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Biodegradation of Azotobacter vinelandii exopolymer by Lake Superior microbes
Author(s) -
Weaver Daniel T.,
Hicks Randall E.
Publication year - 1995
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1995.40.6.1035
Subject(s) - exopolymer , azotobacter vinelandii , bacterioplankton , environmental chemistry , heterotroph , hypolimnion , mineralization (soil science) , biomass (ecology) , scenedesmus , bacterial growth , mesocosm , biology , algae , phytoplankton , botany , bacteria , chemistry , ecology , eutrophication , nutrient , nitrogenase , nitrogen fixation , genetics , soil water
Exopolymer and cells from Azotobacter vinelandii, a soil bacterium, and cells of Scenedesmus bijugatus, a eucaryotic alga, were radiolabeled to experimentally measure their mineralization by hypolimnetic microbes from Lake Superior during July and August 1992. Rates of mineralization were calculated from measurements of microbially respired 14 CO 2 released in respiration bottles during 14–22‐d incubations. Hypolimnetic microbes mineralized the exopolymer from A. vinelandii (0.32–0.36% d −1 ) about twice as fast as they mineralized S. bijugatus cells (0.16–0.20% d −1 ). A. vinelandii cells were mineralized 5 times faster than S. bijugatus cells were mineralized. Bacterial growth efficiencies for these substrates were estimated at the end of the experiments by dividing the cumulative amounts of bacterial biomass produced by the mass of substrate that was utilized in the different respiration bottles. Although the Azotobacter cells were rapidly mineralized, they were a poor substrate for producing new bacterioplankton biomass. Hypolimnetic bacterioplankton were more efficient at converting S. bijugatus into new biomass (growth efficiency = 18–30%) than at converting either the A. vinelandii cells or exopolymer (2% and 8–10% growth efficiencies, respectively). Decaying bacterioplankton blooms may be rapidly mineralized in the upper hypolimnion of Lake Superior, based on the results from the model bacterium ( A. vinelandii ). Conversely, exopolymers or phytoplankton from the epilimnion may support heterotrophic bacterial production throughout the water column and limit bacterioplankton growth during periods when small amounts of these substrates are produced.