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Applied and Environmental Microbiology, July 2005, p. 3519-3523, Vol. 71, No. 7
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.7.3519-3523.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Effects of Incubation Temperature on Growth and Production of Exopolysaccharides by an Antarctic Sea Ice Bacterium Grown in Batch Culture

Carol Mancuso Nichols,^1* John P. Bowman,² and Jean Guezennec³

School of Agricultural Science, University of Tasmania, Hobart, Tasmania, Australia,¹ Australian Food Safety Centre of Excellence, University of Tasmania, Hobart, Tasmania, Australia,² Institute Français de Recherche pour l'Exploitation de la Mer, Centre de Brest, DRV/VP, Plouzané, France³

Received 18 November 2004/ Accepted 31 January 2005

The sea ice microbial community plays a key role in the productivity of the Southern Ocean. Exopolysaccharide (EPS) is a major component of the exopolymer secreted by many marine bacteria to enhance survival and is abundant in sea ice brine channels, but little is known about its function there. This study investigated the effects of temperature on EPS production in batch culture by CAM025, a marine bacterium isolated from sea ice sampled from the Southern Ocean. Previous studies have shown that CAM025 is a member of the genus Pseudoalteromonas and therefore belongs to a group found to be abundant in sea ice by culture-dependent and -independent techniques. Batch cultures were grown at –2°C, 10°C, and 20°C, and cell number, optical density, pH, glucose concentration, and viscosity were monitored. The yield of EPS at –2°C and 10°C was 30 times higher than at 20°C, which is the optimum growth temperature for many psychrotolerant strains. EPS may have a cryoprotective role in brine channels of sea ice, where extremes of high salinity and low temperature impose pressures on microbial growth and survival. The EPS produced at –2°C and 10°C had a higher uronic acid content than that produced at 20°C. The availability of iron as a trace metal is of critical importance in the Southern Ocean, where it is known to limit primary production. EPS from strain CAM025 is polyanionic and may bind dissolved cations such at trace metals, and therefore the presence of bacterial EPS in the Antarctic marine environment may have important ecological implications.

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* Corresponding author. Mailing address: Centre for Marine Science and School of Agricultural Science, GPO Box 252-54, University of Tasmania, Hobart 7000, Australia. Phone: 61 3 6226 2620. Fax: 61 3 6226 2642. E-mail: C.A.Mancuso{at}utas.edu.au.

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Applied and Environmental Microbiology, July 2005, p. 3519-3523, Vol. 71, No. 7
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.7.3519-3523.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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