ISOLATION AND CHARACTERISATION OF SOIL-BORNE UREASE PRODUCING BACTERIA

Abstract

Urease producing bacteria are significant for their increasing roles in human pathogenicity, biocementation and as soil fertilizer. This study was therefore, aimed at isolation of urease producers from urea-rich soil samples collected from various locations in The Federal University of Technology, Akure, Nigeria and their use on seed germination. A total of five urea rich soil samples were aseptically collected randomly from various locations at different depths. Isolation of the various bacterial species was done using nutrient agar, MacConkey agar, eosin methylene blue agar and Salmonella-Shigella agar. Identification of isolates was done using standard microbiological and biochemical procedures. The urease producing strains of bacteria were selected using the urease hydrolysis test. Urea tolerance level was determined using the standard assay technique. The strains which tolerate high urea concentrations were selected and used as biofertilizer for cowpea and maize production. Physicochemical properties of the soils used in the study were determined. Results revealed the presence of thirty-four bacterial strains of nine species; Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Proteus vulgaris, Klebsiella oxytoca, Shigella boydii and Salmonella typhi. Proteus mirabilis, Klebsiella pneumoniae, Proteus vulgaris and Klebsiella oxytoca were selected on the basis of qualitative and quantitative screening analysis for urease activity. Urea tolerance test revealed that Proteus vulgaris had the highest growth rate of 37.00±1.00 at a urea concentration of 10 mg/ml with the growth rate decreasing as urea concentration increased. Klebsiella oxytoca also showed high growth rate of 36.00±1.00 at a urea concentration of 10 mg/ml. Growth rate decreased with increasing urea concentration. Field study of cowpea and maize inoculated with urease producing bacteria revealed that Proteus vulgaris had the fastest germination rate of 116 hours at inoculum concentration of 50 ml for cowpea. Germination decreasing as inoculum concentration decreased. And Klebsiella oxytoca having the fastest germination of 95 hours at inoculum concentration of 50 ml for maize. Germination rate also decreased as inoculum concentration decreased. These bacteria with high urea tolerance level can be used for diverse purposes ranging from enzyme production, medical uses to calcite precipitation in biocementation and in agricultural soils especially in nitrogen volatilization.