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A conservative region of the mercuric reductase gene (merA) as a molecular marker of bacterial mercury resistance
Sotero-Martins, Adriana;Jesus, Michele Silva de;Lacerda, Michele;Moreira, Josino Costa;Filgueiras, Ana Luzia Lauria;Barrocas, Paulo Rubens Guimar?es;
Brazilian Journal of Microbiology , 2008, DOI: 10.1590/S1517-83822008000200020
Abstract: the most common bacterial mercury resistance mechanism is based on the reduction of hg(ii) to hg0, which is dependent of the mercuric reductase enzyme (mera) activity. the use of a 431 bp fragment of a conservative region of the mercuric reductase (mera) gene was applied as a molecular marker of this mechanism, allowing the identification of mercury resistant bacterial strains.
Molecular Cloning and Expression of Bacterial Mercuric Reductase Gene
M Zeyaullah, S Haque, G Nabi, KN Nand, A Ali
African Journal of Biotechnology , 2010,
Abstract: In order to characterize the bacterial mercuric reductase (merA) gene, mercury resistant (Hgr) Escherichia coli strains have been isolated from various mercury contaminated sites of India. Their minimum inhibitory concentration (MIC) for Hg and zone of inhibition for different antibiotics were measured, and finally mer operon was localized by transforming isolated E. coli plasmid into mercury sensitive (Hgs) host E. coli DH5a cells. Oligonucleotide primers were designed by comparing the known reported sequences of merA from Gram-negative bacterium (E. coli plasmid R100) and 1695 bp full length merA gene was amplified by PCR. A 1.695-kb DNA fragment of merA was inserted into isopropyl- -D-thiogalactopyranoside (IPTG) inducible bacterial expression vector pQE-30U/A. E. coli DH5 strains harboring the merA constructs showed higher mercury reductase enzyme (MerA) activity and expressed significantly more MerA than the control strains under aerobic conditions. The purified merA gene over expressed in the specific host E. coli BL21(DE3)Plys cells. Finally, expressed MerA protein was purified by Immobilized Metal-chelate Affinity Chromatography (IMAC) by using Ni- NTA column; and ~66.2 kDa bacterial MerA protein was detected after resolving on 10% sodium dodecyl sulphate poly acrylamide gel electrophoresis (SDS PAGE).
Removal of Mercuric Chloride by a Mercury Resistant Pseudomonas putida Strain  [PDF]
Sayedbager Mortazavi,Abbas Rezaee,Ali Khavanin,Sakina Varmazyar
Journal of Biological Sciences , 2005,
Abstract: In the present study, Pseudomonas putida strain, a mercury resistant bacterium, which is able to reduce ionic mercury to metallic mercury was isolated from chloralkali wastewater and used to remediate ion mercury in liquid medium.The bacterium exhibits high Minimal Inhibitory Concentrations (MICs) for mercuric Chloride. Removal of mercuric chloride by Pseudomonas putida was studied using pepton water medium in the concentration range 1-120 mg L -1. Two processes, adsorption on the cell surface and bioaccumulation have been observed. Maximum removal capacity for the bacterium was found to be 98%. Thus, bacterial removal of mercury is a potential biological treatment for mercury environmental pollutants
Functional profiling of mercuric reductase (mer A) genes in biofilm communities of a technical scale biocatalyzer
Andreas DM Felske, Wanda Fehr, Bj?rg V Pauling, Harald von Canstein, Irene Wagner-D?bler
BMC Microbiology , 2003, DOI: 10.1186/1471-2180-3-22
Abstract: Based on an alignment of 30 merA sequences from Gram negative bacteria, conserved primers were designed for amplification of merA fragments with an optimized PCR protocol. The resulting amplicons of approximately 280 bp were separated by thermogradient gelelectrophoresis (TGGE), resulting in strain specific fingerprints for mercury resistant Gram negative isolates with different merA sequences. The merA profiling of the biofilm community from a technical biocatalyzer showed persistence of some and loss of other inoculum strains as well as the appearance of new bands, resulting in an overall increase of the functional diversity of the biofilm community. One predominant new band of the merA community profile was also detected in a biocatalyzer effluent isolate, which was identified as Pseudomonas aeruginosa. The isolated strain showed lower mercury reduction rates in liquid culture than the inoculum strains but was apparently highly competitive in the biofilm environment of the biocatalyzer where