Magnetotactic bacteria

About: Magnetotactic bacteria is a research topic. Over the lifetime, 1118 publications have been published within this topic receiving 43741 citations.

Ferromagnetic resonance of intact cells and isolated crystals from cultured and uncultured magnetite-producing magnetotactic bacteria.

Abstract: Most magnetotactic bacteria (MB) produce stable, single-domain magnetite nanocrystals with species-specific size, shape and chain arrangement. In addition, most crystals are elongated along the [111] direction, which is the easy axis of magnetization in magnetite, chemically pure and structurally perfect. These special characteristics allow magnetite crystal chains from MB to be recognized in environmental samples including old sedimentary rocks. Ferromagnetic resonance (FMR) has been proposed as a powerful and practical tool for screening large numbers of samples possibly containing magnetofossils. Indeed, several studies were recently published on FMR of cultured MB, mainly Magnetospirillum gryphiswaldense. In this work, we examined both uncultured magnetotactic cocci and the cultured MB M. gryphiswaldense using transmission electron microscopy (TEM) and FMR from 10 K to room temperature (RT). The TEM data supported the FMR spectral characteristics of our samples. The FMR spectra of both bacteria showed the intrinsic characteristics of magnetite produced by MB, such as extended absorption at the low field region of the spectra and a Verwey transition around 100 K. As previously observed, the spectra of M. gryphiswaldense isolated crystals were more symmetrical than the spectra obtained from whole cells, reflecting the loss of chain arrangement due to the small size and symmetrical shape of the crystals. However, the FMR spectra of magnetic crystals isolated from magnetotactic cocci were very similar to the FMR spectra of whole cells, because the chain arrangement was maintained due to the large size and prismatic shape of the crystals. Our data support the use of FMR spectra to detect magnetotactic bacteria and magnetofossils in samples of present and past environments. Furthermore, the spectra suggest the use of the temperature transition of spectral peak-to-peak intensity to obtain the Verwey temperature for these systems.

A Magnetotactic Bacteria Algorithm Based on Power Spectrum for Optimization

Abstract: Magnetotactic bacteria is one kind of bacteria with magnetic particles called magnetosomes in its body The magnetotactic bacteria move towards the ideal living conditions under the interaction between magnetic field produced by the magnetic particles chain and that of the earth In the paper, a new magnetotactic bacteria algorithm based on power spectrum (PSMBA) for optimization is proposed The candidate solutions are decided by power spectrum in the algorithm Its performance is tested on 8 standard functions problems and compared with the other two popular optimization algorithms Experimental results show that the PSMBA is effective in optimization problems and has good and competitive performance

Magnetic studies of magnetotactic bacteria by soft x-ray STXM and ptychography

Abstract: Magnetotactic bacteria (MTB) biomineralize chains of nanoscale magnetite single crystals which align the cell with the earth’s magnetic field and assist the cell to migrate to, and maintain its position at, the oxic-anoxic transition zone, their preferred habitat. Here we describe use of multi-edge scanning transmission X-ray microscopy (STXM) to investigate the chemistry and magnetism of MTB on an individual cell basis. We report measurements of the orientation of the magnetic vector of magnetosome chains relative to the location of the single flagellum in marine vibrio, Magnetovibrio blakemorei strain MV-1 cells from both the southern and northern hemisphere. We also report a major improvement in both spatial resolution and spectral quality through the use of spectro-ptychography at the Fe L3 edge.

Complete Genome Sequence of Strain BW-2, a Magnetotactic Gammaproteobacterium in the Family Ectothiorhodospiraceae, Isolated from a Brackish Spring in Death Valley, California.

Abstract: We report the complete 4.1-Mb genome sequence of strain BW-2, a magnetotactic, sulfur-oxidizing rod, belonging to the family Ectothiorhodospiraceae of the class Gammaproteobacteria, that biomineralizes membrane-bounded magnetite nanocrystals in its magnetosomes. This genome sequence, in comparison with those of other magnetotactic bacteria, is essential for understanding the origin and evolution of magnetotaxis and magnetosome biomineralization.

Environment-dependent swimming strategy of Magnetococcus marinus under magnetic field

Abstract: Magnetotactic bacteria (MTB) are fascinating micro-organisms which possess embodied biomineralized nanomagnets providing them the ability to orient with the Earth's magnetic field. This property is presumably related to an evolutionary advantage in finding the oxic-anoxic interface along the up and down direction in aquatic environments. So far the magnetic field response by MTB, called magnetotaxis, has been well described by a paramagnetic model where bacteria orient passively along the field lines according to a purely physical mechanism where magnetic torque and orientational Brownian noise compete. Here we demonstrate using Magnetococcus marinus strain MC-1 as MTB model that magnetotaxis shows more complex behaviors, which are affected by environmental conditions of different types. Indeed while MC-1 swimmers are found to essentially obey the paramagnetic paradigm when swimming in their growth medium, they exhibit a run-and-tumble dynamics in a medium devoid of energy source. Tumbling events are found to provide isotropic reorientation capabilities causing the cells to escape from their prescribed field direction. This behavior has a major influence on the capabilities of the cells to explore their environment across field lines and represents an alternative search strategy to the back-and-forth motion along field-imposed tracks. Moreover, we show that aside chemical conditions, steric/geometrical constraints are also able to trigger tumbling events through obstacle encountering. Overall, physico-chemical environmental conditions appear to be important parameters involved in the swimming properties of MTB. Depending on environmental conditions, the run-and-tumble mobility may provide advantages in the search for nutrient or ecological niche, in complement to classical magnetotaxis.