Knowing whether or not marine microbes participate in photosynthesis – the use of sunlight to turn carbon dioxide and water into energy – could help scientists find out if ocean bacteria play a role in the global cycle. carbon.
However, most marine microbes remain unstudied, in part because they do not grow in laboratory conditions, which limits the scientific community’s knowledge of the use of photosynthesis by these species.
Researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences (CAS) have directly identified carbon dioxide-fixing cells – or cells that absorb CO2 – seawater and used a Raman spectroscopy technique to determine that their sample contains functional genes for light harvesting, suggesting that the bacteria engage in photosynthesis.
Their results were published in BioDesign Research on October 21.
Chlorophyll-based photosynthesis is a well-known light-harvesting system for CO2 fixation. Photosynthesis based on a type of protein known as proteorhodopsin, or PR, has been reported to fix CO2 in the presence of light. Subsequently, some types of CO2-binding in marine bacteria have been reported. “Bacteria containing PRs might be the most abundant, and microbial rhodopsins, another type of protein, might be a major contributor to solar energy harvesting in the oceans.” However, it remains unclear whether bacteria containing naturally occurring PRs can fix CO2“, said co-first author JING Xiaoyan, senior engineer at the single-cell center of QIBEBT.
Researchers first identified CO2-fix the cells of seawater taken from the euphotic zone – or the highest zone of the ocean, exposed to the sun – of the Yellow Sea of China by monitoring their consumption of a C-bicarbonate compound. To do this, the researchers used single-cell Raman spectra (SCRS), a technique used to study molecules. “Next, we used a technique called Raman-activated Gravity-driven Encapsulation, or RAGE, to isolate target cells of Pelagibacter, the bacterium we studied, which is part of the SAR11 group of bacteria,” said the co- first author XU Teng, postdoc. at the unicellular center of QIBEBT. The researchers amplified the genomes of these isolated Pelagibacter cells and sequenced each cell.
“Using a Raman-enabled enhanced cell sorting technique that sorts and sequences the microbiome at precise one-cell resolution, we reveal that Pelagibacter spp., one of the most abundant marine SAR11 bacteria, can utilize fueled metabolism by light for CO2 fixation in seawater and thereby contribute to the global carbon cycle,” said co-first author GONG Yanhai, adjunct researcher at QIBEBT’s Single-Cell Center.
“This study demonstrates that RAGE-mediated analysis of a single-cell genome can reliably link the phenotype and genotype of uncultured bacteria in the ocean, solving a fundamental problem and paving the way for a dissection based on the function of ‘biological dark matter’ in the environment,” said co-corresponding author Professor HUANG Wei from the University of Oxford.
“Further investigations could be extended to other seawater samples from different depths and regions,” said Professor XU Jian from the QIBEBT Single Cell Center. “Furthermore, it is worth integrating and applying both SCRS and single-cell transcriptomics techniques for further CO studies.2-repair microbes.
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