moderate mercury levels were prevailing.The merA profiling technique allowed to monitor the ongoing selection for better adapted strains during the operation of a biocatalyzer and to direct their subsequent isolation. In such a way, a predominant mercury reducing Ps. aeruginosa strain was identified by its unique mercuric reductase gene.Phylogenetic profiling of microbial communities based on sequence specific separation of phylogenetic marker genes (mainly the 16S rRNA gene or the 16S-23S ribosomal intergenic spacer region) is widely used in microbial ecology to study changes in community diversity in response to environmental parameters or experimental perturbations. However, physiological traits are often dispersed across the phylogenetic tree, and so conclusions regarding the processes driven by the microbes in question cannot be drawn. Functional gene profiling has the potential to provide information about the functional diversity of microbial populations with respect t
DETOXIFICATION OF MERCURIC CHLORIDE BY CEPHALOSPORIUM TABACINUM F2
烟草头孢霉F2对氯化汞解毒作用的研究

Wang Baojun,Yang Huifang,Li Wenzhong,
王保军
,杨惠芳,李文忠

环境科学学报 , 1992,
Abstract: After 16 hours growing of a mercury-resistant fungus, Cephalosporium ta-bacinum, in a liquid medium containing 200mg/L HgCl2, the concentration of HgCl2 reduced 90% and a rapid growth of the fungus was followed. The effects of nutrients, concentration of Hg, precultivation condition, pH, and temperature on the detoxification and the mechanism of the detoxification were investigated. The results indicated that the strain is able to reduce HgCl2 to elemental mercury and 12% of Hg was evaporated, 7% of Hg was uptaken by the cells and the rest was precipitated into the bottom as elemental mercury granules.
Growth Pattern of Hg Resistant Bacteria Isolated from Kor River in the Presence of Mercuric Chloride  [PDF]
F. Kafilzadeh,N. Mirzaei
Pakistan Journal of Biological Sciences , 2008,
Abstract: Different bacterial species were isolated from different areas of the Kor River and growth pattern of these bacteria were evaluated. In this study the samples were collected from four stations throughout the Kor River in four seasons. Isolation of mercury resistant bacteria was performed using the primary enrichment method and directly plating on agar containing Hg(II). Growth kinetics of most mercury resistant and sensitive bacteria were studied in LB broth containing 20 mg L-1 HgCl2 per liter. Pseudomonas sp., E. coli, Serratia morcescens, etc. was identified as mercury resistant bacteria. Isolated bacteria from the most mercury polluted stations showed high levels of resistance to this toxicant. Growth curve of mercury resistant bacteria was obtained the same as the standard growth curve of bacteria. Present results showed that enhancement of mercury levels in the environment will increase the levels of resistance to mercury among the bacterial communities residing in this contaminated sites.
Evaluation of Nitrate Reductase Assay for Rapid Detection of Drug Resistant Tuberculosis  [PDF]
Ranjit Kumar Sah, Dwij Raj Bhatta, Gokarna Raj Ghimire, Jeevan Bahadur Sherchand
Open Journal of Medical Microbiology (OJMM) , 2012, DOI: 10.4236/ojmm.2012.24021
Abstract: Emergence of multidrug-resistant tuberculosis (MDR-TB) urgently demands for simple, rapid and inexpensive methods of its detection for the effective treatment of drug resistant tuberculosis, particularly in low-income countries. A total of 113 clinical isolates of M. tuberculosis were tested for four first line antitubercular drugs by nitrate reductase assay (NRA) and were compared with standard proportion method to evaluate NRA efficacy. Results were available in 7 - 14 days by NRA as compared to proportion method which generally takes 4 - 6 weeks. The sensitivity and specificity of NRA were 98.1% and 100% for isoniazid, 95.1% and 98.6% for rifampicin, 91.4% and 94.9% for streptomycin, and 78.6% and 97.9% for ethambutol, respectively. Agreement between NRA and proportion method were 99.1%, 97.3%, 93.8%, 95.6% for isoniazid, rifampicin, streptomycin and ethambutol, respectively. NRA is easier, inexpensive and reliable method for susceptibility testing of Mycobacterum tuberculosis for isoniazid and rifampicin, the two most im- portant drugs for the treatment of tuberculosis. The reduction in susceptibility testing time, and higher sensitivity and specificity of NRA method is of fundamental importance in detecting MDR-TB.
