A NEWLY ISOLATED FUNGUS PARTICIPATES IN THE CORROSION OF CONCRETE SEWER PIPES

The final microflora in the corrosion process of concrete sewer pipes was investigated. When the corroded sample was examined using several media, bacterial colonies were found only on acid media (pH 2.5); fung i were detected on neutral solid media (pH 6.5) as well as on acid med ia (pH 2.5). The acidophilic bacterial colonies were identified as Thi obacillus thiooxidans using a specific identification method for speci es of acidophilic thiobacilli. The dark green fungi that appeared on t he isolation media showed similar morphological characteristics, even though the media used for isolation varied in pH and nutrient. The fun gi showed tolerance against acid, although the optimum pH for their gr owth was neutral. The results showed that the severely corroded sewer pipe was inhabited by two kinds of micoorganisms, Thiobacillus thiooxi dans and the fungi. An isolated fungus, strain OMSOfl, could oxidize s ulfide to thiosulfate. Thiosulfate can be utilized by T. thiooxidans a s an energy source, and is converted to corrosive sulfate. Continued v igorous growth of T. thiooxidans presumably depends on a mutualistic r elationship with the fungus. It is proposed that a close association b etween the two microorganisms accelerates the corrosion of concrete se wer pipes.