Bioleaching of Sulfide Minerals by Leptospirillum ferriphilum CC from Polymetallic Mine (Armenia)

A strain of Leptospirillum sp. CC previously isolated from Akhtala polymetallic ore (Armenia) was studied. The main morphological and physiological characteristics of CC were revealed. The optimal growth temperature was 40 degrees C and optimal pH 1.5. A phylogenetic analysis based on 16S rRNA gene sequences (GenBank ID OM272948) showed that isolate CC was clustered with L. ferriphilum and possessed 99.8% sequence similarity with the strain L. ferriphilum OL12-2 (KF356024). The molar fraction of DNA (G + C) of the isolate was 58.5%. Bioleaching experiment indicates that L. ferriphilum CC can oxidize Fe(II) efficiently, and after 17 days, 44.1% of copper and 91.4% of iron are extracted from chalcopyrite and pyrite, respectively. The efficiency of L. ferriphilum CC in pyrite oxidation increases 1.7 times when co-cultivated with At. ferrooxidans ZnC. However, the highest activity in pyrite oxidation shows the association of L.ferriphilum CC with heterotrophic Acidocella sp. RBA bacteria. It was shown that bioleaching of copper and iron from chalcopyrite by association of L. ferriphilum CC, At. ferrooxidans ZnC, and At. albertensis SO-2 in comparison with pure culture L. ferriphilum CC for 21 days increased about 1.2 and 1.4-1.6 times, respectively.

Automated summary

A strain of Leptospirillum sp. CC isolated from Akhtala polymetallic ore in Armenia exhibited optimal growth at a temperature of 40 degrees C and at a pH of 1.5. Phylogenetic analysis revealed its close relationship with L. ferriphilum and a high sequence similarity with strain L. ferriphilum OL12-2. The isolate displayed efficient oxidation of Fe(II) and demonstrated increased pyrite oxidation activity when co-cultivated with At. ferrooxidans ZnC. Furthermore, the association of L.ferriphilum CC with heterotrophic Acidocella sp. RBA bacteria showed the highest activity in pyrite oxidation.