This research thrust is sponsored by NSF Ecology and now Frontiers in Integrative Biology Research Programs. After characterizing anaerobic decomposition processes in these mats, we learn how to describe microbial communities in a cultivation-independent manner. Cell components are used as biomarkers to describe each community member. We developed methods for using genes and gene products, especially 16S rRNA gene sequences that enable us to see the true composition of the model community. We found several cyanobacterial and green nonsulfur bacteria-like 16S rRNA variants wildly different and much more diverse than cyanobacteria and filamentous bacteria that can be readily cultivated from the mat. Many genetic variants were closely related; however, distribution analysis suggested that even closely related genetic variants have different distributions along temperature and light gradients, as if each genotype was a distinct ecological population. We observed cases in which ecologically distinct populations have identical 16S rRNA sequences. One current thrust is to demonstrate temperature and light adaptations of genetically relevant cyanobacterial isolates. We will conduct a high resolution population genetics analysis of mat cyanobacterial genetic diversity and determine whether it is organized into anything like species, as we know them from plant and animal biology. We will conduct genomic analysis of two cyanobacterial isolates and the mat itself; genomic information will enable development of microarrays used to examine in situ gene expression of mat phototrophs.
Relationship between mat cell component biomarkers (and their carbon isotope signatures) and the community members that contribute them: How should biomarkers and isotopic signatures in fossilized mats (stromatolites) be interpreted?
This work is supported by the NASA Exobiology Program. In early collaborative work with Dr. Geoffrey Eglinton, we determined lipid biomarker compositions of cultivated microorganisms representative of mat inhabitants. Once our 16S rRNA work revealed the irrelevance
of ordinary isolates, we obtained genetically relevant cyanobacterial and green nonsulfur bacterial isolates and are currently characterizing their lipids and
Determine the effect of cyanobacterial sugar biosynthesis on the isotopic signatures of green nonsulfur-like bacteria.
We are testing the hypothesis that cyanobacterial sugar biosynthesis may impart a heavy isotopic signature that is transferred to green nonsulfur-like bacteria through nighttime fermentation by cyanobacteria and photoheterotrophic carbon assimilation by green nonsulfur-like bacteria the next day.
Ward, Dave 2002 van der Meer, M.T.J., Schouten, S., Hanada, S., Hopmans, E.C., Sinninghe Damsté, J.S., and Ward, D.M. Alkane-1,2-diol based glycosides and fatty glycosides in Roseiflexus castenholzii and hot spring microbial mats Archives of Microbiology
Ward, Dave 2003 M.T.J. van der Meer, S. Schouten, J. S. Sinninghe Damste, J.W. de Leeuw Compound-Specific Isotopic Fractionation Patterns Suggest Different Carbon Metabolisms among Chloroflexus-Like Bacteria in Hot-Spring Microbial Mats Applied and Environmental Microbiology 69:6000-6
Ward, Dave 2003 M.J. Ferris, M Kuhl, A. Wieland Cyanobactieral Ecotypes in Different Optical Microenivronments of a 68°C Hot Spring Mat Community Revealed by 16S-23S rRNA Internal Transcribed Spacer Region Variation Applied and Environmental Microbiology 69:2893-8
Ward, Dave 2003 R.T. Papke, N.B Ramsing, M.M. Bateson Geographical isolation in hot spring cyanobacteria Environmental Microbiology 5:650-9
Ward, Dave 2002 U. Nubel, M.M. Bateson, V. Vandieken, A. Wieland, M. Kuhl Microscopic Examination of Distribution and Phenotypic Properties of Phylogenetically Diverse Chloroflexaceae-Related Bacteria in Hot Spring Microbial Mats Applied and Environmental Microbiology 68:4593-4603