Fig. 4.

Effect of prolonged exposure to sulfur deprivation and subsequent sulfate repletion for wild-type and Δraf1 Synechocystis cells. Independent cyanobacterial cultures were transferred to sulfur-depleted BG-11 medium and grown subsequently for an additional 3, 5, or 7 days. a A total of 20 µg of crude protein extracts from cells collected after treatment were loaded per lane, separated under denaturing conditions, and probed with anti-RbcL antibodies (b). The ability of both strains to recover after sulfur depletion was tested by direct supplementation of starved cultures with MgSO₄ after 3, 5, or 7 days of treatment. c A total of 20 µg of crude protein extracts from cells collected after 2-day sulfate re-supplementation were loaded per lane, separated under denaturing conditions, and probed with anti-RbcL antibodies (d). Positions of proteins with altered amounts specific for “mild starvation phenotype” of mutant cells are indicated with arrows. e Absorbance spectra of wild-type and mutant cells were measured after 7 days of sulfur starvation and following 48 h of sulfate re-supplementation (f; control—untreated wild-type cells)