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J Bacteriol. 1968 November; 96(5): 1474-1483
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

Production of a Capsular Polysaccharide by a Marine Filamentous Fungus

^a Laboratory of Applied Microbiology, Division of Engineering and Applied Physics, Harvard University, Cambridge, Massachusetts 02138

ABSTRACT

The spent seawater medium of 4-day-old-cultures of the filamentous marine fungus Leptosphaeria albopunctata had a high viscosity after the fungus was collected by high-speed centrifugation. Microscopic examination of uncentrifuged mycelium suspended in India ink revealed that the viscosity resulted from capsular material. These capsules became disassociated from the mycelium during centrifugation. Precipitation of the medium of centrifuged cultures with 95% ethyl alcohol yielded a highly anthrone-positive polysaccharide material, composed of large amounts of glucose and minute amounts of mannose. Time course studies of the nutritional requirements for capsular polysaccharide production revealed that the capsular material was produced in large amounts, and on a wide variety of sugars, during the period of rapid growth, but was quickly degraded and presumably remetabolized in older cultures. The amount of capsular material produced was enhanced by NaCl concentrations above that of artificial seawater, and KCl could be substituted for NaCl. The salts MgCl₂ and CaCl₂ were also required for capsule production by L. albopunctata, although growth was obtained in cultures without added amounts of these constituents. The possible role of these salts in the metabolism of the fungus is discussed.

¹ Present address: Department of Microbiology, The University of Texas, Austin, Tex. 78712.

² Present address: Biology Division, Woods Hole Oceanographic Institution, Woods Hole, Mass. 02543.