amino sugars; amino acids; biogeochemistry; microbiology; freshwater lakes; chitin; microbial communities; biomarkers; Organic nitrogen compounds; degradation; microbial community
Koellner Krista E., Carstens Doerte, Schubert Carsten J., Zeyer Josef, Buergmann Helmut (2013), Impact of particulate organic matter composition and degradation state on the vertical structure of particle-associated and planktonic lacustrine bacteria, in AQUATIC MICROBIAL ECOLOGY
, 69(1), 81-81.
Carstens Doerte, Lehmann Moritz F., Hofstetter Thomas B., Schubert Carsten J. (2013), Amino acid nitrogen isotopic composition patterns in lacustrine sedimenting matter, in GEOCHIMICA ET COSMOCHIMICA ACTA
, 121, 328-338.
Carstens Doerte, Schubert Carsten J. (2012), Amino acid and amino sugar transformation during sedimentation in lacustrine systems, in ORGANIC GEOCHEMISTRY
, 50, 26-35.
Carstens Doerte, Koellner Krista E., Buergmann Helmut, Wehrli Bernhard, Schubert Carsten J. (2012), Contribution of bacterial cells to lacustrine organic matter based on amino sugars and D-amino acids, in GEOCHIMICA ET COSMOCHIMICA ACTA
, 89, 159-172.
Koellner Krista E., Carstens Doerte, Keller Esther, Vazquez Francisco, Schubert Carsten J., Zeyer Josef, Buergmann Helmut (2012), Bacterial Chitin Hydrolysis in Two Lakes with Contrasting Trophic Statuses, in APPLIED AND ENVIRONMENTAL MICROBIOLOGY
, 78(3), 695-704.
This proposal seeks a final contribution for one year for the project “Degradation and transformation of lacustrine organic nitrogen compounds: microbiology and biogeochemistry” (Project number 118111). During the last 2.5 years of the current project, we could link biogeochemical and microbial data in various ways. We showed e.g. that the glucosamine concentrations of the particulate organic matter correlate with chitinase activities. Highest chitinase activities were found in the zone of primary production and in the sediments. Bacterial community clusters correlated well with physico-chemical parameters. Studying the fate of the refractory biopolymer chitin, which is composed of the amino sugar glucosamine, we were able to depict different decomposition patterns for two lake systems distinguishing themselves by different nutrient and redox conditions: For the eutrophic Lake Zug the bulk of the chitinase activity was found in the sediments. In comparison, chitinase gene abundance distributed over the oligotrophic water column of Lake Brienz indicates a higher significance of chitin as carbon and nitrogen source as in the eutrophic water column of Lake Zug where more easily assimilable carbon and nitrogen sources are available. In order to improve our understanding of the sources and fates of the amino sugars and amino acids we will apply compound specific isotope measurements. These data will reveal bacterial alteration of the organic material and we can show whether new bacterial biomass is built up in the sediments. As terrestrial organic material buried in the sediments seems to be more refractory than the organic matter from autochthonous material, we want to estimate the fraction of terrestrial matter with the analysis of lipids. With the measurement of D-amino acids the fraction of the bacterial derived glucosamine will be estimated and we will be able to determine if bacteria are the main drivers in lacustrine organic nitrogen turnover.To study the diversity and distribution of bacterial chiA genes we are going to apply the high throughput 454 pyrosequencing technique on DNA extracted from the different lake compartments of the two lakes mentioned above. In order to analyze the proportion of bacterial groups carrying the chiA gene, we will perform fluorescence in-situ hybridization.The combination of isotopic, organic geochemical and molecular methods will significantly advance our understanding of how and by whom organic nitrogen compounds are transformed in lacustrine ecosystems.