Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrate reductase (NR) is found to be expressed in certain mycobacterium sp. whose link with the development of persistence is yet to be resolved. The present study demonstrates the action of selective inhibitors on NR as well as in the survival of Mycobacterium smegmatis using Wayne's model. During gradual shift down to anaerobic stage in Wayne's model, conversion of nitrate to nitrite became apparent in M. smegmatis. More than 97 percent inhibition was observed for the conversion of nitrate to nitrite by azide (0.05 mM) and thiocyanate (20 mM) in both whole-cell as well as its cell-free lysate, respectively. Under identical condition, chlorate (20 mM) inhibited nitrate reduction by 67 and 10 percent, respectively. At these concentrations, neither of azide, thiocyanate nor chlorate had any significant effect on cell growth under aerobic condition. In Wayne's culture model, thiocyanate and chlorate inhibited the growth of M. smegmatis by almost 2 logs at the same concentrations whereas azide inhibited by almost 1.75 log when added at the time of inoculation. Exposure of same culture at 96 h after inoculation in Wayne's model to these inhibitors showed 1.74, 1.95 and 2.37 log inhibition of viable cells with respect to azide, thiocyanate and chlorate. These findings further indicated that NR inhibitors kill the bacilli at anaerobic stage under the experimental condition mentioned. Metronidazole (MTZ) (2 mM) and Nitrofurantoin (NIT) (0.3 mM) reduced the cell number at both stages by <0.7 log. They did not have any effect on NR. Altogether, the results clearly indicate that NR-specific inhibitors could become more promising in killing the bacilli at anaerobic stage than the available conventional drugs.
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PMID:Identification of a respiratory-type nitrate reductase and its role for survival of Mycobacterium smegmatis in Wayne model. 1680 98

Pyruvate carboxylase (PYC) is an ecologically, medically, and industrially important enzyme. It is widespread in all three domains of life, the archaea, bacteria, and eukarya. PYC catalyzes ATP-dependent carboxylation of pyruvate to oxaloacetate. Detailed structure-function studies of this enzyme have been hampered due to the unavailability of a facile recombinant overexpression system. Except for the alpha4 enzyme from a thermophilic Bacillus species, Escherichia coli has been unsuitable for overexpression of PYCs. We show that a Pseudomonas aeruginosa strain carrying the T7 polymerase gene can serve as a host for the overexpression of Mycobacterium smegmatis alpha4 PYC and Pseudomonas aeruginosa alpha4beta4 PYC under the control of the T7 promoter from a broad-host-range conjugative plasmid. Overexpression occurred both in aerobic (LB medium) and nitrate-respiring anaerobic (LB medium plus glucose and nitrate) cultures. The latter system presented a simpler option because it involved room temperature cultures in stationary screw-cap bottles. We also developed a P. aeruginosa Deltapyc strain that allowed the expression of recombinant PYCs in the absence of the native enzyme. Since P. aeruginosa can be transformed genetically and lysed for cell extract preparation rather easily, our system will facilitate site-directed mutagenesis, kinetics, X-ray crystallographic, and nuclear magnetic resonance-based structure-function analysis of PYCs. During this work we also determined that, contrary to a previous report (C. K. Stover et al., Nature 406:959-964, 2000), the open reading frame (ORF) PA1400 does not encode a PYC in P. aeruginosa. The alpha4beta4 PYC of this organism was encoded by the ORFs PA5436 and PA5435.
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PMID:Identification of pyruvate carboxylase genes in Pseudomonas aeruginosa PAO1 and development of a P. aeruginosa-based overexpression system for alpha4- and alpha4beta4-type pyruvate carboxylases. 1699 90

Two pigmented mycobacteria isolated from sputum specimens were described by biochemical tests, whole-cell fatty acid analyses by High Performance Liquid Chromatography (HPLC) and sequencing of 65-kDa heat shock protein gene and 16S rRNA gene. The hsp65 gene and 16S rRNA gene sequences of the Mycobacterium sp. G1368 and Mycobacterium sp. E498 were deposited in DDBJ/EMBL/GenBank under accession numbers AY553874, DQ324791 and AY379074, DQ324792, respectively. Mycobacterium sp. G1368 grew in about one week at 37 degrees C and 42 degrees C and produced smooth, yellow colonies. It reduced tellurite and hydrolyzed urea. Nitrate reduction, aryl sulfatase, pyrazin amidase, heat stable catalase and semiquantitative catalase tests were also positive, while Tween 80 hydrolysis was weakly positive. Mycobacterium sp. E498 grew in about 9 days at 37 degrees C and formed smooth, yellow colonies. It hydrolyzed Tween 80, possessed aryl sulfatase, pyrazin amidase and heat stable catalase, however, it did not possess urease and nitrate reductase. These data, in addition to their position in the phylogenetic tree, strongly support the status of novel species at least for Mycobacterium sp. G1368.
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PMID:[Characterization of two new pigmented mycobacteria isolates]. 1700 47

