Growth and Exopolysachharide composition of nitrogen fixing bacteria Azotobacter spp. in the presence of cadmium

Abstract

Hindersah R. 2015. Growth and Exopolysachharide composition of nitrogen fixing bacteria Azotobacter spp. in the presence of cadmium. Pros Sem Nas Masy Biodiv Indon 1: 1644-1648. Intensive and long-term application of phosphate (P) fertilizer can increase Cd concentration in the soil since they contain higher level Cadmium (Cd) as impurity than that present in the soil. Vegetable production in soil contains low available P rely on P fertilizer so that Cd accumulate in the soil. Nowadays, nitrogen-fixing Azotobacter is already being used in vegetable production. In the presence of Cd, one of resistance mechanism of Azotobacter to avoid Cd toxicity is by exopolysaccharides (EPS) synthesis. The objective of this experiment was to study the difference of growth and EPS composition of some Azotobacter isolates in the presence of Cd in liquid media. Three EPS-producing Azotobacter has been isolated from the rhizosphere of vegetation grown in Lembang Highland by using nitrogen-free media. Each Azotobaterisolate was grown in media containing a particular concentration of Cd for 84 hours at room temperature. Results showed that growth of all Azotobacter isolates was inhibited by 1 mM and 10 mM Cadmium chloride. However, the growth of isolate LKM6 in the presence of 0.1 mM cadmium chloride was better than that of another isolate. In the presence of 0.01 mM cadmium chloride, the growth of all isolates was not inhibited. Exopolysaccharides produced by the three isolates contained polysaccharide and organic acid but the concentration differed; the presence of Cd in liquid culture change EPS composition. These results suggest that for slightly Cd-contaminated soil, using Cdresistance biofertilizer Azotobacter might be recommended.