The Isolation and Characterization of Agarolytic Bacteria from a Lowland River

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Abstract
Several strains of agar-degrading bacteria were isolated from the River Wey, Guildford [UK], during the summer of 1976. All were gram-negative rods and could be divided into 2 groups. Those which only softened the agar belonged to the genus Cytophaga and those which caused extensive liquefaction of the agar were referred to the genus Alteromonas. Attempts to isolate, purify and characterize the enzymes showed some differences between the 2 taxa. The strains of Cytophaga produced at least 2 enzyme complexes, one cell-free and the other cell-bound, and hydrolyzed agar with the formation of oligosaccharides. The strains of Alteromonas readily released agarase into the medium yielding monosaccharides as major end-products. The agar-degrading enzymes of both groups were inducible, not only by agar, but also by other galactans and polysaccharides associated with plants. The enzyme preparations also hydrolyzed a wide range of plant-derived polysaccharides, including some associated with terrestrial and freshwater plants rather than with marine algae. There apparently is no special ecological reason for the presence of agarolytic bacteria in fresh water but their activity may reflect the wide substrate of the polysaccharides of such organisms. The agar-softening strains are considered to belong to a new species for which the name C. saccharophila is proposed.