Autre Publication Scientifique Année : 2023

Intracellular calcium carbonate biomineralization in $Cyanothece$ sp. PCC 7425

Résumé

Cyanobacteria are Gram-negative photosynthetic bacteria that historically have been linked to bacterial carbonate biomineralization, a process involving the precipitation of carbonate minerals made thermodynamically possible by metabolically active bacteria. The recent discovery of intracellular calcium carbonate formation in cyanobacteria has raised numerous questions about the mechanisms underlying cyanobacterial biomineralization. Traditionally believed to occur exclusively extracellularly, this process has now been observed intracellularly in specific cyanobacterial strains. This project aimed to investigate the function of ccyA, a candidate marker gene for intracellular calcium carbonate formation (iACC), in Cyanothece sp. PCC 7425 through overexpression, deletion, and repression. The overexpression experiments of ccyA indicated a potential link between pH changes in growth media and Ca2+ uptake in Cyanothece sp. PCC 7425. While overexpression did not impact growth, it increased extracellular pH, usually an indicator for extracellular biomineralization. However, whether the changes in pH and Ca2+ uptake affected the formation of intracellular calcium carbonate granules remains to be investigated. For deletion, the modern CRISPR/Cas12a system successfully deleted two CAX genes used as technical controls in Cyanothece sp. PCC 7425, establishing the system as a valid method for genomic modification. However, complete chromosome segregation of ccyA deletion was not achieved, indicating that ccyA might be crucial for Cyanothece sp. PCC 7425 survival. Partially segregated mutants obtained can still offer valuable information on ccyA and intracellular biomineralization in future experiments. For repression, a CRISPR/dCas12a (CRISPRi) system was utilized. Experiments aimed at repressing nblA, a reporter gene, in Cyanothece sp. PCC 7425, did not produce a noticeable phenotype, likely due to physiological differences in Cyanothece sp. PCC 7425 as compared to model cyanobacteria used in previous research with nblA as a reporter. It could also be due to limitations in the inducibility of the CRISPRi system, with Cyanothece sp. PCC 7425 lacking the ability to import the inducer, IPTG. Overall, this study provides a foundation for further exploration into the role of ccyA in intracellular biomineralization and offers insights into optimizing genetic tools for studying gene function in Cyanothece sp. PCC 7425
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Dates et versions

hal-04875825 , version 1 (11-01-2025)

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  • HAL Id : hal-04875825 , version 1

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Tove Jonsson. Intracellular calcium carbonate biomineralization in $Cyanothece$ sp. PCC 7425. 2023. ⟨hal-04875825⟩
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