Abstract: Alkalophilic and thermophilic cellulases having high stability to elevated temperatures and pH have been isolated from an organism of unknown species, which most closely resembles those in the Caldicellulosiruptor genus and which has been called by us, Tok7B.1, These cellulases have been cloned and expressed in a recombinant system, so that they can be produced in quantity. These are particularly useful in treating cellulosic materials including cotton-containing fabrics, as detergent additives, and in aqueous compositions. We also provide genomic DNA which can be used in recombinant expression vectors and expression systems to produce enhanced alkali and/or temperature stability properties in cellulases other than those specifically described.