STUDIES ON THE FILAMENTOUS SHEATHED IRON BACTERIUM SPHAEROTILUS NATANS

Abstract

Nine pure cultures of S. natans were isolated from stream, pond, and ditch water. The cultures gave rise to 2 types of colonies a rough, somewhat cottony type composed mainly of filaments and smooth, glistening colonies composed principally of single cells. The filaments consist of chains of rod shaped cells in closely fitting tubes or sheaths. The individual cells are 2.5 to 16[mu] long and 1.2 to 1.8[mu] wide. They are motile, and each cell has a tuft of spirally coiled flagella located usually subpolarly or on the long side of the cell. S. natans grows on a wide variety of organic compounds, including sugars, sugar alcohols, and 4,3 and 2-C compounds as sources of C and energy. Ammonium salts, nitrates, individual amino acids, and complexes such as peptone and meat extract supply the N needs of the organism. An exogenous supply of growth factors is not required. All strains develop in the range of 15 C to 40 C, and opt. temp. is about 30 C. Growth occurs in the range of pH 5.8 to pH 8.1, and the best development is in neutral or slightly alkaline media. S. natans cannot grow without O2 although growth will occur when only small amts. of O2 are present; nitrates cannot replace O2. Non-proliferating cell suspensions oxidize a variety of carbohydrates, amino acids, and related compounds; and for some of these compounds the oxidizing enzymes are adaptively formed. As much as 70 to 80% of carbohydrates may be assimilated oxidatively, and this process is very resistant to inhibition by Na azide and 2,4-dinitrophenol. Glucose is not fermented by cell suspensions under anaerobic conditions.