Isolation and characterization of a novel sulfuroxidizing chemolithoautotroph <i>Halothiobacillus</i> from Pb polluted paddy soil

Abstract

A new mesophilic and chemolithoautotrophic sulfur oxidizing bacterium (SOB) strain HT1 was isolated from a rice rhizosphere soil polluted by Pb using thiosulfate as electron donor at pH 7.0. The 16S rRNA gene sequence showed that the new isolate was a sulfur oxidizing obligate chemolithotroph belonging to Gammaproteobacteria, Halothiobacillus and utilizing different reduced sulfur compounds (sulfide, elemental sulfur, thiosulfate and sulfite) as chemolithotrophic substrates. Strain HT1 was able to use CO₂ as a carbon source responsible for the reduction of nitrate to nitrite, which represented a halophilic SOB capable of growth within a broad salinity range of 0 to 3 M NaCl and a heavy-metals-tolerant SOB. HT1 was Gram negative, motile and was proposed as the type strain of a novel species of sulfur oxidizing bacteria. The soxB gene could not be detected in strain HT1 during thiosulfate oxidation. The metabolism pathway of HT1 was ‘S4 intermediate’ (S4I) pathway. Sulfur globules accumulated in HT1 were mainly S₈.

Keywords:Halothiobacillus, heavy-metals-tolerant, soxB gene, 16S rRNA gene, sulfur globule.