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Assembly and Quantification of Co-Cultures Combining Heterotrophic Yeast with Phototrophic Sugar-Secreting Cyanobacteria
Published on: December 27, 2024
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Cyanophycinase is required for heterotrophy in cyanobacteria
Éva Kiss1, Martin Moos2, Jan Mareš3
1Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czech Republic.
The Journal of Biological Chemistry
|October 8, 2025
Summary
Cyanophycinase (CphB) is crucial for heterotrophic growth in Synechocystis, regulating arginine biosynthesis and carbon-nitrogen balance. Its absence impairs growth by disrupting these metabolic pathways.
Area of Science:
- Microbiology
- Biochemistry
- Metabolic Engineering
Background:
- Cyanophycin, a nitrogen-rich biopolymer, is synthesized by cyanophycin synthase (CphA) and degraded by cyanophycinase (CphB).
- CphB is conserved in cyanobacteria, but its function in non-diazotrophs like Synechocystis remains unclear.
- While CphB is linked to nitrogen metabolism in diazotrophs, its role in non-diazotrophs, particularly during heterotrophy, is not well understood.
Purpose of the Study:
- To investigate the role of cyanophycinase (CphB) in the metabolic adaptation of Synechocystis sp. PCC 6803 to heterotrophic conditions.
- To elucidate the connection between cyanophycin metabolism and arginine biosynthesis in non-diazotrophic cyanobacteria.
- To understand the regulatory mechanisms underlying heterotrophic growth in Synechocystis.
Main Methods:
- Construction and phenotypic analysis of Synechocystis ΔcphB and ΔcphA deletion strains.
- Comparative growth studies under photoautotrophic and heterotrophic conditions.
- Metabolomics profiling to analyze metabolic changes in the ΔcphB mutant.
- In vitro enzyme activity assays to study the interaction between CphB and arginine biosynthetic enzymes.
Main Results:
- The Synechocystis ΔcphB deletion strain exhibited no photoautotrophic growth defect but failed to proliferate heterotrophically.
- Metabolomics revealed that ΔcphB failed to upregulate arginine biosynthesis and showed misregulated carbon and nucleoside metabolism.
- In vitro assays demonstrated that CphB interacts with acetylornithine aminotransferase, stimulating cyanophycin hydrolysis.
Conclusions:
- CphB is essential for heterotrophic growth in Synechocystis, likely by activating arginine biosynthesis pathways.
- Cyanophycin catabolism and arginine biosynthesis appear to be mutually coregulated pathways, crucial for balancing carbon and nitrogen during heterotrophic acclimation.
- The study highlights a novel metabolic role for CphB beyond nitrogen mobilization in non-diazotrophic cyanobacteria.
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