ABSTRACT
       Background and Objective: Nanobacteria are nanometer-scale particles with different shapes, which have been a subject of debate in modern microbiology. They belong to a proposed class of living organisms, specifically cell-walled microorganisms with a size much smaller than the generally accepted lower limit for life. Since some microorganisms are able to continue growth at high temperatures, we aimed to isolate thermophilic bacteria from Gheinarcheh hot spring in Ardabil (Iran) and identify the characteristics of these microorganisms.
       Methods: Microbial mats were found in cultures from Gheinarcheh hot spring in North West of Iran. Synthetic media were prepared and used for isolation of protease-producing thermophilic bacteria, and identification of the features of microbial mats. Cultures were incubated at temperature range of 60-120 oC. Scanning electron microscopy, DNA extraction and polymerase chain reaction were used to further identify characteristics of the microbial biofilms.
        Results: Microbial biofilms of nanoparticles were detected in our samples. Growth of the bacteria increased at all temperatures tested. Results of scanning electron microscopy showed nano-sized particles in the scale of 60 nm. No band was visible in gel electrophoresis of polymerase chain reaction products.
Conclusion: This study is the first to report the presence of hyperthermophilic nanobacteria in Iran.
      Keywords: Nanobacteria, Hyperthermophile, Microbial Mat.