Physiological and ultrastructural characterization of a new acidophilic Thiobacillus species (T. kabobis)

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Abstract
A new autotrophic acidophilic Thiobacillus sp. was isolated from acidic soil adjacent to a natural gas processing plant's sulfur stockpile. This isolate metabolized S2O32− to S4O62− during growth and could not reoxidize this product; instead, the remaining S2O32− substrate was oxidized to SO42− in the stationary phase which represented a significant metabolic change as compared with other acidophilic thiobacilli. In contrast the isolate oxidized S0 to H2SO4 during log-phase growth with no S4O62− being formed. Ultrastructural studies revealed that the isolate's cytoplasm contained unidentified membrane-bound granules, volutin type bodies, and carboxysomes. Cleavage planes within the cell wall revealed a pattern of highly ordered subunits in the outer leaflet of the outer membrane and these ordered subunits were also discerned through the eutectic at the cell surface. This regular structure was not observed at the surface of cells of other acidophilic thiobacilli. The isolate bears a single pilus and one unusually long polar flagellum. The physiological and ultrastructural data are discussed in relation to other known thiobacilli and show this isolate to be a new Thiobacillus sp. named T. kabobis.