Many bacteria considered to be phosphate removing bacteria (PRB) have previously been isolated from phosphate removing activated sludge (PRAS). However, these bacteria have never exhibited the typical function of PRB which take up excessive phosphate (P) in aerobic conditions and release P with a concomitant uptake of organic substrates in anaerobic conditions. We hypothesized that the enzyme system responsible for excess P accumulation (EPA) should be inducible, because PRB can take up organic substrates anaerobically in spite of being obligate aerobes. Therefore, PRB cells grown aerobically have to be additionally treated with alternating anaerobic incubation with organic substrates and aerobic incubation without organic substrates to exhibit the above typical function. We succeeded in the first isolation of a strain of true PRB by this induction method. The isolate is a Gram-positive coccus and its generation time is approximately 12 hours. The anaerobic/aerobic incubation cycle was required at least two times (2 days) to induce the ability of EPA for PRB. The velocity of P removal in the aerobic phase was decreased to approximately half by the existence of organic substrates. Therefore, it is recommended that organic compounds be removed during the anaerobic phase in PRAS systems.

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