Microsporidian Biochemistry and Physiology

Abstract

The microsporidia are a large group of highly specialized obligate intracellular protozoan parasites. Disturbances in the biochemical composition of tissues infected by intracellular parasites are of interest because such infections often significantly alter the electrolyte, carbohydrate, protein, and free amino acid pools of host cells. Until recently, biochemical investigations of the metabolic processes of the microsporidia have suffered because of insufficient numbers of the different parasite stages and inadequate methods for the in vitro cultivation and maintenance of these organisms. The authors have observed the disappearance of glycogen granules in the host cell cytoplasm during the early stages of parasite development without any concomitant change in the size or quantity of lipid droplets. The microsporidian species Spraguea lophii is a model for investigating externally mediated signal transduction and subsequent activation of the internal signal pathway for triggering of a missile cell, the microsporidian spore. Microsporidian meront stages appear to have actin-myosin and kinesin-associated molecular motors. This chapter focuses on keratin filaments found in two domains: (i) within the spore stage, the microsporidian sporophorous vesicle, and (ii) keratin in the host cell cytoplasm domain but situated at its interface with the parasite. Recently, however, some success has been achieved in isolating and maintaining meronts and discharged sporoplasms in extracellular support medium. Developing a simple in vitro model will be useful for many subsequent biochemical analyses.