| Deinococcus radiodurans is well known for its resistance to y-ray, UV radiation, desiccation, oxidants and damaging agents. The robustness of this bacterium is due to its strong oxidative species (ROS) resistance mechanisms that protect proteins from oxidative damage and a DNA repair process that accomplishes an efficient and precise reassembly of DNA fragments. But there are still a lot of uninvestigated genes and protein, these gene’s functions and mechanisms may be related to its extreme resistance. In this paper. DR1790and carotenoids fermentation preparation were studied for their functions in cellular resistance and protection in vivo, respectively, which will help to further understand the extreme resistance of D radiodurans.1. The DR1790was analyzed using bioinformatics methods, it is located on a chromosome1in D. radiodurans. Multiple sequence alignments showed that it is homologous with yellow protein, containing major royal jelly protein motif.2. The D. radiodurans DR1790mutant (Rl△dr1790) and complementation strain (mutant Dr1790com) were constructed using a deletion replacement method. Compared with wild type, R1△dr1790mutant in carotenoid was not be changed, but showed low growth rate, a high proportion of damaged membranes, sensitivie to hydrogen peroxide of above10mmol/L and radiation of above4kGy, and had significantly increasing protein carbonyl content (P<0.05). These were all recovered in the complementation strain mutant Dr1790com. These results indicated that DR1790in D. radiodurans is related with cellular resistance to radiation and oxidants.3. Fluorescence labeling assay demonstrated that dr1790-encoded yellow-related protein is a membrane protein. Transcript profiling by microarray and QRT-PCR analysis of the R1△dr1790mutant suggested that some genes involved in protein quality control such as chaperones and proteases were induced, while others involved in protein secretion and transport were strongly reppressed. In additional, the expression of genes with predicted functions involved in antioxidant system, electron transport, and energy metabolism were significantly altered by the disruption of DR1790. However some genes in carotenoid biosynthesis were not significant changed. These results indicate that DR1790plays a pleiotropic role in survival of prokaryote cell and contributes to the extraordinary resistance of D. radiodurans.4. Soy whey is used as culture medium of D. radiodurans for fermentation carotenoids. The suitable fermentation extraction conditions were determined (pH7.0-7.3, adding1%glucose and0.1%MgSO4, acid hot wall-breaking ethanol extract). The combination of soy whey and prokaryotic bacterium of D. radiodurans to produce natural carotenoids was realized with characteristics of waste utilization, low cost, product with high safety etc. The major component in the ethanol extract of carotenoids from D. radiodurans (EDR) was deinoxanthin with56.8%. EDR was proved to display strong reducing activity and lipid peroxidation inhibition activity in vitro. At a concentration10μg/ml. the reducing ability of EDR is6.4times and20.1times higher than β-carotene and ascorbic acid, respectively. At a concentration10.0μg/mL. the inhibitory effect of extract on lipid peroxidation was greater than that of ascorbic acid at a concentration50μg/mL.5. Carbon tetrachloride (CCI4) is a well-known hepatotoxin. which cause liver damage. In this study, we report for the first time the effects of deinoxanthin-rich extract derived from D. radiodurans on CCl4-induced hepatic damage in mice. Pretreatment with EDR (400mg/kg b.w.) significantly reduced activities of serum ALT. AST and ALP. as well as hepatic MDA levels (P<0.05), but increased the activities of GSH-Px. CAT and SOD. Histopathological assessment showed that liver tissue damage was decreased by the protective effect of EDR. The results show that EDR can protect mice against CCl4-induced hepatic damage by its antioxidant activities. |
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