| In this dissertation I describe studies in biodegradation by two different strains of Rhodocuccus. Rhodococcus zopfii, a new species of Rhodocuccus, is described. This species is capable of using phenol, toluene, and biphenyl as sole sources of carbon. It displays a biphasic life cycle, consisting of initial growth as a hyphal mat of intertwined, branching cells, followed by marked fragmentation into irregular rod-shaped and coccoid units. DNA:DNA hybridization, as well as analysis of other phenotypic characteristics, confirmed that Rhodococcus zopfii is a new species. Rhodocuccus NO1-1, is a strain of Rhodocuccus isolated from a crude-oil seeded enrichment. It degrades alkanes of varying length, and produces bioemulsifiers that allow the emulsification of crude oil and aqueous phases. We describe the discovery of a two-component regulatory system that controls the expression of an emulsion-stabilizing capsule. This system consists of two genes, cprS, a two-component sensor, and cprR a two component response regulator. Site-directed mutagenesis studies confirm the roles of these genes in capsule production and emulsion stability. In the course of these studies, many novel techniques for the study of Rhodococccus were developed, including an ultrapure DNA isolation technique, an electrotransformation protocol, a method for assaying emulsion stability, and the first Rhodocuccus expression vector. |
