Growth of an aquatic-derived bacterium in the presence of long-chained alkanes.

In a study of microbial utilization of paired hydrocarbon and nonhydrocarbon substrates, an isolate derived from the Mary's River, Benton County, Oregon, was found to have limited growth on glucose alone in a mineral salts medium at 30 C (L. D. Bushnell and H. F. Haas, J. Bacteriol. 41:653, 1944). However, in the presence of 0.5% n-hexadecane (99% purity; Humphrey Chemical Co., North Haven, Conn.), vigorous growth ensued under the same conditions. In Nutrient Broth (Difco), this organism was found to be pleomorphic, growing from a gramvariable coccoid stage through a rod stage where gram-positive granules were present (36 to 48 hr). After this period, the organism fragmented to gram-variable cocci. The isolate, growing in a thin surface pellicle, wasaerobic, catalase-positive, unable to reduce nitrates, indoleand hydrogen sulfide-negative, urease-positive, and gelatin-negative. Starch was hydrolyzed, but the organism produced no acid or gas with glucose, lactose, sucrose, mannitol, and galactose. These tests were performed by standard methods (Manual of Microbiol. Methods, Soc. Am. Bacteriologists, Geneva, N.Y., 1957). Colonies of the organism, after growth on nutrient agar at 30 C for 24 hr, were circular, entire, creamy white, raised, glistening, translucent by transmitted light, and viscous. Based on these data, this organism, isolate 1-80-3, was tentatively considered to be a member of the genus Arthrobacter. Growth of the organism with and without 0.5% n-hexadecane, in the presence of other carbon sources at 0.5% (w/v), was carried out in 250-ml Erlenmeyer flasks containing 50 ml of mineral salts medium incubated at 30 C with reciprocal agitation. The inoculum was grown in nutrient broth for 24 hr at 30 C, washed three times in 0.1 M phosphate buffer, pH 7.2, and added to the flasks to give an initial population of 5 X 104 organisms per ml. The cells were in a gram-variable coccoid state at this culture age. All studies were carried out by use of filter-sterilized carbon