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Biomedical subjects

G K Robinson

Publications and source records attributed to G K Robinson.

15 recordsLinked to original sources
PubMed2005

Monitoring changes in nisin susceptibility of Listeria monocytogenes Scott A as an indicator of growth phase using FACS.

Listeria monocytogenes has previously been shown to adapt to a wide variety of environmental niches, principally those associated with low pH, and this compromises its control in food environments. An understanding of the mechanism(s) by which L. monocytogenes survives unfavourable environmental conditions will aid in developing new food processing methods to control the organism in foodstuffs. The present study aimed to gain a further understanding of the physiological basis for the differential effects of one control strategy, namely the use of the lantibiotic nisin. Using propidium iodide (PI) to probe membrane integrity it was shown that L. monocytogenes Scott A was sensitive to nisin (8 ng mL(-)) but this was growth phase dependent with stationary phase cells (OD600=1.2) being much more resistant than exponential phase cells (OD600=0.38). We demonstrate that, using a combination of techniques including fluorescence activated cell sorting (FACS), the membrane adaptations underpinning nisin resistance are triggered much earlier (OD600<0.5) than the onset of stationary phase. The significance of these findings in terms of mechanism and application are discussed.

Anti-Bacterial Agents↗
PubMed2003

Bacterial community structure and physiological state in a biofilm reactor degrading 4-chloroaniline.

Degradation of 4-chloroaniline in the presence of aniline by a microbial community in a laboratory-scale biofilm reactor was evaluated. The starter inoculum was isolated and reconstructed from a percolating column enrichment of Indonesian agricultural soil. The capacity to mineralise and detoxify 4-chloroaniline in the presence of aniline was demonstrated by the biofilm reactor when operated at high hydraulic retention time (HRT; 0.87 h). At low HRT (0.23 h and 0.39 h) 4-chlorocatechol accumulated in the effluent, accompanied by a decrease in dechlorination and detoxification. When returned to high HRT (2.14 h), the accumulation of 4-chlorocatechol stopped and the extent of dechlorination and detoxification increased. Bacteria other than the original inoculum appeared in the reactor when the operating mode was switched from closed cycle to open cycle. One of these bacteria, identified as Pseudomonas putida R1 by partial 16S rDNA sequencing, subsequently dominated the reactor at every HRT imposed. PCR-based single-strand conformational polymorphism of 16 s rDNA and traditional cultivation procedures indicated that the bacterial composition in the reactor shifted in response to applied HRT. The relationship between the bacterial abundance and the degradation capacity of the reactor is discussed.

Aniline Compounds↗
PubMed2001

The pancreas-specific protein disulphide-isomerase PDIp interacts with a hydroxyaryl group in ligands.

Using a cross-linking approach, we have recently demonstrated that radiolabelled model peptides or misfolded proteins specifically interact in vitro with two members of the protein disulphide- isomerase family, namely PDI and PDIp, in a crude extract from sheep pancreas microsomes. In addition, we have shown that tyrosine and tryptophan residues within a peptide are the recognition motifs for the binding to PDIp. Here we examine non-peptide ligands and present evidence that a hydroxyaryl group is a structural motif for the binding to PDIp; simple constructs containing this group and certain xenobiotics and phytoestrogens, which contain an unmodified hydroxyaryl group, can all efficiently inhibit peptide binding to PDIp. To our knowledge this is the first time that the recognition motif of a molecular chaperone or folding catalyst has been specified as a simple chemical structure.

Animals↗
PubMed2000

Ultrastructure of two oil-degrading bacteria isolated from the tropical soil environment.

Two oil-degrading bacteria identified as Pseudomonas aeruginosa and Micrococcus luteus were isolated from crude-oil-polluted soils in Nigeria. The organisms were grown on n-hexadecane and sodium succinate and then examined for the presence of hydrocarbon inclusions. Inclusion bodies were found in n-hexadecane-grown cells and were absent in succinate-grown cells. Formation of hydrocarbon inclusion bodies appears to be a general phenomenon among hydrocarbon utilizers.

Alkanes↗
PubMed1999

Biocatalysts for clean industrial products and processes.

Biocatalysis inherently offers the prospect of clean industrial processing and has become an accepted technology throughout most sectors. The convergence of biology and chemistry has enabled a plethora of industrial opportunities to be targeted, while discoveries in biodiversity and the impact of molecular biology and computational science are extending the range of natural and engineered biocatalysts that can be customised for clean industrial requirements.

