Isolation of actinomycete strains and screening of heavy metals resistance

BONNOT, G.; POLTI M. A.; AMOROSO M. J.; ABATE C. M.

Rosario

Congreso; V Congreso Argentino de Microbiología General (SAMIGE); 2008

SAMIGE

Heavy metals (HM) constitute a potential hazard for waters, soils and sediments. It has been shown that HM at certain concentrations can have long-term toxic effects within ecosystems. One of the biggest problems of contaminated soil and/or sediments in our province (Tucumán) as well as that of other regions is the co-contamination with various metals. Actinomycetes constitute a significant component of the microbial population in most soils. Their metabolic diversity and particular growth characteristics, mycelial form and relatively rapid colonization of selective substrates, indicate them as well suited agents for bioremediation of metal and organic compounds. Microorganisms have developed changes in its genome that have enabled them to the acquisition of resistance to various heavy metals. By sharing complex habitat, such as soil, such resistance can be expressed in a cooperative manner and carry out successfully the bioremediation of environments contaminated with heavy metals. The aim of this work was to determine the presence of multimetal resistance in new isolated actinomycetes. Thirty-six isolated actinomycetes were used to carry out a qualitative screening of chromium (VI), copper (II) and cadmium (II) resistance. Twenty-four were isolated from the Pocitos Channel, four from Amaicha, five from Guillermina Channel, two from common soil of Tucumán city and one from heavy metal contaminated soil. Primary qualitative screening assays were carried out in plates containing Minimal Medium supplemented with Cr(VI) (100, 300 and 500 ppm), copper (II) (200, 500 and 1000 ppm) and cadmium (II) (10, 50 and 100 ppm). In this case, rectangular wells were made in the center of Petri dishes by aseptically removing strips of agar which were filled with the heavy metal solutions. Isolates were inoculated by streaking spore suspension perpendicularly to the troughs. Thirty-eight percent of isolated strains were resistant up to 500 ppm of chromium, thirteen percent were resistant up to 1000 ppm of copper and thirty-eight percent were resistant up to 100 ppm of cadmium. Only two isolates were resistant to the highest concentrations of the three metals, and twelve isolates were resistant up to the middle concentration of each metal. This study showed the potential ability of actinomycetes as tools for bioremediation of co-contaminated soil with Cr(VI), Cu and Cd.