AimsThe aim of this study was to analyse arsenic (As) transformation and biosorption by indigenous As-resistant bacteria both in planktonic and biofilm modes of growth. Methods and ResultsAs-resistant bacteria were isolated from industrial waste water and strain PT2, and identified as Exiguobacterium profundum through 16S rRNA gene sequencing was selected for further study. As transformation and biosorption by E. profundumPT2 was determined by HPLC-ICP-MS analysis. Planktonic cultures reduced 373mmoll(-1) As5+ into As3+ from artificial waste water effluent after 48-h incubation. In case of biosorption, planktonic cultures and biofilms exhibited 252 and 294mgg(-1) biomass biosorption, respectively. As biosorption kinetics followed Freundlich isotherm and pseudo second-order model. Biofilm formation peaked after 3days of incubation, and in the presence of As stress, biofilm formation was significantly affected in contrast to control (P<005). Homogeneous nature of mature biofilms with an increased demand of nutrients was revealed by minimum roughness and maximum surface to biovolume ratio measured through CLSM analysis. ConclusionIndigenous As-resistant E. profundumPT2 was found capable of As transformation and biosorption both in the form of planktonic cultures and biofilms. Significance and Impact of the StudyIndigenous biofilm forming E. profundumPT2 revealing As biosorption and biotransformation potential is presented an eco-friendly and cost-effective source for As remediation that can be implemented for waste water treatment.