Bacteriogenic iron oxides (BIOS) produced by neutrophilic and acidophilic bacteria are widespread in the environment. Although BIOS have been recognized to have great potential for remediation in acidic mining environments, the importance of such bioremediation processes under near-neutral pH conditions is less documented (1,2). In this context, previous research on iron biomineralization at circumneutral pH has focused on Gallionella ferruginea and different Leptothrix species (3,4). Moreover, these stalk and sheath-forming bacteria cause numerous industrial issues such as bulking, clogging, etc. (5) and therefore understanding the role of iron on the ecology and physiology of these species could help better predicting their occurrence and activity in various surface environments. In this work we will present the iron biomineralization by a Leptothrix-like microorganism and we will discuss possible interactions between this process and the morphological characters of this bacterium species. The aim of this work is hence to investigate its iron biomineralization and how this impacts and/or is impacted by the filamentation and sheathforming process. For that purpose, we developed a protocol to test factors affecting filamentation by combining different molecular biology, microscopy and mineralogy techniques. Our results indicate various Fe biomineralization patterns specially related to the sheath surface depending on the growth conditions. Eventually, this study will help in better understanding the processes of iron biomineralization by sheath-forming bacteria and it will shed light on the mechanisms of filamentation, provinding material for further investigations on the potential of BIOS in sorbing heavy metals and radionuclides in near-neutral pH environments.