Cyanobacteria as a Host Organism

Fabienne Duchoud, Derrick S.W. Chuang, and James C. Liao 15.1 

This chapter first gives a general introduction to cyanobacteria physiology as well as their genetic tools, which are important background for utilizing these organisms for industrial apphcations. We then review works on the development of strains as potential cell factories for the production of commercially relevant compounds, with a focus on primary metabolites. 

Introduction of foreign DNA into cyanobacteria has been demonstrated in laboratory for several strains, and is now a common practice [50]. A few unicellular cyanobacteria are naturally competent for transformation, and can uptake foreign DNA from their environment in the form of plasmid or linear DNA [51]. Among naturally competent strains are the model freshwater cyanobacteria S. elongatus PCC 7942 and Synechocystis PCC 6803, as well as the marine Synechococcus PCC 7002 and the thermophile Jhermosynechococcus elongatus BP-1 [52—56]. 

DNA has allowed the generation of mutants with gene disruption or heterologous gene overexpression when the incoming DNA is incorporated into a neutral site. 

Gene expression in cyanobacteria, whether on a self-replicating plasmid or integrated in the genome, needs to be driven by a specific promoter that can be recognized by the host. Only a limited number of promoters have been evaluated for this purpose in cyanobacteria [50]. Most known promoters are native to the host organism from genes required for photosynthesis and expressed in relatively 

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Varnishes host a wide array of organisms (Kuhlman et al., 2005, 2006 Schelble et al., 2005) such as lichens (Laudermilk, 1931), microcolonial fungi (Boms et al., 1980 Staley et al., 1983 Gorbushina et al., 2002) gram-positive bacteria (Perry et al., 2003), cyanobacteria and other organisms (Krumbein, 1969)... 

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