Abstract: Slr0351 is an unknown protein and its homologs exist widely in many cyanobacteria and iron-sulfur bacteria.We constructed pET-slr0351 and expressed Slr0351 successfully in E.coli BL21.Using affinity chromatography purification,we obtained purified Slr0351.Under anaerobic conditions,Slr0351 was brown and had absorption peak at 460 nm,which was the characteristic absorption peak of 2Fe-2S cluster.The brown Slr0351 is sensitive to oxygen and could be reduced with sodium dithionite,showing that Slr0351 was iron-sulfur protein.By homologous double-crossover,slr0351 was replaced by Kana,resulting in the knockout mutant of Synechocystis sp. PCC 6803,Δslr0351.Via scanning the absorption spectra of Δslr0351 and WT with ultraviolet-visible spectrometer,we found that chlorophyll a content of Δslr0351 is only 68.8% that of WT under the medium light condition.The depletion of slr0351 reducing the content of chlorophyll a in Synechocystis cells.Compared the growth rate of cyanobacteria under different culture conditions,Δslr0351 showed the following changes compared to the wild type:(1)more sensitive to sulfur and iron starvation;(2)lower efficiency of light utilization and lower growth rate under LL conditions,which is related to the lower content of chlorophyll a in Δslr0351.This paper is beneficial to gene function research of Cyanobacteria,and provides a certain reference value for the treatment of Cyanobacteria bloom and pollution in freshwater.