<I>Escherichia coli</I> mutants impaired in growth and survival at low external pH in minimal medium were selected and attempts made to identify the disrupted genes. This study suggested that <I>clpX</I>, encoding a heat-shock induced protease and molecular chaperone, was functional in survival of <I>E. coli </I>at pH 3.3. Promoter probe plasmid libraries of <I>Salmonella typhimurium </I>LT2 DNA were created in <I>E. coli </I>and screened for acid-inducible transcriptional elements, and transcriptionally active fragments of degradative amino-acid decarboxylase genes recovered. Chromosomal gene fusions to the reporter gene <I>lacZ </I>in <I>E. coli</I> generated by Mu DII 1734 insertion were screened in a similar way and suggested that the gene encoding adenylate cyclase (<I>cya</I>) could be induced by mild cytoplasmic acidification. The sequence of a gene known to be inducible by cytoplasmic acidification, <I>inaA, </I>became available during the course of this study. The 5' region of this gene was used to generate a set of plasmids carrying fragments of the acid-inducible promoter transcriptionally fused to a luciferase based reporter system. Elements of the sequence required for induction by cytoplasmic acidification were identified. One of these reporter constructs was used to screen an <I>E. coli </I>Tn<I>10</I> chromosomal insertional mutant library for genes involved in the regulation of <I>inaA. </I>One such mutant had a multiple antibiotic resistant (<I>mar</I>) phenotype. The disrupted loci in 2 other mutants were identified by inverse PCR, sequence analysis and database searches. Both were known only as open reading frames (ORFs) discovered during the sequencing of the entire <I>E. coli</I> genome, and were tentatively identified as <I>yddB </I>(closely linked to <I>gadB </I>and <I>gadC</I>; required for glutamate dependent acid resistance) and <I>f300</I> (closely linked to <I>pldA; </I>required for detergent resistance). The promoter of <I>f300</I> was shown to be sensitive to cytoplasmic acidification. The <I>inaA</I> promoter was also demonstrated to be induced at the onset of stationary phase, and to be independent of the stationary phase and weak-acid inducible σ factor RpoS and also of cAMP levels.

Graduation date: 1969

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1972. / Bibliography: leaves 91-96. / ix, 96 l illus

Integral membrane proteins perform a wide range of biological processes, including respiration, signal transduction and molecular transport. Structural information is necessary for a full understanding of the mechanisms by which integral membrane proteins work. Ferrous iron transporter protein B (FeoB) is an integral membrane protein of Escherichia coli which is considered to transport ferrous iron in to bacteria. But there are no definite proofs or clear indications of the precise mechanism of ferrous transport. By expressing and crystallizing the G-protein domain (FeoGP) and FeoB, it will be helpful to know about the iron transport system. In order to express FeoB and FeoGP, expression vector pFeoB (FeoB in pGEX-4T-1) and pFeoGP (FeoB in pGEX-4T-1) were made. FeoB and FeoGP proteins were expressed and purified. Using vapour diffusion method crystallization trials of FeoB and FeoGP were done. Crystals of FeoGP are observed and no crystal formation for FeoB. Native crystals of FeoGP diffracted to 2.2 ?? resolution, and mant-GMPPNP crystals to 2.6 ??. Preliminary data processing indicate space group P212121 for native crystals, with cell dimensions 46 x 119 x 146 ??. The data set is 100% complete, Rmerge 0.08, and I/ ?? 3.2.

vii, 185 leaves : ill., tables ; 29 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology, 1977?

No description available.

No description available.

The tryptophan productivity of the genetically-manipulated strain JP4153 was increased 2.5-fold by introducing pMU78, a medium copy-number plasmid carrying a feedback-resistant trp operon. JP4153(pMU78) produced 23.5 g/l of tryptophan at a rate of 0.7 g/l/h when grown at 37 degrees C in a defined glucose and ammonium salts medium in a bench-scale fermentor. / During prolonged cultivation in the presence of antibiotic, the recombinant strain generated faster-growing, production-defective variants, which harboure mutated derivatives of pMU78. Insertion sequences were responsible for the two predominant types of mutation. The plasmid element ISI02 mediated deletions extending into the promoter-proximal region of the plasmid-borne trp operon. ISI0-Right, a chromosomal element, inserted into the promoter/trpE region of the plasmid. Three methods were employed to increase the structural stability of JP4153(pMU78) during the course of the production process. First, the growth of seed cultures was carried out at 30 degrees C, the permissive temperature for the trpS378 mutation carried by the host strain. Second, the seed culture medium was modified by the addition of yeast extract, which appeared to reduce the selective disadvantage conferred by the plasmid. Third, ISI02was deleted from pMU78 to create pMU88. (For complete abstract open document)

Thesis (M. S. - Soil, Water and Environmental Science)--University of Arizona, 2001. / Includes bibliographical references (leaves 48-50).

Proefschrift Universiteit van Amsterdam. / Met lit. opg. - Met samenvatting in het Nederlands.