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Magnetotactic Bacteria Algorithm for Function Optimization  [PDF]
Hongwei Mo, Lifang Xu
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.512B014
Abstract: Magnetotactic bacteria is a kind of polyphyletic group of prokaryotes with the characteristics of magnetotaxis that make them orient and swim along geomagnetic field lines. A magnetotactic bacteria optimization algorithm(MBOA) inspired by the characteristics of magnetotactic bacteria is researched in the paper. Experiment results show that the MBOA is effective in function optimization problems and has good and competitive performance compared with the other classical optimization algorithms.
Velocity condensation for magnetotactic bacteria  [PDF]
Jean-Francois Rupprecht,Nicolas Waisbord,Lydéric Bocquet
Physics , 2015,
Abstract: Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g. active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that L\'evy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior.
DYNA , 2011,
Abstract: to date, no complete study of magnetotactic bacteria's (mtb) natural microcosms in estuarine or tropical environments has been reported. besides, almost all the studies around magnetotactic bacteria have been based on fresh waters away from the equator. in this work, we focused the experimental region at the equator and present a comprehensive mineralogical and physicochemical characterization of two estuarine bacterial microcosms. the results show that mineral lixiviation in the sediments may be an important factor in the solubilization of elements required by magnetotactic bacteria. specifically, we show that clinochlore, phlogopite, nontronite, and halloysite could be among the main minerals that lixiviate iron to the estuarine microcosms. we conclude that nitrate concentration in the water should not be as low as those that have been reported for other authors to achieve optimal bacteria growth. it is confirmed that magnetotactic bacteria do not need large amounts of dissolved iron to grow or to synthesize magnetosomes.
Micromanipulation of magnetotactic bacteria with a microelectromagnet matrix  [PDF]
H. Lee,A. M. Purdon,V. Chu,R. M. Westervelt
Physics , 2004,
Abstract: Micromanipulation of magnetotactic bacteria with a microelectromagnet matrix was demonstrated. Magnetotactic bacteria synthesize a chain of magnetic nanoparticles inside their body to guide their motion in the geomagnetic field. A microelectromagnet matrix consists of two arrays of lithographically patterned wires, one array perpendicular to the other, that are separated and covered by insulating layers. By adjusting the current in each wire, a matrix can create versatile magnetic field patterns on microscopic length scale. Using a matrix, magnetotactic bacteria were trapped, continuously moved, rotated, and assembled in water at room temperature.
Intracellular inclusions of uncultured magnetotactic bacteria
Keim,Carolina N.; Solórzano,Guilhermo; Farina,Marcos; Lins,Ulysses;
International Microbiology , 2005,
Abstract: magnetotactic bacteria produce magnetic crystals in organelles called magnetosomes. the bacterial cells may also have phosphorus-containing granules, sulfur globules, or polyhydroxyalkanoate inclusions. in the present study, the ultrastructure and elemental composition of intracellular inclusions from uncultured magnetotactic bacteria collected in a marine environment are described. magnetosomes contained mainly defect-free, single magnetite crystals with prismatic morphologies. two types of phosphorus-containing granules were found in magnetotactic cocci. the most common consisted of phosphorus-rich granules containing p, o, and mg; and sometimes also c, na, al, k, ca, mn, fe, zn, and small amounts of s and cl were also found. in phosphorus-sulfur-iron granules, p, o, s, na, mg, ca, fe, and frequently cl, k, and zn, were detected. most cells had two phosphorus-rich granules, which were very similar in elemental composition. in rod-shaped bacteria, these granules were positioned at a specific location in the cell, suggesting a high level of intracellular organization. polyhydroxyalkanoate granules and sulfur globules were less commonly seen in the cells and had no fixed number or specific location. the presence and composition of these intracellular structures provide clues regarding the physiology of the bacteria that harbor them and the characteristics of the microenvironments where they thrive.
Comment on: "On the swimming motion of spheroidal magnetotactic bacteria" [arXiv:1302.5787]  [PDF]
B. U. Felderhof
Physics , 2013,
Abstract: It is pointed out that a recent article [arXiv:1302.5787] on swimming of magnetotactic bacteria is conceptually wrong.
