Biomedical subjects

Xin-Hui Xing

Publications and source records attributed to Xin-Hui Xing.

4 recordsLinked to original sources

PubMed2006

Simple and sensitive bacterial quantification by a flow-based kinetic exclusion fluorescence immunoassay.

A flow-based immunoassay system utilizing secondary-antibody coated microbeads and Cy5-secondary antibody for signal production was successfully developed to quantitate target bacteria with a kinetic exclusion assay (KinExA 3000 Instrument). It directly measured the concentration of unliganded antibody separated from the equilibrated mixture of antibody and bacteria through a 0.2 microm polyethersulfone membrane, enabling it to quantify the concentration of bacteria. The novel method demonstrated the qualities of rapidness, sensitivity, high accuracy and reproducibility, and ease to perform. Detection of Pseudomonas aeruginosa and Staphylococcus aureus was accomplished with low detection limits of 4.10 x 10(6) and 5.20 x l0(4)cells/mL, respectively, with an assay time of less than 15 min. The working ranges for quantification were 4.10 x l0(6) to 1.64 x l0(10)cells/mL for P. aeruginosa, and 5.20 x l0(4) to 1.04 x l0(9)cells/mL for S. aureus. It yielded an assay with at least 10-fold greater sensitivity than ELISA and could correctly assess the concentration of predominant bacterium spiked in the mixture of P. aeruginosa and S. aureus. With this reliable platform, the average amount of antibody bound by one cell in the maximum capability could be further provided: (1.6-2.5) x l0(5) antibodies for one P. aeruginosa cell and (2.2-2.7) x l0(8) antibodies for one S. aureus cell. The KinExA system is flexible to determine different kinds of bacteria conveniently by using anti-mouse IgG as the same immobilizing agent. However, a higher specificity of the antibodies to the target bacteria will be required for the use of this system with higher detection sensitivity.

Biosensing Techniques↗

PubMed2006

Functional expression of the particulate methane mono-oxygenase gene in recombinant Rhodococcus erythropolis.

In order to construct an expression system for the particulate methane mono-oxygenase (pMMO) gene (pmo), the structural gene cluster pmoCAB amplified from Methylosinus trichosporium OB3b was inserted into a shuttle vector pBS305 under the control of a dsz promoter and transformed into Rhodococcus erythropolis LSSE8-1. A stable transformant was successfully obtained using ethane as the sole carbon source. Fluorescence in situ hybridization results showed that the dsz promoter allowed the pmo genes to be transcribed in the recombinant strain. The effects of Cu2+ and Zn2+ concentrations on cell growth and pMMO activity in ethane-containing medium were examined. It was discovered that 7.5 microM Cu2+ and 1.8 microM Zn2+ were suitable to achieve high cell concentration and pMMO activity, but the amount of methanol accumulated during methane oxidation by the recombinant strain was still low.

DNA, Bacterial↗

PubMed2006

Biological wastewater treatment by a bioreactor with repeated coupling of aerobes and anaerobes aiming at on-site reduction of excess sludge.

Activated sludge has been widely used in wastewater treatment throughout the world. However, the biggest disadvantage of this method is the by-production of excess sludge in a large amount, resulting in difficulties in operation and high costs for wastewater treatment. Technological innovations for wastewater treatment capable of reducing excess sludge have thus become research topics of interest in recent years. In our present research, we developed a new biological wastewater treatment process by repeated coupling of aerobes and anaerobes (rCAA) to reduce the excess sludge during the treatment of wastewater. During 460-day continuous running, COD (300-700 mg/L) and TOC (100-350 mg/L) were effectively removed, of which the removal rate was above 80 and 90%, respectively. SS in the effluent was 13 mg/L on average in the rCAA bioreactor without a settling tank. The on-site reduction of the excess sludge in the rCAA might be contributed by several mechanisms. The degradation of the grown aerobes after moving into the anaerobic regions was considered to be one of the most important factors. Besides, the repeatedly coupling of aerobes and anaerobes could also result in a complex microbial community with more metazoans and decoupling of the microbial anabolism and catabolism.

Aerobiosis↗

PubMed2005

Rapid detection of a gfp-marked Enterobacter aerogenes under anaerobic conditions by aerobic fluorescence recovery.

A gfp- and kanamycin-resistance gene-containing plasmid pUCGK was successfully constructed and transformed into Enterobacter aerogenes to develop a rapid GFP-based method for quantifying the bacterial concentration under anaerobic conditions for production of biohydrogen. Since the use of GFP as a molecular reporter is restricted by its requirement for oxygen in the development of the fluorophore, fluorescence detection for the fluorescent E. aerogenes grown anaerobically for hydrogen production was performed by developing a method of aerobic fluorescence recovery (AFR) of the anaerobically expressed GFP. By using this AFR method, rapid and non-disruptive cell quantification of E. aerogenes by fluorescence density was achieved for analyzing the hydrogen production process.

Aerobiosis↗