No description available.

Pseudomonas aeruginosa ATCC 9027 grew in a chemically defined medium with n-hexadecane or glucose, 0.5% (v/v or w/v, respectively), as the sole carbon source, and the K$ sb2$HPO$ sb4$, concentration was either 0.6 mM or 2.3 mM with both carbon sources. Only cells grown on n-hexadecane and 0.6 mM K$ sb2$HPO$ sb4$ produced pyocyanine. The variable lag period associated with cells grown on n-hexadecane was regulated by the state of the inoculating culture, grown on glucose and 2.3 mM K$ sb2$HPO$ sb4$. It was found that organic phosphate was more prevalent in cells grown on both phosphate concentrations with glucose and the high phosphate concentration with n-hexadecane, than it was for the low phosphate, n-hexadecane grown cells. The inorganic phosphate levels remained low under all conditions, decreasing as the cell culture became older. The inorganic polyphosphate level remained stable for all conditions, except in the high phosphate, n-hexadecane grown cells, where there was an increase.

The MexCD-OprJ multidrug efflux pump of Pseudomonas aeruginosa confers resistance to a range of antimicrobials. Although not expressed under normal laboratory conditions, exposure to the membrane-active biocides, chlorhexidine or benzalkonium chloride, results in mexCD-oprJ expression. This suggests that membrane disruption provides the inducing signal. Consistent with this, increased mexCD-oprJ expression was demonstrated in the presence of additional membrane-damaging agents including polymyxin B, ethanol, SDS, EDTA, the organic solvents n-hexane and p-xylene, and the antimicrobial peptides melittin, V8 and V681. MexCD-OprJ expression was initially verified through increased resistance to known MexCD-OprJ antimicrobial substrates and subsequently using a mexC-lacZ transcriptional fusion and RT-PCR. Since the P. aeruginosa sigma factor AlgU is responsive to envelope stress, it was of interest to ascertain whether AlgU is capable of mediating this increased mexCD-oprJ expression. Thus, the impact of AlgU loss on mexCD-oprJ expression in response to membrane-damaging agents was assessed in a algU strain. In contrast with above, little or no mexCD-oprJ expression (assessed using resistance to MexCD-OprJ antimicrobial substrates, the mexC-lacZ transcriptional fusion and RT-PCR) occurred in response to membrane-damaging agents in the algU strain, consistent with AlgU playing a role in the envelope stress inducibility of mexCD-oprJ. Overall, envelope stress, and the ability to react to this stress through AlgU, appears to play an important role in mexCD-oprJ induction. This suggests an important role for MexCD-OprJ in alleviating envelope stress, independent of its ability to export and provide resistance to antimicrobials. A gene, PA4596, whose product shows substantial homology to the NfxB repressor of mexCD-oprJ expression, occurs downstream of mexCD-oprJ and shows AlgU-dependence and chlorhexidine inducibility, suggesting a role in the chlorhexidine-induced, AlgU-mediated expression of mexCD-oprJ. Thus, the impact of PA4596 loss on mexCD-oprJ expression was assessed. Paradoxically, the loss of PA4596 increases mexCD-oprJ expression in wild-type cells in response to chlorhexidine treatment (as assessed through RT-PCR), while its loss compromises mexCD-oprJ expression in an nfxB mutant. Nonetheless, this suggests that PA4596 is involved in the induction of mexCD-oprJ and that its ability to induce mexCD-oprJ differs depending on the state of nfxB. / Thesis (Master, Microbiology & Immunology) -- Queen's University, 2007-07-31 12:03:52.535

The extraction of oil from microalgae was investigated. The study focused on the hydrothermal liquefaction of the microalgae Microcystis aeruginosa, Cyclotella meneghinia and Nitzschia pusilla. M. aeruginosa was collected from the Hartebeespoort dam, while C. meneghinia and N. pusilla were cultured in the laboratory. The experiments were conducted in a high pressure autoclave with an inert atmosphere. Sodium carbonate was studied as a potential catalyst. The hydrothermal liquefaction of M. aeruginosa, C. meneghinia and N. pusilla was carried out at various reaction temperatures and catalyst loads. For the liquefaction of M. aeruginosa the residence times were also varied. The reaction temperatures ranged from 260 to 340 °C, while the catalyst loads varied between 0 and 10 wt% Na2CO3. The residence time was varied between 15 and 45 minutes. The study showed that hydrothermal liquefaction of M. aeruginosa produced a maximum oil yield of 15.60 wt% at 300 °C, whereas the thermochemical liquefaction of C. meneghinia and N. pusilla produced maximum yields of 16.03 wt% and 15.33 wt%, respectively, at 340 °C. The residence time did not influence thermochemical liquefaction of the algae, while an increase in the catalyst load reduced the oil yield. The reaction conditions had no effect on the elemental composition or the calorific value of the thermochemical liquefaction oil. The calorific value of the hydrothermal liquefaction oils ranged from 28.57 to 35.90 MJ.kg -1 . Hydrothermal liquefaction of microalgae produced oil that can be used as substitute for coal in simple gasification processes. The study showed that microalgal blooms, such as the M. aeruginosa blooms of the Hartebeespoort dam, can be used for the extraction of oil through hydrothermal liquefaction. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2010.

The extraction of oil from microalgae was investigated. The study focused on the hydrothermal liquefaction of the microalgae Microcystis aeruginosa, Cyclotella meneghinia and Nitzschia pusilla. M. aeruginosa was collected from the Hartebeespoort dam, while C. meneghinia and N. pusilla were cultured in the laboratory. The experiments were conducted in a high pressure autoclave with an inert atmosphere. Sodium carbonate was studied as a potential catalyst. The hydrothermal liquefaction of M. aeruginosa, C. meneghinia and N. pusilla was carried out at various reaction temperatures and catalyst loads. For the liquefaction of M. aeruginosa the residence times were also varied. The reaction temperatures ranged from 260 to 340 °C, while the catalyst loads varied between 0 and 10 wt% Na2CO3. The residence time was varied between 15 and 45 minutes. The study showed that hydrothermal liquefaction of M. aeruginosa produced a maximum oil yield of 15.60 wt% at 300 °C, whereas the thermochemical liquefaction of C. meneghinia and N. pusilla produced maximum yields of 16.03 wt% and 15.33 wt%, respectively, at 340 °C. The residence time did not influence thermochemical liquefaction of the algae, while an increase in the catalyst load reduced the oil yield. The reaction conditions had no effect on the elemental composition or the calorific value of the thermochemical liquefaction oil. The calorific value of the hydrothermal liquefaction oils ranged from 28.57 to 35.90 MJ.kg -1 . Hydrothermal liquefaction of microalgae produced oil that can be used as substitute for coal in simple gasification processes. The study showed that microalgal blooms, such as the M. aeruginosa blooms of the Hartebeespoort dam, can be used for the extraction of oil through hydrothermal liquefaction. / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2010.

No description available.

Diss. (sammanfattning) Umeå : Univ., 2004. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of New South Wales, 2005. / Also available online.

Stuttgart, Univ., Diss., 2006.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.