摘要：The object of this research are the neutrophilic sheath forming iron bacteria from genus Leptothrix isolated from natural stream located in Vitosha Mountain. These bacteria facilitate the iron mineralization and formation the insoluble ferric oxides/(oxy)hydroxides after Fe2+-oxidation at neutral pH. The aim of this investigation is establishing the conditions for the formation of tubular structures (sheaths) typical for these bacteria. For this goal cultivation on an elective growth medium and the characterization of the structures formed by optical microscopy and SEM, SEM/EDX, TEM and XRD were performed. The formation of the sheaths was observed at 20оС using a flask-shaking technique. It started after 7 days of the cultivation. Light micrograph images and SEM unveiled that the average size of the sheaths is around 7 – 10 μm, and the average diameter is up to 1 μm. SEM/EDX revealed the elemental composition of the tubular structures. The XRD data showed single-phase composition of the iron oxides on the sheaths obtained. TEM micrographs unveiled the shape of the biogenic nanoparticles. The bacterial mediated formation of iron containing tubular structures and their magnetic properties are of great interest for application in the nanotechnologies and different biomedical and bioengineering applications
关键词：Leptothrix sp.; iron-oxidizing bacteria; sheath forming bacteria; iron oxide