Magnetotactic Bacteria from Extreme Environments  [PDF]
Dennis A. Bazylinski,Christopher T. Lefèvre
Life , 2013, DOI: 10.3390/life3020295
Abstract: Magnetotactic bacteria (MTB) represent a diverse collection of motile prokaryotes that biomineralize intracellular, membrane-bounded, tens-of-nanometer-sized crystals of a magnetic mineral called magnetosomes. Magnetosome minerals consist of either magnetite (Fe 3O 4) or greigite (Fe 3S 4) and cause cells to align along the Earth’s geomagnetic field lines as they swim, a trait called magnetotaxis. MTB are known to mainly inhabit the oxic–anoxic interface (OAI) in water columns or sediments of aquatic habitats and it is currently thought that magnetosomes function as a means of making chemotaxis more efficient in locating and maintaining an optimal position for growth and survival at the OAI. Known cultured and uncultured MTB are phylogenetically associated with the Alpha-, Gamma- and Deltaproteobacteria classes of the phylum Proteobacteria, the Nitrospirae phylum and the candidate division OP3, part of the Planctomycetes- Verrucomicrobia- Chlamydiae (PVC) bacterial superphylum. MTB are generally thought to be ubiquitous in aquatic environments as they are cosmopolitan in distribution and have been found in every continent although for years MTB were thought to be restricted to habitats with pH values near neutral and at ambient temperature. Recently, however, moderate thermophilic and alkaliphilic MTB have been described including: an uncultured, moderately thermophilic magnetotactic bacterium present in hot springs in northern Nevada with a probable upper growth limit of about 63 °C; and several strains of obligately alkaliphilic MTB isolated in pure culture from different aquatic habitats in California, including the hypersaline, extremely alkaline Mono Lake, with an optimal growth pH of >9.0.
Magnetic Torque of Microfabricated Elements and Magnetotactic Bacteria  [PDF]
Lars Zondervan,?zlem Sardan Sukas,Islam S. M. Khalil,Marc P. Pichel,Sarthak Misra,Leon Abelmann
Physics , 2014,
Abstract: We present a thorough theoretical analysis of the magnetic torque on microfabricated elements with dimensions in the range of 100 to 500 {\mu}m and magneto-somes of magnetotactic bacteria of a few {\mu}m length. We derive simple equations for field dependent torque and magnetic shape anisotropy that can be readily used to replace the crude approximations commonly used. We illustrate and verify the theory on microfabricated elements and magnetotactic bacteria, by field depedent torque magnetometry and by observing their rotation in water under application of a rotating magnetic field. The maximum rotation frequency of the largest microfabricated elements agrees within error boundaries with theory. For smaller, and especially thinner, elements the measured frequencies are a factor of three to four too low. We suspect this is caused by incomplete saturation of the magnetisation in the elements, which is not incorporated in our model. The maximum rotation frequency of magnetotactic bacteria agrees with our model within error margins, which are however quite big due to the large spread in bacteria morphology. The model presented provides a solid basis for the analysis of experiments with magnetic objects in liquid, which is for instance the case in the field of medical microrobotics.
Magnetotactic Bacteria as Potential Sources of Bioproducts  [PDF]
Ana Carolina V. Araujo,Fernanda Abreu,Karen Tavares Silva,Dennis A. Bazylinski,Ulysses Lins
Marine Drugs , 2015, DOI: 10.3390/md13010389
Abstract: Magnetotactic bacteria (MTB) produce intracellular organelles called magnetosomes which are magnetic nanoparticles composed of magnetite (Fe 3O 4) or greigite (Fe 3S 4) enveloped by a lipid bilayer. The synthesis of a magnetosome is through a genetically controlled process in which the bacterium has control over the composition, direction of crystal growth, and the size and shape of the mineral crystal. As a result of this control, magnetosomes have narrow and uniform size ranges, relatively specific magnetic and crystalline properties, and an enveloping biological membrane. These features are not observed in magnetic particles produced abiotically and thus magnetosomes are of great interest in biotechnology. Most currently described MTB have been isolated from saline or brackish environments and the availability of their genomes has contributed to a better understanding and culturing of these fastidious microorganisms. Moreover, genome sequences have allowed researchers to study genes related to magnetosome production for the synthesis of magnetic particles for use in future commercial and medical applications. Here, we review the current information on the biology of MTB and apply, for the first time, a genome mining strategy on these microorganisms to search for secondary metabolite synthesis genes. More specifically, we discovered that the genome of the cultured MTB Magnetovibrio blakemorei, among other MTB, contains several metabolic pathways for the synthesis of secondary metabolites and other compounds, thereby raising the possibility of the co-production of new bioactive molecules along with magnetosomes by this species.
Applications of Magnetosomes Synthesized by Magnetotactic Bacteria in Medicine  [PDF]
Edouard Alphandéry
Frontiers in Bioengineering and Biotechnology , 2014, DOI: 10.3389/fbioe.2014.00005
Abstract: Magnetotactic bacteria belong to a group of bacteria that synthesize iron oxide nanoparticles covered by biological material that are called magnetosomes. These bacteria use the magnetosomes as a compass to navigate in the direction of the earth’s magnetic field. This compass helps the bacteria to find the optimum conditions for their growth and survival. Here, we review several medical applications of magnetosomes, such as those in magnetic resonance imaging (MRI), magnetic hyperthermia, and drug delivery. Different methods that can be used to prepare the magnetosomes for these applications are described. The toxicity and biodistribution results that have been published are summarized. They show that the magnetosomes can safely be used provided that they are prepared in specific conditions. The advantageous properties of the magnetosomes compared with those of chemically synthesized nanoparticles of similar composition are also highlighted.
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