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Structural proteins (SP) were obtained from chloroplast thylakoid membranes of tobacco leaf tissues 6 h after infiltration with either water or 108 cells/ml of Erwinia amylovora. Lipids were extracted from the thylakoid membranes of normal tobacco leaf tissues. Each of these three preparations was solubilized with sodium dodecyl sulfate and dialyzed against dilute beta buffer containing 20 m m -Mg2+. The SP from water-infiltrated tissues formed spherical aggregates whereas the SP from bacteria-infiltrated tissues aggregated into irregular clumps. The extracted lipid coalesced to form globules. Thin sections of the lipid revealed alternating light and dark bands. When solubilized lipid and the solubilized SP from water-infiltrated tissues were mixed and dialyzed, membrane-like structures approximating those of thylakoids in thickness were formed. Very few membrane-like structures were formed when the lipids were mixed with SP from bacteria-infiltrated tissues. Since the lipid used in these two experiments was identical, the inability to form membrane-like structures was attributed to the alteration in SP properties by hypersensitive reaction-induding bacteria.

Filamentous cells of Erwinia amylovora were usually 3 to 35 times longer than the normal rod-shaped ones, and only the former produced minicells.

Die Rontgen-Mikrographie benutzt Photoschicht und Lichtmikroskop zur Sichtbarmachung des Rontgen-Kontaktbildes. Die Auflosung ist durch die Leistung des Lichtmikroskops begrenzt. Das neue, von G.Mollenstedt angegebene Verfahren verwendet eine 200 A dicke, strukturlose Silberfolie und ein Elektronen-Immersionsobjektiv.

A toxin isolated from apple fruit tissue infected by Erwinia amylovora is 98 percent galactose in polymeric form, 0.375 percent protein, and has an average molecular weight of approximately 165,000. Young shoots of rosaceous, but not nonrosaceous, species wilt in a manner characteristic of the disease when placed in toxin solutions with concentrations as low as 10 micrograms per milliliter. Varieties of apple and pear susceptible to Erwinia amylovora wilt in 1 to 3 hours, whereas resistant varieties display symptoms 12 to 24 hours after treatment.

Thin sectioned cells of Erwinia amylovora revealed two electron-dense layers in their walls when fixed at 24 to 27 C and three when fixed at 4 C.