Diel metabolomics analysis of a hot spring chlorophototrophic microbial mat leads to new hypotheses of community member metabolisms.
Dynamic environmental factors such as light, nutrients, salt, and temperature continuously affect chlorophototrophic microbial mats, requiring adaptive and acclimative responses to stabilize composition and function. Quantitative metabolomics analysis can provide insights into metabolite dynamics for understanding community response to such changing environmental conditions. In this study, we quantified volatile organic acids, polar metabolites (amino acids, glycolytic and citric acid cycle intermediates, nucleobases, nucleosides, and sugars), wax esters, and polyhydroxyalkanoates, resulting in the identification of 104 metabolites and related molecules in thermal chlorophototrophic microbial mat cores collected over a diel cycle in Mushroom Spring, Yellowstone National Park. A limited number of predominant taxa inhabit this community and their functional potentials have been previously identified through metagenomic and metatranscriptomic analyses and in situ metabolisms, and metabolic interactions among these taxa have been hypothesized. Our metabolomics results confirmed the diel cycling of photorespiration (e.g., glycolate) and fermentation (e.g., acetate, propionate, and lactate) products, the carbon storage polymers polyhydroxyalkanoates, and dissolved gasses (e.g., H2 and CO2) in the waters overlying the mat, which were hypothesized to occur in major mat chlorophototrophic community members. In addition, we have formulated the following new hypotheses: (1) the morning hours are a time of biosynthesis of amino acids, DNA, and RNA; (2) photo-inhibited cells may also produce lactate via fermentation as an alternate metabolism; (3) glycolate and lactate are exchanged among Synechococcus and Roseiflexus spp.; and (4) fluctuations in many metabolite pools (e.g., wax esters) at different times of day result from species found at different depths within the mat responding to temporal differences in their niches.
Biological Sciences Division, Pacific Northwest National Laboratory Richland, WA, USA.
Young-Mo
YM
Kim
Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA ; Department of Mathematical Sciences, Montana State University Bozeman, MT, USA.
Shane
S
Nowack
Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA.
Millie T
MT
Olsen
Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA.
Eric D
ED
Becraft
Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA.
Jason M
JM
Wood
Department of Biochemistry and Molecular Biology, The Pennsylvania State University University Park, PA, USA.
Vera
V
Thiel
Department of Mathematical Sciences, Montana State University Bozeman, MT, USA ; Department of Mathematics, Temple University Philadelphia, PA, USA.
Isaac
I
Klapper
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.
Michael
M
Kühl
Biological Sciences Division, Pacific Northwest National Laboratory Richland, WA, USA.
James K
JK
Fredrickson
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.
Donald A
DA
Bryant
Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA.
David M
DM
Ward
Biological Sciences Division, Pacific Northwest National Laboratory Richland, WA, USA.
Thomas O
TO
Metz
Roseiflexus; Synechococcus; gas chromatography-mass spectrometry; metabolomics; microbial mats; polyhydroxyalkanoates; wax esters