title: Mercury resistance in bacterial strains isolated from tailing ponds in a gold mining area near El Callao (Bolívar State, Venezuela).
abstract: Bacterial resistance to mercury (Hg) was investigated in strains isolated from Hg-contaminated tailing ponds located in the gold mining area of El Callao (Bolívar State, Venezuela). High frequencies of resistance were detected to both inorganic-Hg and organomercurials among these strains. A broad range of resistance levels was observed when determining minimal inhibitory concentrations of Hg(2+). Some strains were able to grow in liquid medium containing 25 muM: Hg(2+), whereas others grew at 300 muM: Hg(2+). Of 190 Hg-resistant strains tested, 58.2% were additionally shown to be resistant to ampicillin (40 mg/L), 33.3% to chloramphenicol (30 mg/L), 24.9% to streptomycin (30 mg/L), 23.3% to tetracycline (30 mg/L), and 1.6% to kanamycin (30 mg/L). Furthermore, we found that 20% of the Hg-resistant strains were simultaneously resistant to as many as four of these antibiotics, at the concentrations tested. The presence of large plasmids in 62.9% of 53 Hg-resistant strains screened prompted us to investigate the horizontal transfer of resistance determinants. Mating experiments were performed using Escherichia coli and Pseudomonas aeruginosa as recipient strains. The results obtained confirmed that indigenous Hg-resistant bacteria colonizing the tailing ponds can effectively transfer the phenotype to potentially pathogenic species.
authors.affiliation: Laboratorio de Microbiología Molecular y Biotecnología, Departamento de Biología, Facultad de Ciencias, Núcleo de La Hechicera, Universidad de Los Andes, Mérida, 5101, Venezuela.
authors.forename: María Mercedes
authors.initials: MM
authors.lastname: Ball
authors.forename: Pablo
authors.initials: P
authors.lastname: Carrero
authors.forename: David
authors.initials: D
authors.lastname: Castro
authors.forename: Luis Andrés
authors.initials: LA
authors.lastname: Yarzábal
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005618:Fresh Water / Q000382:microbiology*; D006046:Gold; D008628:Mercury / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D008906:Mining; D010957:Plasmids; D014687:Venezuela; D014874:Water Pollutants, Chemical / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D006046:Gold; D008628:Mercury