Cyanobacterial Alkanes Modulate Photosynthetic Cyclic Electron Flow to Assist Growth under Cold Stress

Bertram M. Berla, Rajib Saha, Costas D. Maranas, Himadri B. Pakrasi

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

All cyanobacterial membranes contain diesel-range C15-C19 hydrocarbons at concentrations similar to chlorophyll. Recently, two universal but mutually exclusive hydrocarbon production pathways in cyanobacteria were discovered. We engineered a mutant of Synechocystis sp. PCC 6803 that produces no alkanes, which grew poorly at low temperatures. We analyzed this defect by assessing the redox kinetics of PSI. The mutant exhibited enhanced cyclic electron flow (CEF), especially at low temperature. CEF raises the ATP:NADPH ratio from photosynthesis and balances reductant requirements of biosynthesis with maintaining the redox poise of the electron transport chain. We conducted in silico flux balance analysis and showed that growth rate reaches a distinct maximum for an intermediate value of CEF equivalent to recycling 1 electron in 4 from PSI to the plastoquinone pool. Based on this analysis, we conclude that the lack of membrane alkanes causes higher CEF, perhaps for maintenance of redox poise. In turn, increased CEF reduces growth by forcing the cell to use less energy-efficient pathways, lowering the quantum efficiency of photosynthesis. This study highlights the unique and universal role of medium-chain hydrocarbons in cyanobacterial thylakoid membranes: they regulate redox balance and reductant partitioning in these oxygenic photosynthetic cells under stress.

Original languageEnglish (US)
Article number14894
JournalScientific reports
Volume5
DOIs
StatePublished - Oct 13 2015
Externally publishedYes

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Alkanes
Electrons
Oxidation-Reduction
Growth
Hydrocarbons
Reducing Agents
Photosynthesis
Plastoquinone
Synechocystis
Thylakoids
Temperature
Membranes
Recycling
Cyanobacteria
Chlorophyll
Electron Transport
NADP
Computer Simulation
Adenosine Triphosphate
Maintenance

ASJC Scopus subject areas

  • General

Cite this

Cyanobacterial Alkanes Modulate Photosynthetic Cyclic Electron Flow to Assist Growth under Cold Stress. / Berla, Bertram M.; Saha, Rajib; Maranas, Costas D.; Pakrasi, Himadri B.

In: Scientific reports, Vol. 5, 14894, 13.10.2015.

Research output: Contribution to journalArticle

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