Figure 1.

Phosphorylation state of PII in wild-type (wt) and sll1771 inactivated (MPphA) cells of Synechocystis PCC6803. (A) Response to ammonium treatment; cells were first grown in BG11-medium (lane 1), then NH₄Cl was added (5 mM final concentration) and after 5 min (2), 15 min (3), and 30 min (4) aliquots were removed and the phosphorylation state of PII was analyzed. (B) Response to different carbon conditions: (Left) Cells grown in BG11-medium were treated with an inhibitor of CO₂-fixation, d,l-glyceraldehyde (d,l-GA). Negative control (−) and after 5 min in the presence of 30 mM d,l-GA (+); (Right) cells grown under CO₂-poor conditions in Allan and Arnon's medium, which is devoid of carbonate and bicarbonate. (C) Response toward methylviologen (MV): to BG11-grown cells 0.1 mM MV was added and, after 5 min, the phosphorylation state of PII was analyzed.