Study of the Influence of Electric Field Exposure on Some Soil Microbial Activities

In this study, the focus on response of soil microbes to electric field (EF) different exposure periods was detected. Exposure of different soil samples to electric field EF strength 6kV/m for 1,2 and 3 months slighty decreased the total viable counts of numbers of general bacteria, as well as Azotobacter and Azospirellum, however, the total viable counts of fungi reflected noticeable decrease comparing with bacteria. Data of unexposed soil are recorded significant increase in CTMB (total microbial biomass C), CAMB (ctive microbial biomass C), qR (metabolic quotients), BR (basal respiration), while significant decrease in qCO2 at the end of incubation period was observed . Also significant decrease in CTMB, CAMB and BR of soil under the effect of three months of exposure to electric field was indicated. Soil enzyme activities were decreased by increasing exposure period up to 3 months. Soit nitrogenase was more respond to EF followed by, acidic phosphatase, urease, dehydrogenase and alkaline phosphatase, they decreased by 30, 23.6, 20, 13 and 7.7% respectively comparing with the unexposed samples after the same exposure period. Growth rate of the selected Azotobacter isolate indicated significant decrease in the viable cell number when grown in liquid medium and exposed to the electric field for 1,2,3,4,5 and 6 days comparing with unexposed ones. Regarding to the electrophoresis analysis of extracted protein, 14 bands were obtained from exposed and unexposed Azotobacter liquid culture which incubated for 3 and 6 days. Two bands (Mw83.4 and 15.9kDa) were lost, and two others bands (Mw 86.3 and 16.2 kDa) were appeared after exposure for 3 and 6 days. The average optical density of bands decreased at exposure period 6 days compared with the unexposed ones. This study concluded that the action of EF causes an intensified slow down of either growth an activities in soil microorganisms.