Yoshiko Okamura1
Hiroshima University1
Biomineralization, especially biological controlled mineralization (BCM) is known as well-organized manufacturing system to form the elaborate morphology. Moreover, the unit of crystal is identical to an inorganic synthesized crystal so that organic matrices may play important roles of a template, blocking reagent, condenser and etc. to form quite elaborate morphology. Biological induced minerals, on the other hand, are considered to be formed along with biological metabolisms within a limited space, and believed to be low in crystallinity, heterogeneous in size, to have no specific crystal morphology to contain impurities. However, bacterial BIM can form heavy metal crystals based on the mechanisms of heavy metal resistance.<br/>In my culture collections, the bacteria can produce nanoparticles of metal or metal compound, that are well-uniformed in size. Metal sulfides are generated by bacterial sulfate reducing respiratory. Lead sulfide (PbS; group IV-VI) and Cadmium sulfide (CdS; group II-VI) show quantum dot size and fine lattice fringe. Tellurium [Te(0)] nanoparticles formed by photosynthetic bacterium show spherical shape with a diameter of 10-20 nm . By electron beam diffraction analysis, the electron diffraction pattern showed a hexagonal system although the morphology is spherical. In addition, we obtained a novel gene which can confer tellurium nanorod forming ability on <i>Escherichia coli, </i>from nanorod forming bacterium <i>Pseudomonas stutzeri</i> starin Hiro-3. Interestingly, the tellurium nanorod generated in<i> E. coli</i> reached lengths greater than 500 nm and the length and thickness are different from the one in strain Hiro-3, however X-ray crystallography of both nanorods indicated also hexagonal patterns. Based on these observations, the elemental tellurium would bind each other and grow as crystal according to inorganic reaction however some biological factors such as dark concentration of proteins, electric charges of polymers and masking effects, etc., would limit the crystal growth. Since the recombinant <i>E. coli</i> did not have original species’ factor, the crystal morphology was different from original.<br/>As a conclusion, metal crystals generated by bacteria are fine nanoparticles within a nano space. The problem is how to extract and handle it in a large space. This challenge will open a low-carbon manufacturing method for sustainable materials.