Separation of the factor inducing medium alkalinization by anion exchange chromatography and SDS-PAGE. Coomassie-blue stained SDS gel with bacterial extract (1), and elicitor-active fraction obtained after separation on anion exchange chromatography (2). Lanes (1) and (2) were cut in slices of 2 mm, eluted and eluates assayed for induction of alkalinization in tomato cells.