Some Properties of Discharged Glugea hertwigi (Microsporida) Sporoplasms

Glugea hertwigi spores were activated to discharge sporoplasms in Medium 199 with 3% gelatin at pH 9.0; the liberated sporoplasms were transferred to a maintenance medium with 6% gelatin (pH 7.0) supplemented with 2 mM ATP and 10% (v/v) fetal calf scrum. The spherical sporoplasms (measuring 3.5-4 m?m in diameter) had single nuclei and had a cytoplasm rich in free ribosomes. Each G. hertwigi sporoplasm was initially bounded by an external (0.1-0.2 m?m) satellite body adjoining the plasma membrane. The satellites displayed ordered membrane and appeared to merge with the sporoplasm 15-30 min after spore discharge. The external location of the satellite (in reference to the discharged sporoplasm) seems to be part of the normal sequence of events under the in vitro conditions provided. The surface of G. hertwigi sporoplasms does not bear an obvious surface coat; however, our cytochemical observations indicate the plasma membrane of the sporoplasm was somewhat responsive to concanavalin A-peroxidase, colloidal iron, and native ferritin. During the short term incubations of sporoplasms with ferritin, the particles permeated membrane channels extending into the sporoplasm cytoplasm.