ULTRASTRUCTURE, MORPHOLOGY, AND SPOROGENESIS OF PASTEURIA-PENETRANS

Pasteuria penetrans is a bacterial parasite of root-knot nematodes tha t shows great potential as a biocontrol agent. Scanning and transmissi on electron microscopy were used to study the ultrastructure, morpholo gy, and sporogenesis of four isolates of P. penetrans. The effects of different Meloidogyne spp. and tobacco cultivars on sporangium size an d morphology of endospores attached to the cuticle of second-stage juv eniles (J2) of root-knot nematodes also were investigated. The P. pene trans isolates and their origins were P-20 from M. arenaria race 1 in Levy County, FL; P-100 from Meloidogyne sp. in Pasco County, FL; B-4 f rom Pratylenchus scribneri in Seminole County, FL; and P-120 from Melo idogyne spp. in Alachua County, FL. Sporangia of the four isolates wer e identical morphologically and similar in their dimensions, ranging f rom 2.39 to 3.42 mu m in diameter and from 1.38 to 2.38 mu m in height . Different Meloidogyne spp. and tobacco cultivars had no effect on sp orangium size. Endospores attached to J2 were visualized in three form s: endospores retaining the sporangium wall, endospores covered with a thin exosporium, and endospores without covering. Sporogenesis of P. penetrans was similar to that of other gram-positive bacteria and gene rally matched the seven-stage scheme reported for Bacillus thuringiens is.