COMPARISON OF 2 SYMPATRIC PASTEURIA POPULATIONS ISOLATED FROM A TROPICAL VERTISOL SOIL

An isolate of Pasteuria (designated PPMJ) recovered from the root-knot nematode Meloidogyne javanica, was characterized using host preferenc e, spore morphometrics, and serology, and compared with another sympat ric Pasteuria isolate (designated PPHC) collected from the cyst nemato de, Heterodera cajani. PPMJ spores were larger (X 1.5) than the PPHC s pores and had a mean diameter of 3.4 mu m after fixation for electron microscopy. The central body of PPMJ spores was about twice as big as the central body of PPHC spores. The host preference tests, based on s pore attachment to the nematode cuticle, revealed that Meloidogyne inc ognita, M. javanica, M. hapla, Pratylenchus coffeae, and Pratylenchus sp. were hosts of PPMJ but not of PPHC. It was found that males of Rad opholus similis were hosts of PPHC. Western blot analysis of spore ext racts probed with a polyclonal antiserum raised against PPHC spores sh owed an antigenic ladder which had similarities to lipopolysaccharide; another antiserum revealed differences in the molecular weight of ant igens of the different spore isolates. Population diversity can theref ore be vastly altered by the maintenance and culture of the bacterium on a particular host. The implications of these results are discussed in relation to the use of Pasteuria as a biological control agent.