Magnetotactic bacteria, magnetosomes and their application

Yan, Lei; Zhang, Shuang; Chen, Peng; Liu, Hetao; Yin, Huanhuan; Li, Hongyu

doi:10.1016/j.micres.2012.04.002

Cited by 186 publications

(131 citation statements)

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“…Through microbial production of CO 2 , precipitation of calcium carbonates is favored, especially in the presence of Ca 2+ . Thus, the process clearly may be defined as microbially induced biomineralization, in contrast to microbially controlled processes best seen with intracellular, compartment-bound formation of magnetite by magnetotactic bacteria (Yan et al, 2012, and citations therein). The cell surface can act as a nucleation site for mineralization in induced biomineralization (SchultzeLam et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Calcium carbonates: induced biomineralization with controlled macromorphology

et al. 2017

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Abstract. Biomineralization of (magnesium) calcite and vaterite by bacterial isolates has been known for quite some time. However, the extracellular precipitation has hardly ever been linked to different morphologies of the minerals that are observed. Here, isolates from limestone-associated groundwater, rock and soil were shown to form calcite, magnesium calcite or vaterite. More than 92 % of isolates were indeed able to form carbonates, while abiotic controls failed to form minerals. The crystal morphologies varied, including rhombohedra, prisms and pyramid-like macromorphologies. Different conditions like varying temperature, pH or media components, but also cocultivation to test for collaborative effects of sympatric bacteria, were used to differentiate between mechanisms of calcium carbonate formation. Single crystallites were cemented with bacterial cells; these may have served as nucleation sites by providing a basic pH at short distance from the cells. A calculation of potential calcite formation of up to 2 g L −1 of solution made it possible to link the microbial activity to geological processes.

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Section: Introductionmentioning

confidence: 99%

Calcium carbonates: induced biomineralization with controlled macromorphology

et al. 2017

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“…Magnetospirillum gryphiswaldense (MSR-1) which is also spiral in shape. 212 The steps for the mutation-selection cycle are shown in Fig. 1B ], the maximum number of unique AMB-1 we could generate was 1.27 million.…”

Section: Ie Size Of the Bacterium (Appendix C Equation 1-5)mentioning

confidence: 99%

“…211 To be useful for these applications, ideally, MNPs should possess the following properties: (1) uniform sizes for consistent results, (2) high stability in aqueous solutions to reduce aggregation, (3) high thermal stability for controlled rise in temperature, (4) low cytotoxicity for interfacing with biological entities and (5) high flexibility for surface chemistry to enable drug and biological polymer conjugation. 212 Although advances in nanotechnology such as microfluidic-assisted nanoparticle synthesis have made some of these properties possible, 213 it usually comes with a compromise on the manufacturing costs and time that can be prohibitive for industrial production and research/medical use of MNPs. 214 Remnants of organic and inorganic solvents used to chemically synthesize MNPs does not yield a long-term green manufacturing solution and can also result in high cytotoxicity.…”

Section: Introductionmentioning

confidence: 99%

“…Although various bioreactor designs and media conditions have been created to optimize their growth, the production rate of these biologically produced MNPs is still much lower than chemical synthesis. 212 This has motivated some groups to make use of MTB-inspired method for chemical synthesis of NPs. 274 Gao and co-workers utilized hydrogels as nano-reactors, similar to magnetosome vesicles, for in situ fabrication of MNPs.…”

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confidence: 99%

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Acute and Chronic Neural Stimulation via Mechano-Sensitive Ion Channels

Tay

2018

Springer Theses

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Neural stimulation techniques for eliciting calcium influx can elucidate the physiological roles of specific neural populations. To overcome some of the limitations of existing techniques such as poor specificity and noxious effects of heat, I developed a technology for non-invasive control of neural activities using magnetic forces and magnetic nanoparticles (MNPs) which offer deep tissue penetration and controllable dosage. Extensive investigations with different neurotoxins and experimental conditions support that the mechanism of magnetic stimulation that involves membrane-bound MNPs transducing magnetic forces into mechanical stretching of the cell membrane to enhance the opening probability of mechano-sensitive N-type calcium ion channels to induce calcium influx.Making use of the ability of neural networks to actively regulate their ratio of excitatory to inhibitory ion channel/receptor, I also performed chronic magnetic stimulation on fragile X iii syndrome (FXS) model neural networks. We found that chronic magnetic stimulation reduced the density of N-type calcium ion channels whose expression is increased in FXS. This technique demonstrates the potential of using bio-magnetic/mechanical forces to modulate expressions of mechano-sensitive ion channels where they are over-expressed in diseases such as abnormal nociception.Nonetheless, there are still a few areas where the technique can be improved. Firstly, it is the use of MNPs with more uniform properties to have greater control on magnetic stimulations.Secondly, the technique needs to be useful for in vivo studies. Therefore, I started researching on magnetotactic bacteria (MTB) which produce biological MNPs with superior properties such as uniform sizes and highly homogenous magnetic properties with the goal of harvesting MNPs from them.MTB, however, grow extremely slowly and the number of MNPs produced/bacterium is low. One way to overcome this problem is to evolve MTB over-producers of MNPs but this strategy is constrained by the absence of a selection platform that is quantitative and offer high throughput. To overcome this problem, I combined random chemical mutagenesis and selection using a magnetic ratcheting platform to generate and isolate MTB over-producers that produce twice as many MNPs/bacterium after 5 rounds of mutation/selection. I next designed a magnetic microfluidic device and demonstrate as a proof of concept, that it can be coupled to a bioreactor for high throughput microfluidic selection of MTB over-producers.iv

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“…The iron minerals found in the magnetotactic bacteria are of nanometer-size. 11 These particles are found to adopt organized chainlike structures. The directional movement of magnetotactic bacteria has relevance to develop artificial materials to mimic magnetic properties shown by them.…”

Section: Bio-inspired Concepts In the Development Of Molecular Machinesmentioning

confidence: 99%

Introduction to Molecular Machines

Baruah¹

2017

Concepts for Molecular Machines

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Magnetotactic bacteria, magnetosomes and their application

Cited by 186 publications

References 134 publications

Calcium carbonates: induced biomineralization with controlled macromorphology

Calcium carbonates: induced biomineralization with controlled macromorphology

Acute and Chronic Neural Stimulation via Mechano-Sensitive Ion Channels

Introduction to Molecular Machines

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