ON THE ECOLOGY OF THE LOWER MARINE FUNGI l > -HELEN S. VISHNIAC Department of .Microbiology, Yale University, Neiv Haven 11, Connecticut The lower marine fungi (i.e., Myxomycetes and aquatic Phycomycetes) have generally been described as occurring on plant and animal hosts. While several forms have been described as saprophytes, the only genus known to occur on debris is Labyrinthula (Sparrow, 1936). All other described species are endobiotic or epibiotic with rhizoids penetrating living or dead host cells. They are also sporadic in occurrence. The application of a semi-quantitative plating technique to sea water has now established that lower fungi are far more common in littoral waters than previous studies indicate, and has suggested a new ecological niche for these fungi. The plating technique which we used consisted of spreading samples of sea water with a bent glass rod on the surface of a solid isolation medium (Table I). TABLE I Isolation Medium Sea water 80 ml./ 100 ml. Gelatin hydrolysate 0.1% Glucose (added aseptically) 0.1% Liver 1:20 0.001% B-vitamins Agar 1.5% adjusted to pH 7.5 Marine mineral base (Vishniac, 1955) was sometimes substituted for sea water. Gelatin hydrolysate and the B-vitamin mixture were prepared as by Vishniac and Watson (1953). Liver extract concentrate 1:20 was obtained from the Nutri-tional Biochemicals Co. The moisture content of the medium is critical : the agar plates should be dried overnight, but not allowed to stand for more than two days. Just before use the plates are spread with 2000 units of Penicillin G (Squibb, buffered) and 0.5 mg. of dihydrostreptomycin sulfate (Wyeth) in concentrated aqueous solution. These plates will then absorb a 0.2-ml. sea water sample in an hour or two. After inocu-lation, the plates were incubated at 20 degrees or less. Such plates support the growth of lower fungi, yeasts, molds, and some diatoms, but few or no bacteria. We have found unfortunately incomplete suppression of bacterial growth when water samples taken from City Point, New Haven, near the sewage disposal plant, 1 Contribution No. 869 from The Woods Hole Oceanographic Institution. 2 It is a pleasure to acknowledge the hospitality of Dr. J. Ryther and other members of The Woods Hole Oceanographic Institution, the kindness of Dr. W. R. Taylor in identifying Polysiphonia urccolata, and the excellent technical assistance of Miss E. A. Adair. This study was aided by a contract between Yale University and the Office of Naval Research, Department of the Navy, NR 135-241. Reproduction in whole or part is permitted for any purpose of the United States Government. 410
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