Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole
Little Salt Spring (Sarasota County, FL, USA) is a sinkhole with groundwater vents at ~77 m depth. The entire water column experiences sulfidic (~50 μM) conditions seasonally, resulting in a system poised between oxic and sulfidic conditions. Red pinnacle mats occupy the sediment–water interface in...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
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Wiley Blackwell
2018
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| Online Access: | http://hdl.handle.net/1721.1/118593 https://orcid.org/0000-0002-7144-8537 |
| _version_ | 1811087121434279936 |
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| author | Hamilton, T. L. Welander, P. V. Albrecht, H. L. Fulton, J. M. Schaperdoth, I. Bird, L. R. Freeman, K. H. Macalady, J. L. Summons, Roger E |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Hamilton, T. L. Welander, P. V. Albrecht, H. L. Fulton, J. M. Schaperdoth, I. Bird, L. R. Freeman, K. H. Macalady, J. L. Summons, Roger E |
| author_sort | Hamilton, T. L. |
| collection | MIT |
| description | Little Salt Spring (Sarasota County, FL, USA) is a sinkhole with groundwater vents at ~77 m depth. The entire water column experiences sulfidic (~50 μM) conditions seasonally, resulting in a system poised between oxic and sulfidic conditions. Red pinnacle mats occupy the sediment–water interface in the sunlit upper basin of the sinkhole, and yielded 16S rRNA gene clones affiliated with Cyanobacteria, Chlorobi, and sulfate-reducing clades of Deltaproteobacteria. Nine bacteriochlorophyll e homologues and isorenieratene indicate contributions from Chlorobi, and abundant chlorophyll a and pheophytin a are consistent with the presence of Cyanobacteria. The red pinnacle mat contains hopanoids, including 2-methyl structures that have been interpreted as biomarkers for Cyanobacteria. A single sequence of hpnP, the gene required for methylation of hopanoids at the C-2 position, was recovered in both DNA and cDNA libraries from the red pinnacle mat. The hpnP sequence was most closely related to cyanobacterial hpnP sequences, implying that Cyanobacteria are a source of 2-methyl hopanoids present in the mat. The mats are capable of light-dependent primary productivity as evidenced by13C-bicarbonate photoassimilation. We also observed13C-bicarbonate photoassimilation in the presence of DCMU, an inhibitor of electron transfer to Photosystem II. Our results indicate that the mats carry out light-driven primary production in the absence of oxygen production—a mechanism that may have delayed the oxygenation of the Earth's oceans and atmosphere during the Proterozoic Eon. Furthermore, our observations of the production of 2-methyl hopanoids by Cyanobacteria under conditions of low oxygen and low light are consistent with the recovery of these structures from ancient black shales as well as their paucity in modern marine environments. |
| first_indexed | 2024-09-23T13:39:47Z |
| format | Article |
| id | mit-1721.1/118593 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T13:39:47Z |
| publishDate | 2018 |
| publisher | Wiley Blackwell |
| record_format | dspace |
| spelling | mit-1721.1/1185932022-10-01T16:24:32Z Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole Hamilton, T. L. Welander, P. V. Albrecht, H. L. Fulton, J. M. Schaperdoth, I. Bird, L. R. Freeman, K. H. Macalady, J. L. Summons, Roger E Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Summons, Roger E Little Salt Spring (Sarasota County, FL, USA) is a sinkhole with groundwater vents at ~77 m depth. The entire water column experiences sulfidic (~50 μM) conditions seasonally, resulting in a system poised between oxic and sulfidic conditions. Red pinnacle mats occupy the sediment–water interface in the sunlit upper basin of the sinkhole, and yielded 16S rRNA gene clones affiliated with Cyanobacteria, Chlorobi, and sulfate-reducing clades of Deltaproteobacteria. Nine bacteriochlorophyll e homologues and isorenieratene indicate contributions from Chlorobi, and abundant chlorophyll a and pheophytin a are consistent with the presence of Cyanobacteria. The red pinnacle mat contains hopanoids, including 2-methyl structures that have been interpreted as biomarkers for Cyanobacteria. A single sequence of hpnP, the gene required for methylation of hopanoids at the C-2 position, was recovered in both DNA and cDNA libraries from the red pinnacle mat. The hpnP sequence was most closely related to cyanobacterial hpnP sequences, implying that Cyanobacteria are a source of 2-methyl hopanoids present in the mat. The mats are capable of light-dependent primary productivity as evidenced by13C-bicarbonate photoassimilation. We also observed13C-bicarbonate photoassimilation in the presence of DCMU, an inhibitor of electron transfer to Photosystem II. Our results indicate that the mats carry out light-driven primary production in the absence of oxygen production—a mechanism that may have delayed the oxygenation of the Earth's oceans and atmosphere during the Proterozoic Eon. Furthermore, our observations of the production of 2-methyl hopanoids by Cyanobacteria under conditions of low oxygen and low light are consistent with the recovery of these structures from ancient black shales as well as their paucity in modern marine environments. National Science Foundation (U.S.) (Grant EAR‐0525503) United States. National Aeronautics and Space Administration (Grant NNA04CC06A) United States. National Aeronautics and Space Administration (Grant NNA13AA90A) 2018-10-16T19:48:43Z 2018-10-16T19:48:43Z 2017-10 2016-09 2018-10-02T17:55:05Z Article http://purl.org/eprint/type/JournalArticle 1472-4677 1472-4669 http://hdl.handle.net/1721.1/118593 Hamilton, T. L. et al “Microbial Communities and Organic Biomarkers in a Proterozoic-Analog Sinkhole.” Geobiology 15, 6 (October 2017): 784–797 © 2017 The Authors https://orcid.org/0000-0002-7144-8537 http://dx.doi.org/10.1111/GBI.12252 Geobiology Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/ application/pdf Wiley Blackwell Wiley |
| spellingShingle | Hamilton, T. L. Welander, P. V. Albrecht, H. L. Fulton, J. M. Schaperdoth, I. Bird, L. R. Freeman, K. H. Macalady, J. L. Summons, Roger E Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole |
| title | Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole |
| title_full | Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole |
| title_fullStr | Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole |
| title_full_unstemmed | Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole |
| title_short | Microbial communities and organic biomarkers in a Proterozoic-analog sinkhole |
| title_sort | microbial communities and organic biomarkers in a proterozoic analog sinkhole |
| url | http://hdl.handle.net/1721.1/118593 https://orcid.org/0000-0002-7144-8537 |
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