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Publisher Summary The chapter discusses the developments in the construction of host–vector systems for gene cloning and analysis. On evaluating the present state of the cyanobacterial systems, it can be said that for Anacystis nidulans R2 (unicellular, obligately photoautotrophic, nonnitrogen fixing), a complete system has been developed and the first results have been obtained. Two strategies have been employed for developing host–vector systems. One uses hybrid plasmids that contain both a cyanobacterial and an Escherichia coli origin of replication. The other makes use of the integrational vectors that employ the extremely efficient recombination documented for at least two species, A. nidulans R2 and Synechocystis PCC6803. Anacystis nidulans is an obligately photoautotrophic organism, implying that along with benefits from light, it is also continuously exposed to the hazardous effects of solar radiation. Thus, A. nidulans R2 has an extremely efficient system of recombination, because recombination is intimately involved in the repair of radiation damage. The main characteristics of a good vector, in addition to easy manipulation in E. coli, are high transformation efficiency and stable maintenance in the cyanobacterium. |
