Thermosynechococcus as a thermophilic photosynthetic microbial cell factory for CO 2 utilisation.

Thermophilic unicellular cyanobacterium Thermosynechococcus elongatus PKUAC-SCTE542, has been developed as a thermophilic photosynthetic microbial cell factory for CO2 utilisation. The strain exhibits its highest growth rate around 55 °C, can withstand up to 15% CO2 , and up to 0.5 M concentration of sodium bicarbonate. The strain is also capable of resisting a 200 ppm concentration of NO and SO2 in simulated flue gasses, and these compounds have a positive effect on its growth. Whole genome sequencing of the strain revealed the presence of numerous forms of active transport of nutrients and additional chaperones acting as the predominant mechanism of strain adaptation to high temperatures. Based on the sequenced genome, two neutral gene insertion sites have been identified and engineered using modular vectors. Site-specific knock-ins and knock-outs have been performed using the spectinomycin resistance gene and proved functional, enabling future application of the strain to produce biofuels and biochemicals from waste CO2 .