Resistência aos metais cobre, chumbo, cromo e zinco em bactérias gram-positivas isoladas de ambiente aquático

Abstract

Environmental pollution by toxic metals through their accumulation in water, sediments and not soil. Bioremediation by microorganisms stands out as a tool for the decontamination of environments with toxic metals. The use of bacteria with proven remediation potential and ability to survive without a contaminated environment is important for the success of bioremediation. The objective of this study was to evaluate the tolerability of bacteria isolated from the aquatic environment to the toxic metals copper, lead, chromium and zinc. A total of 72 bacterial isolates, characterized as Gram-positive proved of water bodies of the Apucarana-PR region were aspirated to study. The gradient plate technique was used as an initial test to select the metal copper isolates. Genetic identification was performed to characterize resistance genes for metal copper, using the polymerase chain reaction (PCR) technique. The isolates were subjected to a minimum inhibitory concentration (MIC) for copper, lead, chromium and zinc by means of the broth microdilution method. In addition, he performed the CIM agar test for copper metal. And to evaluate antimicrobial resistance for the test disc-diffusion. The results revealed that 97% of the bacterial isolates showed resistance to copper metal. Only 7 isolates showed a resistance gene for copper, which represents approximately 10% of the total isolates. Enterococcus lactis (EL03), Bacillus aerius (BA04), Bacillus licheniformis (BL05), Enterococcus casseliflavus (EC06), Enterococcus casseliflavus (EC07) were also submitted to genotype identification by the sequencing of the 16S region to make ribosomal DNA, and two isolates IS01 and IS02 were not identified. The isolates that presented the best growth in high concentration of copper, IS01, IS02 and EL03. For the other metals, lead, chromium and zinc, the isolates EL03 and EC07 were highlighted. Most of the isolates were sensitive to the antibiotics tested, only the EL03 isolate presented phenotypic resistance to tetracycline, showing a sensitive or resistance intermediate for the other antibiotics tested. These results reveal that as analyzed bacteria showed resistance to tested toxic metals that characterize a potential for bioremediation, since many bacteria found naturally in the environment may be related to the bioremediation process reducing the toxicity of the metals.