Papers by Keyword: Magnetotactic Bacteria

Abstract: Magnetotactic bacteria are the bacteria which synthesize nano-sized magnetic particles within their cell body. In the present study, the cells of a magnetotactic bacteria M. magnetotacticum MS-1 was fractionated and the iron amount of the cell fractions were measured. In order to study the relationship between the process of the biosynthesis of magnetosome and the intracellular transport of iron, MS-1 cells were cultured under iron limited culture conditions and the amount of iron in the cell fractions were compared with those under optimal culture conditions. The whole amount of iron was measured colorimetrically. To estimate the number of ferric ion, the number of spin was determined from the ESR spectrum. The cell fractions obtained after removing magnetosome (non-magnetic fractions) contained 30-40 % of the total iron in the intact cells. There was a good correlation between the number of spin and the iron amount of non-magnetic fractions under optimal culture conditions. Under iron limited conditions, the iron amount decreased not only in the fraction containing magnetosome but also in the non-magnetic fractions. The number of spin in the soluble fraction decreased remarkably. So, the correlation between the number of spin and the amount of iron was not observed under iron limited conditions. These results imply that the ratio of ferrous ion to whole amount of iron increased in the non-magnetic fractions under iron limited conditions as compared with that under optimal conditions.

Abstract: This study used nickel wire to trap the magnetotactic bacteria which had adsorbed Au(III), and a magnetic separation model was built to describe this process. Kinetics of the movement of metal loaded bacteria in the whole magnetic field was investigated both experimentally and theoretically. It was found that the magnetic intensity had evident effect on the separation efficiency, but little effect on the separation rate. The period of trapping bacteria to capacity for the nickel wire was proved about 100 minutes. It was found that the trapped bacteria were deposited in multi-layers, showing the ability of multi-layer trapping for the wires. The theoretical results could reach a good agreement with the experimental, which indicated the feasibility of applying the model to the optimization of magnetic separation process using magnetotactic bacterium.

Abstract: All the times we study a lot about Acidithiobacillus ferrooxidans (A.f) in mineral leaching, but when it is discovered that it can synthesize magnetosomes(Ms) in its body, researchers start to pay attention to its synthesis mechanism of Ms, while there is still few studies about the influence to A.f by external environment change. This article mainly aims at exploring the influence on A.f growth and magnetism under the outside magnetic field strength change. The findings show that not all A.f can synthesize magnetic substance. Under the most primary culture, there are few thalli can synthesize Ms; magnetic field at about 5mT, 10mT may promote thalli growth (quantity); magnetic field at about 25mT and 30mT may be harmful or beneficial to thalli response to time length; magnetic field at about 15mT, 20mT, 35mT, 40mT, 50mT may restrain thalli growth and reduce thalli activeness.

Abstract: The motion of magnetotactic bacteria was observed using an optical darkfield microscopy. The images were taken using video cameras, and measured by image processing techniques. In our experiment, it was found that the bacteria motion was found to follow to magnetic field frequency within some range. The observation results indicate the possibility of the bacteria behavior control by magnetic field.

Abstract: A new species of single-cell magnetotactic bacteria, the NMV-1 bacteria, has been found by us. Each NMV-1 bacterium synthesizes itself a chain of magnetic nanoparticles inside its body. When an external magnetic field is applied, long bacteria chains come into being in the direction of the field in the water. More than 30 µm long chains of live bacteria have been observed. Length of bacteria chains is field dependant: the higher the magnetic field is, the longer the bacteria chains are. The bacteria chains orientation is controllable and the chains can be stably trapped. The mechanism of the assembly of long bacteria chains is also discussed. The results show that, while an external magnetic field is applied, the NMV-1 bacteria have strong enough interactions between each other to assemble long bacteria chains. After positioning the bacteria chain, cellular membranes of the bacteria were removed by cell lysis, leaving long chains of magnetic nanoparticles on a substrate. These magnetic nanochains can be potentially used as building blocks for magnetic nanostructures.