Get access

Hopanoids in marine cyanobacteria: probing their phylogenetic distribution and biological role

Authors

  • J. P. SÁENZ,

    1. Joint Program in Chemical Oceanography, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, Cambridge, MA, USA
    Search for more papers by this author
    • Present address: Max Planck Institute of Molecular Cell Biology and Genetics, 108 Pfotenhauestr., 01307 Dresden, Germany

  • J. B. WATERBURY,

    1. Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
    Search for more papers by this author
  • T. I. EGLINTON,

    1. Department of Marine Chemistry & Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
    Search for more papers by this author
    • Present address: ETH Zurich, 8092 Zurich, Switzerland

  • R. E. SUMMONS

    1. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
    Search for more papers by this author

Corresponding author: J. P. Sáenz. Tel.: +49 351 210-2425; fax: +49 351 210-1209; e-mail: saenz@mpi-cbg.de

Abstract

Cyanobacteria are key players in the global carbon and nitrogen cycles and are thought to have been responsible for the initial rise of atmospheric oxygen during the Neoarchean. There is evidence that a class of membrane lipids known as hopanoids serve as biomarkers for bacteria, including many cyanobacteria, in the environment and in the geologic record. However, the taxonomic distributions and physiological roles of hopanoids in marine cyanobacteria remain unclear. We examined the distribution of bacteriohopanepolyols (BHPs) in a collection of marine cyanobacterial enrichment and pure cultures and investigated the relationship between the cellular abundance of BHPs and nitrogen limitation in Crocosphaera watsonii, a globally significant nitrogen-fixing cyanobacterium. In pure culture, BHPs were only detected in species capable of nitrogen fixation, implicating hopanoids as potential markers for diazotrophy in the oceans. The enrichment cultures we examined exhibited a higher degree of BHP diversity, demonstrating that there are presently unaccounted for marine bacteria, possibly cyanobacteria, associated with the production of a range of BHP structures. Crocosphaera watsonii exhibited high membrane hopanoid content consistent with the idea that hopanoids have an important effect on the bulk physical properties of the membrane. However, the abundance of BHPs in C. watsonii did not vary considerably when grown under nitrogen-limiting and nitrogen-replete conditions, suggesting that the role of hopanoids in this organism is not directly related to the physiology of nitrogen fixation. Alternatively, we propose that high hopanoid content in C. watsonii may serve to reduce membrane permeability to antimicrobial toxins in the environment.

Get access to the full text of this article

Ancillary