone formation by this Arthrobacter isolate.

Alcohols↗
PubMed1970

Cometabolism of m-chlorobenzoate by an Arthrobacter.

Twenty isolates representing nine bacterial genera were obtained from enrichment cultures and were shown to cometabolize one or more of 22 substituted benzoates. One of the isolates, an Arthrobacter sp., cometabolized m-chlorobenzoate to a product identified as 4-chlorocatechol by thin-layer chromatography and ultraviolet and infrared spectroscopy. The data indicate that cometabolism by the arthrobacter results from the formation of products by its benzoate-oxiding enzyme system that are not acted upon by the catechol-metabolizing enzymes of the bacterium.

Amines↗
PubMed1993

Expression and secretion of an Arthrobacter dextranase in the oral bacterium Streptococcus gordonii.

We have constructed a plasmid to express and secrete dextranase in the oral bacterium Streptococcus gordonii. The dextranase gene from Arthrobacter sp. strain CB-8 was linked to a promoter and a DNA sequence encoding the signal peptide of Streptococcus downei glucosyltransferase I (gtfI) followed by the Escherichia coli rrnBt1t2 terminator and inserted in the shuttle vector pVA838. S. gordonii transformed with this plasmid (pMNK-4) expressed and secreted mature Arthrobacter dextranase. The transformant was found to repress the firm adherence of water-insoluble glucan in a coculture experiment with cariogenic bacteria, Streptococcus sobrinus, in the presence of sucrose. Such genetically engineered oral bacteria could provide a therapy to prevent dental caries.

Amino Acid Sequence↗
PubMed1972

Heterotrophic nitrifiction by Arthrobacter sp.

Arthrobacter sp. isolated from sewage oxidized ammonium to hydroxylamine, a bound hydroxylamine compound, a hydroxamic acid, a substance presumed to be a primary nitro compound, nitrite, and nitrate. The concentration of free hydroxylamine-nitrogen reached 15 mug/ml. The identification of hydroxylamine was verified by mass spectrometric analysis of its benzophenone oxime derivative. The bound hydroxylamine was tentatively identified as 1-nitrosoethanol on the basis of its mass spectrum, chemical reactions, and infrared and ultraviolet spectra. Hydroxylamine formation by growing cells was relatively independent of pH, but the accumulation of nitrite was strongly favored in alkaline solutions. The formation of hydroxylamine but not nitrite was regulated by the carbon to nitrogen ratio of the medium. The hydroxamic acid was the dominant product of nitrification in iron-deficient media, but hydroxylamine, nitrite, and 1-nitrosoethanol formation was favored in iron-rich solutions. Heterotrophic nitrification by Arthrobacter sp. was not inhibited by several compounds at concentrations which totally inhibited autotrophic nitrification.

Acetates↗
PubMed1972

Inhibition of isocitrate lyase: the basis for inhibition of growth of two Arthrobacter species by pyruvate.

Growth of Arthrobacter atrocyaneus and A. pyridinolis on certain growth substrates was found to be inhibited by pyruvate and compounds which can be converted to pyruvate. Growth of A. atrocyaneus on acetate, for example, was completely inhibited by 5 mm pyruvate; growth of this organism on glucose was less sensitive and growth on succinate was insensitive to inhibition by pyruvate. Growth of a third Arthrobacter species, A. crystallopoietes, on acetate and other substrates was not inhibited by pyruvate. The site of pyruvate inhibition was shown to be the isocitrate lyase reaction. Glyoxylate, which affords a bypass of this reaction, restored the ability of A. atrocyaneus to evolve (14)CO(2) from acetate in the presence of pyruvate. The isocitrate lyases from A. atrocyaneus and A. pyridinolis were competitively inhibited by concentrations of pyruvate as low as 1 mm, whereas the enzyme from A. crystallopoietes was unaffected by this concentration of pyruvate. Comparable levels of phosphoenolpyruvate did not inhibit the isocitrate lyases from any of the species. A mutant strain of A. atrocyaneus, PW11, which is deficient in isocitrate lyase activity, grew on glucose at a reduced rate that was comparable to the rate of growth of the wild-type strain on glucose plus lactate. Addition of lactate to PW11 did not further reduce its rate of growth on glucose. Thus, the glyoxylate pathway appears to be used as an anaplerotic pathway during growth of A. atrocyaneus on glucose. Two other considerations suggest that A. atrocyaneus and A. pyridinolis, but not A. crystallopoietes, may be deficient in the ability to convert pyruvate to 4-carbon acids. First, the former two species accumulate intracellular pyruvate from exogenous l-alanine to a much greater extent than does A. crystallopoietes. Moreover, A. atrocyaneus and A. pyridinolis are incapable of growth on lactate as sole source of carbon whereas A. crystallopoietes can grow on lactate.

Acetates↗
PubMed1973

Gram characteristics and wall ultrastructure of Arthrobacter crystallopoietes during coccus-rod morphogenesis.