Mycobacterium shimoidei (Tsukamura 1982) is an uncommon but widely distributed pathogen usually isolated from respiratory specimens. We report two cases of lung disease due to M. shimoidei and the associated bacteriological results. A 45-year-old man (Case 1) admitted to National Hospital Organization (NHO) Miyagi Hospital, a 75-year-old man (Case 2) admitted to NHO Higashi-Hiroshima Medical Center were found in initial chest X-ray and thoracic computed tomography (CT) to have a tuberculosis-like cavity in the left apex (Case 1) and the right apex (Case 2). In Case 1, the patient was treated with isoniazid and rifampicin for one month and lesions showed a partial response. In Case 2, the patient responded favorably with rifampicin, ethambutol, streptomycin, and clarithromycin therapy. Mycobacteria were repeatedly detected in smear and culture from sputum specimens in both patients. Isolates were nonphotochromogenic and rough. Isolated colonies developed after two to three weeks on 2% Ogawa egg medium. Organisms grew on 2% Ogawa egg medium at 30, 37, 42, and 45 degrees C, but not 25 degrees C. Both organisms were susceptible to 500 microg of p-nitrobenzoate per mL and 5mg of sodium chloride per mL. Isolates were negative for niacin accumulation, nitrate reduction, semiquantitative catalase, 68 degrees C catalase, 3-day aryl-sulfatase, iron uptake, and MPB64 antigen production, but positive for Tween 80 hydrolysis (5 and 10 days), acid phosphatase, and pyrazinamidase. Isolates had typical uv-HPLC chromatograms similar to M. shimoidei, demonstrating triple-peak clusters with peaks in the early cluster. 16S rRNA gene sequencing showed isolates to be consistent with Mycobacterium shimoidei. Based on composite characterization, isolates were identified as M. shimoidei. This is, to our knowledge, the third case of M. shimoidei infection reported in Japan.
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PMID:[Two cases of lung infection due to Mycobacterium shimoidei, with special reference to bacteriological investigation]. 1733 11

Several new methods to detect drug resistance in Mycobacterium tuberculosis have been proposed in recent years. Colourimetric methods that use redox indicators or the nitrate reduction assay have received increasing attention because of their simplicity and the absence of any requirement for sophisticated equipment or highly trained personnel. Several studies have evaluated their accuracy and performance in comparison with reference standard methods, particularly for the detection of resistance to rifampicin and isoniazid, which are the two most important drugs used for the treatment of tuberculosis. This review describes the development, evaluation and implementation of these methods as rapid alternative tests for the detection of multidrug resistance in M. tuberculosis. Based on published evidence and the high accuracy of colourimetric methods for detecting drug resistance in M. tuberculosis, these methods seem to be appropriate for implementation in high-burden low-resource countries.
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PMID:Rapid drug resistance detection in Mycobacterium tuberculosis: a review of colourimetric methods. 1737 33

Truncated hemoglobin-N is believed to constitute a defense mechanism of Mycobacterium tuberculosis against NO produced by macrophages, which is converted to the harmless nitrate anion. This process is catalyzed very efficiently, as the enzyme activity is limited by ligand diffusion. By using extended molecular dynamics simulations we explore the mechanism that regulates ligand diffusion and, particularly, the role played by residues that assist binding of O2 to the heme group. Our data strongly support the hypothesis that the access of NO to the heme cavity is dynamically regulated by the TyrB10-GlnE11 pair, which acts as a molecular switch that controls opening of the ligand diffusion tunnel. Binding of O2 to the heme group triggers local conformational changes in the TyrB10-GlnE11 pair, which favor opening of the PheE15 gate residue through global changes in the essential motions of the protein skeleton. The complex pattern of conformational changes triggered upon O2 binding is drastically altered in the GlnE11-->Ala and TyrB10-->Phe mutants, which justifies the poor enzymatic activity observed experimentally for the TyrB10-->Phe form. The results support a molecular mechanism evolved to ensure access of NO to the heme cavity in the oxygenated form of the protein, which should warrant survival of the microorganism under stress conditions.
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PMID:Dynamical regulation of ligand migration by a gate-opening molecular switch in truncated hemoglobin-N from Mycobacterium tuberculosis. 1748 73

A fundamental challenge in the redox biology of Mycobacterium tuberculosis (Mtb) is to understand the mechanisms involved in sensing redox signals such as oxygen (O2), nitric oxide (NO), and nutrient depletion, which are thought to play a crucial role in persistence. Here we show that Mtb WhiB3 responds to the dormancy signals NO and O2 through its iron-sulfur (Fe-S) cluster. To functionally assemble the WhiB3 Fe-S cluster, we identified and characterized the Mtb cysteine desulfurase (IscS; Rv3025c) and developed a native enzymatic reconstitution system for assembling Fe-S clusters in Mtb. EPR and UV-visible spectroscopy analysis of reduced WhiB3 is consistent with a one-electron reduction of EPR silent [4Fe-4S]2+ to EPR visible [4Fe-4S]+. Atmospheric O2 gradually degrades the WhiB3 [4Fe-4S]2+ cluster to generate a [3Fe-4S]+ intermediate. Furthermore, EPR analysis demonstrates that NO forms a protein-bound dinitrosyl-iron-dithiol complex with the Fe-S cluster, indicating that NO specifically targets the WhiB3 Fe-S cluster. Our data suggest that the mechanism of WhiB3 4Fe-4S cluster degradation is similar to that of fumarate nitrate regulator. Importantly, Mtb DeltawhiB3 shows enhanced growth on acetate medium, but a growth defect on media containing glucose, pyruvate, succinate, or fumarate as the sole carbon source. Our results implicate WhiB3 in metabolic switching and in sensing the physiologically relevant host signaling molecules NO and O2 through its [4Fe-4S] cluster. Taken together, our results suggest that WhiB3 is an intracellular redox sensor that integrates environmental redox signals with core intermediary metabolism.
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PMID:Mycobacterium tuberculosis WhiB3 responds to O2 and nitric oxide via its [4Fe-4S] cluster and is essential for nutrient starvation survival. 1760 86

