Editor: Karl Ritz
A common soil flagellate (Cercomonas sp.) grows slowly when feeding on the bacterium Rhodococcus fascians in isolation, but does not discriminate against it in a mixed culture with Sphingopyxis witflariensis
Article first published online: 28 JUN 2008
© 2008 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved
FEMS Microbiology Ecology
Volume 65, Issue 1, pages 113–124, July 2008
How to Cite
Lekfeldt, J. D. S. and Rønn, R. (2008), A common soil flagellate (Cercomonas sp.) grows slowly when feeding on the bacterium Rhodococcus fascians in isolation, but does not discriminate against it in a mixed culture with Sphingopyxis witflariensis. FEMS Microbiology Ecology, 65: 113–124. doi: 10.1111/j.1574-6941.2008.00486.x
- Issue published online: 28 JUN 2008
- Article first published online: 28 JUN 2008
- Received 3 October 2007; revised 11 February 2008; accepted 18 February 2008.First published online 6 May 2008.
- flagellate growth;
- Cercomonas sp.;
- food quality of bacteria;
- prey selectivity
Flagellates are very important predators on bacteria in soil. Because of their high growth rates, flagellate populations respond rapidly to changes in bacterial numbers. Previous results indicate that actinobacteria are generally less suitable than proteobacteria as food for flagellates. In this study, we investigated the growth of the flagellate Cercomonas sp. (ATCC 50334) on each of the two bacteria Sphingopyxis witflariensis (Alphaproteobacteria) and Rhodococcus fascians (actinobacteria) separately and in combination. The growth rate of the flagellate was lower and the lag phase was longer when fed with R. fascians than when fed with S. witflariensis. This supports our initial hypothesis that the actinobacterium is less suitable as food than the alphaproteobacterium. However, after longer periods of growth the peak abundance of flagellates was higher on R. fascians, indicating that the food quality of bacterial prey depends on the time perspective of the flagellate–bacterial interaction. There was no evidence that the flagellates selected against the actinobacterium when feeding in mixed cultures of the two bacteria. Experiments where flagellates were fed with washed bacterial cells or with bacteria growing with different substrate concentrations suggested that the low food quality of R. fascians is related both to the intrinsic cell properties and to the extracellular metabolites.