Cyanobacteria Are Oxygenic, Photosynthetic Prokaryotes Which Have Recently Been Recognized As Having Potential In Biotechnology As Biofertlizer As Well As Producer of Novel Bioactive Molecules. the Present Study Focuses on Temperature Induced Alterations In the Lipid and Fatty Acid Composition of the Cyanobacterium Scytonema Geitleri Bharadwaja Isolated from the Roof-Top of Botany Department, Banaras Hindu University, and Varanasi, India. S. Geitleri Bharadwaja Was Grown In Chu-10 Medium and Maintained at 28 ±10C Under 14:10H Light-Dark Rhythm. Fatty Acids Recovered After Tlc Were Analyzed In a Gas Chromatograph Fitted With Flame Ionization Detector. Temperature Induced Alterations In Lipid and Fatty Acids Composition of S. Geitleri Were Assessed By Measuring the Lipids and Fatty Acids of the Cyanobacterium Grown at 15 and 30Oc For 15 Days. a Significant Reduction In the Level of Total As Well As Individual Class Lipid Namely Mgdg, Dgdg, Sqdg and Pg Was Observed In S. Geitleri at 150C to That of 300C. In Contrast, the Levels of Polyunsaturated and Unsaturated Fatty Acids Increased at 150C to That of 300C.The Results Suggest That at Low Temperature Stress, S. Geitleri Had a Much Higher Content of Pufas and Lower Content of Mufas, Leading to a Higher Degree of Fatty Acid Unsaturation. the Shift In Growth Temperature Could Induce the Processes of Desaturation and Acyl Chain Elongation to a Greater Extent Through the Feedback of an Array of Desaturases and Elongases.