Endocrine disrupting compounds (EDCs) are considered as high research priority being a source of potential adverse ecological health effects in environmental waters. 17 beta-Estradiol (E2), a recalcitrant natural estrogen, is typically encountered in wastewater treatment plants (WWTPs) at levels ranging 10-30 ng L-1 in the influent flow and 1-3 ng L-1 in the effluent flow. The exposure to even extremely low concentrations of E2 may interfere with the normal function of the endocrine system of organisms. In this study, five bacteria isolated from enrichment cultures of sediments of mud volcanoes of the Gulf of Cadiz (Moroccan-Iberian margin) were identified as aerobic E2 biodegraders, which produce low amounts of biotransformed estrone (El). Analysis of 16S rDNA gene sequences identified three of them as VirgibacilIns halotolerans, Bacillus flexus and Bacillus licheniformis. Among the set of strains, Bacillus licheniformis showed also ability to biodegrade E2 under anaerobic conditions. (C) 2016 Elsevier B.V. All rights reserved.