ORIGINAL PAPER Isolation and characterization of Pseudoalteromonas ruthenica (SBT033), an EPS-producing biofilm bacterium from the seawater intake point of a tropical power station EPS producing Pseudoalteromonas ruthenica Periasamy Saravanan S. R. Prabagaran Y. Venkata Nancharaiah M. Krishnaveni Vayalam P. Venugopalan Seetharaman Jayachandran Received: 23 January 2007 / Accepted: 12 July 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Biofilm formation in bacteria is closely linked with production of exopolysaccharides (EPS). This study examined the quantitative variations in EPS production and biofilm-forming ability among bacteria isolated from the seawater intake point of a power station located on the east coast of India. Of the 233 isolates obtained from the intake site, 71 bacterial isolates displayed different colony mor- phological characteristics. Thirteen isolates that produced wide and thick mucoid colonies were further tested for their ability to attach and form biofilms by microtitre plate assay and confocal microscopy. EPS production among the selected bacterial isolates ranged from 826 to 1838 lg ml –1 . Strain SBT033, which produced the maximum amount of EPS also displayed the maximum biofilm-forming ability among the 13 isolates. This strain was selected for further characterization using biochemical and molecular methods. The pale orange-pigmented isolate was a Gram negative, aerobic, short rod-shaped and grew well only in the presence of 2% NaCl. On the basis of phenotypic characteristics the isolate SBT033 is shown to belong to the genus Pseudoalteromonas. Analysis of 16S rRNA of the isolate revealed 99% homology with Pseud- oalteromonas ruthenica. Keywords Biofilm formation  Confocal laser scanning microscopy  Exopolysaccharides  Intake point  Pseudoalteromonas ruthenica  16S rRNA Introduction Biofilms are commonly associated with economic and health problems in industrial and medical settings (Hall- Stoodley and Stoodley 2002; Donlan and Costerton 2002). In many industrial processes where water is used as coolant, biofilm formation is quite common and involves detrimental consequences, entailing significant financial losses. Adverse impacts of undesirable biofilms include impediment to heat transfer across heat exchange surfaces (Bott 1990), mechanical blockages in cooling conduits and condenser tubes and enhanced corrosion of structural materials (Flemming and Schalule 1994). The development of a biofilm community on surfaces proceeds via an ordered series of steps, involving initial colonization by primary colonisers and subsequent colonization by other organisms. The information on biofilm-forming bacteria and their role in biofilm community development in industrial cooling water systems, particularly using sea- water as coolant, is limited (Dang and Lovell 2000). P. Saravanan  M. Krishnaveni  S. Jayachandran (&) Department of Biotechnology, School of Life Sciences, Pondicherry University, Puducherry 605 014, India e-mail: sr_jayachandran@yahoo.com P. Saravanan e-mail: saravanandbt@gmail.com M. Krishnaveni e-mail: krishnaveni177@gmail.com Present Address: P. Saravanan Oral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-2190, USA S. R. Prabagaran Department of Biotechnology, Bharathiar University, Coimbatore 641 046, India e-mail: prabagaran1@yahoo.com Y. Venkata Nancharaiah  V. P. Venugopalan Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, BARC Facilities, Kalpakkam 603 012, India 123 World J Microbiol Biotechnol DOI 10.1007/s11274-007-9501-9