ABSTRACT Biofiltration of industrial carbon disulfide (CS ₂ )-contaminated waste air streams results in the acidification of biofilters and therefore reduced performance, high water use, and increased costs. To address these issues, we isolated 16 extremely acidophilic CS ₂ -converting Acidithiobacillus thiooxidans strains that tolerated up to 6% (vol/vol) sulfuric acid. The ecophysiological properties of five selected strains (2Bp, Sts 4-3, S1p, G8, and BBW1) were compared. These five strains had pH optima between 1 (2Bp) and 2 (S1p). Their affinities for CS ₂ ranged between 80 (G8) and 130 (2Bp) μM. Strains S1p, G8, and BBW1 had more hydrophobic cell surfaces and produced less extracellular polymeric substance than did strains 2Bp and Sts 4-3. All five strains converted about 80% of the S added as CS ₂ to S ⁰ when CS ₂ was supplied in excess. The rate of S ⁰ consumption varied between 7 (Sts 4-3) and 63 (S1p) nmol O ₂ min ⁻¹ ml culture ⁻¹ . Low S ⁰ consumption rates correlated partly with low levels of cell attachment to externally produced S ⁰ globules. During chemostat growth, the relative amount of CS ₂ hydrolase in the cell increased with decreasing growth rates. This resulted in more S ⁰ accumulation during CS ₂ overloads at low growth rates. Intermittent interruptions of the CS ₂ supply affected all five strains. Strains S1p, G8, and BBW1 recovered from 24 h of starvation within 4 h, and strains 2Bp and Sts 4-3 recovered within 24 h after CS ₂ was resupplied. We recommend the use of mixtures of Acidithiobacillus strains in industrial biofilters.