Growth and nitrogen fixation by immobilized cyanobacteria

Abstract

The nitrogen-fixing photosynthetic cyanobacteria have significant potential for utilization as a biological system for the production of reduced nitrogen compounds, either by industrial fermentation or in the environment as soil inocula. In either system, the ability to immobilize cyanobacteria on the external surface of fibrous substrata would significantly improve the ease of manipulation of the cells, control of growth, and product recovery without the complications inherent in immobilization by entrapment. We have shown that the filamentous heterocystous species Nostoc muscorum is naturally able to attach to a variety of different fibres, both natural and artificial. Attached cells are able to grow and fix nitrogen in both liquid and plate culture. Nitrogen-fixing cells attach to the fibres much more readily than do non-fixing cells, suggesting that the physiological and morphological changes accompanying heterocyst differentiation result in the production of specific attachment sites. Scanning electron microscopy of attached cells shows that heterocysts act as attachment sites and that the external cell wall material specifically synthesized around the heterocysts may be acting as the biological “glue” for this attachment.