GROWTH OF RHODOCOCCUS S1 ON ANTHRACENE

Three slow-growing bacteria were isolated from a mixed culture enriche d for growth on anthracene, using creosote-contaminated soil as the in oculum. Organisms were shown to use anthracene by the production of a clear zone around the colony after a mineral salts agar plate was spra yed with anthracene. All three bacteria were nonmotile, nonsporulating , gram-positive rods and stained acid-fast. Physiological and biochemi cal tests, GC content, and cell wall lipid patterns of whole cell meth anolysates indicated that they belonged to the Nocardia-Mycobacterium- Rhodococcus group. On the basis of these characteristics and pyrolysis gas chromatography, they were assigned to the genus Rhodococcus. Grow th of the isolates was slow on crystalline anthracene, giving a doubli ng time of 1.5-3 days, and they grew mainly on the crystal surface. Wh en anthracene was supplied by precipitation from a solvent, doubling t ime was reduced to 1 day. All three isolates mineralized anthracene bu t not phenanthrene or naphthalene, nor could they grow on naphthalene, phenanthrene, fluorene, fluoranthene, acenaphthene, pyrene, chrysene, or naphthacene as sole carbon source. One isolate, Rhodococcus S1, wa s able to use 2-methylanthracene or 2-chloroanthracene as carbon sourc e but not 1- or 9-substituted analogs. These results suggest that the initial enzyme attacking anthracene in these isolates has a narrow sub strate specificity.