alicyclobacillus tolerans alicyclobacillus tolerans alicyclobacillus tolerans is a species of gram positive, strictly aerobic, bacterium. the bacteria are acidophilic and produced endospores. it was first isolated from oxidizable lead–zinc ores in uzbekistan. the strain was first identified in 1983, but was classified as sulfobacillus thermosulfidooxidans subsp. thermotolerans strain k1. it was reclassified as alicyclobacillus in 2005. the species name refers to the ability to tolerate changes in temperature and ph. alicyclobacillus tolerans scientific classification domain: bacteria phylum: bacillota class: bacilli order: bacillales family: alicyclobacillaceae genus: alicyclobacillus species: a. tolerans binomial name alicyclobacillus toleranskaravaiko et al. 2005 a. tolerans was reclassified to alicyclobacillus along with sulfobacillus disulfidooxidans, which was classified as alicyclobacillus disulfidooxidans. the optimum growth temperature for a. tolerans is 37-42 °c, and can grow in the 20-50 °c range. the optimum ph is 2.5-2.7, and can grow in ph 1.5-5.0.