Investgating Physiological Roles Of Aliphatic Hydrocarbon Biosynthesis In Stress Response Of Cyanobacteria

Cyanobacterium is a kind of prokaryotic microorganism which can perform oxygenic photosynthesis.Due to its unique biological characteristics,including fast growth,low nutrition requirement,and easy for genetic engineering,cyanobacteria have been widely used in the research of renewable biofuels and chemicals recently.Alkanes are the major constituents of liquid fuels,such as gasoline,diesel and jet fuels.Alka(e)ne biosynthesis is ubiquitous in cyanobacteria.Alkane biosynthesis pathways were identified,while the physiological role of alkanes in cyanobacteria is not clear.This study aims to investigate the physiological roles of alka(e)ne biosynthesis in cyanobacteria.The model cyanobacterium Synechocystis sp.PCC 6803 was cultivated under different stress conditions to analyze profiles of alka(e)nes,fatty acids,and lipids.Heptadecane and heptadecene are the most abundant hydrocarbons in Synechocystis sp.PCC 6803.The alka(e)ne content increased when the temperature converted from normal condition to low temperature,and resulted in the marked increase of heptadecene and decrease of heptadecane.It is indicated that temperature reduction prompt alka(e)ne biosynthesis,especially the alkenes.After high salt stress to Synechocystis sp.PCC 6803,the content of the alka(e)ne increased,and this phenomenon was more significant in high alka(e)ne production mutant LX56.The results also showed that alka(e)ne biosynthesis can be improved to some extent under hypoxia condition.Besides,we also conducted the cultivation of the cyanobacteria in natural environment.The content of alka(e)nes appeared periodic cycle changes.It is indicated that alka(e)ne biosynthesis plays important roles in stress response in cyanobacteria.These studies will help to understand physiological roles of aliphatic hydrocarbons in microorganisms.Approaches and strategies will also be provided for aliphatic hydrocarbon production in cyanobacteria.