Published: Dec. 12, 2017

Mushroom Spring, Yellowstone National Park,

WY: a panoply of phototrophs and their friends


Donald A. Bryant

Department of Biochemistry and Molecular Biology,

The Pennsylvania State University;

Department of Chemistry and Biochemistry, Montana State University

Date:  Thursday, December 14th, 2017 at 3:00pm

Location: SEEC (east campus) Room C120


We have been studying the microbial mats associated with the effluent channel of Mushroom Spring (and Octopus Spring to a lesser extent), a thermal feature in the Lower Geyser Basin in Yellowstone National Park, WY, for more than a decade. Often described as “cyanobacterial mats,” in which thermophilic Synechococcus sp. are the predominant primary producers, the mats are in fact dominated by Chloroflexi, principally members of the genus Roseiflexus. The mats can be divided vertically into two zones: an upper green-colored, euphotic layer that is ~1–2 mm in thickness, and an orange-colored undermat that is about 1.0–2.0 cm in thickness, although only the uppermost 0.5 cm is biologically active. We have applied metagenomics, genomics, metatranscriptomics, metaproteomics, metametabolomics, and traditional enrichment and cultivation methods to the study of this mat community. The upper green layer is principally composed of chlorophototrophic members of four phyla (Cyanobacteria, Chloroflexi, Chlorobi, and Acidobacteria). The undermat is more complex—more than 300 operational taxonomic units are detected by iTag analysis. However, the undermat community is highly uneven and is also dominated by members of the Chloroflexi. We have detected 18 different chlorophototrophs from the seven phyla known to contain such organisms between ~50 to 65°C. The diel transcription patterns of the mats were studied in 2009 and again in 2014. The patterns observed for major phototroph populations were identical for these two studies. Light does not appear to control transcriptional patterns in the undermat population. A novel non-chlorophototrophic member of the Chlorobi has been detected in the metagenome, and it contains all of the genes required for sulfate reduction. These genes were identically regulated in the upper green layer and in the undermat, which suggests that their transcription is not regulated by light but instead is regulated by oxygen. Oxygen has been suggested to control gene expression for some other metabolic processes as well in other mat members. Enrichment and cultivation approaches to the study of this mat system will be discussed, using the example of Chloracidobacterium thermophilum, a novel chlorophototrophic member of the phylum Acidobacteria, which was first detected in the metagenome and eventually isolated as an axenic culture using –omics information as a guide.



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