ISSN:
1574-6968
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract Ligh emitted by the bioluminescent bacterium, Xenorhabdus luminescens (isolated from a nematode host), can be measured to monitor reductions of these bacteria in the presence of phagotrophs. X. luminescens is relatively large (0.6 ? 3 μm), but comparable in size to many cyanobacteria. We used the light emission method to examine phagotroph feeding on X. luminescens using uni-specific cultures of two chrysomonads, Ochromonas sp. and Spulemma sp. From light decay rates in control and experimental vials, we computed an apparent filtration rate (FR); then, for a concentration (C) of 1 ? 106 bacteria ml−1, we estimated capture rate (CR) as FR ? C. The Ochromonas sp. did not ingest the bacterium. The maximum estimated FR for Spumella, observed at 6.0 ? 103 flagellates ml−1 (medium density), was 0.37 ml h−1, for a volume-specific clearance rate (FR/cell volume) of 7.9 ? 105 h−1 and a CR of 62 bacteria ? flagellate−1 h−1. Video microscopy indicated these were accurate estimates of capture rates.Microscopic counts were used to monitor growth of a flagellate, Spumella sp., on X. luminescens as the sole food supply. The flagellate doulbed in number every 3.2, while consuming bacteria at a rate of 23 bacteria flagellate−1 h−1. The Spumella grazed the bacteria to a minimum of 5 ? 105 cells ml−1, a concentration comparable to observed field densities of other bacteria.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1574-6968.1990.tb03922.x
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