Tolerance to Various Toxicants by Marine Bacteria Highly Resistant to Mercury

Abstract

Bacteria highly resistant to mercury isolated from seawater and sediment samples were tested for growth in the presence of different heavy metals, pesticides, phenol, formaldehyde, formic acid, and trichloroethane to investigate their potential for growth in the presence of a variety of toxic xenobiotics. We hypothesized that bacteria resistant to high concentrations of mercury would have potential capacities to tolerate or possibly degrade a variety of toxic materials and thus would be important in environmental pollution bioremediation. The mercury-resistant bacteria were found to belong to Pseudomonas, Proteus, Xanthomonas, Alteromonas, Aeromonas, and Enterobacteriaceae. All these environmental bacterial strains tolerant to mercury used in this study were capable of growth at a far higher concentration (50 ppm) of mercury than previously reported. Likewise, their ability to grow in the presence of toxic xenobiotics, either singly or in combination, was superior to that of bacteria incapable of growth in media containing 5 ppm mercury. Plasmid-curing assays done in this study ascertained that resistance to mercury antibiotics, and toxic xenobiotics is mediated by chromosomally borne genes and/or transposable elements rather than by plasmids.

Characterization of a marine-isolated mercury-resistant Pseudomonas putida strain SP1 and its potential application in marine mercury reduction

“…NaCl at the concentration of less than 24 g L -1 was suitable for P. putida Spi3 to remove mercury; however, P. putida SP1 could remove almost 100% of Hg 2+ from seawater, in which the concentration of NaCl is up to about 36 g L -1 (Von Canstein et al 1999). P. putida SP1 possessed a mer operon as a mercury-resistant determinant like most of the other mercury-resistant bacteria, and the mer operon of P. putida SP1 was located on the chromosomal DNA as described in other strains (De et al 2003;Bafana et al 2010). Because multiple resistance genes are often located on mobile genetic elements (Mindlin et al 2001;Partridge et al 2001;Barkay et al 2003) and genes encoding for heavy metal resistance are often linked to antibiotic resistance genes on the same mobile element (Mindlin et al 2002;Barkay et al 2003), the similarity between the mer operon of P. putida SP1 and the mer operon located on Tn5041 suggested that the environmental bacterium P. putida SP1 may have acquired this chromosomal mer operon and other heavy metal or antibiotic resistance determinants through transposable elements that confer resistance to HgCl 2 and a variety of other xenobiotics.…”

“…P. putida SP1 also exhibited higher levels of resistance to antibiotics and a variety of toxic heavy metals than did the strain Pseudomonas sp., Proteus sp., Aeromonas sp., Enterobacteriaceae sp., and Xanthomonas sp. described previously (De et al 2003;Bafana et al 2010). To our knowledge, this was the highest concentration of HgCl 2 that the Pseudomonas sp.…”

“…To determine the localization of the mer operon, plasmid curing and PCR analysis were carried out. Plasmid harbored in SP1 was knocked out according the method described by De et al (2003) to generate strain SP1M. Plasmids were isolated from both SP1 and SP1M using the method of Kado and Liu (1981).…”

Hydrocarbon Pollution: Effects on Living Organisms, Remediation of Contaminated Environments, and Effects of Heavy Metals Co-Contamination on Bioremediation

“…Ueki et al (2003) identified two vanadium binding proteins and expressed them in E. coli, which showed the capability of accumulating twenty times more copper than their control strain. Marine bacteria are also known to have metal resistance capabilities (De et al, 2003,). Keramati et al (2011) isolated multi metal resistant bacteria highly resistant to mercury.…”

Potential of Mercury-Resistant Marine Bacteria for Detoxification of Chemicals of Environmental Concern

“…This extensively studied resistance system based on clustered genes in the mer operon, allowing bacteria to detoxify Hg 2+ into volatile mercury by enzymatic reduction, has been thoroughly investigated 4,20,26,30,43,45) . Several studies 2,3,14,18) have examined mercury-resistant bacteria (MRB) and their potential to catabolize toxic xenobiotics. The ability of bacteria to detoxify mercury can be utilized to bioremediate mercury-contaminated wastewaters and sites 7,10,13,40,46) as well as other toxic chemicals 14) .…”