Biofilm formation by Pseudoalteromonas ruthenica and its removal by chlorine

Abstract

The distribution of a recently described marine bacterium, SBT 033 GenBank Accession No. AY723742), Pseudoalteromonas ruthenica, at the seawater intake point, outfall and mixing point of an atomic power plant is described, and its ability to form biofilm was investigated. The effectiveness of the antifouling biocide chlorine in the inactivation of planktonic as well as biofilm cells of P. ruthenica was studied in the laboratory. The results show that the planktonic cells were more readily inactivated than the cells enclosed in a biofilm matrix. Viable counting showed that P. ruthenica cells in biofilms were up to 10 times more resistant to chlorine than those in liquid suspension. Using confocal laser scanning microscopy it was shown that significant detachment of P. ruthenica biofilm developed on a glass substratum could be accomplished by treatment with a dose of 1 mg l⁻¹ chlorine. Chlorine-induced detachment led to a significant reduction in biofilm thickness (up to 69%) and substratum coverage (up to 61%), after 5-min contact time. The results show that P. ruthenica has a remarkable ability to form biofilms but chlorine, a common biocide, can be used to effectively kill and detach these biofilms.

Keywords:

• Pseudoalteromonas ruthenica
• chlorination
• biofilm
• confocal laser scanning microscopy (CLSM)
• biofilm removal
• BacLight LIVE/DEAD stain

Acknowledgements

This work was supported by the Research fund of the Department of Atomic Energy- Board of Research in Nuclear Sciences, Mumbai, India, Project No. 96/36/18/BRNS/1803. The authors thank Dr S. V. Narasimhan, WSCD, Head, Kalpakkam for providing laboratory facilities.