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The leucine incorporation method estimates bacterial growth equally well in both oxic and anoxic lake waters
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Department of Limnology, Uppsala University, Sweden.
2001 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 67, no 7, 2916-2921 p.Article in journal (Refereed) Published
Abstract [en]

Bacterial biomass production is often estimated from incorporation of radioactively labeled leucine into protein, in both oxic and anoxic waters and sediments. However, the validity of the method in anoxic environments has so far not been tested. We compared the leucine incorporation of bacterial assemblages growing in oxic and anoxic waters from three lakes differing in nutrient and humic contents, The method was modified to avoid O-2 contamination by performing the incubation in syringes. Isotope saturation levels in oxic and anoxic waters were determined, and leucine incorporation rates were compared to microscopically observed bacterial growth. Finally, we evaluated the effects of O-2 contamination during incubation with leucine, as well as the potential effects of a headspace in the incubation vessel, isotope saturation occurred at a leucine concentration of above about 50 nM in both ode and anoxic waters from all three lakes. Leucine incorporation rates were linearly correlated to observed growth, and there was no significant difference between oxic and anoxic conditions. O-2 contamination of anoxic water during I-h incubations with leucine had no detectable impact on the incorporation rate, while a headspace in the incubation vessel caused leucine incorporation to increase in both anoxic and O-2-contaminated samples. The results indicate that the leucine incorporation method relates equally to bacterial growth rates under oxic and anoxic conditions and that incubation should be performed without a headspace.

Place, publisher, year, edition, pages
2001. Vol. 67, no 7, 2916-2921 p.
National Category
Social Sciences
URN: urn:nbn:se:liu:diva-49209DOI: 10.1128/​AEM.67.7.2916-2921.2001OAI: diva2:270105
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2012-06-27Bibliographically approved
In thesis
1. Anoxic degradation of organic matter in lakes: implications for carbon cycling and aquatic food webs
Open this publication in new window or tab >>Anoxic degradation of organic matter in lakes: implications for carbon cycling and aquatic food webs
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Considerable evidence from laboratory studies and marine environments suggests that degradation of organic matter (OM) is restricted under anoxic conditions compared to when molecular oxygen (O2) is present. However, other studies contradict this view since they found similar OM degradation rates and bacterial growth rates under both oxic and anoxic conditions in aquatic environments. Studies from freshwater environments are rare, and have been primarily based on bacterial production estimates. Anoxic degradation of OM in lakes is commonly considered to be slow and of little importance for overall lake food webs compared to oxic degradation. The present thesis and the work it is based on challenge this view. First, the performance of a commonly used method to measure bacterial production was tested in both oxic and anoxic lake water. Then, the oxic and anoxic potentials of bacterial growth and OM mineralization were compared in lake water and sediment. In addition, I assessed the potential of carbon transfer from methane (CH4; i.e. an end-product of anoxic degradation) to pelagic food webs. Three methods for measuring water column methane oxidation were evaluated. Then, the potential transport of methane carbon into the microbial community via methane oxidation, and further -up the food web- into the zooplankton community was estimated. Results indicate 1) that OM degradation and bacterial growth may be similar in oxic and anoxic lake environments, 2) that OM characteristics may be more important for the mineralization than the O2 regime per se in the short term (daysweeks), and 3) that methane can be a significant source of carbon and energy for pelagic food webs. This suggests that the anoxic carbon metabolism may be extensive and potentially important for pelagic organisms in many lakes.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2002. 55 p.
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 262
Ekonsystem i vatten
National Category
Social Sciences Interdisciplinary
urn:nbn:se:liu:diva-29575 (URN)14951 (Local ID)91-7373-436-5 (ISBN)14951 (Archive number)14951 (OAI)
Public defence
2002-11-01, Sal Elysion, Hus-T, Universitetsområdet Valla, Linköping, 10:00 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2014-08-29Bibliographically approved

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Bastviken, David
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