从土壤中分离筛选一株高产胞外多糖的菌株PYQ4，运用分子生物学技术对其进行鉴定，并探究其胞外多糖(EPS)对短波紫外线(UVC)引起人永生化角质细胞(HaCaT)损伤的保护作用和保护机制。结果表明，筛选并分离得到的菌株PYQ4为罗氏假单胞菌(Pseudomonas rhodesiae)。菌株PYQ4发酵48 h后多糖产量可达2.50 g/L，其所产EPS在100~1000 μg/mL的浓度范围内对HaCaT细胞均无细胞毒性。在UVC辐照后，EPS的加入使得HaCaT细胞存活率上升，细胞内活性氧(ROS)含量下降同时减轻线粒体膜电位(MMP)的降低，差异均具有统计学意义(p < 0.05)，说明该EPS对UVC辐射HaCaT细胞引起的氧化损伤有显著保护作用。
A strain PYQ4 with high production of exopolysaccharide (EPS) was isolated from soil and identified by molecular biology techniques. The protective effect and its mechanism of the EPS produced by PYQ4 against UVC radiation on HaCaT cells were evaluated. The results showed that the strain PYQ4 was identified as Pseudomonas rhodesiae. After cultured for 48 h, the yield of EPS reached 2.50 g/L. The EPS was non-cytotoxic to HaCaT cells in the concentration range of 100 - 1000 μg/mL. After UVC irradiation, the treatment with EPS increased the survival rate of HaCaT cells, decreased the intracellular reactive oxygen species (ROS) content, and mitigated the collapse of mitochondrial membrane potential (MMP). The differences were all statistically significant (p <0.05), indicating that the EPS has a significant protective effect against oxidative damage caused by UVC radiation on HaCaT cells.