|1454-2||Potential application in aquatic mercury reduction of a marine sponge-isolated Bacillus sp. strain Pj1|
|Autores:||Juliana de Fatima Santos Gandelman (IMPG-UFRJ - UNIVERSIDADE FEDERAL DO RIO DE JANEIRO) ; Marcia Giambiagi de Marval (IMPG-UFRJ - UNIVERSIDADE FEDERAL DO RIO DE JANEIRO) ; Tamar Barkay (RUTGERS - RUTGERS UNIVERSITY) ; Marinella Laport (IMPG-UFRJ - UNIVERSIDADE FEDERAL DO RIO DE JANEIRO) |
Metal-resistant microorganisms have been isolated from polluted environments and studies on the interactions between heavy metals and microorganisms have focused on bacterial transformation and conversion of metallic ions by reduction. The Bacillus sp. strain Pj1 was isolated from a marine sponge, Polymastia janeirensis, and was found to be resistant to 280 &muM HgCl2 and to 10 &muM MHg (methylmercury). Pj1 was also highly resistant to other metals, including CdCl2 and PbCl2. The biochemical basis of resistance to inorganic mercury compounds such as HgCl2 involves the reduction of Hg2+ to volatile Hg0 by an inducible enzyme, mercuric reductase (MerA). The broad-spectrum resistance to organomercurials involves, in addition to mercuric reductase, another inducible, soluble enzyme: organomercurial lyase (MerB). On the other hand, the merR gene encodes a regulatory protein, which activates transcription of the mer operon in the presence of inducing concentrations of Hg2+. In order to observe the presence of mer genes in Bacillus Pj1, we used different sets of primers and we could amplify all the three genes surveyed: merA, merB and merR. Volatilization test indicated that the isolated Bacillus sp. strain Pj1 was able to reduce Hg2+ to Hg0. Cold vapor atomic absorption spectrometry demonstrated that Pj1 was able to volatilize almost 100% of the total mercury it was exposed to and produced elemental Hg when incubated with 1.5 &muM MHg. Biofilm developed by Bacillus sp. Pj1 was 1- to 3- fold lower than biofilm developed by an aquatic pathogen Pseudomonas fluorescens TSS and also Pj1 demonstrated sensibility to all the antibiotics tested (cefalexin, ciprofloxacin, chloramphenicol, gentamicin, trimethoprim/sulfamethoxazol, tetracycline, erythromycin and penicillin G). By hydrophobicity test and hemolytic activity Pj1 demonstrated a potential for biosurfactant production. Also, we investigated the growth kinetics of Bacillus sp. Pj1 in media containing HgCl2 as well the growth of this bacteria in different salt concentration. The results of this study indicate that Bacillus sp. Pj1 is a low virulence strain that can potentially be applied in the bioremediation of HgCl2 and MHg contamination in aquatic environments.
Palavras-chave: antibiotic resistance, bioremediation, mercury resistance, sponge-associated bacteria