Cytoplasmic glycogen inclusions in cells of anaerobic gram-negative rumen bacteria

Abstract

Megasphaera elsdenii, an anaerobic rumen bacterium, produced intracellular polysaccharide granules varying in size from 0.05 to 0.15 μm during growth in batch culture. This polysaccharide material was purified and was found to contain D-glucose as the only reducing sugar. The polyglucose polymer was highly opalescent in aqueous solution and formed a strong reddish-brown iodine complex with a maximum absorbance at 493 nm. Its infrared spectrum had characteristic absorption bands at 8.70, 9.25, and 9.75 μm and was identical with that of the glycogen of enteric bacteria and beef liver. When these polysaccharide granules were observed with an electron microscope, they resembled the glycogen granules produced by Arthrobacter globiformis and Escherichia coli. These properties indicate that the polysaccharide was a type of glycogen. The yield of crude glycogen was 16.82% of the dry weight of late log-phase cells (14-h).The lysis of cells of M. elsdenii and other rumen bacteria that store polysaccharide granules inside the cells, in the rumen of cows fed a feed of fine-particle size (344 μm, geometric mean particle size) and high-energy content, may contribute to the high-carbohydrate level and high viscosity of the cell-free rumen fluid of these cows. Cows fed a coarse feed (519 μm, geometric mean particle size) of the same composition have rumens that contain few bacteria with polysaccharide granules. The cell-free rumen fluid of these cows has low viscosity and low-carbohydrate content.