Study On The Formation And The Properties Of Magnetic Particles Isolated From Ferroplasma Thermophilum L1

This research focused on finding out other bioleaching microbes which could synthesize magnetic particles except Acidithiobacillus ferrooxidans YN-3and Leptospirillum ferriphilum YSK. This finding would widen the scope of the bioleaching microbes which could form magnetic particles.First of all, magnetic force microscopy (MFM) was used to detect magnetism of four bioleaching microbes under different culture conditions in order to find out which microbe could form magnetic particles. Acidithiobacillus ferrooxidans YN-3, Leptospirillum ferriphilum YSK, Sulfobacillus thermosulfidooxidans and Ferroplasma thermophilum L1were cultured under FeSO4·7H2O and pyrrhotite culture condition, respectively. The results showed that four bioleaching microbes had weak magnetism under the culture condition of FeSO·7H2O, while Acidithiobacillus ferrooxidans YN-3, Leptospirillum ferriphilum YSK, and Ferroplasma thermophilum L1showed strong magnetism and Sulfobacillus thermosulfidooxidans remained weak magnetism under the culture condition of pyrrhotite. Then transmission electron microscopy (TEM) was used to test Ferroplasma thermophilum L1. It was found that there existing some electron dense particles which located in the middle or around the membrane in the cell.In order to ascertain the properties of these electron dense particles, magnetic particles were extracted from Ferroplasma thermophilum L1after large-scale culture. MFM image showed that these particles had two poles which revealed the magnetism. Shapes of the particles were hexagon-like and spherical-like. Sizes of the particles were from47nm to100nm. The components of the particles were Fe and O (at%of Fe and O was43.05%and56.95%respectively).Finally, Ferroplasma thermophilum L1was used to study changes of magnetic particles under different concentrations of cobalt ions. The results showed that Ferroplasma thermophilum L1grew best under10mmol/L cobalt ions. Then cells of Ferroplasma thermophilum L1which were cultured under5mmol/L and10mmol/L cobalt ions were detected by TEM. Results showed that there were more particles in Ferroplasma thermophilum L1when it cultured in5mmol/L cobalt ions. Some particles were of uniform size and arranged in chains in Ferroplasma thermophilum L1and some particles were of varying shapes and sizes. There were only a few particles in Ferroplasma thermophilum L1which was cultured in10mmol/L cobalt ions. Some cells only had one to two particles and major axis of the particles was from85nm to125nm. Most of the cells could not form particles.