鉄酸化細菌T. ferrooxidansにおけるサルファイドの存在

It was found that iron-salts grown cells of Thiobacillus ferrooxidans, Leptospirillum ferrooxidans, and moderately thermophilic iron-oxidizing bacterial strain TH3 had 2.1-3.7 nmol hydrogen sulfide per mg of cell protein. The hydrogen sulfide in T. ferrooxidans AP19-3 cells was oxidized by hydrogen sulfide: ferric ion oxidoreductase in this bacterium with Fe3+ as an electron acceptor to produce Fe2+. [14C]-C02 was taken into the cells concomitantly with the oxidation of Fe2+ by iron oxidase. Since carbon dioxide fixation is absolutely dependent on energy supplied to the cells, the results suggest that hydrogen sulfide in T. ferrooxidans plays a role as an energy reserve

Iron Oxidation by Thiobacillus thiooxidans

The iron-oxidizing activity of Thiobacillus thiooxidans cultured in the ONM medium was very weak. When the bacteria were successively cultured in the 9K medium containing sulfur, whose content was decreased step by step, the activity of iron-oxidation adaptically increased to 25-fold as much as that of the non-acclimatized organism. However, this activity was only about 5% of that of Thiobacillus ferrooxidans. The optimum pH value of the ferrous iron-oxidation of the acclimatized organism was very low. As the pH of the reaction mixtures was decreased down to 1.2, the activities gradually increased. The non-acclimatized bacteria contained B-, C- and A-type cytochromes, but B-type cytochrome could not be detected in the acclimatized organism. When ferrous iron was added to the cell-free extracts of both bacteria, C- and A-type cytochromes were reduced, but the reduction of B-type cytochrome could not be observed. The iron-oxidizing activity of the non-acclimatized bacteria was found in the particulate fraction. On the other hand, the activity of the acclimatized organism was found neither the particulate fraction, nor in the soluble fraction. However, the activity was recovered to the same level as the cell-free extracts when both fractions were combined. From these results it is postulated that the iron-oxidizing system of acclimatized T. thiooxidans was modified to a system which is similar to those of T. ferrooxidans.T.thiooxidansの鉄酸化について検討し,以下の結果を得た. 1)T.thiooxidansをイオウを含む9K培地で培養を続けると,添加イオウの減少に伴い菌体量も減少し,無添加の段階では生育は認められず,鉄の酸化エネルギーを生育に利用することはできなかった. しかし,添加イオウ0.5%の段階までは,鉄は85%以上酸化され,この菌の鉄酸化能の適応的増大がみられた. 2)適応菌の鉄酸化活性は,非適応菌の25借に増加したが,イオウ酸化活性は減少した. 3)適応菌のチトクロム組成は,非適応菌のもの(B型,C型,A型チトクロム)とは異なり,C型とA型チトクロムのみであり,その両者がFe2+によって還元された. 4)適応菌による鉄酸化の至適pHは,この菌の生育環境のPHとよく一致し,1.2まではpHが低い程,活性が高かった. 5)鉄酸化活性は,可溶性画分あるいは顆粒画分のみではほとんど認められず,両者の混合によってはじめて現われた

Improvement of a Plate Culture Method for Thiobacillus thiooxidans and Isolation of a New Strain

Thiobacillus thiooxidansは固体平板培地上でのコロニー形成が悪く,遺伝子操作を行うために欠かせない技術であるクローンの選抜が困難であったため,遺伝学的研究は従属細菌のそれに比して著しく遅れていた.本論文では,T.thiooxidansの個体平板培養法の改良を目的として,エネルギー源,ゲル化剤について検討し,得られた新しい固体培養法を用いて固体平板培地上で生育の速い菌株を分離した.新しい培地はSilvermanとLundgrenの9K培地の無機塩にエネルギー源として0.3% の四チオン酸,ゲル化剤として0.6% のジェランガムを用いた.分離株には,従属栄養生育能は認められなかったが,元素硫黄および四チオン酸を含む9K培地での良好な生育は確認できた.さらに,キノンがユビキノン8であり,菌体脂肪酸には3-ヒドロキシミリスチン酸が含まれること,GC含量が52% であること等の菌学的諸性質から分離株はT.thiooxidansに属する菌株であることが確認できた.この菌株と新しい平板培地を用いると,従属栄養細菌に匹敵する大型コロニーが得られ,細胞選抜を容易に行うことが出来る

チオバチルス・チオオキシダンスに関する研究

京都大学0048新制・論文博士農学博士論農博第224号新制||農||81(附属図書館)学位論文||S43||N303(農学部図書室)2249(主査)教授 緒方 浩一, 教授 川口 桂三郎, 教授 小野寺 幸之進学位規則第5条第2項該当Kyoto UniversityDA

Role of Ferrous Ions in Synthetic Cobaltous Sulfide Leaching of Thiobacillus ferrooxidans

Microbiological leaching of synthetic cobaltous sulfide (CoS) was investigated with a pure strain of Thiobacillus ferroxidans. The strain could not grow on CoS-salts medium in the absence of ferrous ions (Fe(2+)). However, in CoS-salts medium supplemented with 18 mM Fe(2+), the strain utilized both Fe(2+) and the sulfur moiety in CoS for growth, resulting in an enhanced solubilization of Co(2+). Cell growth on sulfur-salts medium was strongly inhibited by Co(2+), and this inhibition was completely protected by Fe(2+). Cobalt-resistant cells, obtained by subculturing the strain in medium supplemented with both Fe(2+) and Co(2+), brought a marked decrease in the amount of Fe(2+) absolutely required for cell growth on CoS-salts medium. As one mechanism of protection by Fe(2+), it is proposed that the strain utilizes one part of Fe(2+) externally added to CoS-salts medium to synthesize the cobalt-resistant system. Since a similar protective effect by Fe(2+) was also observed for cell inhibition by stannous, nickel, zinc, silver, and mercuric ions, a new role of Fe(2+) in bacterial leaching in T. ferrooxidans is proposed