Position description: A postdoc position is available within the Austrian Science Fund (FWF) project Illuminating the ecology of nitrite-oxidizing bacteria in soil and aquatic ecosystems.
Project description: Nitrite-oxidizing bacteria (NOB) are key players of the biogeochemical nitrogen cycle. By catalyzing the second step of nitrification, the oxidation of nitrite to nitrate, NOB are the biological source of nitrate, which is a major form of fixed nitrogen in the biosphere and an important nitrogen source for many microorganisms and plants. Moreover, the activity of NOB determines whether fixed nitrogen is retained in ecosystems as nitrate or is lost to the atmosphere via other processes that convert nitrite to gaseous N-compounds. Despite the huge ecological importance of NOB, current knowledge of their microbiology and ecology is severely limited. Past research on NOB, which are difficult to culture in the laboratory, mainly focused on few pure cultures or representatives in wastewater treatment plants. The NOB communities in natural ecosystems have been neglected and thus, their composition, population dynamics, and responses to shifts of environmental conditions and human impact remain enigmatic. This project will bridge this knowledge gap by studying the structure and function of NOB communities in representative pristine or human-affected terrestrial and aquatic ecosystems: soils from the Arctic and from tropical or temperate forests, agricultural soils, waters and sediments from freshwater streams and lakes, and moderately saline lakes in the East Austrian national park Neusiedler See-Seewinkel. The saline lakes are characterized by highly variable environmental conditions, but host extremely productive microbial communities that have barely been studied. To analyze the phylogenetically diverse NOB independently from cultivation, a novel and highly specific marker gene will be used. Sequences of this gene, nxrB coding for the beta subunit of nitrite oxidoreductase, have become available only recently with the first sequenced genomes from all known lineages of NOB. As nxrB is a key functional gene of nitrite oxidation, it is present in all NOB, but occurs in distinct forms characteristic for each phylogenetic NOB clade. In a highly parallelized approach, the NOB community structures in plenty of environmental samples will be analyzed by cutting-edge next-generation sequencing of nxrB genes, and the in situ nitrite-oxidizing activities of the different populations will be studied by monitoring nxrB transcription. In a series of incubation experiments, the responses of NOB to changing environmental conditions and structure-function relationships of NOB communities will be investigated. NOB will also be enriched from selected samples, and the potential of these autotrophs to use various organic substrates will be examined by molecular single-cell methods. The project will provide for the first time a broad picture of environmental NOB populations and their ecology in diverse habitats. This knowledge is urgently needed to better understand the effects of natural environmental fluctuations on the nitrogen cycle and to assess the consequences of human impact, such as an increasing nitrogen deposition, for vulnerable ecosystems.
Required qualifications: We are looking for a highly motivated and independently working scientist with interest in collaborative & fundamental microbial ecology research. Applicants should have a strong conceptual and practical background on the application of molecular techniques for characterizing the identity and ecophysiology of microbial community members. Experience in one or more of the following areas/techniques will be of advantage: microbial ecology of nitrifying microorganisms, rRNA or functional gene amplicon pyrosequencing and the associated bioinformatics, isotope labelling of uncultivated microbes, and cultivation of chemolithoautotrophic microorganisms. Proficiency in spoken and written English is mandatory.
Conditions of appointment: We offer up to 2.5 years of appointment as a postdoctoral scientist according to the salary scheme of the Austrian Science Fund (FWF). The University of Vienna is an equal opportunity employer.
Mode of application. To apply, please send an email (subject: Postdoc NOB) to Dr. Holger Daims, firstname.lastname@example.org containing a pdf-file with your application, a detailed CV (including a brief description of research interests, previous employments, and publication list), reprints of your two most important published articles, and contact details of at least two references (letters of recommendation are optional).
Job start date is Spring/Summer 2013.