Isolation and identification of a strain of Leptospirillum ferriphilum from an extreme acid mine drainage site

Based on a new selective isolation strategy that mimicked physiological characteristics of leptospirilla, such as pH, temperature and its less sensitivity to the high ferric-ferrous iron ratio, a bacterial strain, called strain YSK, was isolated from an extreme acid mine drainage (AMD) site. Cells were Gram-negative, small curved rods measuring 0.27-0.52 by 0.81-3.17 pm. The cell shape suggested that strain YSK was likely a strain of Leptospirillum ferrooxidans. However, based on the 16S rDNA sequence analysis, strain YSK possessed 100% sequence similarity with that of the typical Leptospirillum ferriphilum strain Fairview; furthermore, the G+C content, the size of the 16S-23S rRNA gene spacer regions and the ability to grow at 45 degrees C further indicated that strain YSK belonged to the species Leptospirillum ferriphilum.