The Greening Organism is a Gram Negative Bacterium

Abstract

One of four periwinkle plants connected by dodder to a Madame Vinous sweet orange seedling infected with Indian greening developed yellowing symptoms within 6 months. Electron microscopy of leaf midribs of chlorotic leaves revealed the bacteria-like organisms in the sieve tubes morphologically and ultra structurally identical to those found in greening-affected citrus, and indicated that the greening organism (GO) was transmitted from affected citrus to periwinkle by dodder. The GO was graft-transmitted from periwinkle to periwinkle and GO multiplied more actively in periwinkle than in citrus. The cytochemical treatments previously developed to visualize the PG layer of E. coli were applied to the GO. Papain digestion revealed an additional layer between the outer and the inner membrane of the GO which disappeared after lysozyme digestion and is therefore thought to be PG. The presence of PG in the envelope of the GO is direct proof for the bacterial nature of the GO and since the structure of the GO envelope was found to be similar to that of E. coli, but quite different from that of Staph~yloccocus aureus, the GO is very probably a Gram-negative bacterium.