In search of cyanobacteria strains with bioconditioning and biofertilization effects for degraded soils in the semi arid and arid areas of South Africa

摘要

The ability of cyanobacteria to fix N_2and produce exopolysacharides varies widely among different strains. The objective of this study was to identify and isolate cyanobacteria strains with ability to fix N_2 and produce exopolysaccharides with a view to evaluate them for their biofertilization and conditioning potential of degraded soils in arid and semi arid areas of the Eastern Cape Province, South Africa. Cyanobacteria were isolated from four sites by culture and plating techniques using growthmedia BG11 for all strains and BG110 for atmospheric N2-fixing strains. The numbers of strains isolated were 2, 28, 35, and 32 for Guquka, Hertzog, Fort Cox College, and Qunu soils, respectively. Only three of the 97 strains had bioconditioning and biofertilization potential emphasizing the importance of screening in order to identify cyanobacteria strains suitable for improving the physical and chemical fertility of soils. Other isolated cyanobacteria strains produced no exopolysaccharide and exhibitednegligible nitrogenase activity under the assay conditions used. The results suggested that soils in arid and semi arid areas of South Africa have cyanobacteria strains with potential to improve the physical and chemical fertility of degraded soils.