Enhancing Chlorobenzene Biodegradation by Delftia tsuruhatensis Using a Water-Silicone Oil Biphasic System.

In this study, a water-silicone oil biphasic system was developed to enhance the biodegradation of monochlorobenzene (CB) by Delftia tsuruhatensis LW26. Compared to the single phase, the biphasic system with a suitable silicone oil fraction (v/v) of 20% allowed a 2.5-fold increase in the maximum tolerated CB concentration. The CB inhibition on D. tsuruhatensis LW26 was reduced in the presence of silicone oil, and the electron transport system activity was maintained at high levels even under high CB stress. Adhesion of cells to the water-oil interface at the water side was observed using confocal laser scanning microscopy. Nearly 75% of cells accumulated on the interface, implying that another interfacial substrate uptake pathway prevailed besides that initiated by cells in the aqueous phase. The 8-fold increase in cell surface hydrophobicity upon the addition of 20% (v/v) silicone oil showed that silicone oil modified the surface characteristics of D. tsuruhatensis LW26. The protein/polysaccharide ratio of extracellular polymeric substances (EPS) from D. tsuruhatensis LW26 presented a 3-fold enhancement. These results suggested that silicone oil induced the increase in the protein content of EPS and rendered cells hydrophobic. The resulting hydrophobic cells could adhere on the water-oil interface, improving the mass transfer by direct CB uptake from silicone oil.

[Isolation and Identification of a Chlorobenzene-degrading Bacterium and Its Degradation Characteristics].

A bacterium strain LW26 which could utilize chlorobenzene (CB) as sole carbon and energy source was isolated from a biotrickling filter reactor treating CB-contaminated off-gas. Based on its morphological and physiological characteristics, as well as the analysis of 16S rRNA gene sequence and Biolog test, the strain LW26 was identified as Delftia tsuruhatensis. To our best knowledge, it is the first time that the strain Delftia tsuruhatensis was applied for CB purification. In this study, the effects of temperature, pH, initial CB concentration and Cl- concentration on the biodegradation were investigated. The results showed that the optimal temperature and pH for CB biodegradation were 25℃ and 7.0,respectively; the maximum CB tolerated concentration for LW26 was as high as 500 mg·L-1; when the concentration of Cl- was above 0.14 mol·L-1, the CB degradation was significantly restrained. The degrading process of the strain LW26 followed the Haldane kinetic model and the maximum specific growth rate and the maximum specific degradation rate were 0.42 h-1 and 2.53 h-1, respectively.GC-MS analysis of the metabolites revealed that CB was firstly converted to o-chlorophenol by strain LW26. Combined with the activity of catechol dioxygenase, it can be speculated that CB was finally mineralized to CO2, or converted to cell biomass after processes of ortho cleavage,dechlorination and oxidation.

Repression of Slc24a5 can reduce pigmentation in chicken.

Slc24a5 is a putative cation transporter, which is a member of the potassium-dependent sodium-calcium ion exchanger family. Association of the Slc24a5 gene with pigmentation has been established in Zebrafish, mice and humans. Despite these findings, its function in chicken remains unknown. The intent of this study was to describe the association of Slc24a5 with respect to melanin deposition in the chicken using RNAi. The objective was to detect the variety of melanin deposition caused by the down-regulation of Slc24a5 in chicken retinal pigment epithelium (RPE) cells. Nine siRNAs that targeted against Slc24a5 mRNA were found to be effective in suppressing Slc24a5 gene expression in 293FT cells. The most effective target tested effectively inhibited Slc24a5 expression in mRNA and subsequently reduced protein levels in RPE cells. These results show that down-regulation of Slc24a5 results in a reduction of melanin content, as well as a decrease of melaeneous type ß and type χ melanosomes simultaneously. Taken together, this work suggests that Slc24a5 function is conserved in the chicken, and necessary for melanin synthesis.