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At least 1,135 records · Page 63Linked to original sources
PubMed2005

Allophanate hydrolase, not urease, functions in bacterial cyanuric acid metabolism.

Growth substrates containing an s-triazine ring are typically metabolized by bacteria to liberate 3 mol of ammonia via the intermediate cyanuric acid. Over a 25-year period, a number of original research papers and reviews have stated that cyanuric acid is metabolized in two steps to the 2-nitrogen intermediate urea. In the present study, allophanate, not urea, was shown to be the 2-nitrogen intermediate in cyanuric acid metabolism in all the bacteria examined. Six different experimental results supported this conclusion: (i) synthetic allophanate was shown to readily decarboxylate to form urea under acidic extraction and chromatography conditions used in previous studies; (ii) alkaline extraction methods were used to stabilize and detect allophanate in bacteria actively metabolizing cyanuric acid; (iii) the kinetic course of allophanate formation and disappearance was consistent with its being an intermediate in cyanuric acid metabolism, and no urea was observed in those experiments; (iv) protein extracts from cells grown on cyanuric acid contained allophanate hydrolase activity; (v) genes encoding the enzymes AtzE and AtzF, which produce and hydrolyze allophanate, respectively, were found in several cyanuric acid-metabolizing bacteria; and (vi) TrzF, an AtzF homolog found in Enterobacter cloacae strain 99, was cloned, expressed in Escherichia coli, and shown to have allophanate hydrolase activity. In addition, we have observed that there are a large number of genes homologous to atzF and trzF distributed in phylogenetically distinct bacteria. In total, the data indicate that s-triazine metabolism in a broad class of bacteria proceeds through allophanate via allophanate hydrolase, rather than through urea using urease.

Allophanate Hydrolase↗
PubMed1982

Some characteristics of a urease-negative, temperature- sensitive strain of Bordetella bronchiseptica as a live, attenuated vaccine.

Strain ts-S34 of Bordetella bronchiseptica was treated jointly with two mutagens, nitrosoguanidine and UV irradiation, and a urease-negative (u-), temperature-sensitive (ts) mutant strain indistinguishable from Alcaligenes faecalis in its biochemical characteristics was isolated. However, the mutant isolated was a phase III organism. By repeating selection of smaller, hemolytic colonies observed among phase III colonies after prolonged incubation, a phase I organism, strain ts-S34.u-, was isolated. The u- and ts properties of the mutant strain were hereditarily stable, and heat-labile toxin production was very low. Growth in KCN broth and on Simmons citrate agar was reduced. Agglutinability of the strain against anti-S1 and anti-ts-S34.u- hyperimmune sera was as high (X20,480) as that of wild-type strain S1. The live ts-S34.u- strain vaccination protected guinea pigs from challenge exposure with 15,000 X the 50% lethal dose of virulent strain S1 of B. bronchiseptica. In these studies, it appeared that the ts-S34.u- strain has favorable properties, including a useful hereditary marker and low heat-labile toxin production, for use as a live attenuated vaccine.

Agglutination↗
PubMed1993

Identification of the Yersinia enterocolitica urease beta subunit as a target antigen for human synovial T lymphocytes in reactive arthritis.

The local T-cell response to bacterial antigens is involved in the pathogenesis of reactive arthritis (ReA). Here, we have identified a 19-kDa antigen of Yersinia enterocolitica O:9 recognized by Yersinia-specific synovial fluid CD4+ T cells in two patients with Yersinia-induced ReA. N-terminal amino acid sequencing of this protein revealed that it was identical to the 19-kDa urease beta subunit of Y. enterocolitica O:9. This protein has previously been shown to be arthritogenic in preimmunized rats after intra-articular injection. Analysis of the T-cell response to this protein showed that it contains several T-cell epitopes, one of which cross-reacts with other enterobacteria not able to induce ReA. This indicates that the arthritogenicity of the 19-kDa antigen is not a property of the 19-kDa protein alone but is dependent on its expression in bacteria able to induce ReA.

