Original Article

Subject Category: Microbial population and community ecology

The ISME Journal (2008) 2, 457–470; doi:10.1038/ismej.2008.6; published online 21 February 2008

A salinity and sulfate manipulation of hypersaline microbial mats reveals stasis in the cyanobacterial community structure

Stefan J Green1,2, Cameron Blackford2,4, Patricia Bucki3, Linda L Jahnke2 and Lee Prufert-Bebout2

  1. 1SETI Institute, Mountain View, CA, USA
  2. 2Exobiology Branch, NASA Ames Research Center, Moffett Field, CA, USA
  3. 3The Agricultural Research Organization of Israel, The Volcani Center, Bet-Dagan, Israel

Correspondence: L Prufert-Bebout, Exobiology Branch, NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035, USA. E-mail: Leslie.E.Bebout@nasa.gov

4Current address: Pioneer Hi-Bred International, El Cerrito, CA, USA

Received 9 November 2007; Revised 30 December 2007; Accepted 3 January 2008; Published online 21 February 2008.

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Abstract

The cyanobacterial community structure and composition of hypersaline mats were characterized in an experiment in which native salinity and sulfate levels were modified. Over the course of approximately 1 year, microbial mats collected from Guerrero Negro (Baja, California Sur, Mexico) were equilibrated to lowered salinity (to 35p.p.t.) and lowered sulfate (below 1mM) conditions. The structure and composition of the cyanobacterial community in the top 5mm of these mats were examined using a multifaceted cultivation-independent molecular approach. Overall, the relative abundance of cyanobacteria—roughly 20% of the total bacterial community, as assayed with a PCR-based methodology—was not significantly affected by these manipulations. Furthermore, the mat cyanobacterial community was only modestly influenced by the dramatic changes in sulfate and salinity, and the dominant cyanobacteria were unaffected. Community composition analyses confirmed the dominant presence of the cosmopolitan cyanobacterium Microcoleus chthonoplastes, but also revealed the dominance of another Oscillatorian cyanobacterial group, also detected in other hypersaline microbial mats. Cyanobacterial populations increasing in relative abundance under the modified salinity and sulfate conditions were found to be most closely related to other hypersaline microbial mat organisms, suggesting that the development of these mats under native conditions precludes the development of organisms better suited to the less restrictive experimental conditions. These results also indicate that within a significant range of salinity and sulfate concentrations, the cyanobacterial community is remarkably stable.

Keywords:

cyanobacteria, Microcoleus chthonoplastes, Oscillatoriales, salinity, sulfate

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