Cyanobacteria: Multiple Stresses, Desiccation-Tolerant Photosynthesis and Di-nitrogen Fixation

Abstract

Cyanobacteria are gram-negative photoautotrophic prokaryotes. Their traditional name, i.e., blue green algae, alludes to an aquatic life. Indeed, many cyanobacteria are bound to a submerged life. However, cyanobacteria are ubiquitous on our planet (Whitton and Potts 2000), and as shown in Chap. 2 cyanobacteria also have very successfully conquered habitats outside the water all over the world ranging from the occupation of all kinds of surfaces including rocks of high elevation mountains, rocks in the tropics as well as the Antarctic, soil crusts in deserts and man-made structures from concrete buildings to plastic garbage bins. Terrestrial cyanobacteria are also symbionts in lichens (Chaps. 5–7). In their terrestrial habitats, cyanobacteria are subject to a multitude of stress factors or stressors, such as high light intensities including ultraviolet radiation, high and low temperatures including freezing, osmotic stress, salinity and drought including desiccation (Allakhverdiev et al. 2000; Singh et al. 2002; Lin et al. 2004; Potts et al. 2005; Büdel et al. 2008). In-depth studies of ecophysiological adaptations of cyanobacteria to a plethora of stresses are increasingly facilitated by the accumulation of sequence data, available e.g., for Prochlorococcus, Nostoc punctiforme, Gloeobacter and Synechococcus. Complete genomic sequences have been obtained for the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 and the filamentous, heterocyst-forming Anabaena sp. strain PCC 7120 (see Introduction of Singh et al. (2002) with references).