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Cyanobacterial microborings

Cyanobacterial microborings in carbonate rocks – molecular mechanisms and biogeochemical implications

Experimental setup and work packages for the comparison of microboring capacity of cyanobacteria with no (-), moderate (+), or high (++) eCA-activity. The cyanobacteria are applied to varying calciumcarbonate surfaces. Resulting micro-borings are first evaluated two-dimensionally via thin sections. Afterwards, the total volume of the borings is assessed three-dimensionally using a micro-computer-tomograph (micro-CT). Finally, correlation analysis is used to compare boring volume with eCA-activity.
Experimental setup and work packages for the comparison of microboring capacity of cyanobacteria with no (-), moderate (+), or high (++) eCA-activity. The cyanobacteria are applied to varying calciumcarbonate surfaces. Resulting micro-borings are first evaluated two-dimensionally via thin sections. Afterwards, the total volume of the borings is assessed three-dimensionally using a micro-computer-tomograph (micro-CT). Finally, correlation analysis is used to compare boring volume with eCA-activity.

Duration: 7.24 – 6.25

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Project team:

Prof. Dr. Marcel Dann
FB 10, Bio-Inspired Energy Conversion

Dr. Michaela Falkenroth
FB 11, Applied Sedimentary Geology

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Project description:

The vast majority of carbonate rocks is considered biological in origin, but our understanding of the molecular mechanisms underlying bio-mediated carbonate rock formation and dissolution is very patchy. Especially microbial corrosion of carbonate rocks under alkaline and calcium carbonate (CaCO3) saturated conditions remains an elusive process at the interface of geology and biology. Cyanobacteria are microbes mediating both carbonate precipitation and corrosion, but while the former is reasonably well understood, the latter remains a puzzle regarding both its molecular mechanism and physiological relevance. In this project we set out to experimentally determine the involvement of cyanobacterial extracellular carbonic anhydrase enzymes (eCAs) in mediating localized carbonate corrosion, resulting in microbial boring tunnels and reprecipitation of highly specific carbonate minerals (micrites) frequently observed in natural carbonate rocks. The results of this work will not only inform geological models for paleoclimate reconstruction, but also strategies for long-term carbonate stabilization as a means of carbon sequestration.