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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.

Synechococcus sp. PCC7002 was cultured in the medium A2, rotary shaker and initial cell concentration are the same as the last experiment. DCMU is diluted with A2 medium into different concentration, and 10 mM of sodium sulfide is added to the experimental group. The measurement method and frequency of cell growth has been described previously.

With the result of previous experiment, the concentration of both sodium sulfide and DCMU is adjusted. Sodium sulfide is diluted from 40mM to 2.5mM, while DCMU 0.5 μM is added into the experimental group.

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.