Arthrobacter crystallopoietes growing exponentially as cocci were changed to rods by adding succinate to the medium. Cells were sampled before, during, and after this transition for Gram-staining and ultrastructural studies. Cells were Gram stained by the standardized method of Bartholomew, and all samples were fixed and prepared for thin sectioning in an identical manner. Cocci were gram positive, and thin sections demonstrated a gram-positive type of cell wall having an average thickness of 31 nm. Cells sampled during morphogenesis appeared as cocci with most having a single rodlike projection. The coccus portion of these transition cells was gram positive and bound by a gram-positive type of wall having an average thickness of 29 nm. The rodlike projection of the transition cells appeared to be gram negative; it was also surrounded by a gram-positive type of wall, but its average thickness was only 22 nm. Gram-negative rods of the type species, Arthrobacter globiformis, were also examined and found to produce a gram-positive type of wall with a 19-nm average thickness. Evidence for the trilaminar region, characteristic of most gram-negative bacterial cell walls, was totally lacking in both species. These results suggest that variations in cell wall thickness may be an important contributing factor to the variable Gram-staining characteristics of this genus.

Arthrobacter↗
PubMed1975

Induction of morphogenesis in the genus Arthrobacter.

Thirty-eight different compounds were used with 17 species of Arthrobacter to determine their ability to support growth and to induce the morphogenic cycle. In most cases, when a compound supported growth, it also induced the rod phase of growth. However, in a few cases, a compound would support growth with cells remaining in the coccoidal phase throughout the growth cycle. Arthrobacter crystallopoietes was unique in the most compounds that supported growth did not induce the rod phase of the morphogenic cycle.

Amino Acids↗
PubMed1978

Bacterial xanthine oxidase from Arthrobacter S-2.

Arthrobacter S-2, originally isolated by enrichment on xanthine, produced high levels of xanthine oxidase activity, requiring as little as a 20-fold purification to approach homogeneity with some preparations. Molecular oxygen, ferricyanide, and 2,6-dichlorophenol-indophenol served as electron acceptors, but nicotinamide adenine dinucleotide did not. The enzyme was relatively specific when compared with previously studied xanthine-oxidizing enzymes, but at least one purine was observed to be oxidized at each of the three positions of the purine ring that have been subject to oxidation by this type of enzyme. The enzyme had a relatively high Km for xanthine (1.3 X 10(-4) M), and substrate inhibition was not observed with this compound, in contrast to the enzyme from cow's milk. In fact, an opposite effect was observed, and double-reciprocal plots with xanthine as the variable substrate showed a concave downward deviation at high concentrations. At 2.5 mM xanthine the enzyme had a specific activity approximately 50 times that of the most active preparations of the milk enzyme. The spectrum of the Arthrobacter enzyme resembled that of milk xanthine oxidase, suggesting a similarity of the prosthetic centers of the two enzymes. The bacterial enzyme was relatively small and may be dimeric, with approximate native and subunit molecular weights of 146,000 and 79,000, respectively.

2,6-Dichloroindophenol↗
PubMed1978

Isolation and characterization of morphogenetic mutants of Arthrobacter crystallopoietes.

Mutants of Arthrobacter crystallopoietes that exhibited altered ability to undergo the normal sphere-to-rod-to-sphere morphogenetic cycle were isolated. The procedure used to isolate these mutants involved velocity sedimentation in a sterile sucrose gradient to separate morphogenesis-deficient spherical cells from rod-shaped cells capable of normal morphogenesis. Three classes of mutants were obtained: (i) those that cannot form rods, (ii) those that cannot form long rods, and (iii) those that form long rods but exhibit more extensive rudimentary branching than the wild type. The isolation and characterization of these mutants are described, and the use of these mutants in the study of the morphogenetic cycle of arthrobacters is discussed.

Arthrobacter↗
PubMed1978

Induction and regulation of neuraminidase synthesis in Arthrobacter sialophilus.

A variety of N-acetylneuraminic acid (AcNeu) derivatives and analogs were examined as inducers of the extracellular neuraminidase of Arthrobacter sialophilus. Neuraminidase inductions were primarily studied with tryptone-yeast extract-grown cells after washing and resuspension in a defined replacement medium. The addition of readily metabolizable carbon sources to the latter, such as 0.1% casein hydrolysate, glutamate, or glucose, enhanced enzyme synthesis. Enzyme appearance occurred after a lag in the uptake of inducers, suggesting the participation of a co-inducible transport system. Neuraminidase formation during exponential growth in the presence of AcNeu ceased after depletion of this end product from the medium. It was found, besides AcNeu, that its methyl ester, 2-deoxy-2,3-dehydro-N-acetylneuraminic acid and 2-deoxy-2,3-dehydro-N-acetyl-neuraminic acid methyl ester are each active inducers, whereas beta-anomers of AcNeu-ketosides are not. These results, in comparison to known enzyme specificity, have revealed significant differences and parallels between the inductive and catalytic processes for neuraminidase. In particular, it would appear that the free carboxylate and oxygenation at C-2 of AcNeu, essential for enzyme catalysis with traditional AcNeu substrates, are not necessary for induction and, furthermore, that transition state analogs can specifically induce this enzyme. The failure to observe catabolite repression in this system is discussed in relation to the intermediary metabolism of the genus Arthrobacter.

Arthrobacter↗