Does temperature determine the variation in bacterial membrane lipids (brGDGTs) and community composition along an altitudinal gradient in subarctic soils?

Certain bacterial membrane lipids (branched glycerol dialkyl glycerol tetraethers: brGDGTs) find a use as proxies of past climates and environmental conditions. They are very promising proxies, as they are found in a diversity of geological archives (fi. lacustrine and marine sediments) for up to 200 Ma. A correct interpretation of their diversity through time however depends on the knowledge on the drivers on their distribution in modern samples. Recently, the applicant showed that the bacterial community composition explains part of the temperature-dependent behavior observed on a global scale. It also became clear that, in bacterial communities encountered in typically cold soils, temperature and pH only explain 20% of the variability in the brGDGT distribution (De Jonge et al., in preparation, PNAS). To shed light on this unexplained variability, we are applying for funding to analyze a dataset of well-described soils in subarctic Norway and Sweden, to determine which other environmental factors influence the brGDGT distribution. We will analyse these soils with a combination of geochemical and biological methods, to determine both the direct (acting on the physiological plasticity) as the indirect (acting on the bacterial community composition) environmental factors that influence the brGDGT composition. The soils (n=60) are sampled along 3 height transects that has been studied for several years, where soil temperature is measured in-situ by temperature loggers. pH and alkalinity will be determined in the laboratory, as well as the distribution of cations and anions. Bacterial lipids will be extracted and analysed on GC and HPLC-MS. The bacterial community composition is based on the diversity of the 16S rDNA fragment, which will be analysed on an Illumina Miseq platform. The requested funds will cover the analysis of a pilot study, which will be performed in collaboration with Jonas Lembrechts, who has been working extensively on these specific height transects during his PhD project. This research will result in the better understanding of a promising proxy for past climates that is used internationally. It will also contribute to the hot topic research on the nature of the bacterial producers of this class of lipids.

Keywords:SOIL COMMUNITIES, LIPID BIOMARKER

Disciplines:Other chemical sciences, Geochemistry, Ecology, Other biological sciences, Environmental science and management, Other environmental sciences