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* Abbreviations for members ofthe folic acidgroup, based on PtG for pteroylglutamate: H4PtG, tetrahydropteroylmonoglutamate; H4PtG3, tetrahydropteroyltriglutamate; derivatives of these compounds are indicated as, e.g., N5-methyl-H4PtG.

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Erythrocytes and different strains of plant pathogenic bacteria agglutinated with aqueous and saline 1M NaCl extracts from Phaseolus vulgaris L. seeds, which showed similar gel electrophoretic patterns of proteins. Haemagglutinating activity in aqueous extracts was inhibited by some carbohydrates, especially N‐acetyl‐D‐galactosamine, D‐galactose and lactose. The agglutinin in this extract was purified by utilizing its ability to bind to Pseudomonas pisi cells followed by its removal from the bacteria by 0.3M galactose. Mitogenic activity of purified agglutinin was calculated as incorporation of 125I‐iododesoxy‐uridine into DNA of lymphocytes in vitro, which gave values between 25 and 50 μg/ml. The molecular weight of the subunits was found to be 31,500, estimated by mobility in SDS‐PAGE. A solid phase competition‐binding radioimmunoassay for bean agglutinin was developed in order to determine the affinity of this lectin in bean plants to phytopathogenic bacteria. The highest level of affinity was associated with the system formed by, Ps. pisi and lectin from fresh seeds.

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Die Entwicklung phytopathogener und nicht phytopathogener Bakterienpopulationen in einem Pflanzengewebe verliiuft nach KLEMENT et al. (1964) Von den eingesetzten Salzen hat Ca(NO,), eine starke Wirkung auf das Wachstum von E. carotovora. Wie Abbildung 1 zeigt, geniigt eine Konzentration von 0,5y0, um eine Wachstumshemmung von 12% zu erreichen. Bei 1,5% betriigt die Wachstumshemmung 60%. MgSO, beeinflulit das Wachstum der Bakterien bei einer Konzentration von 1,5% kaum, und eine 60y0ige Wachstumshemmung wird erst bei 8% erreicht (Abb. 2). Die Enzymsynthese ulrd von beiden Salzen gehemmt, obgleich sich der Versuchsstamm gegenuber Ca(NO,), als vie1 empfindlicher erwies (Abb. 3). Bei Anwesenheit von Ca(NO,), entstehen auch bereits bei einer Konzentration von 0,5% Filamente, die 15 bis 20mal so lang sind wie die normalen Zellen, wiihrend sich die Zellform der Bakterien beim Vorhandensein von MgSO, (bis 8%) nicht veriindert.Dieser unterschiedliche Effekt scheint bei beiden Kationen nicht mit der Konzentration korreliert zu sein, sondern konnte vielmehr mit den Prozessen auf metabolischer Ebene in Verbindung gebracht werden. Das Entstehen von filamentosen Formen bei gramnegativen Bakterien wurde von WEBB (1949) dem Mange1 an Magnesium

Extracellular components of plant pathogenic bacteria were obtained from their culture medium as well as from the whole cells by using NaCl 1 M, pH 6.0; 20% sucrose dissolved in 0.03 M Tris buffer, pH 8.0; or 0.05 M Na2EDTA. All the extracts from Erwinia carotovora subsp. carotovora, Xanthomonas campestris pv. campestris, Pseudomonas syringae pv. phaseolicola, Xanthomonas campestris pv. phaseoli, Pseudomonas solanacearum, and Erwinia carotovora subsp. atroseptica, were assayed for hemagglutinating activity on sheep, rabbit and chicken red blood cells (RBCs). The only active extracts were those obtained by NaCl treatment. They agglutinated sheep and rabbit erythrocytes. Extracts from E. carotovora subsp. atroseptica gave rise to the high agglutination titer on rabbit RBCs. These extracts had the lowest polysaccharide/protein ratio. E. carotovora subsp. carotovora extracts showed only a low titer (18.5 units). The agglutinating activity present in NaCl extracts of the bacteria tested was inhibited by different carbohydrates to various extent. Extracts from E. carotovora subsp. atroseptica appeared to be the most sensitive ones while those of E. carotovora subsp. carotovora least sensitive to the presence of sugar. It is suggested that hemagglutinins observed in plant pathogenic bacteria and those in plant host are similar and that both may, in some way, be involved in the plant-parasite relationship.