Autoradiographic method to screen for soil microorganisms which accumulate zinc

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Radioisotope tracing

Background:

• Soil microorganisms play crucial roles in nutrient cycling.
• Understanding microbial metal accumulation is vital for environmental remediation.
• Zinc (Zn) is an essential micronutrient but can be toxic at high concentrations.

Purpose of the Study:

• To develop and validate an autoradiographic method for screening and isolating soil microorganisms that accumulate zinc.
• To identify specific microbial species responsible for significant zinc bioaccumulation in soil.

Main Methods:

• Development of an autoradiographic plate technique using radioactive 65Zn.
• Incubation of diluted soil samples on agar medium containing 65Zn.
• Detection and isolation of colonies with high 65Zn accumulation via autoradiography.
• Confirmation of zinc accumulation using energy-dispersive X-ray analysis (EDX) in a scanning electron microscope (SEM).

Main Results:

• The autoradiographic method successfully detected and isolated zinc-accumulating soil microorganisms.
• Filamentous fungi, primarily Penicillium janthinellum, Aspergillus fumigatus, and Paecilomyces sp., were the most common zinc accumulators.
• Bacillus spp. were identified as the most abundant zinc-accumulating bacteria.
• Energy-dispersive X-ray analysis confirmed that autoradiographically positive fungal isolates significantly bioaccumulated more zinc than negative isolates.

Conclusions:

• The developed autoradiographic plate technique is a valid and effective tool for specifically screening and isolating environmental microbes that bioaccumulate zinc.
• This method facilitates the discovery of microbial resources for potential bioremediation applications.
• Penicillium janthinellum emerges as a prominent soil microorganism with high zinc accumulation capacity.