Affiliation:
1. Center for the Management, Utilization and Protection of Water Resources, Tennessee Technological University, Cookeville, Tennessee 38505
Abstract
Bacteriovorous protozoa harboring symbiotic algae are abundant in aquatic ecosystems, yet despite a recent interest in protozoan bacterivory, the influence of light on their ingestion rates has not been investigated. In this study,
Paramecium bursaria
containing endosymbiotic
Chlorella
was tested for the effect of light on its ingestion rate.
P. bursaria
was grown for 4 to 6 days under five different light fluxes ranging from 1 to 90 microeinsteins s
-1
m
-2
. Ingestion rates were determined by using 0.77-μm-diameter fluorescent microspheres. 4′,6-Diamidino-2-phenylindole dihydrochloride-labeled
Enterobacter cloacae
was used in one experiment to confirm differences in uptake rates of bacteria by
P. bursaria.
Unlike phagotrophic phytoflagellates, the ciliates demonstrated different ingestion rates in response to different light intensities. Although symbionts contribute carbon to their host via photosynthesis, the paramecia of the present study fed faster after exposure to higher light intensities, whereas their aposymbiotic counterparts (lacking endosymbionts) were unaffected. Light-induced changes in ingestion rates were not immediate, but corresponded to the period of time required for endosymbiont populations to change significantly. This strongly suggests that the symbionts, stimulated by higher light levels, may dictate the feeding rates of their hosts. Thus, light, apart from temperature, may influence the impact of certain protists on natural bacteria and may affect laboratory-based determinations of protistan feeding rates.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
14 articles.
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