Impact of γ-irradiation on biofilm-formation by corrosion-relevant heterotrophic bacteria

At nuclear hazard sites, such as the Chernobyl reactor sarcophagus or Fukushima Nuclear Power Plant, radiation is one of the main factors influencing microbial communities including those involved in microbially influenced corrosion (MIC) of metal structures. By studying the impact of radiation on corrosion-relevant bacteria it may be possible in the future to predict changes in MIC. We believe that the composition and function of natural multi-species biofilms will change when exposed to the stress of ionizing radiation. To address this possibility, biofilm formation by Pseudomonas pseudoalcaligenes and Stenotrophomonas maltophilia were studied after exposure to a range of radiation dosages. Altered planktonic cell morphologies and biofilm architectures on submerged glass surfaces were noted 3 – 7 days after low-doasage sub-lethal irradiation (5.3 Gy) of samples at the micro-colony, macro-colony and mature biofilm stages of development. Furthermore, significant differences in the percentage area covered by biofilms and the release of viable planktonic cells was also noted. These observations suggested that exposure, considered as insignificant levels of irradiation, can be enough to alter biofilm formation of corrosion-relevant bacteria. Such low dosage radiation may have significant impact on soil microbial communities in nuclear hazard sites, potentially altering the MIC of exposed metal structures, their stability and service life of underground metal constructions.