The Sugar Content and Density of Living and Dead Microsporidian (Protozoa: Microspora) Spores

ISSN： 0022-2011

Source： Journal of Invertebrate Pathology, Vol.67, Iss.1, 1996-01, pp. : 80-91

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Abstract

Microsporidian (Microspora) spores were subjected to several kinds of stress: ultraviolet light ( Nosema algerae ); chilling in ice water ( Edhazardia aedis ); freezing and thawing, with or without glycerol as a cryoprotectant ( Nosema disstriae, Thelohania sp.); long-term cold storage ( Vairimorpha spp., Endoreticulatus sp., Thelohania sp., and Microsporidium sp.); and extended periods at room temperature ( Microsporidium sp. and Vairimorpha lymantriae ). N. algerae spores were inactivated by incubation in 0.05 m NaCl or 24 hr at 23#°C. Viability of the spores was assessed either by infectivity to a susceptible host or by in vitro germination. Carbohydrates were extracted from the spores for measurement of the total sugars (anthrone reactive) and reducing sugars (Nelson's test), and quantities and ratios of the two classes of sugars were compared. Buoyant density differences associated with sugar concentration and viability changes were estimated by Ludox density gradient centrifugation. Reducing sugar levels increased after germicidal ultraviolet radiation, chilling, or freezing, concurrent with loss of infectivity or capacity for germination. The smaller reducing sugar molecules apparently diffused slowly from the inviable spores, causing a gradual reduction in the total concentration of sugars. Many samples of spores held for long periods in cold storage were almost devoid of sugar. These changes were not seen in N. algerae spores that were temporarily inactivated. In all cases, spores that were severely depleted in carbohydrates had a significantly lower buoyant density. The bands of heavy spores had a mean density ± SE of 1.197 ± 0.010 g/ml and the mean density of the light, sugar-depleted spores was 1.137 ± 0.024 g/ml. These results suggest that, where no other means are possible, sugar concentrations or spore density might be used to assess the viability of spores.