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Resistance of Cyanobacteria (Synechococcus SP. PCC 7002) to Sulfide compound

Synechococcus sp. PCC7002 was cultured in the medium A2, a modification of Stevens et al. (1973) on a rotary shaker (100 rpm). The initial concentration of cells is controlled to an OD730 of 0.1 in fresh medium. Different concentration of sodium sulfide is added, and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was put into experimental group. Cells are grown in the six-well-plates and monitored under OD730 every 24 hour.

This experiment is similar to the second one of Synechococcus SP. PCC 7002 testing series. The main idea was to find the suitable DCMU concentration for Synechococcus SP. PCC 7942. As a matter of fact, both wild type and sqr expressing strain are used in the experiment.

It was expected that SQR expressing strain and wild type counterpart would have different growth rate under the presence of sulfide compounds. Though sulfide is naturally toxic to Synechococcus SP. PCC 7942, the strain with sqr should be able to metabolize sulfide and therefore prosper. As the result, we analyze H2S amount to detect whether sqr gene work or not. Therefore, we perform Chemical microvolume turbidimetry method to detect H2S concentration (see Sulfur Oxide Terminator part)

Repots have it that Escherichia coli can express functional sulfide-quinone reductase (SQR). Therefore, we slightly adjusted the previous experiment and applied to the SQR gene from Synechococcus SP. PCC 7002. With methylene blue method, we would test the efficiency of SQR sulfide oxidation. Since such method involved in measurement of optical density, it is more appropriate to perform such experiment on colorless bacteria instead of engineered cyanobacteria strain.