Biomedical subjects

Wei E Huang

Publications and source records attributed to Wei E Huang.

8 recordsLinked to original sources

PubMed2006

Rapid characterization of microbial biodegradation pathways by FT-IR spectroscopy.

Fourier transform-infrared (FT-IR) spectroscopy has become an important tool for rapid analysis of complex biological samples. The infrared absorbance spectrum could be regarded as a "fingerprint" which is characteristic of biochemical substances. In this study, Pseudomonas putida NCIMB 9869 was grown with either 3,5-xylenol or m-cresol as the sole carbon source, each inducing different metabolic pathways for m-cresol biotransformation. FT-IR spectroscopy was capable of differentiating both induced cultures of P. putida NCIMB 9869 as well as the resulting biotransformation product mixtures. FT-IR spectral analysis indicated that carboxylic acids were key chemicals responsible for distinguishing the products of the two catabolic pathways. Gas chromatography-mass spectrometry (GC-MS) was performed to validate the FT-IR analysis, indicating that two carboxylic acids, 3-hydroxybenzoic acid and 2,5-dihydroxybenzoic acid, were present as m-cresol biotransformation products from 3,5-xylenol-grown cells, but were absent in m-cresol-grown cells. The ability to use FT-IR to rapidly distinguish between biotransformation product mixtures as well as differentially induced bacterial strains suggests this approach might be a valuable tool for screening large biotransformation assays for novel products and metabolic mutants.

Cresols↗

PubMed2006

Consideration of future requirements for Raman microbiology as an examplar for the ab initio development of informatics frameworks for emergent OMICS technologies.

Raman spectroscopy of single bacteria provides an OMIC-like view of the chemical status of individual cells, reporting on metabolism, cell stress and growth, and is likely to become a significant tool in environmental and medical microbiology. We advocate the early development of integrated data models and informatics frameworks, in parallel with the development of Raman hardware and experimental protocols, in order to maximize the benefits of this emerging OMIC technology to the research community.

Computational Biology↗

PubMed2006

Quantitative in situ assay of salicylic acid in tobacco leaves using a genetically modified biosensor strain of Acinetobacter sp. ADP1.

Salicylic acid (SA) plays important roles in plants, most notably in the induction of systemic acquired resistance (SAR) against pathogens. A non-destructive in situ assay for SA would provide new insights into the functions of SA in SAR and other SA-regulated phenomena. We assessed a genetically engineered strain of Acinetobacter sp. ADP1, which proportionally produces bioluminescence in response to salicylates including SA and methylsalicylate, as a reporter for salicylate accumulation in the apoplast of plant leaves. SA was measured quantitatively in situ in NN genotype tobacco (Nicotiana tabacum L. cv Xanthi-nc) leaves inoculated with tobacco mosaic virus (TMV). The biosensor revealed accumulation of apoplastic SA before the visible appearance of hypersensitive response (HR) lesions. When the biosensor was infiltrated into TMV-inoculated leaves displaying HR lesions at 90 and 168 h post-inoculation, salicylate accumulation was detected predominantly in tissues surrounding the lesions and in veins adjacent to HR lesions. These images are consistent with previous data demonstrating that SA accumulation occurs prior to and following the onset of visible HR lesions. We also used the biosensor to observe apoplastic SA accumulation in tobacco leaves inoculated with virulent and HR-eliciting strains of the bacterial plant pathogen Pseudomonas syringae. The work demonstrates that the Acinetobacter sp. ADP1 biosensor is a useful new tool to non-destructively assay salicylates in situ and to map their spatial distribution in plant tissues.

Acinetobacter↗

PubMed2005

Insight into pollutant bioavailability and toxicity using Raman confocal microscopy.

Raman confocal microscopy was used to discriminate between cultures of Burkholderia xenovorans LB400 exposed to four different common environmental pollutants: phenanthrene, dodecane, 3-chlorobiphenyl and pentachlorophenol. Evidence is presented for the application of Raman spectroscopy as a bioassay for pollutant bioavailability and toxicity.

Alkanes↗

PubMed2005

Chromosomally located gene fusions constructed in Acinetobacter sp. ADP1 for the detection of salicylate.

