Microbial Nitrogen and Sulfur Cycles at the Gypsum Dunes of White Sands National Monument, New Mexico

Abstract

The White Sands National Monument from New Mexico (U.S.A) contains one of the largest known gypsum dune fields with unique, rapidly migrating, arid, evaporitic habitats. Deposits from dune sides and interdune areas were collected in order to determine the characteristics of microbial habitat and communities through mineral assemblages, microbial pigments along with investigations of nitrogen and sulfur cycles. The most abundant pigments, scytonemin and carotenoids, were common UV protective pigments. Predominance of nitrite and nitrate over ammonium nitrogen (2.16: 1) implies that nitrification processes might be important in this ecosystem. Ammonium oxidizers from groups of β-, γ-proteobacteria and archaea were detected in all deposits, thereby indicating microbial involvement in nitrification. Additionally, denitrifying organisms with nirS and nirK genes were also present in most of the analyzed samples. The presence of trace carbonate mineral phases in association with biofilm implies possible microbial sulfate reduction. Microbes with metabolic abilities for sulfur cycling (i.e., dissimilatory sulfite reducers, purple sulfur bacteria, green sulfur and non-sulfur bacteria, and organisms with the APS enzyme) were identified in all samples. These particular organisms have the ability to reduce sulfate and to re-oxidize reduced sulfur compounds back to sulfate.

Keywords:

• Gypsum
• Dunes
• Nitrogen cycling
• Sulfur cycling

Acknowledgments

This work was funded by NASA Astrobiology Institute (NNA09DA81A), Carnegie Institution of Washington (PI G. Cody), Geophysical Laboratory, Carnegie Institution of Washington Postdoctoral Fellowship Program (to M. Glamoclija), NASA Astrobiology Technology for Exploring Planets grant NNX09AB74G (PI A. Steele) and the W. M. Keck Foundation (PI M. Fogel). We would like to thank the White Sands National Monument and D. Bustos for his hospitality and help during the fieldwork. We are thankful to D. Bower for field assistance; V. Starke assisted with DNA extractions. We are grateful to V. Starke, P. Griffin and two anonymous reviewers for their suggestions and constructive reviews, which significantly strengthened and improved the paper.