Role of Marine Fungi in the Biochemistry of the Oceans. V. Patterns of Constitutive Nutritional Growth Responses

SUMMARY

Halosphaeria mediosetigera, Culcitalna achraspora, and Humicola alopallonella, cellulolytic marine isolates, were grown in shake flasks in a variety of liquid artificial seawater media designed to demonstrate the value of 38 inorganic and organic compounds as nitrogen (N) sources and 79 organic compounds as carbon (C) sources. Inoculum production and experimental growth was standardized and gravimetrically quantitated. The effects of tris(hydroxymethyl) aminomethane (THAM) buffer on growth and pH changes in the presence of quantitative variations of the best nitrogen sources were assessed. High C/N source ratios, ranging from 18 to 55, were preferred. While pH remained stable in the presence of THAM, omission of the buffer confirmed the acidogenic nature of NH₄⁺ salts, pH values of 3.0 or less being recorded. Patterns of C source utilization were compared, emphasizing the effect of sugar derivatives, with those of terrestrial cellulolytic species. In spite of generic differences, marine test organisms responded with remarkable similarity. Generally, all inorganic N sources, urea, valine, leucine, alanine, arginine, glutamate, glutamine, aspartate, asparagine, hypoxanthine, and xanthine promoted significant growth for all three species with glucose as the C source. Cultures proved far more selective in their use of C sources, good growth occurring consistently only in the presence of glucose, fructose, mannose, cellobiose, and xylose. Those organic substrates which acted as good N sources were unable to furnish required C even in the presence of sparking quantities of glucose. Carbohydrate, substituted carbohydrate, and glycoside utilization patterns compared favorably with those of terrestrial species. In the absence of explicit permeability data, it is suggested that these cultures are narrowly saccharolytic, but may be only insignificantly proteolytic, lipolytic, nucleolytic, or ligninolytic. Broader studies are required before adaptive recalcitrance can be used to describe marine fungi in general.