Acinetobacter sp. ADP1 is a common soil-associated bacterium with high natural competency, allowing it to efficiently integrate foreign DNA fragments into its chromosome. This property was exploited to engineer salicylate-inducible luxCDABE and green fluorescent protein (GFP) variants of Acinetobacter sp. ADP1. Specifically, Acinetobacter sp. ADPWH_lux displayed the higher sensitivity when comparing the two variants (minimum detection c. 0.5-1 microM salicylate) and a faster turnover of the lux marker gene, making it suitable for whole-cell luminescence assays of salicylate concentration. In contrast, the longer maturation and turnover times of the GFP protein make the Acinetobacter sp. ADPWH_gfp variant more suited to applications involving whole-cell imaging of the presence of salicylate. The sensitivity of the luxCDABE variant was demonstrated by assaying salicylate production in naphthalene-degrading cultures. Assays using ADPWH_lux specifically mapped the kinetics of salicylate production from naphthalene and were similar to that observed by high-performance liquid chromatography (HPLC) data. However, ADPWH_lux exhibited the higher sensitivity, when compared with HPLC, for detecting salicylate production during the first 24 h of naphthalene metabolism. These data demonstrate that the engineered Acinetobacter variants have significant potential for salicylate detection strategies in laboratory and field studies, especially in scenarios where genetic stability of the construct is required for in situ monitoring.

Acinetobacter↗

PubMed2004

Raman microscopic analysis of single microbial cells.

We demonstrate the utility of the Raman confocal microscope to generate a spectral profile from a single microbial cell and the use of this approach to differentiate bacterial species. In general, profiles from different bacterial taxa shared similar peaks, but the relative abundances of these components varied between different species. The use of multivariate methods subsequently allowed taxa discrimination. Further investigations revealed that the single-cell spectra could be used to differentiate between growth phases of a single species, but these differences did not obscure the overall interspecies discrimination. Finally, we tested the efficacy of the method as a means to identify cells responsible for the uptake of a specific substrate. A single strain was grown in media containing incrementally varying ratios of (13)C(6) to (12)C(6) glucose, and it was found that (13)C incorporation shifted characteristic peaks to lower wavenumbers. These findings suggest that Raman microscopy has significant potential for studies requiring the taxonomic identity and functioning of single microbial cells to be determined.

Bacteria↗

PubMed2003

Dissolved oxygen imaging in a porous medium to investigate biodegradation in a plume with limited electron acceptor supply.

A novel combination of noninvasive imaging with an oxygen sensitive fluorescent indicator was developed to investigate the biodegradation processes occurring at the fringe of a solute plume, where the supply of oxygen was limited. A thin transparent porous matrix (156 x 120 x 3 mm) was made from quartz plates and quartz sand (212-300 microm) and enriched with acetate-degrading bacteria. A degrading plume developed from a continuous acetate source in the uniform flow field containing dissolved oxygen. Ruthenium (II)-dichlorotris(1,10-phenanthroline) (Ru(phen)3Cl2), a water-soluble fluorescent dye, was used as an indicator of dissolved oxygen. The fluorescence intensity was dependent on the concentration of oxygen because the dissolved oxygen acted as collisional quencher. The oxygen distribution was interpreted from images recorded by a CCD camera. These two-dimensional experimental results showed quantitatively how the oxygen concentrations decreased strongly at the narrow plume fringe and that oxygen was depleted at the core of the plume. Separately, dispersivity was measured in a series of nonreactive transport experiments, and biodegradation parameters were evaluated by batch experiments. Two-dimensional numerical simulations with MT3D/RT3D used these parameters, and the predicted oxygen distributions were compared with the experimental results. This measurement method provides a novel approach to investigate details of solute transport and biodegradation in porous media.

Biodegradation, Environmental↗

PubMed2002

Physical modelling of solute transport in porous media: evaluation of an imaging technique using UV excited fluorescent dye.

The development and evaluation of a 2-dimensional physical model, which is designed to assist in the characterisation of complex solute transport problems in porous media, is described. The laboratory model is a transparent 2-dimensional porous media of nominal thickness and uses a non-invasive imaging technique in conjunction with a fluorescent dye tracer (sodium fluorescein) to monitor solute movements. Under ultraviolet (UV) illumination the dye emits visible light which is imaged by a CCD (Charge Coupled Device) camera. The image is processed to estimate the 2-dimensional distribution of tracer concentrations. The system can successfully model a simple contaminant plume within a homogenous porous matrix constructed from glass beads (60-100 microm). Experimental results show that transverse dispersion coefficient was 3.9 x 10(-10) m2/s when sodium fluorescein transported in porous matrix with a walter velocity of 5.71 x 10(-6) m/s. The low transverse dispersion coefficient suggests that the molecular diffusion of solute cannot be neglected under low velocity of the water. The advantages of using UV rather than an ordinary light system are a reduction in noise and experimental errors. Errors due to light dispersion within the model are shown to be negligible for the current model. Since contaminant with aromatic rings are usually fluorescent and biological samples can be labelled by fluorescent dye, this imaging technique using UV excited fluorescent dye will be used to investigate biodegradation process in porous media.

Calibration↗