Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 19-21).

Thesis--University of Chicago. / Bibliography: p. 15.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1931. / Typescript. With this bound: Oxidation-reduction potentials in relation to the growth of an aerobic form of bacteria, [by] W.P. Allyn and I.L. Baldwin, reprinted from Journal of bacteriology, v. 23, no. 5 (May 1932), p. 369-398. Includes bibliographical references (leaves 59-64).

Thesis - Univ. of Chicago. / Bibliography: p. 15. Also available on the Internet.

M.Tech / Atomic force microscopy (AFM) has been an integral tool in bacterial studies for resolving surface structures. Novel applications of this instrument in research require the development of sample preparation techniques and improvement of existing ones. Careful selection of the scanning parameters is particularly crucial when exploring the full potential of the AFM. The objective of this study was to design sample preparation methods for AFM imaging bioleaching bacteria and optimise the scanning parameters (deflection setpoint, feedback loop and the scan rate) for contact mode (CM) imaging in air. The method should be simple, fast and cost effective. The strategy used in this study of (i) evaluation of support substrates for bacterial attachment, (ii) investigation of the effect of pH and centrifugation on cell samples during imaging. Centrifuged and noncentrifuged cell samples suspended in either deionised water (pH 7) or acidified water (pH 1.5) were tested for imaging. Mica and glass cover slips were used as potential substrates for attachment. Cells were attached to substrates for imaging by simple adsorption (‘air-drying’ method). To optimise the scanning parameters, the effect of different values of the scan rate, deflection setpoint and the feedback gains on the quality of AFM imaging was investigated. Optimisation of these parameters was found to be instrumental when imaging weakly adsorbed samples prepared by simple adsorption and ‘soft’ samples such as bacterial cells. The results obtained from these experiments were used during preparation of iron- oxidising leaching bacteria for AFM imaging. The surface morphology of iron-grown bacterial samples was investigated with contact mode AFM in air. Reproducible results obtained in each scan shown by the stability of morphological characteristics of bacterial samples indicate that (i) mica can be used successfully as a substrate for attaching cells, (ii) centrifuged bacterial samples can be easily imaged (iii) scanning with scan rate values of <0.5Hz, deflection setpoint of between 0.2-0.5V and feedback values of < 5.000V improve the image quality and can prevent deformation of the bacterial cells by the tip. Non-centrifuged samples could not be imaged, indicating that bacterial cells need to be separated from growth residues as a prerequisite for successful AFM imaging.

No description available.

Thiobacillus ferrooxidans is an industrially important bacterium which is used in bioleaching operations. The work reported in this investigation extends current knowledge of the genetics of this organism. Conjugation was attempted as a means for plasmid DNA transfer to T. ferrooxidans. Recombinant T. ferrooxidans plasmids, pDER401 and pDER405, were shown to code for mobilization and replication functions in Escherichia coli and Thiobacillus novellus strains. The plasmids were mobilizable at high frequency by the IncP plasmid, R68.45. Attempts to transfer the T. ferrooxidans recombinant plasmids directly from E. coli to T. ferrooxidans were unsuccessful. In multistage mating experiments, plasmid DNA was transferred from E. coli to T. novellus, and from T. novellus to Thiobacillus intermedius. However, in subsequent matings, plasmid transfer from these thiobacilli to T. ferrooxidans could not be shown. A genomic library of T. ferrooxidans ATCC 33020 was constructed in the plasmid vector, pEcoR251, for the purpose of cloning a recA-like gene from this organism. The library consisted of approximately 1,78 X 10⁴ clones carrying chromosomal DNA fragments of about 3-12 kilobases (kb). The library was successfully screened for functional complementation of E. coli auxotrophic mutants. Clones that conferred resistance to methyl methane sulfonate (MMS), a DNA-damaging agent, were isolated in an E. coli recA⁻ mutant. In an attempt to clone a homologous marker, T. ferrooxidans ATCC 33020 was mutated to rifampicin resistance (Rifʳ) and DNA from the mutant strain was used in the construction of plasmid- and cosmid-based libraries. The plasmid library contained approximately 1,35 X 10⁴ clones with inserts of about 1-13 kb. The cosmid library consisted of approximately 8.2 X 10³ colonies, 4.0 X 10⁴ in vitro packaged cosmids, and an amplified in vivo-packaged cosmid lysate containing approximately 1.82 X 10¹¹ infectious particles, carrying inserts of about 35-55 kb. Complementation of E. coli auxotrophic mutants was observed with the plasmid and cosmid library of the T. ferrooxidans Rifʳ strain. Screening both libraries for a Rifʳ marker was unsuccessful. Three recombinant plasmids, pRSR100, pRSR101, and pRSR102, each containing the functional analogue of the E. coli recA gene, were isolated from the plasmid-based genomic library of T. ferrooxidans ATCC 33020. The plasmid, pRSR100, was used for further characterization of the cloned recA-like gene. pRSR100 complemented defects in DNA repair and homologous recombination in an E. coli recA- strain. Antiserum raised against E. coli RecA⁻ protein reacted with two protein bands with an apparent Mᵣ of approximately 40 000 and 38 000 in extracts of the recA deletion mutant, E. coli JK696, containing pRSR100. A single band with an apparent Mᵣ of approximately 40 000 was detected in T. ferrooxidans cell extracts with the E. coli RecA antiserum. The nucleotide sequence of the T. ferrooxidans recA gene has been determined. No SOS box characteristic of LexA- regulated promoters could be identified in the 196-bp region upstream of the coding region. The T. ferrooxidans recA gene specifies a protein of 346 amino acids that has 66% and 69% homology to the RecA proteins of E. coli and P. aeruginosa, respectively. Most amino acids that have been identified as being of functional importance in the E. coli RecA protein are conserved in the T. ferrooxidans RecA protein. Although some amino acids that have been associated with ATPase and constitutive protease activity have been substituted, the cloned protein has retained these activities. The cloned recA gene was expressed in E. coli from both the λ Pᵣ and lac promoters. However, no expression from the 2.2 kb T. ferrooxidans DNA preceding the gene was evident.

No description available.

No description available.