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Appl Environ Microbiol. 1988 May; 54(5): 1091-1095
Copyright © 1988, American Society for Microbiology. All Rights Reserved.

Rates of Digestion of Bacteria by Marine Phagotrophic Protozoa: Temperature Dependence {dagger}

Barry F. Sherr*, Evelyn B. Sherr and Fereidoun Rassoulzadegan

1 University of Georgia Marine Institute, Sapelo Island, Georgia 31327, and Station Zoologique, 06230 Villefranche-sur-mer, France2

ABSTRACT

The effect of temperature on length of time for digestion of bacteria was evaluated, by using fluorescently labeled bacteria (FLB), for phagotrophic flagellates and ciliates isolated from coastal northwest Mediterranean waters. Accumulation of FLB in protozoan food vacuoles was followed until a plateau of FLB per cell occurred; then after a 1:10 dilution of FLB with unlabeled bacteria, disappearance of FLB in food vacuoles was monitored. For both 3- to 5-µm flagellates and 10- to 40-µm ciliates, the absolute linear slopes of FLB uptake and disappearance were nearly identical in individual experiments over a temperature range of 12 to 22°C. We inferred from these results that the leveling off of the uptake curves resulted when equilibrium between ingestion and digestion of bacteria was attained. The time to leveling off then represented the average time needed for complete digestion of the bacteria ingested at the start of the experiment, and the inverse of this time represented a bacterial digestion rate. The digestion rate increased exponentially from 12 to 22°C for both a mixed flagellate assemblage and the oligotrichous ciliate Strombidium sulcatum, with a Q10 of 2.8 for the flagellates and 2.0 for the ciliate. Although bacterial ingestion rates varied greatly, depending on protozoan cell size, total bacterial abundance, and temperature, digestion times appeared to be significantly influenced only by protozoan cell size (or type of protozoan) and by temperature.

FOOTNOTES

* Corresponding author.

{dagger} Contribution no. 600 of the University of Georgia Marine Institute.

Appl Environ Microbiol. 1988 May; 54(5): 1091-1095
Copyright © 1988, American Society for Microbiology. All Rights Reserved.



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Copyright © 1988 by the American Society for Microbiology. All rights reserved.