title: The molecular dimension of microbial species: 1. Ecological distinctions among, and homogeneity within, putative ecotypes of Synechococcus inhabiting the cyanobacterial mat of Mushroom Spring, Yellowstone National Park.
abstract: Based on the Stable Ecotype Model, evolution leads to the divergence of ecologically distinct populations (e.g., with different niches and/or behaviors) of ecologically interchangeable membership. In this study, pyrosequencing was used to provide deep sequence coverage of Synechococcus psaA genes and transcripts over a large number of habitat types in the Mushroom Spring microbial mat. Putative ecological species [putative ecotypes (PEs)], which were predicted by an evolutionary simulation based on the Stable Ecotype Model (Ecotype Simulation), exhibited distinct distributions relative to temperature-defined positions in the effluent channel and vertical position in the upper 1 mm-thick mat layer. Importantly, in most cases variants predicted to belong to the same PE formed unique clusters relative to temperature and depth in the mat in canonical correspondence analysis, supporting the hypothesis that while the PEs are ecologically distinct, the members of each ecotype are ecologically homogeneous. PEs responded differently to experimental perturbations of temperature and light, but the genetic variation within each PE was maintained as the relative abundances of PEs changed, further indicating that each population responded as a set of ecologically interchangeable individuals. Compared to PEs that predominate deeper within the mat photic zone, the timing of transcript abundances for selected genes differed for PEs that predominate in microenvironments closer to upper surface of the mat with spatiotemporal differences in light and O2 concentration. All of these findings are consistent with the hypotheses that Synechococcus species in hot spring mats are sets of ecologically interchangeable individuals that are differently adapted, that these adaptations control their distributions, and that the resulting distributions constrain the activities of the species in space and time.
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT USA ; Single Cell Genomics Center, Bigelow Laboratory for Ocean Sciences, East Boothbay, ME USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Becraft
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT USA.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Wood
authors.affiliation: J. Craig Venter Institute, Rockville, MD USA.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Rusch
authors.affiliation: Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør Denmark ; Plant Functional Biology and Climate Change Cluster, University of Technology Sydney, Ultimo, NSW Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Kühl
authors.affiliation: Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør Denmark ; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Hellerup Denmark.
authors.forename: Sheila I
authors.initials: SI
authors.lastname: Jensen
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA USA ; Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT USA.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
authors.affiliation: Department of Ecology, Montana State University, Bozeman, MT USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Roberts
authors.affiliation: Department of Biology, Wesleyan University, Middletown, CT USA.
authors.forename: Frederick M
authors.initials: FM
authors.lastname: Cohan
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Ward
keywords: Mushroom Spring; microbial ecology; microbial species; population genetics; thermophilic Synechococcus