Abstract
Cyanobacteria are potential organisms being exploited for a wide range of
biotechnological applications. They are photosynthetic bacteria and grow in a carbonfree medium and become attractive hosts for biotechnology industries. Cyanobacteria
can utilize solar energy and atmospheric CO2
for the growth and synthesis of
biomolecules. It is used in many large-scale preparations of various bioproducts such as
pharmaceuticals, biofuels, etc. Cyanobacteria become target organisms for the next
generation of biofactories for producing desired products with a low-cost technology.
The problem in the metabolic engineering of Cyanobacteria is due to ploidy. It has
multiple copies of chromosomes ranging from 3-218 copies. There are 12 copies of the
genome in Synechocystis PCC 6803 and 3 copies in Synechococcus PCC 7942.
Segregation analysis in the conventional genetic approaches of Cyanobacteria becomes
laborious due to its polyploidy. Modern genome editing tools such as CRISPR-Cas9
and 12 are available to perform genome editing. CRISPR-Cas9 has been used in a wide
range of Cyanobacteria such as Synechococcus elongates UTEX 2973, Synechocystis
sp. PCC 6803. To avoid toxic effects caused by Cas-9, a low-level expression system is
adopted in Cyanobacteria. Cas-9 base genome editing was applied in Synechococcus
and produced succinate 11-fold higher than the normal. Cas-9 is used to cure plasmids
in Synechocystis sp. PCC 6803 to develop a shuttle vector for heterologous expression.
Another variant of genome editing tool is CRISPR-Cas12a, which is successfully used
in Synechocystis sp.