Characterization of a new less acidophilic Thiobacillus isolate (Thiobacillus capsulatus)

A motile, sulfur-oxidizing gram-negative bacterium was isolated from soil adjacent to a sulfur block pad. This isolate was found to grow only autotrophically by oxidizing S° and reduced sulfur oxyanions under aerobic conditions over a pH range of 3.0–7.0. This placed it in the less acidophilic group of Thiobacillus. The mole percent G + C of this organism was 54.5%. Ultrastructure studies showed the presence of a single polar flagellum, cytoplasmic volutin granules, and carboxysomes. An extensive glycocalyx was observed radiating outward from the outer membrane. The physiological and ultrastructure data were compared with other known thiobacilli and indicated that this isolate is a new Thiobacillus species, named T. capsulatus.