Selective inhibition of photosynthesis
is a fundamental strategy
to solve the global challenge caused by harmful cyanobacterial blooms.
However, there is a lack of specificity of the currently used cyanocides,
because most of them act on cyanobacteria by generating nontargeted
oxidative stress. Here, for the first time, we find that the simplest
β-diketone, acetylacetone, is a promising specific cyanocide,
which acts on Microcystis aeruginosa through targeted binding on bound iron species in the photosynthetic
electron transport chain, rather than by oxidizing the components
of the photosynthetic apparatus. The targeted binding approach outperforms
the general oxidation mechanism in terms of specificity and eco-safety.
Given the essential role of photosynthesis in both natural and artificial
systems, this finding not only provides a unique solution for the
selective control of cyanobacteria but also sheds new light on the
ways to modulate photosynthesis.
The regulation of photosynthetic
machinery with a nonoxidative
approach is a powerful but challenging strategy for the selective
inhibition of bloom-forming cyanobacteria. Acetylacetone (AA) was
recently found to be a target-selective cyanocide for Microcystis aeruginosa, but the cause and effect
in the studied system are still unclear. By recording of the chemical
fingerprints of the cells at two treatment intervals (12 and 72 h
with 0.1 mM AA) with omics assays, the molecular mechanism of AA in
inactivating Microcystis aeruginosa was elucidated. The results clearly reveal the effect of AA on ferredoxin
and the consequent effects on the physiological and biochemical processes
of Microcystis aeruginosa. In addition
to its role as an electron acceptor of photosystem I, ferredoxin plays
pivotal roles in the assimilation of nitrogen in cyanobacterial cells.
The effect of AA on ferredoxin and on nonheme iron of photosystem
II first cut off the photosynthetic electron transfer flow and then
interrupted the synthesis of adenosine triphosphate (ATP) and reduced
nicotinamide adenine dinucleotide phosphate (NADPH), which ultimately
might affect carbon fixation and nitrogen assimilation metabolisms.
The results here provide missing pieces in the current knowledge on
the selective inhibition of cyanobacteria, which should shed light
on the better control of harmful blooms.
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