The phytopathogenic fungi Phytophthora cryptogea and Phytophthora capsici cause systemic leaf necrosis on their non‐host tobacco; in culture they release proteins, called cryptogein and capsicein, which elicit similar necrosis. In addition, both proteins protect tobacco against invasion by the pathogen Phytophthora nicotianae, the agent of the tobacco black shank, that is unable to produce such an elicitor. Cryptogein causes visible leaf necrosis starting at about 1 μg/plant, whereas 50‐fold as much capsicein is required for the same reaction. Capsicein induces protection even in near absence of leaf necrosis. The activities of both elicitors are eliminated upon pronase digestion. They are proteins of similar Mr (respectively 10323 and 10155) and their complete amino acid sequences were determined. They consist of 98 residues, with some internal repetitions of hexapeptides and heptapeptides. 85% identity was observed between both sequences: only two short terminal regions are heterologous, while the central core is entirely conserved. Secondary structure predictions, hydropathy and flexibility profiles differ only around position 15 and at the C‐terminus; these modifications could play a role in the modulation of their biological activities. After a search of the sequence data bases, they appear to be novel proteins.

The Yersinia genus includes human and animal pathogens (plague, enterocolitis). The fine structures of the endotoxin lipids A of seven strains of Yersinia enterocolitica, Yersinia ruckeri and Yersinia pestis were determined and compared using mass spectrometry. These lipids differed in secondary acylation at C-2P P: this was dodecanoic acid (C 12 ) for two strains of Y. enterocolitica and Y. ruckeri, tetradecanoic acid (C 14 ) in two other Y. enterocolitica and hexadecenoic acid (C 16:1 ) in Y. pestis. The enterocolitica lipids having a mass identical to that of Escherichia coli were found to be structurally different. The results supported the idea of a relation between membrane fluidity and environmental adaptability in Yersinia.z 2000 Federation of European Biochemical Societies.

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