Amino Acid Sequence↗
PubMed1996

Urease activity does not contribute dramatically to persistence of Mycobacterium bovis bacillus Calmette-Guérin.

Multiplication of BCGure-, an isogenic urease-negative mutant of Mycobacterium bovis BCG constructed by allelic exchange (J. M. Reyrat, F. X. Berthet, and B. Gicquel, Proc. Natl. Acad. Sci. USA 92:8768-8772, 1995), was examined in human macrophages and mice. Although ureolytic activity was not essential to BCGure-growth, a slight decrease in the multiplication and persistence of the mutated strain compared with wild-type BCG was observed in lungs of infected mice.

Animals↗
PubMed1998

Transcriptional regulation of the Streptococcus salivarius 57.I urease operon.

The Streptococcus salivarius 57.I ure cluster was organized as an operon, beginning with ureI, followed by ureABC (structural genes) and ureEFGD (accessory genes). Northern analyses revealed transcripts encompassing structural genes and transcripts containing the entire operon. A sigma70-like promoter could be mapped 5' to ureI (PureI) by primer extension analysis. The intensity of the signal increased when cells were grown at an acidic pH and was further enhanced by excess carbohydrate. To determine the function(s) of two inverted repeats located 5' to PureI, transcriptional fusions of the full-length promoter region (PureI), or a deletion derivative (PureIDelta100), and a promoterless chloramphenicol acetyltransferase (CAT) gene were constructed and integrated into the chromosome to generate strains PureICAT and PureIDelta100CAT, respectively. CAT specific activities of PureICAT were repressed at pH 7.0 and induced at pH 5.5 and by excess carbohydrate. In PureIDelta100CAT, CAT activity was 60-fold higher than in PureICAT at pH 7.0 and pH induction was nearly eliminated, indicating that expression was negatively regulated. Thus, it was concluded that PureI was the predominant, regulated promoter and that regulation was governed by a mechanism differing markedly from other known mechanisms for bacterial urease expression.

Amino Acid Sequence↗
PubMed1980

Urease-positive Vibrio parahaemolyticus strain.

An unusual strain of Vibrio parahaemolyticus was isolated from the site of a perforated appendix. This was the first reported case in which the vibrios demonstrated a positive urease reaction. In other respects, the strain conformed to the general characteristics of V. parahaemolyticus. It was susceptible to chloramphenicol, sulfamethoxazole-trimethoprim, tetracycline, neomycin, triple sulpha, gentamicin, and polymyxin B and produced the "Kanagawa phenomenon". However, its role as a causative pathogen of the diarrhea of the patient was debatable.

Acute Disease↗
PubMed1988

Disseminated infection caused by urease-negative Cryptococcus neoformans.

We report a case of fungemia and disseminated disease caused by a urease-negative strain of Cryptococcus neoformans in a patient with the acquired immune deficiency syndrome. Except for failure to hydrolyze urea, the microbiological characteristics of the isolate were typical of C. neoformans. Laboratory specialists should be aware of the occurrence of atypical strains of C. neoformans, particularly those recovered from patients with the acquired immune deficiency syndrome.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Isoelectric focusing of ureases from Campylobacter pylori and related organisms.

Agarose gel isoelectric focusing was used to determine the isoelectric points of ureases from strains of gastric campylobacterlike organisms isolated from ferrets (pI 5.4), baboons (pI 5.7), and pigs (pI 5.9) and from isolates of Campylobacter pylori in humans (pI 5.9). This technique may help differentiate these closely related bacteria.

Campylobacter↗
PubMed1989

Comparison of rapid urease tests, staining techniques, and growth on different solid media for detection of Campylobacter pylori.

