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Physiology and Biochemistry

Comparative Membrane Characterization of Xanthomonas campestris pv. cassavae and X. campestris pv. manihotis. R. M. D. B. dos Santos, Former graduate student, Departamento de Biologia Vegetal, Universidade de Brasília, 70910, Brasília, DF, Brazil; J. C. Dianese, associate professor, Departamento de Biologia Vegetal, Universidade de Brasília, 70910, Brasília, DF, Brazil. Phytopathology 75:581-587. Accepted for publication 15 November 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-581.

Cell envelopes of Xanthomonas campestris pv. manihotis (Xcm) ENA-2648 and X. campestris pv. cassavae (Xcc) CIAT-1165 were obtained by sonication in the presence of lysozyme and fractionated into two bands by sucrose density gradient centrifugation. In both pathovars, the light band (density = 1.142 g/cm³) showed high nicotinamide adenine dinucleotide oxidase and succinate dehydrogenase activities, low contents of 2-keto-3-deoxyoctonate, and larger numbers of peptides in SDS-PAGE than are usually found in inner membrane. The heavy band (density = 1.255 g/cm³) showed a high level of 2-keto-3-deoxyoctonate, low enzymatic activity, and characteristic outer membrane pattern in SDS-PAGE. Changes in incubation temperature did not affect the SDS-PAGE patterns of the cell envelope of Xcm ENA-2648; however, a major 15-kdalton protein present in Xcc CIAT-1165 changed into a minor component when incubation was at 27.5 and 35 C. Four strains of Xcm and five of Xcc revealed major peptide bands at 114, 100, 41, 28.5, 26, and 22 kdaltons in SDS-PAGE. Membranes treated with 2% SDS at different temperatures showed heat-modifiable proteins in cell envelopes of both pathovars. A 41-kdalton, heat-modifiable peptide, shared in common by both pathovars, is apparently the OmpA protein of X. campestris. Major differences in peptide profiles between strains of Xcm and Xcc in SDS-PAGE were detected which suggested that the Colombian strains of Xcc are phylogenetically more related to Xcm than to the African strains of Xcc.