Fate of heterotrophic bacteria in lake Tanganyika (East Africa)

PIRLOT, S.; UNREIN, F.; DESCY, J-P.; SERVAIS, P.

FEMS MICROBIOLOGY ECOLOGY

Wiley Blackwell

Año: 2007 vol. 62 p. 354 - 364

0168-6496

Bacterial mortality was studied using two complementary methods between 2002and 2004 in the two main basins (north and south) of Lake Tanganyika. Thedisappearance of radioactivity from the DNA of natural assemblages of bacteriapreviously labeled with tritiated thymidine was used to estimate the mortality dueto grazing by predators (72%) and due to the cell lysis (28%). Measurements ofingestion rate of bacteria by protozoa using fluorescent micro-particles yieldedprotozoan grazing rates similar to those provided by the thymidine method, andshowed that heterotrophic nano-flagellates were responsible for most of thegrazing pressure on the bacterial community of the pelagic zone (92–99%).Bacterial cell lysis was the second process involved in bacterial mortality, rankingbefore ciliate grazing. Overall, bacterial mortality was balanced with bacterialproduction. With regard to the assessment of the trophic role of bacteria, it wasestimated that c. 5–8% of the organic carbon taken up by bacteria was convertedinto protozoan biomass and was thus available for metazoans.