Table 1.

Common cyanobacterial model organisms.

Strain	Genome size	Endogenous plasmids	Lifestyle features	DNA transfer methods
Nostoc sp. PCC 7120	6.4 Mb	6 plasmids size ranging from 5.6 to 408 kb	Freshwater; filamentous	Conjugation (Wolk et al., 1984), electroporation (Thiel and Poo, 1989)
Synechococcus elongatus PCC 7942	2.7 Mb	46 kb plasmid (& 7.6 kb non-essential plasmid)	Freshwater; unicellular	Conjugation (Tsinoremas et al., 1994), natural transformation (Shestakov and Khyen, 1970), electroporation (Marraccini et al., 1993)
Synechococcus elongatus UTEX 2973	2.7 Mb	46 kb plasmid	Freshwater; unicellular	Conjugation (Yu et al., 2015)
Synechococcus sp. PCC 7002	3.0 Mb	6 plasmids size ranging from 4.8 to 186 kb	Euryhaline; unicellular	Conjugation (Kopka et al., 2017), natural transformation (Stevens and Porter, 1980)
Synechocystis sp. PCC 6803	3.6 Mb	7 plasmids size ranging from 2.3 to 120 kb	Freshwater; unicellular	Conjugation (Marraccini et al., 1993), natural transformation (Grigorieva and Shestakov, 1982), ultrasonic transformation (Zang et al., 2007), electroporation (Marraccini et al., 1993)

Features of the most frequently-used model organisms for studies on cyanobacterial physiology and metabolic engineering. Size of primary genome, endogenous extrachromosomal plasmids, osmotolerance, and routinely utilized genetic transformation methods are reported.