STARVED PSEUDOMONAS-SYRINGAE CELLS RELEASE STRONG CU2+-COMPLEXING COMPOUNDS

Pseudomonas syringae cells suspended in Na+-piperazinediethanesulphonate (PIPES) buffer at 24.5-degrees-C released UV-absorbing materials, free and purine-bound ribose and inorganic phosphate. When the filtrates of the suspensions were titrated with Cu2+, a significant fraction of added copper was not free in solution. An increase in the starvation period resulted in an increase in the amount of released UV-absorbing materials, free and purine-bound ribose and inorganic phosphate, and an increase in the Cu2+-binding capacity of the filtrates. The results indicate that starved P. syringae cells released strong Cu2+-binding substances, which were partially products of endogenous metabolism, and suggest that inorganic phosphate contributed significantly to the Cu2+-binding capacity of the filtrates.