Seasonal Changes of Coliphage in Septic Tank Sludge and Quantification of P1 Phage Mediated Gene Transfer

概要

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Seasonal changes of coliphages, an auxiliary indicator of fecal coliforms for indexing enteric viral pollution, in septic tank sludge and night soil sludge were investigated. Relatively abundant coliphages, 1 × 102−1 × 104 [PFU/ml], were detected in the night soil sludge. Most of the phages, 0−1 × 103 [PFU/ml], found in the septic tank sludge were adsorbed on suspended solids. On the other hand, phages in the night soil sludge were found both suspending in the liquid medium and attaching on the solid matter. Aerobic treatment of this sludge reduced concentration of suspending phages, indicated this treatment might effective to reduce pathogenic viruses, too. On the other hand, aerobic conservation at 4°C did not reduce phage concentration. To investigate the factors influencing transduction frequency, P1 phage mediated tetracycline resistance marker DNA transfer was analyzed as a model system. The frequency increased according to the increase of multiplicity of infection (MOI) and reached maximum at MOI = 1.6, then started to decrease. Multiple infection of the phages on the single cell decreased viability of the host cell, followed by the decrease of transduction frequency. Mathematical model based on the kinetics of phage-host cell interaction was developed to predict transduction frequency.
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