General Information: Isolation: Sulfide-rich natural spa; Temp: Mesophile; Temp: 30 - 40C. Halothiobacillus neapolitanus is a sulfur-oxidizing, chemoautotrophic, Gram-negative bacterium able to tolerate high concentrations of sulfide. This organism fixes CO2 using a polyhedral body called a carboxysome which contains the primary carbon fixing enzyme, ribulose bisphosphate carboxylase/oxygenase.