Microsporidian Intrasporal Sugars and Their Role in Germination

The hypothesis that spores of terrestrial and aquatic microsporidia differ in their utilization of sugars was tested by evaluating the sugars in germinated and ungerminated spores of several species in each category. The aquatic species tested wereVavraia culicis, Edhazardia aedis,andNosema algeraeand the terrestrial species wereVairimorpha necatrix, Nosema disstriae, Nosema apis, Vairimorpha lymantriae,andNosemaspp. fromSpodoptera exiguaandPlutella xylostella.The percentage germination varied between species, ranging between 40 and 92%. Total sugars (anthrone reactive) and reducing sugars (Nelson's test) remained unchanged through germination in the three terrestrial species tested; however, reducing sugars increased significantly in the aquatic species. High-performance liquid chromatography and gas chromatography revealed a preponderance of trehalose in all species and large quantities of sorbitol in all species exceptN. algeraeandE. aedis.Other sugars were present in some species in much lower concentrations. After germination no changes in sugar content were observed in terrestrial species; however, all aquatic species lost trehalose with a concomitant increase in fructose and/or glucose concentrations. Increased osmotic potential from breakdown of trehalose has been postulated to induce germination of the aquatic species, but another explanation must be found for the terrestrial species.