A Study on Concentration method for Microorganisms in Water with Electropositive Filter

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An experimental study for concentrating the microorganisms from water using electropositive filter (Zeta plus Virosorb 1MDS, Cuno Inc.) was conduced. Microorganisms tested were Escherichia coli, Clostridium perfringens, and coliphages of Q-beta, MS2 and an environmental strain. Results obtained are summarized as follows ; (1) Recovery rates of the electropositive filter for Clostridium perfringens and Escherichia coli were greater than 95% and 80% respectively. (2) Recovery of coliphages was low with 20-50% for Q-beta and 30-50% for MS2 in wide range of pH 4-9. (3) Recovery rates for unidentified strain isolated from river water were decreased with increased pH and the values of the rates were greater than 90% at pH 4-6, around 70% at pH 7 and 40-50% at pH 8-9. (4) From these results, it was suggested that the electropositive filter was applicable for concentrating bacteria from water without any pretreatment, while pH adjusting to less than 6 would be necessary for phage.Additionally, a trial of isoelectric focussing to determine the isoelectric point of phages was conducted using a commercially available equipment divided and separated into twenty small chambers by membrane filters (Rotophore, Bio-Rad Inc.). From this trial, it was concluded that the system used would be inadequate for the determination of isoelectric point of phages in water because these phages were recovered with extremely low rate after isoelectric focussing.