Heavy-Metal Resistant Actinomycetes

SIÑERIZ, M.,; BENITO, J.M.; ALBARRACÍN, V.H.; LEBEAU, T.; AMOROSO, M.J.,; ABATE, C.M.

Environmental Chemistry. Green Chemistry and Pollutants in Ecosystems

Springer

Lugar: Berlin/Heidelberg; Año: 2005; p. 757 - 767

Water and soil pollution has become a major concern in the world, as much of the population relies on groundwater as its major source of drinking water as well as on soil as cultivable land. Heavy-metal contamination brings a potential health hazard that can cause metal toxicoses in animals and humans. Microorganisms play an important role in the environmental fate of toxic metals and radionuclides and they are potentially useful tools for both in situ and ex situ bioremedial treatment processes for solid and liquid wastes. Among them are actinomycetes, Gram-positive bacteria with high content of guanine and cytosine (G + C) (55-75 mol %) that generally exhibit a filament growth with ramifications. Their metabolically versatility and their enormous morphologic diversity pose them as potential microorganisms to be used in bioremediation experiences. Copper and cadmium are heavy metals found in high concentrations in contaminated soils thus being a threat to soil population. There is a copper filter plant near an agricultural area of Tucumán, Argentina that flows its wastewater to a natural channel. It has been determined that during the process copper contamination is produced in the environment. In the other hand, the accelerated growing of industrial activities has increased the cadmium liberation at a higher rate than the one of the natural geochemical processes. Nevertheless, bacteria exposure to toxic levels of heavy metals has led to the development and evolution of various genetics mechanisms that regulate the uptake and resistance to them Plasmid pRJ1004, that confers copper resistance to E. coli, is one example of these mechanisms There is a lot of information available on copper resistance genetic mechanisms in Gram-negatives bacteria  but little has been done in Gram-positives. There is still less information about the genes that codifies heavy metal resistance in actinomycetes. The monitoring of the viability of cadmium resistant actinomycetes in culture medium and in soil samples is of considerable importance because of the potential capacity of these strains in the bioremediation of cadmium. One of the easier ways is to follow the viability by fluorescence using the enhanced green fluorescent protein (EGFP), a useful and sensitive gene reporter. Using actinomycetes strains isolated from heavy metals contaminated soils we studied their resistance to copper at different concentrations and then assayed an hybridisation experience with probes constructed using two copper resistance genes (pcoR y pcoA) from pRJ1004 of E. coli. With the aim to study the survival of the cadmium resistance strain Streptomyces R25 in cadmium contaminated soil we carried out transformations experiments using pIJ8660 that contain the EGFP gene to transform this strain and analyze their survivals.