Hyo Bong Hong

Biodegradation of dibenzo-p-dioxin, dibenzofuran, and chlorodibenzo-p-dioxins by Pseudomonas veronii PH-03

The dioxin-degrading strain Pseudomonas veronii PH-03 was isolated from contaminated soil by selective enrichment techniques. Strain PH-03 grew on dibenzo-p-dioxin and dibenzofuran as a sole carbon source. Further, 1-chlorodibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin and other dioxin metabolites, salicylic acid, and catechol were also metabolized well. Resting cells of strain PH-03 transformed dibenzo-p-dioxin, dibenzofuran, 2,2′,3-trihydroxybiphenyl, and some chlorodioxins to their corresponding metabolic intermediates such as catechol, salicylic acid, 2-hydroxy-(2-hydroxyphenoxy)-6-oxo-2,4-hexadienoic acid, and chlorocatechols. The formation of these metabolites was confirmed by comparison of gas chromatography–mass spectrometry (GC–MS) data with those of authentic compounds. Although we did observe the production of 3,4,5,6-tetrachlorocatechol (3,4,5,6-TECC) from 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) with resting cell suspensions of PH-03, growth of strain PH-03 in the presence of 1,2,3,4-TCDD was poor. This result suggests that strain PH-03 is unable to utilize 3,4,5,6-TECC, even at very low concentration (0.01 mM) due to its toxicity. In cell-free extracts of DF-grown cells, 2,2′,3-trihydroxybiphenyl dioxygenase, 2-hydroxy-6-oxo-6-phenyl-2,4-hexadienoic acid hydrolase, and catechol-2,3-dioxygense activities were detected. Moreover, the activities of meta-pyrocatechase and 2,2′,3-trihydroxybiphenyl dioxygenase from the crude cell-free extracts were inhibited by 3-chlorocatechol. However, no inhibition was observed in intact cells when 3-chlorocatechol was formed as intermediate.

Centrifugal enhancement of Kaposi's sarcoma-associated virus infection of human endothelial cells in vitro

In order to improve the efficiency of infection of primary human endothelial cells in vitro of Kaposis sarcoma-associated herpesvirus (KSHV), the effect of low speed centrifugation was investigated. The recombinant KSHV, BAC36, was used to examine the centrifugal enhancement of KSHV. Infectivity was estimated by green fluorescent protein (GFP) expression and real-time RT-PCR. The enhancement of infectivity was dependent upon the time and force of centrifugation in human umbilical vein endothelial cells (HUVECs). Centrifugation enhanced the infectivity of KSHV by up to 70 fold compared to non-centrifugal control infection for the same period of time; viral mRNA expression was also enhanced by centrifugation. HUVECs that were centrifuged before infection with KSHV displayed no enhancement in infectivity; therefore, enhancement is believed to occur during centrifugation. In addition, the mechanisms of infection including the initial viral attachment to cells, lipid rafts, and clathrin-mediated and caveolae endocytosis appear to be similar in KSHV infection with and without centrifugal enhancement. These results show that low speed centrifugation could be a useful tool for improving the efficiency of KSHV infection in vitro.

Degradation of dibenzofuran by Pseudomonas putida Ph-01

Abstract The ability of a Pseudomonas putida PH-01 to degrade the dioxin-like compound dibenzofuran was characterized and the effect of extracellular substance produced during the incubation was determined. The strain grew aerobically on dibenzofuran as the sole source of carbon and energy, and the solubility of dibenzofuran was rapidly increased with the appearance of those extracellular substances. During the incubation, production of salicylic acid, catechol, gentisic acid, and other unidentified trace metabolic products was observed. After six days of incubation, catechol accumulated mainly in the culture medium.

Production of PDMS microparticles by emulsification of two phases and their potential biological application

ABSTRACT Poly(dimethylsiloxane) (PDMS) has been widely used for prototyping of chips. Among many kinds of microstructures, it is almost impossible to make few micron-sized PDMS particles through microfluidic focusing methods because of the highly viscous property of uncured PDMS. Vigorous mixing of PDMS with water resulted in small, spherical particles was found. Furthermore, a simple and easy method was devised to assure an emulsion state. The PDMS–water emulsion was made using two syringes connected by a needle. This emulsion was rapidly heated to cure the PDMS within the emulsion. The resultant PDMS was examined using spectroscopic methods to determine the particulate morphology and size distribution. PDMS particles of which the size was around 1 µm with a narrow size distribution was produced. DNA delivery into cultured animal cells through these PDMS microparticles was also demonstrated as an illustrative application. These biologically inert microparticles will find many more practical applications with additional fine-tuning modifications based on discussed considerations. GRAPHICAL ABSTRACT