Abstract
A new method was developed for estimating the grazing rate of live bacteria by protists. Bacterial cells (Escherichia coli bearing plasmid pEGFP) expressing enhanced green fluorescent protein (EGFP) were used as a live bacterial tracer. Ciliates (Tetrahymena thermophila) were fed with EGFP-tagged bacterial cells, and the individual cells taken up by the ciliates were detected by epifluorescence microscopy. The EGFP fluorescence was stable during the storage of samples fixed with glutaraldehyde. Comparison of clearance rates based on the uptake of EGFP-tagged live cells and fluorescently-labeled heat-killed cells suggested that the use of heat-killed cells underestimates the clearance rates. We suggest that EGFP-tagged bacteria are a useful tracer for determining protist bacterivory in culture and aquatic environments.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
