Aquatic Sciences Meeting, Albuquerque 2001

SS14 Microbial Diversity (Disciplinary Connections)

Date: Tuesday, February 13, 2001, Time: 12:00:00 PM

Location: Mesilla

Steward, G, F, University of California, Santa Cruz, USA, gsteward@cats.ucsc.edu

Jellison, R, S, Sierra Nevada Aquatic Research Laboratory, Mammoth Lakes, USA, rjellison@earthlink.net

Joye, S, B, University of Georgia, Athens, USA, mjoye@arches.uga.edu

Hollibaugh, J, T, University of Georgia, Athens, USA, aquadoc@uga.edu

Zehr, J, P, University of California, Santa Cruz, USA, zehrj@cats.ucsc.edu

DETECTION OF NOVEL AND DIVERSE NITROGENASE GENES SUGGESTS POTENTIAL FOR PELAGIC DIAZOTROPHY IN ALKALINE, HYPERSALINE MONO LAKE

We investigated the molecular diversity of nitrogenase in Mono Lake as part of a collaborative Microbial Observatories project. A fragment of the nifH gene, which encodes the Fe component of nitrogenase, was amplified by PCR from picoplankton DNA in samples from 0 to 29 m depth. Sequencing of PCR products from surface, oxycline, and anoxic deep waters revealed nifH genes related to those from a variety of bacterial groups including firmicutes, alpha, beta, gamma, and delta proteobacteria and green sulfur bacteria. We found no identical matches to any of the more than 600 nifH gene sequences in genbank (79 to 87 percent identity). A nifH gene fragment with 91percent identity to a filamentous cyanobacterium was also amplified from "Ctenocladus balls" (CBs) collected in the littoral zone. These balls are associations of a green alga with diazotrophic cyano- and heterotrophic bacteria. To date, N2-fixation in Mono Lake has only been detected in CBs and benthic samples. Our results suggest that a variety of potential diazotrophs also exist in the picoplankton which may prove important to understanding productivity and biogeochemical cycling within the system.

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Aquatic Sciences Meeting, Albuquerque 2001

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