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Applied and Environmental Microbiology, April 2004, p. 2072-2078, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2072-2078.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Effect of Trophic Status on the Culturability and Activity of Bacteria from a Range of Lakes in the English Lake District

Jonathan Porter,* Samantha A. Morris, and Roger W. Pickup

Centre for Ecology and Hydrology, Windermere Laboratory, The Ferry House, Far Sawrey, Ambleside, Cumbria LA22 0LP, United Kingdom

Received 14 July 2003/ Accepted 2 January 2004

The bacterioplankton from a number of lakes that differed in nutrient status in the English Lake District was examined with a number of techniques for enumeration and activity assessment. Natural water samples showed a clear correlation between total counts and trophic status. Esterase activity measurements with Chemchrome B were able to distinguish high- and low-nutrient-status lakes, whereas tetrazolium salt (5-cyano-2,3-ditoyltetrazolium chloride) reduction, the direct viable count-cell elongation assay, and culturability measurements could not. Tetrazolium salt reduction and esterase activity measurements labeled a significant number of cells from water of all nutrient levels, whereas the direct viable count-cell elongation method was of use only in oligotrophic waters. Size fractionation of samples showed that the culturable cells were retained by the larger filters, especially in nutrient-rich waters. Esterase activity measurements also favored the larger cells. The differences observed between assays using water that differed in trophic status raise questions about the use of these tests as a definitive measure of viability.

* Corresponding author. Present address: Department of Biological Sciences, Hatherly Laboratories, University of Exeter, Exeter EX4 4PS, United Kingdom. Phone: 44 1392 264607. Fax: 44 1392 263700. E-mail: J.D.Porter{at}exeter.ac.uk.

Applied and Environmental Microbiology, April 2004, p. 2072-2078, Vol. 70, No. 4
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.4.2072-2078.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.





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