تأثير العوامل البيئية على بكتيريا النيتروزوموناس والنيتروباكتر المعزولة من بعض الترب الليبية

Abstract

The aims of the present study were to determine the effect of some environmental and biochemical factors (pH, Salinity "EC", Sodicity "SAR", Temperature, Soil extracts, Substrate "NH+4" & NO₂", Antibiotics.) on the strains of Nitrosomonas and Nitrobacter isolated from Sabha and Al-Bieda soils. The isolation of such bacterial strains was carried out by using ammonium oxidizing and nitrite oxidizing media for both genera, respectively as well as the efficiency of isolates of nitrification was examined. The count of both strains in Sabha soils, which fertilized by urea, was higher than Albieda soils. Nitrobacter numbers were higher in soils exposed to sewage in both soils. The optimum pH values was 8.5 and 10 for Nitrsomonas and Nitrobacter, respectively. The optimum temperature was 30° and 25° for both isolates. With respect to NH4, and NO2 treatments, which uses as the energy source for Nitrsomonas and Nitrobacter, a significant increase (p<0.001) was observed especially in sabha soils. Penicillin did not inhibit the growth of such gram negative bacteria, whereas Gentamicin and Streptimicin caused detrimental effects on Sabha and Albieda isolates. Also, negative effects were observed on the growth with increasing salinity and sodicity levels and such effects were clearly occurred to Albieda isolates. The efficiency of NO3 production "Nitrification" was significantly increased (p<0.05) specially with the increase of NH4 addition to the both soils. The pH values were relatively decreased as a result of hydrogen ions released during NO3 production. In conclusion, more studies are needed for identifying the species of these isolates natively found in Libyan soils. To reduce the time for growing of such bacterial strains, the optimum pH and temp. as well as NH4, addition is recommended.