Antibiotic Resistance of Azotobacter Isolated from Mercury-Contaminated Area

Abstract

Nitrogen-fixing Azotobacter is a renewable source of biofertilizer for plant growth. Increased of antibiotic level in soil due to intensive used manure is believed to induce bacterial sensitivity to antaibiotic. An antibiotic sensitivity test has been carried out to study the inhibition effect of ampicillin, streptomycin, tetracycline and chloramphenicol on Azotobacter isolated from mercury-contaminated taling. The resistance test was performend by using disc plate method in Nitrogen-free Ashby’s agar with and without mercury. The results showed that the presence of 20 mg/L mercury in plate agar totally inhibited Azotobater growth. In the absence of mercury chloride, all isolates showed different sensitivity to antibiotics. Growth of Azotobacter buru1 was only inhibited by tetracycline. Azotobacter buru2 was susceptible to high and low concentration of tetracycline and streptomycin but they were resistance to low concentration of chloramphenicol as well as ampicillin; while Azotobacter bd3a were sensitive to all tested antibiotic. In conclusion, order of Azotobacter resistance to antibiotics in the absence of mercury was Bd3a<Buru2<Buru1. This research have not revealed the resistance of Azotobacter to antibiotic in the presence of mercury.