Mycobacterium genus includes over 100 species and subspecies; new species are discovered every year. Minimal standard criteria are represented by the resistance to acid-alcohol (e.g. in the Ziehl - Neelsen staining), the presence of some mycolic acids containing 60-90 carbon atoms that can be cleaved by pyrolysis in fatty acids with 22 - 26 carbon atoms and a guanine + cytosine content of the DNA of 61 to 71 mol %. The species with the highest rate of involvement are those from Mycobacterium tuberculosis complex, and tuberculosis is still one of the most widespread world diseases. The most important for a laboratory is to be able to identify the species from M. tuberculosis complex. We have done a series of experiments, their goal being to evaluate and establish a minimal set of useful tests for identification of mycobacterial species. We used strains from "Cantacuzino" Institute collection and applied a series of classical and modern methods. We appreciate that the minimal set of tests could be represented by the microscopic examination for acid-fast bacilli (AFB), the examination for the preferred growth temperature, the growth rate, the colonies morphology, pigmentation and photo reactivity, the niacin accumulation test, the test of nitrate reduction, the catalase test (in both variants), plus the susceptibility to Para-Amino Salicylic Acid, Para-Nitro-Benzoic Acid andto Tiophene-2-Carboxylic Acid Hydrazide.
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PMID:Establishing of a minimal set of tests (minimal standards) to identify species included in the genus Mycobacterium. 1787 9

Ability of Mycobacterium smegmatis to assimilate nitrate was evaluated in its active and dormant phase. Nitrate (10 mM), nitrite (0.5 mM) and ammonia (10mM) allowed growth of M. smegmatis concomitant with their complete depletion from the culture in 144, 120 and 96 h, respectively, when used as sole nitrogen source. Azide (50 microM) stopped the growth of M. smegmatis when nitrate was used as sole nitrogen source. l-methionine-S-sulfoximine (l-MSO), which is a well-known inhibitor of glutamine synthetase, an enzyme also involved in nitrogen metabolic pathway, when applied at 10 microg/ml concentration, completely inhibited the growth of the organism when nitrate or nitrite was used as sole nitrogen source. There was no effect of either azide or l-MSO at above concentrations on the growth of the organism when asparagine or ammonia was used as sole nitrogen source. More significantly, utilization of nitrate, nitrite and ammonia continued even in oxygen depletion induced dormant culture at the rates of 289, 25 and 354 microM/day, respectively. These rates were 5-8 times slower than the rates of 1966, 127 and 2890 microM/day, respectively, in active replicating phase. In the presence of azide (50 microM) and l-MSO (10 microg/ml), 2.1 and 1.51 logs reduction in viability of dormant M. smegmatis was observed using nitrate and nitrite, respectively, as sole nitrogen source. Altogether, the results indicated the presence of nitrate assimilation pathway operating in both active and dormant stage of M. smegmatis.
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PMID:Presence of a functional nitrate assimilation pathway in Mycobacterium smegmatis. 1788 19

cAMP Receptor Protein (CRP)/Fumarate Nitrate Reductase Regulator (FNR) family proteins are ubiquitous regulators of cell stress in eubacteria. These proteins are commonly associated with maintenance of intracellular oxygen levels, redox-state, oxidative and nitrosative stresses, and extreme temperature conditions by regulating expression of target genes that contain regulatory cognate DNA elements. We describe the use of informatics enabled comparative genomics to identify novel genes under the control of CRP regulator in Mycobacterium tuberculosis (M.tb). An inventory of CRP regulated genes and their operon context in important mycobacterial species such as M. leprae, M. avium subsp. paratuberculosis and M. smegmatis and several common genes within this genus including the important cellular functions, mainly, cell-wall biogenesis, cAMP signaling and metabolism associated with such regulons were identified. Our results provide a possible theoretical framework for better understanding of the stress response in mycobacteria. The conservation of the CRP regulated genes in pathogenic mycobacteria, as opposed to non-pathogenic ones, highlights the importance of CRP-regulated genes in pathogenesis.
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PMID:Genome scale portrait of cAMP-receptor protein (CRP) regulons in mycobacteria points to their role in pathogenesis. 1802 70


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