¹³C-labeled single-cell Raman sorting reveals sulfur-driven dark carbon fixation in coastal sediments

Area of Science:

• Microbial Ecology
• Biogeochemistry
• Spectroscopy

Background:

• Chemoautotrophs are vital for carbon fixation in coastal sediments but are difficult to study due to being largely uncultured.
• Understanding their in situ activities is crucial for marine carbon cycling and blue carbon ecosystems.

Purpose of the Study:

• To develop a cultivation-independent single-cell method for identifying active chemoautotrophs in coastal sediments.
• To establish function-specific spectral biomarkers for direct in situ activity assessment.
• To link microbial activity with genomic potential for a mechanistic understanding of carbon fixation.

Main Methods:

• Combined Raman spectroscopy with 13C-stable isotope probing for single-cell analysis.
• Identified functional spectral biomarkers (cytochrome c, phenylalanine Raman bands) for active chemoautotrophs.
• Utilized targeted metagenomic sequencing and pure culture verification for dominant species identification.

Main Results:

• Successfully identified active chemoautotrophs and their carbon fixation pathways (Calvin-Benson-Bassham cycle) in sulfur-oxidizing guilds.
• Isolated a novel sulfur-oxidizing chemoautotroph, Guyparkeria sp. TX1, validating the Raman-based screening approach.
• Established Raman-based functional biomarkers for mapping microbial carbon fluxes in situ.

Conclusions:

• This study provides a robust method for in situ functional screening of chemoautotrophs using Raman spectroscopy.
• Advances the understanding of sulfur-driven dark carbon fixation, a key process in coastal blue carbon ecosystems.
• Integrates single-cell activity with genomic data to reveal microbial carbon flux mechanisms.