Fig. 1. Scanning electron micrographs of developmental stages of Pasteuria penetrans (isolate P-100) parasitizing Meloidogyne arenaria race 2 cultured on tomato plants (cv. Florida Petite) in a hydroponic system. A, B, C) Vegetative growth stage: (A) mycelial colonies (mc); (B) Dichotomously branched thalli; (C) prominent bifurcation of the vegetative mycelium and swollen thalli. D, E, F, G) Fragments of filamentours stages differentiated: (D) quintets, (E) quartets, (F) triplets, (G) doublets fragments appear attached near the centers of the cells (arrows). H, I, J) Sporulation: (H) swelling of terminal cells led to the formation of the developing sporangia (en), followed by a change in shape from oval to elliptical; (I) Arrow indicates remnants connecting hyphal strands of separated endospores. (J) After the formation of the external membranes, the immature endospores appeared swollen at one polar point, and several longitudinal lines or ridges (r) formed in the endospore wall. (K) Single mature endospore within the sporangium. Bars = 1 micrometer.