TY - JOUR T1 - Non-cyanobacterial diazotrophs dominate dinitrogen fixation in biological soil crusts during early crust formation JF - bioRxiv DO - 10.1101/013813 SP - 013813 AU - Charles Pepe-Ranney AU - Chantal Koechli AU - Ruth Potrafka AU - Cheryl Andam AU - Erin Eggleston AU - Ferran Garcia-Pichel AU - Daniel H Buckley Y1 - 2015/01/01 UR - http://biorxiv.org/content/early/2015/01/15/013813.abstract N2 - Biological soil crusts (BSC) are key components of ecosystem productivity in arid lands and they cover a substantial fraction of the terrestrial surface. In particular, BSC N2-fixation contributes significantly to the nitrogen (N) budget of arid land ecosystems. In mature crusts, N2-fixation is largely attributed to heterocystous cyanobacteria, however, early successional crusts also fix N2 but possess few N2-fixing cyanobacteria and this suggests that microorganisms other than cyanobacteria mediate N2-fixation during the critical early stages of BSC development. DNA stable isotope probing (DNA-SIP) with 15N2 revealed that Clostridiaceae and Proteobacteria are the most common microorganisms that assimilate 15N in early succes-sional crusts. The low abundance of these groups in BSC may explain why these heterotrophic diazotrophs have not previously been characterized. Diazotrophs play a critical role in BSC formation and characterization of these organisms represents a crucial step towards understand-ing how anthropogenic change will affect the formation and ecological function of BSC in arid ecosystems. ER -