Evaluation of Nitrate Reductase Assay for Rapid Detection of Drug Resistant Tuberculosis  [PDF]
Ranjit Kumar Sah,DR Bhatta,GR Ghimire,BP Kandel,BR Tiwari,JB Sherchand
SAARC Journal of Tuberculosis, Lung Diseases and HIV/AIDS , 2012, DOI: 10.3126/saarctb.v9i2.7971
Abstract: Introduction: Emergence of multidrug-resistant tuberculosis (MDR-TB) urgently demands for simple, ?rapid and inexpensive methods of its detection for the effective treatment of drug resistant tuberculosis, ?particularly in low-income countries. Methodology: This prospective study was carried out at National Tuberculosis Reference Laboratory ?and South Asian Association of Regional Cooperation (SAARC) Tuberculosis and HIV/AIDS Centre, ?Thimi, Bhaktapur, Nepal, from November 2009 to May 2010 to evaluate nitrate reductase assay (NRA) ?efficacy for rapid determination of streptomycin, isoniazid, rifampicin and ethambutol susceptibility of ? Mycobacterium tuberculosis strains. Results : A total of 113 clinical isolates of M. tuberculosis were tested for four first line antitubercular drugs ?by nitrate reductase assay and were compared with standard proportion method. Results were available ?in 7-14 days by NRA as compared to proportion method which generally takes 4-6 weeks. The sensitivity ?and specificity of NRA were 98.1% and 100% for isoniazid, 95.1% and 98.6% for rifampicin, 91.4% and ?94.9% for streptomycin, and 78.6% and 97.9% for ethambutol, respectively. Agreement between NRA ?and proportion method were 99.1%, 97.3%, 93.8%, 95.6% for isoniazid, rifampicin, streptomycin and ?ethambutol, respectively. Conclusion: NRA is easier, inexpensive and reliable method for susceptibility testing of Mycobacterum ?tuberculosis for isoniazid and rifampicin, the two most important drugs for the treatment of tuberculosis. ?The reduction in susceptibility testing time, and higher sensitivity and specificity of NRA method is of ?fundamental importance in detecting MDR-TB. SAARC Journal of Tuberculosis, Lung Diseases & HIV/AIDS; 2012; IX(2) 5-8 DOI: http://dx.doi.org/10.3126/saarctb.v9i2.7971
Study of mercury (II) chloride tolerant bacterial isolates from Baghmati River with estimation of plasmid size and growth variation for the high mercury (II) resistant Enterobacter spp.
Vivek Bhakta Mathema,Bal Krishna Chand Thakuri,Mika Sillanp??,Reena Amatya Shrestha
Journal of Biotech Research , 2011,
Abstract: A total of three mercury resistant belonging to genus Enterobacter, Streptococcus and Pseudomonas were isolated from river banks of Baghmati in Kathmandu and were further categorized on the basis of their tolerance to mercury (II) chloride. Among all these isolates Enterobacter strain expressed highest degree of resistance towards Hg (II) chloride showing distinct growth in medium with upto 80 μg/ml of HgCl2 . Excessive slime production along with delayed pattern of growth and lower viability was observed for the isolate under increasing concentrations of Hg (II) supplemented liquid culture medium. Upon investigating total genetic content of this isolate, occurrence of plasmid with approximate 18 kb size and susceptible to mercuric chloride after plasmid curing suggests a plasmid mediated tolerance.
Utility of nitrate reductase assay for detection of multidrug-resistant Mycobacterium tuberculosis in a low resource setting
López,Marcela; álvarez,Claudia; Imaz,María Susana;
Biomédica , 2011,
Abstract: introduction. the performance of a drug susceptibility test may change when moving from the research stage to implementation on a population level in actual public health practice. objective. the performance of a rapid drug susceptibility test was described for detecting multidrug-resistant mycobacterium tuberculosis when implemented in the routine workflow of a low-resource reference laboratory. materials and methods. a prospective study was done comparing the performance of the nitrate reductase assay with the conventional proportion method for rifampicin and isoniazid on 364 isolates were obtained from multidrug-resistant tuberculosis risk patients referred from diffrent colombian laboratories. results. when compared with the proportion method, the nitrate reductase assay sensitivity was 86.8% and 84.9% for rifampicin and isoniazid, respectively, whereas nitrate reductase assay specificity was 100% for isoniazid and rifampicin. nitrate reductase assay sensitivity was significantly higher when the age of isolate was less than 70 days. a sensitivity of 94.4% dropped to 78.1% for rifampicin resistance for fresh and old isolates, respectively (fisher exact test, p=0.05). for isoniazid resistance using fresh and old isolates, 94.7% vs.74.3% sensitivities, were achieved (chi square test, p=0.03). the proportion of nitrate reductase assay ambiguous results was significantly higher in multidrug-resistant than in non-multidrug-resistant isolates (17.6% vs. 4.0%, chi square test, p<0.005). conclusions. the nitrate reductase assay demonstrated provided reliable results for antibiotic resistance. however, using old cultures leds to a higher proportion of false sensitive results; furthermore, the nitrate reductase assay capability to detect multidrug-resistant tuberculosis decreased due to a higher proportion of non-interpretable results.
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