title: Comparisons of diazotrophic communities in native and agricultural desert ecosystems reveal plants as important drivers in diversity.
abstract: Diazotrophs provide the only biological source of fixed atmospheric nitrogen in the biosphere. Although they are the key player for plant-available nitrogen, less is known about their diversity and potential importance in arid ecosystems. We investigated the nitrogenase gene diversity in native and agricultural desert soil as well as within root-associated microbiota of medicinal plants grown in Egypt through the combination of nifH-specific qPCR, fingerprints, amplicon pyrosequencing and fluorescence in situ hybridization-confocal laser scanning microscopy. Although the diazotrophic microbiota were characterized by generally high abundances and diversity, statistically significant differences were found between both soils, the different microhabitats, and between the investigated plants (Matricaria chamomilla L., Calendula officinalis L. and Solanum distichum Schumach. and Thonn.). We observed a considerable community shift from desert to agriculturally used soil that demonstrated a higher abundance and diversity in the agro-ecosystem. The endorhiza was characterized by lower abundances and only a subset of species when compared to the rhizosphere. While the microbiomes of the Asteraceae were similar and dominated by potential root-nodulating rhizobia acquired primarily from soil, the perennial S. distichum generally formed associations with free-living nitrogen fixers. These results underline the importance of diazotrophs in desert ecosystems and additionally identify plants as important drivers in functional gene pool diversity.
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria martina.koeberl@tugraz.at.
authors.forename: Martina
authors.initials: M
authors.lastname: Köberl
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria.
authors.forename: Armin
authors.initials: A
authors.lastname: Erlacher
authors.affiliation: Faculty of Agriculture, Ain Shams University, 11566 Cairo, Egypt Biotechnology Laboratory, Heliopolis University, 11777 Cairo, Egypt.
authors.forename: Elshahat M
authors.initials: EM
authors.lastname: Ramadan
authors.affiliation: Faculty of Agriculture, Ain Shams University, 11566 Cairo, Egypt Biotechnology Laboratory, Heliopolis University, 11777 Cairo, Egypt.
authors.forename: Tarek F
authors.initials: TF
authors.lastname: El-Arabi
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria.
authors.forename: Henry
authors.initials: H
authors.lastname: Müller
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Bragina
authors.affiliation: Institute of Environmental Biotechnology, Graz University of Technology, 8010 Graz, Austria.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Berg
mesh_terms: D000383:Agriculture; D020838:Calendula / Q000378:metabolism / Q000382:microbiology*; D003889:Desert Climate; D017753:Ecosystem; D004534:Egypt; D014644:Genetic Variation / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D031168:Matricaria / Q000378:metabolism / Q000382:microbiology*; D064307:Microbiota / Q000235:genetics / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation / Q000502:physiology*; D009591:Nitrogenase / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics*; D018517:Plant Roots / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D032322:Solanum / Q000378:metabolism / Q000382:microbiology*
chemical_list: D012336:RNA, Ribosomal, 16S; D012987:Soil; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase; D009584:Nitrogen
keywords: Rhizobiales; desert farming; diazotrophs; medicinal plants; nitrogen-fixing communities; organic agriculture