Training of Iron-oxidizing Bacteria Capable of Oxidizing Ferrous Ion at pH below 1

Research Project

Project/Area Number	61550460
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	資源開発工学
Research Institution	TOHOKU UNIVERSITY
Principal Investigator	KOUNOSU Akira Associate Professor, Faculty of Engineering, Tohoku University, 工学部, 助教授 (20089791)
Co-Investigator(Kenkyū-buntansha)	SAKAI Noboru Research Associate, Faculty of Engineering, Tohoku University, 工学部, 助手 (20134009)
Project Period (FY)	1986 – 1987
Project Status	Completed (Fiscal Year 1987)
Budget Amount *help	¥1,700,000 (Direct Cost: ¥1,700,000) Fiscal Year 1987: ¥700,000 (Direct Cost: ¥700,000) Fiscal Year 1986: ¥1,000,000 (Direct Cost: ¥1,000,000)
Keywords	acid-resistance / iron-oxidizing bacterium / sulfur-oxidizing bacterium / elemental sulfur / ferrous ion / plasmid / transformation / 集積培養 / 硫酸第一鉄 / 酸化反応 / 強酸性 / 硫黄酸化細菌
Research Abstract	It's been believed that the autotrophic iron-oxidizing bacterium Thiobacillus ferrooxidans cannot grow at pH below 1.4. The objective of this project was to train bacteria capable of oxidizing ferrous ions at pH below 1.0 and to study its character for oxidation of the substrate. For training acid-resistant iron-oxidizing bacteria, it was assumed that the transmissible plasmid of Thiobacillus thiooxidans, a sulfur-oxidizing bacterium which can grow at pH as low as 0.5, could be transmitted to T. ferrooxidans , and T. ferrooxidans might assume the acid-resistance encoded on the plasmid. At first, a culture consisting mainly of T. thiooxidans and T. ferrooxidans was subcultured repeatedly with elemental sulfur as energy source so that it got to oxidize sulfur at pH below 1.0. Then, the microorganisms were cultured at initial pH 0.6 with ferrous ions as energy source, and it was observed that ferros ions were oxidized and ion-oxidizing bactera grew. There-fore, it was speculated that transmission of plasmid had occured from T. thiooxidans to T. ferrooxidans, and in consequence, T. ferrooxidans which had assumed the acid-resistance of T. thiooxidans had grown and oxidized the ferrous ions at pH below 1.0. Several months later, however,when the acid-resistant ion-oxidizing bacteria above were cultured with ferrous ions at initial pH 0.6, ion-oxidizing bacteria showed little growth in the case no elemental sulfur was added to the medium, while active growth and ion oxidation was observed with elemental sulfur added. Moreover, in experiments in which bacteria which were enrichment-cultured either with elemental sulfur or ferrous ions as energy source were cultured at initial pH 0.6 with ferrous ions, ion-oxidizing bacteria grew and oxidized the ferrous ions if elemental sulfur was added to the medium. Thus, it is suggested that elemental sulfur itself is engaged directly in T. ferrooxidans' assuming acid-resistance apart from plasmid of T.thiooxidans.