Effect of iron and other nutrient limitations on the pattern of outer membrane proteins in the cyanobacterium Synechococcus PCC7942

When cells of Synechococcus PCC7942 were subjected to either iron or magnesium limitation, there was an appearance of specific proteins in the outer membrane (isolated as the cell wall fraction). Under iron limitation outer membrane polypeptides of M sub(r) 92,000, 48,000-50,000 and 35,000 appeared. Specific iron-limited outer membrane proteins (IRMPs) of M sub(r) 52,000 and 36,000 were also induced in iron-limited cultures of Synechocystis) PCC6308. Under magnesium limitation polypeptides of M sub(r) 80,000, 67,000, 62,000, 50,000, 28,000 and 25,000 appeared in the outer membrane. Phosphate limitation caused minor changes in the outer membrane protein pattern, with polypeptides of M sub(r) 32,000 and one of over 100,000 being induced, whereas calcium limitation had no apparent affect.