Comparative Protein Studies of SeveralPythiumSpecies Using Isoelectric Focusing

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Abstract
Buffer-soluble mycelial proteins of six species of Pythium were compared by isoelectric focusing. Species studied included P. aphanidermatum (P.a.), P. deliense (P.de.), P. myriotylum (P.m.), P. dissotocum (P.di.), P. violae (P.v.), P. ultimum var. ultimum (P.u.u.) and P.u. var. sporangiferum (P.u.s.). Each species had one or more distinct bands, in addition to many common bands of protein, when focused between pH 4–8. A higher concentration of proteins focused in the acidic region of broad pH range gels. Major protein bands were detected with Coomassie stain. Silver staining increased detection of proteins in low concentration (minor bands) in acidic, neutral, and alkaline regions. Other distinct bands of protein were identified for each species when protein samples were further resolved by focusing in the acidic region (pH 3–6). Several isolates each of P.a., P.u., and P.de., collected from various regions of North America, produced consistent protein banding patterns with minor variations. Although banding patterns of P. aphanidermatum differed slightly when isolates were cultured on different media, protein patterns were still specifically identifiable. No differences in protein bands were observed between P.u.u. and P.u.s. The utility of isoelectric focusing for the differentiation of species of Pythium is discussed.