title: Mercury (II) removal by resistant bacterial isolates and mercuric (II) reductase activity in a new strain of Pseudomonas sp. B50A.
abstract: This study aimed to isolate mercury resistant bacteria, determine the minimum inhibitory concentration for Hg, estimate mercury removal by selected isolates, explore the mer genes, and detect and characterize the activity of the enzyme mercuric (II) reductase produced by a new strain of Pseudomonas sp. B50A. The Hg removal capacity of the isolates was determined by incubating the isolates in Luria Bertani broth and the remaining mercury quantified by atomic absorption spectrophotometry. A PCR reaction was carried out to detect the merA gene and the mercury (II) reductase activity was determined in a spectrophotometer at 340 nm. Eight Gram-negative bacterial isolates were resistant to high mercury concentrations and capable of removing mercury, and of these, five were positive for the gene merA. The isolate Pseudomonas sp. B50A removed 86% of the mercury present in the culture medium and was chosen for further analysis of its enzyme activity. Mercuric (II) reductase activity was detected in the crude extract of this strain. This enzyme showed optimal activity at pH 8 and at temperatures between 37 °C and 45 °C. The ions NH4(+), Ba(2+), Sn(2+), Ni(2+) and Cd(2+) neither inhibited nor stimulated the enzyme activity but it decreased in the presence of the ions Ca(2+), Cu(+) and K(+). The isolate and the enzyme detected were effective in reducing Hg(II) to Hg(0), showing the potential to develop bioremediation technologies and processes to clean-up the environment and waste contaminated with mercury.
authors.affiliation: Department of Microbiology - Institute of Health Science, Federal University of Rio Grande do Sul, 500 Sarmento Leite St, 90050-170 Porto Alegre - RS, Brazil. Electronic address: patricia.giovanella@hotmail.com.
authors.forename: Patricia
authors.initials: P
authors.lastname: Giovanella
authors.affiliation: Centro Pluridisciplinar de Pesquisas Químicas, Biológicas e Agrícolas (CPQBA/Unicamp), Rua Alexandre Cazelatto, 999, Caixa Postal: 6171, 13081-970 Vila Betel, Paulínia - SP, Brazil. Electronic address: luc.g.cabral@gmail.com.
authors.forename: Lucélia
authors.initials: L
authors.lastname: Cabral
authors.affiliation: Department of Microbiology - Institute of Health Science, Federal University of Rio Grande do Sul, 500 Sarmento Leite St, 90050-170 Porto Alegre - RS, Brazil.
authors.forename: Fátima Menezes
authors.initials: FM
authors.lastname: Bento
authors.affiliation: Department of Soil Science, Federal University of Rio Grande do Sul, 7712 Bento Gonçalves Ave, 91540-000 Porto Alegre - RS, Brazil.
authors.forename: Clesio
authors.initials: C
authors.lastname: Gianello
authors.affiliation: Department of Soil Science, Federal University of Rio Grande do Sul, 7712 Bento Gonçalves Ave, 91540-000 Porto Alegre - RS, Brazil.
authors.forename: Flávio Anastácio Oliveira
authors.initials: FA
authors.lastname: Camargo
mesh_terms: D001673:Biodegradation, Environmental; D045424:Complex Mixtures; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008628:Mercury / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D010088:Oxidoreductases / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D045424:Complex Mixtures; D007477:Ions; D010088:Oxidoreductases; C021551:mercuric reductase; D008628:Mercury