A new diatom strain MD1 was isolated from seawater Spirulina culture at Guangzhou, China, and identified as Nitzschia sp.MD1.The biotechnological potential of MD1 was assessed through observation and studies on its growth, physiology and biochemistry.Results showed that the maximum average specific growth rate of MD1 was 0.62 d-1.It was proved that MD1 was poly-extremophilic, including adaptations to wide range of salinities, high bicarbonate concentration, and high pH.MD1 was thermophilic, and grew well under high level CO2 up to 99%.The optimal light intensity for MD1 was 140 μE m-2 s-1.It was also observed that significant upward pH shift of the culture took place corresponding to the photosynthetic.growth of MD 1.The total lipid content in MD1 biomass (dry weight) was 45.94%, and the unsaturated fatty acids and eicosapentaenoic acid (EPA) content of total fatty acids in MD1 was 64.69% and 13.38% respectively.It was also indicated that MD1 contained β-carotene and several secondary carotenoids.Nitzschia sp.MD1 should have promising potential to produce bio-diesel, high voluble EPA and other bio-products, and to be applied to sequestrate CO2 as well.