DIVERSITY AND PARTIAL CHARACTERIZATION OF PUTATIVE VIRULENCE DETERMINANTS IN PASTEURIA-PENETRANS, THE HYPERPARASITIC BACTERIUM OF ROOT-KNOTNEMATODES (MELOIDOGYNE SPP)

Antigens recognized by monoclonal antibodies (Mabs) raised to the surf ace of the obligate nematode hyperparasite Pasteuria penetrans were ch aracterized. Using the attachment of spores of the bacterium to host n ematodes to determine the biological variability present on the spore surface greatly underestimated the amount of surface heterogeneity pre sent compared with estimates from immunological techniques. This heter ogeneity differed not only between different individual spores from th e same population but also between different spore populations. None o f the Mabs completely inhibited any spore population from attaching to the nematode cuticle, suggesting that the mechanism of attachment may be more complex than previously supposed. Chemical degradation of one particular epitope recognized by monoclonal antibody PP1/117, and des ignated ep117, occurred after treatment with NaOH, periodate or Protei nase K, suggesting that an O-linked glycoprotein may be involved. Fibr onectin, which had been found to bind to Pasteuria spores through hydr ophobic interactions, also prohibited the Mab from recognizing ep117. However, SDS-PAGE of spore extracts followed by immunoblotting showed that none of the Mabs could detect this epitope and so ep117 may be co nformational in nature. Thus, the conformation of any particular epito pe recognized by a Mab may be important in determining to which nemato de a particular spore will attach. The distribution of a particular ep itope within a population of spores will in turn therefore determine i ts virulence on a particular nematode.