5:15 PM - 6:45 PM
[BBG01-P02] Mapping cyanobacterial biomarkers in modern hot spring stromatolites by MALDI-TOF/MS imaging method
Keywords:Biomarker, MALDI-TOF/MS, Stromatolite, Cyanobacteria
Biomarkers are essential tools for identifying specific groups of organisms within geological samples, providing valuable insights into the origin and evolution of life on Earth. Traditional biomarker detection methods, such as gas or liquid chromatography/mass spectrometry, require sample pulverization and extraction, resulting in the loss of spatial distribution information of the targeted biomarkers within the sample. However, spatial information regarding biomarkers within the sample is crucial for assessing contamination in newer geological periods. In this study, we investigated a method for biomarker mapping using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) to preserve positional information within sediment samples.
The focus of the study was on stromatolites, which are considered to be part of the geological record of cyanobacteria. Modern hot spring stromatolite samples were examined, following prior investigations via phylogenetic analysis and microscopic observation. The samples were embedded in resin, cut into 50 µm-thick sections, mounted on indium-coated glass slides, covered with 2,5-Dihydroxybenzoic Acid (DHB) as a matrix reagent, and analyzed in positive ion mode. 2-methylhopane served as the standard material for cyanobacterial biomarker analysis. Analysis of the standard material revealed major peaks at m/z=191/192 and 368/369, corresponding to fragments where the end of the 2-methylhopane molecule was replaced by a hydrogen group instead of a methane group. These fragments were also found in hopane, a biomarker of eubacteria. Fragments containing a methane group from 2-methylhopane (m/z=205 and 383) were also detected in the standard materials, albeit with relatively lower counts. A similar peak trend was observed in the modern stromatolite samples, particularly in areas densely populated by cyanobacteria. This examination demonstrated that the distribution pattern of cyanobacteria in stromatolites can be mapped using the MALDI-TOF/MS imaging method, mainly by hopane fragments. Especially, m/z=368 peak was also detected within a 2.7 Ga fossil stromatolite (Yamaguchi et al. 2023). Our results will lead to developing techniques to verify cyanobacteria traces from fossil stromatolite samples.
[Ref] Yamaguchi et al. (2023) In 6th International Archean Symposium, Abstracts (Compilers: Gessner et al.), Geological Survey of Western Australia, Record 2023/8,196p, Perth, Australia, July 25-27, p.46.
The focus of the study was on stromatolites, which are considered to be part of the geological record of cyanobacteria. Modern hot spring stromatolite samples were examined, following prior investigations via phylogenetic analysis and microscopic observation. The samples were embedded in resin, cut into 50 µm-thick sections, mounted on indium-coated glass slides, covered with 2,5-Dihydroxybenzoic Acid (DHB) as a matrix reagent, and analyzed in positive ion mode. 2-methylhopane served as the standard material for cyanobacterial biomarker analysis. Analysis of the standard material revealed major peaks at m/z=191/192 and 368/369, corresponding to fragments where the end of the 2-methylhopane molecule was replaced by a hydrogen group instead of a methane group. These fragments were also found in hopane, a biomarker of eubacteria. Fragments containing a methane group from 2-methylhopane (m/z=205 and 383) were also detected in the standard materials, albeit with relatively lower counts. A similar peak trend was observed in the modern stromatolite samples, particularly in areas densely populated by cyanobacteria. This examination demonstrated that the distribution pattern of cyanobacteria in stromatolites can be mapped using the MALDI-TOF/MS imaging method, mainly by hopane fragments. Especially, m/z=368 peak was also detected within a 2.7 Ga fossil stromatolite (Yamaguchi et al. 2023). Our results will lead to developing techniques to verify cyanobacteria traces from fossil stromatolite samples.
[Ref] Yamaguchi et al. (2023) In 6th International Archean Symposium, Abstracts (Compilers: Gessner et al.), Geological Survey of Western Australia, Record 2023/8,196p, Perth, Australia, July 25-27, p.46.