[Growth and polysaccharide formation in Sinorhizobium meliloti strains in an air-lift-type fermentor. Effect on nodulation velocity in alfalfa plants]

Abstract

In this paper the influence of the exopolysaccharides produced by Sinorhizobium meliloti strains on the nodulation rates in alfalfa plants has been considered. The experiments were performed in a rotary shaker and in an air-lift type fermentor. Different Sinorhizobium meliloti strains were used. Bacterial growth rates were determined by viable cell counts. Exopolysaccharide concentration was determined by precipitation with ethanol. It was observed that maximum cell concentration was in the order of 1 x 10(10) cell/ml and exopolysaccharide content was approximately 11 g/l. The experiments performed with alfalfa plants in a controlled environment chamber showed that, when inoculation was carried out with diluted suspensions (1/10), nodulation time was reduced from 10 to 4 days, while the strains retained their symbiotic properties.