PT  - JOURNAL ARTICLE
AU  - Charles Pepe-Ranney
AU  - Chantal Koechli
AU  - Ruth Potrafka
AU  - Cheryl Andam
AU  - Erin Eggleston
AU  - Ferran Garcia-Pichel
AU  - Daniel H Buckley
TI  - Non-cyanobacterial diazotrophs dominate dinitrogen fixation in biological soil crusts during early crust formation
AID  - 10.1101/013813
DP  - 2015 Jan 01
TA  - bioRxiv
PG  - 013813
4099  - http://biorxiv.org/content/early/2015/01/15/013813.short
4100  - http://biorxiv.org/content/early/2015/01/15/013813.full
AB  - 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.