Following a request by the European Commission (EC), the European Food Safety Authority (EFSA) assessed the genetically modified microorganism (GMM) ‘Arsenic Biosensor’, a derivative of Bacillus subtilis 168 trpC2, for the purpose of its inclusion in Part C Annex II of Council Directive 2009/41/EC. EFSA assessed whether the GMM meets both the general and specific criteria establishing the safety of GMMs for human health and the environment set out in Part B of Annex II of Directive 2009/41/EC taking into account the guidance notes supplementing part B of Annex II to Directive 2009/41/EC (Commission Decision 2005/174/EC). Information in the dossier was not sufficient to evaluate if the GMM meets the criteria described in the guidance notes in the case for the criteria on documentation of safety, absence of pathogenicity, genotoxicity or allergenicity, transfer of genetic material and dispersal in the environment. For the remaining criteria, the requirements are met: strain verification/authentication, genetic stability, absence of adventitious pathogenic agents, survival of the organisms and establishment of the organisms in the environment. Evidence does not fully support compliance with the requirement to determine the capacity of the genetic material that was introduced to be transferred to other organisms and have a harmful effect, as there were no data establishing the absence, in the final GMM strain, of antibiotic resistance marker genes used during the genetic modifications. The specific criteria relevant for the safety for the environment are met, except for potential methods for dispersal and the probability of survival during dispersal. As a consequence, if dispersal is considered to happen as a worst-case scenario, genetic modifications introduced in the GMM would limit its survival outside containment. This would reduce any risk associated with an interaction with the environment, including a possible involuntary dissemination in the food chain.