This thesis was written to study photoreactivation in different physiological conditions of the vegetative cell as well as the photoreactivation of the two morphological states of the Azotobacter cell: the vegetative cell and the cyst.

Previous methods for genetic transformation in Azotobacter vinelandii have employed poorly defined genetic markers or crude DNA extracts. An improved transformation technique has been developed for use in Azotobacter. The technique was used to transform several strains of Azotobacter with DNA carrying a defined genetic marker. A method for isolating pure, high molecular weight, biologically active DNA from Azotobacter is also presented. Purity of the extracted DNA was determined by standard chemical assays. The molecular weight was determined by boundary sedimentation techniques to be 18.2 megadaltons. DNA was obtained from several mutant strains of Azotobacter. Biological activity of these samples was demonstrated by using them to accomplish both intra- and interstrain transformation. Thermal denaturation profiles of several DNA samples are presented, from which guanine plus cytosine content was determined. Among the Azotobacter species examined, GC content ranged from 65.1 to 67.8%. The use of the new transformation and DNA isolation methods in taxonomic and mapping studies is discussed.

No description available.

No description available.

No description available.

In Azotobacter chroococcum the hydrogenase gene (hup) cluster spans about 14 kb of DNA. In this study about 12 kb of the hup region beginning immediately downstream of the structural genes (hupSL) were sequenced. This revealed 14 additional open reading frames (ORFs) which we designated hupZMNOQRTVABYCDE. All of them are transcribed from the same strand as hupSL and are closely linked. The polypeptides predicted from all these genes are homologous to products of the gene clusters of membrane-bound (NiFe) hydrogenases from other bacteria, including Azotobacter vinelandii, Alcaligenes eutrophus, Rhodobacter capsulatus, Rhizobium leguminosarum and Escherichia coli. The products of hupR and hupZ may be involved in hydrogenase-linked electron transport since they are similar to rubredoxins and b-type cytochromes, respectively. / Site-directed mutagenesis of hupB, hupY, hupD and hupE abolished Hup activity with either O$ sb2$ or methylene blue as the electron acceptor whereas two insertions downstream of the hupE gene had no effect on Hup activity. A 10.5 kb fragment of DNA beginning in hupR was able to complement hupD and hupE mutants, supporting earlier evidence for a promoter downstream of hupSL. / Mutations in hupB, hupY and hupD had little effect on $ beta$-galactosidase activity in a strain also carrying a hupL-lacZ fusion, indicating that hupB, hupY and hupD are probably not involved in regulating the transcription of hupSL. / Adding nickel to the medium restored wild-type Hup activity to a hupB mutant and about half of the activity in a hupA mutant, indicating that the hupB and hupA gene products may be involved in Ni metabolism.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 160-179). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [94]-103).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1955. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 40-42).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 112-119.