Requirement of alkanes for salt tolerance of Cyanobacteria: characterization of alkane synthesis genes from salt-sensitive Synechococcus elongatus PCC7942 and salt-tolerant Aphanothece halophytica

摘要

Cyanobacteria have been attracting great interest in the research area of biofuel production. All Cyanobacteria contain C-15-C-19 hydrocarbons, but physiological roles of hydrocarbons remain to be clarified. Recently, two universal but mutually exclusive hydrocarbon production pathways in Cyanobacteria were discovered. In this study, we constructed a deletion mutant of alkane synthesis genes in fresh water cyanobacterium Synechococcus elongates PCC 7942. The mutant was incapable to produce alkanes and exhibited normal growth phenotype at low salinity. But, the mutant became salt sensitive. Overexpression of alkane synthesis genes from halotolerant Aphanothece halophytica in Synechococcus PCC7942 restored the growth defect. The alkane synthesis gene from halotolerant cyanobacterium A.halophytica was salt induced and produced a significant amount of alkanes at high salinity. These results indicate the requirement of alkanes for salt tolerance, and the alkane synthesis genes from A.halophytica could be a promising candidate for future biofuel application.