Biodegradation, Environmental↗
PubMed1996

Influence of chlorobenzoates on the utilisation of chlorobiphenyls and chlorobenzoate mixtures by chlorobiphenyl/chlorobenzoate-mineralising hybrid bacterial strains.

Chlorobenzoates (CBA) arise as intermediates during the degradation of polychlorinated biphenyls (PCBs) and some chlorinated herbicides. Since PCBs were produced as complex mixtures, a range of mono-, di-, and possibly trichloro-substituted benzoates would be formed. Chlorobenzoate degradation has been proposed to be one of the rate-limiting steps in the overall PCB-degradation process. Three hybrid bacteria constructed to have the ability to completely mineralise 2-, 3-, or 4-monochlorobiphenyl respectively, have been studied to establish the range of mono- and diCBAs that can be utilised. The three strains were able to mineralise one or more of the following CBAs: 2-, 3-, and 4-monochlorobenzoate and 3,5-dichlorobenzoate. No utilisation of 2,3-, 2,5-, 2,6-, or 3,4-diCBA was observed, and only a low concentration (0.11 mM) of 2,4-diCBA was mineralised. When the strain with the widest substrate range (Burkholderia cepacia JHR22) was simultaneously supplied with two CBAs, one that it could utilise plus one that it was unable to utilise, inhibitory effects were observed. The utilisation of 2-CBA (2.5 mM) by this strain was inhibited by 2,3-CBA (200 microM) and 3,4-CBA (50 microM). Although 2,5-cba and 2,6-cba were not utilised as carbon sources by strain jhr22, they did not inhibit 2-cba utilisation at the concentrations studied, whereas 2,4-cba was co-metabolised with 2-cba. The utilisation of 2-, 3-, and 4-chlorobiphenyl by strain JHR22 was also inhibited by the presence of 2,3- or 3,4-diCBA. We conclude that the effect of the formation of toxic intermediates is an important consideration when designing remediation strategies.

Biodegradation, Environmental↗
PubMed1992

Environmental regulation of alcohol metabolism in thermotolerant methylotrophic Bacillus strains.

The thermotolerant methylotroph Bacillus sp. C1 possesses a novel NAD-dependent methanol dehydrogenase (MDH), with distinct structural and mechanistic properties. During growth on methanol and ethanol, MDH was responsible for the oxidation of both these substrates. MDH activity in cells grown on methanol or glucose was inversely related to the growth rate. Highest activity levels were observed in cells grown on the C1-substrates methanol and formaldehyde. The affinity of MDH for alcohol substrates and NAD, as well as Vmax, are strongly increased in the presence of a Mr 50,000 activator protein plus Mg(2+)-ions [Arfman et al. (1991) J Biol Chem 266: 3955-3960]. Under all growth conditions tested the cells contained an approximately 18-fold molar excess of (decameric) MDH over (dimeric) activator protein. Expression of hexulose-6-phosphate synthase (HPS), the key enzyme of the RuMP cycle, was probably induced by the substrate formaldehyde. Cells with high MDH and low HPS activity levels immediately accumulated (toxic) formaldehyde when exposed to a transient increase in methanol concentration. Similarly, cells with high MDH and low CoA-linked NAD-dependent acetaldehyde dehydrogenase activity levels produced acetaldehyde when subjected to a rise in ethanol concentration. Problems frequently observed in establishing cultures of methylotrophic bacilli on methanol- or ethanol-containing media are (in part) assigned to these phenomena.

Alcohol Dehydrogenase↗
PubMed1991

Deinstitutionalization and mental health.

Better understanding of the problems related to deinstitutionalization is essential for all those involved with community care. Finding ways to address the issues raised by deinstitutionalization is the key to using all community resources-including home care-in building a better system of mental health care.

Community Mental Health Centers↗
PubMed1987

Radiological and magnetic resonance imaging of cervical spine instability: a case report.

Hypermobility and instability following injury and degenerative joint disease is poorly understood and often not recognized as the cause of the patients symptoms. Routine radiographs should be complemented by flexion/extension studies. Magnetic resonance imaging has been found useful in demonstrating degenerative disc disease, disc herniations, cord impingements and instabilities that are not amenable to diagnosis by myelograms and computed tomography.

Adult↗