Thirty-nine single antral biopsies (phase 1) and 99 sets of six antral biopsies (phase 2) were collected from 132 patients, and 87 (63%) yielded positive cultures for Campylobacter pylori. Of several primary media tested in phase 1, tryptic soy agar and Skirrow agar, each supplemented with 10% whole sheep blood, supported relatively good growth of C. pylori. In phase 2, four of the six biopsies in each set were tested with different urease systems. Selective urea agar for rapid identification was the most sensitive (39 of 63 [62%] at 1 h) and specific (100%); however, the difference between this system and the CLOtest was not statistically significant. The remaining two biopsies, one transported in saline and the other transported in a supplemented tryptic soy broth, were ground separately and inoculated onto tryptic soy agar and Skirrow agar, each supplemented with 10% whole sheep blood. In selected instances, 10% horse serum or 10% horse serum and 5 mM urea or 1% cholesterol were also added to the media. Smears stained with a modified Gram stain or acridine orange detected 68% of 63 culture-positive biopsies; no false-positive results were reported. Skirrow agar supported better growth of C. pylori than did tryptic soy agar; the nonselective medium was also overgrown with contaminants in 25 to 30% of the positive cultures. Based on colony size, Skirrow agar supplemented with 10% whole sheep blood, 10% horse serum, and 1% cholesterol supported optimal growth of C. pylori. Fresh media supported better growth than did prepoured commercial media (P less than or equal to 0.004). Saline was a convenient and satisfactory transport medium for antral biopsies.

Acridine Orange↗
PubMed1990

Urease-negative Nocardia asteroides causing cutaneous nocardiosis.

We report a case of cutaneous nocardiosis, caused by a urease-negative strain of Nocardia asteroides, in a patient who had undergone long-term corticosteroid therapy. The microbiological characteristics of the isolate were typical of N. asteroides except for the failure of the isolate to hydrolyze urea. During the course of routine identification, laboratory specialists should be aware of the occasional occurrence of atypical strains of N. asteroides.

Aged↗
PubMed1992

New plate medium for growth and detection of urease activity of Helicobacter pylori.

A new medium for detection of urease activity and isolation of Helicobacter pylori is proposed. This medium, containing Columbia Agar Base, was supplemented with IsoVitaleX, hemin, urea, and phenol red (nonselective medium [NSM]). Both bacterial growth and color change were evaluated and compared with growth in the same medium supplemented with cefsulodin, vancomycin, polymyxin B sulfate, and amphotericin B (selective medium [SM]). Twenty-five recent clinical isolates and antral biopsy specimens from 33 patients who underwent endoscopy were examined. The isolates showed a rapid color change and good growth at 5 days of incubation with NSM and SM. H. pylori-positive biopsies revealed a color change within 36 h, and bacterial growth was better appreciated in NSM, but with more contaminating flora than in SM.

Culture Media↗
PubMed1992

Evaluation of a urease-based confirmatory enzyme-linked immunosorbent assay for diagnosis of Neisseria gonorrhoeae.

A new urease-based enzyme-linked immunosorbent assay utilizing novel monoclonal antibodies was evaluated for the culture confirmation of Neisseria gonorrhoeae, with 270 isolates of N. gonorrhoeae, 56 isolates of diverse Neisseria spp., and 29 Moraxella isolates. The test was highly specific (100.00%) and sensitive (97.83%). No cross-reactions were observed with any of the Neisseria or Moraxella isolates tested. Fifty percent (3 of 6) of the false-negative results were obtained with isolates of serovar IA-4, a serovar rarely encountered in North America.

Antibodies, Monoclonal↗
PubMed1998

Development of a scheme for genotyping Helicobacter pylori based on allelic variation in urease subunit genes.

Helicobacter pylori urease subunit genes in 383 isolates from 10 countries were investigated by PCR-restriction fragment length polymorphism (HaeIII) analysis. Eighty-two different ureAB profiles were documented by reference to known sequences. Variation among 51% of strains was accounted for by 10 predominant patterns, which provided a unique framework for categorizing isolates with geographically diverse origins.

Alleles↗