Biogeography of soil nitrogen fixing bacteria in the western Swiss Alps
Davide Ciccareseª, E. Yashiroª, E. Pintob, A. Burib, H. Niculita-Hirzelc, A. Guisanb, J.R. van der Meerª
a Department of Fundamental Microbiology, University of Lausanne, Switzerland.
b Department of Ecology and Evolution, University of Lausanne, Switzerland.
c Institut universitaire romand de santé au travail, Switzerland.
The Alps represent an important opportunity for biogeographical studies thanks to their heterogeneous topography and broad range of different climate and physico-chemical conditions along a wide elevation gradient. The western Swiss Alps region of canton Vaud has been the subject of a long standing series of studies by the University of Lausanne that has investigated the ecology of plants and insects as a function of climate and land use change. More recently focus has also shifted toward the biogeography of alpine microorganisms in this same study area. In this project the goal was to characterize the bacteria involved in nitrogen cycling in alpine soils. The nitrogen cycle is one of the most important biogechemical processes in terrestrial ecosystems. It includes nitrogen fixation, mineralization, nitrification and denitrification. Bacteria and Archaea that possess the enzyme nitrogenase are responsible for the fixation of atmospheric nitrogen into more bioavailable ammonia. Among the different genes that encode for the multiple subunits of the nitrogenase enzyme complex, the nifH gene is the most sequenced and has become a standard marker gene for styding the ecology of the nitrogen-fixing microorganisms in various ecosystems. Here we present the methods used for amplifying and sequencing the nitrogenase gene from the alpine soil metagenome and first results on the distribution and ecology of the nitrogen fixing bacteria along an elevation gradient of 700 to 3000 m across the alpine landscape.