Stafylococcus aureus, Stafylococcus epidermidis, Escherichia coli, Streptococcus pyogenes och Bacillus sp. är bakterier som förekommer i vår normalflora eller runt om i vår omgivning. De är i de allra flesta fall harmlösa men kan orsaka sjukdom ifall de hamnar i t.ex. sår eller kontaminerar mat. Vissa av dessa bakterier har även en tendens att utveckla resistens mot antibiotika, infektioner orsakade av resistenta bakterier kan bli allvarliga och väldigt svåra att behandla. Detta är det främsta skälet till varför vi har valt att undersöka ifall de ovan nämnda bakterierna förkommer på avdelningen SET på Halmstad högskola. För att kunna identifiera de bakterier vi fann använde vi oss av en rad olika biokemiska tester och resistensbestämningen utfördes bl.a. med hjälp av en PCR körning. Vi fann alla de bakterier vi sökte efter förutom S. pyogenes och ingen av de funna visade på någon resistens mot antibiotika.

Ribosomes are multicomponent macromolecular particles and are essential for the survival of cells in all organisms. The ribosome's universal function is to catalyze polypeptide synthesis through translation of mRNA transcripts. Ribosomes from Escherichia coli, eubacterial organisms, have a sedimentation coefficient of 70S and are composed of 30S and 50S ribonucleoprotein subunits. The small ribosomal subunit is an assembly of 21 different proteins and a 16S ribosomal RNA. Within the 16S rRNA there are a few short stretches of universally conserved sequences spanning positions 517-533, 1394-1408, and 1492-1506. Clear functions for these sequence zones have not yet been assigned. Here I report a kinetic analysis of these highly conserved regions in the 16S rRNA and within the 30S ribosomal subunits. Binding affinity was measured in experiments that were based on protection from nuclease 51 digestion of short oligodeoxynucleotides hybridized to the designated regions. DNAs hybridized to regions 1400 and 1500 show significant differences in the apparent dissociation constants when measured in 30S particles as opposed to those found for 16S rRNA. Region 525 showed no difference in kinetic behavior. To further elucidate the functional and structural role played by the region centered about C1400 in 16S rRNA, a four nucleotide deletion was constructed within this region. The deletion was introduced by direct RNA manipulation using DNA/RNA hybridization, RNase H digestions, and ligation of the correct RNA fragments with T4 RNA ligase. I improved ligation efficiency of large RNA molecules by including a connector looped short DNA oligomer. Recycling products through phenyl boronate agarose (PBA-30) column also improved the efficiency of ligation. The mutagenized 16S rRNA fully reassembles into 30 particles and the altered 30S subunit possesses all of the normal ribosomal proteins. Altered ribosomes were functional in in vitro translation of MS2 mRNA. The altered ribosomes have lower translational activity relative to controls. Here I present indirect evidence suggesting that the decrease in the synthesis of MS2 coat proteins is the result of premature termination. The altered 16S RNA in ribosomes had an apparent dissociation constants with DNA probes comparable to those found for normal 16S rRNA. This suggest that the RNA is less flexible in the particle relative to normal 30S subunits. The deletion at 1400 did not have any effect on the physical properties of the 1500 region, as measured by DNA hybridization. A minor, but significant, effect on the 525 region was observed. A possible RNA/RNA interaction within the 30S particle is proposed to account for this observation. / Graduation date: 1992

E. coli thioredoxin (TRX) was modified by the episulfonium ion derived from S-(2-chloroethyl)glutathione (CEG) or S-(2-chloroethyl)cysteine (CEC). The alkylation site was located at Cys-32, which was confirmed by tandem mass spectrometry. Two forms of native TRX, Oxi- and Red-TRX, and two modified TRXs, GS- and Cys-TRX, were examined by hydrogen/deuterium (H/D) exchange reactions using electrospray ionization mass spectrometry (ESI-MS) for the analysis. Conformational dynamics during thermal denaturation were probed by H/D exchange-in experiments. Under conditions in which the folded conformational state is marginally stable, H/D exchange-in experiments resulted in mass spectra differing in the number of incorporated deuteriums which indicates the presence of two distinct populations of molecules. As the exchange-in time increased, the population representing the unfolded state increased and the population for the folded state decreased. The rate of conversion was used to estimate the rate constant of unfolding. ESI mass spectra were also recorded as a function of temperature without H/D exchange, and the observed bimodal charge state distributions were analyzed in order to estimate melting temperatures. GS-TRX showed increased resistance to hydrogen isotope exchange in comparison with Red-TRX indicating that there were enhanced intramolecular interactions in the former protein. Pepsin digestion was performed on deuterated TRXs to analyze different structural regions. The amount of deuterium incorporated was monitored with peptic peptides from deuterated TRXs with different exchange-in incubation periods. Deuterium levels of each peptide were plotted versus the exchange time and fitted with a series of first-order rate terms. The regions 59-80 and 81-108 of Oxi- and Red-TRX showed an EX1 mechanism as evidenced by two distinct mass envelopes that appeared after a short incubation time in deuterated solvent. Tandem mass spectrometry (MS/MS) was carried out to obtain the information on individual amide linkages. MS/MS data showed generally excellent correlations with the exchange rate constants from published NMR data on Oxi- and Red-TRXs. Two residues, Ile-75 and Ala-93 in GS-TRX indicated the most probable sites responsible for induced H-bonding by the attached glutathionyl group, which was consistent with the energy minimized structure predicted by AMBER force field constants. / Graduation date: 2001

Con el objetivo de determinar los serotipos más frecuente de Escherichia coli Enteropatógena (EPEC) en los cuadros diarreicos agudos de niños menores de cinco años, se diseñó una investigación de tipo descriptivo, transversal, y observacional. La población de estudio estuvo constituida por 251 niños tratados en forma ambulatoria en el Hospital Nacional Docente Madre Niño “San Bartolomé” durante los meses de noviembre del 2000 a marzo del 2001. Se encontró 42 % (105 casos) de coprocultivos positivos a bacterias enteropatógenas, siendo Escherichia coli enteropatógena (EPEC) con 29,2 % (35 casos), la segunda causa más frecuente después de Shigella sp. Los serotipos de EPEC encontrados fueron: 9 casos del O119, 8 casos de O26, 6 casos del O55 y 2 casos del O86. Se concluye que lo serotipos más frecuentes de EPEC en los cuadros diarreicos agudos de niños menores de cinco años fueron el O119 y el O26.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 149-164). Available also in a digital version from Dissertation Abstracts.

Thèse doctorat : Ecologie Microbienne : Villeurbanne, INSA : 2005. / Titre provenant de l'écran-titre. Bibliogr. p. 107-121.

Reproduction de : Thèse de doctorat : Écologie microbienne : Lyon 1 : 2007. / Titre provenant de l'écran titre. 335 réf. bibliogr.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Hung-wen Liu. Vita. Includes bibliographical references. Also available from UMI.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.