Optical study of the effect of gamma radiation and heavy metals on microorganisms (Bacteria)

Radionuclide and heavy metal pollution are the main concerns for the environment nowadays as thousands of waste sites around the world pose a serious threat to all living organisms and humans, in particular. Therefore, the focus of this study is on the development of novel-sensing technologies for the detection of radionuclides and heavy metals in water utilizing microorganisms. Several optical methods, i.e., fluorescence microscopy, fluorescence spectroscopy, and UV-vis spectrophotometer were exploited here for studying the effect of γ-radiation (from Co-57 source) and one of the heavy metal ions (Cd+2) on two types of bacteria, namely Escherichia coli (E. coli) and Deinococcus radiodurans (D. radiodurans). All three optical methods gave consistent and correlated results in regards to the gamma radiation. An exponential decay in bacterial counts with the increase in γ-radiation dose was observed in E. coli bacteria samples, while D. radiodurans bacteria appeared to be much less affected by γ-radiation and showed even a small increase in the bacteria counts at low-radiation doses followed by a rather moderate decay at intermediate and high doses. The effect of Cd2+ on bacteria is more complex, however, and the method of fluorescence microscopy gave the most reliable account in live bacteria concentration. Both E. coli and D. radiodurans bacteria showed similar effects of a moderate decay of bacteria counts with the increase in CdCl2 concentration. Comparative analysis of the results obtained shows a clear possibility of pattern recognition of the presence of γ-radiation and heavy metals using the above two bacteria.