Magnetotactic bacteria

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

Magnetotactic molecular architectures from self-assembly of β-peptide foldamers.

Abstract: The design of stimuli-responsive self-assembled molecular systems capable of undergoing mechanical work is one of the most important challenges in synthetic chemistry and materials science. Here we report that foldectures, that is, self-assembled molecular architectures of β-peptide foldamers, uniformly align with respect to an applied static magnetic field, and also show instantaneous orientational motion in a dynamic magnetic field. This response is explained by the amplified anisotropy of the diamagnetic susceptibilities as a result of the well-ordered molecular packing of the foldectures. In addition, the motions of foldectures at the microscale can be translated into magnetotactic behaviour at the macroscopic scale in a way reminiscent to that of magnetosomes in magnetotactic bacteria. This study will provide significant inspiration for designing the next generation of biocompatible peptide-based molecular machines with applications in biological systems.

Inactivation of the Flagellin Gene flaA in Magnetospirillum gryphiswaldense Results in Nonmagnetotactic Mutants Lacking Flagellar Filaments

Abstract: Magnetotactic bacteria synthesize magnetosomes, which cause them to orient and migrate along magnetic field lines. The analysis of magnetotaxis and magnetosome biomineralization at the molecular level has been hindered by the unavailability of genetic methods, namely the lack of a means to introduce directed gene-specific mutations. Here we report a method for knockout mutagenesis by homologous recombination in Magnetospirillum gryphiswaldense. Multiple flagellin genes, which are unlinked in the genome, were identified in M. gryphiswaldense. The targeted disruption of the flagellin gene flaA was shown to eliminate flagella formation, motility, and magnetotaxis. The techniques described in this paper will make it possible to take full advantage of the forthcoming genome sequences of M. gryphiswaldense and other magnetotactic bacteria.

Abundant bacterial magnetite occurrence in oxic red clay

Abstract: Magnetotactic bacteria (MTB) produce chains of intracellular magnetite and/or greigite crystals and respond to an ambient magnetic field. MTB are considered to be microaerophilic to anaerobic organisms that live at and below the oxic-anoxic transition zone of aquatic environments. On the basis of rock magnetic analyses, including first-order reversal curve diagrams and isothermal remanent magnetization component analyses, along with transmission electron microscopy, we demonstrate that bacterial magnetites (magnetofossils) dominate magnetic mineral assemblages throughout a 76 m thickness of red clay at Integrated Ocean Drilling Program Site U1365 in the South Pacific Gyre, as well as in subsurface red clay of the North Pacific Gyre, where the sediment column contains abundant dissolved oxygen and no oxic-anoxic transition zone exists. This implies that MTB inhabit red clay; this conflicts with widespread interpretations of MTB ecology, namely that they are microaerophilic, requiring low levels of oxygen to grow and produce magnetite, and that magnetotaxis is used to help them find optimal positions in a strong vertical chemical gradient. Most magnetofossils in the red clay have cubo-octahedral morphology. This supports the notion that magnetofossil morphology can be a paleoenvironmental indicator; the proportion of elongated magnetofossils increases in less oxic environments. Our results also have implications for red-clay paleomagnetism in that magnetofossils may cause much-delayed remanence acquisition if MTB can live at decimeter depths within red clay.

The effect and role of environmental conditions on magnetosome synthesis

Abstract: Magnetotactic bacteria (MTB) are considered the model species for the controlled biomineralization of magnetic Fe oxide (magnetite, Fe3O4) or Fe sulfide (greigite, Fe3S4) nanocrystals in living organisms. In MTB, magnetic minerals form as membrane-bound, single-magnetic domain crystals known as magnetosomes and the synthesis of magnetosomes by MTB is a highly controlled process at the genetic level. Magnetosome crystals reveal highest purity and highest quality magnetic properties and are therefore increasingly sought after as novel nanoparticulate biomaterials for industrial and medical applications. In addition, “magnetofossils”, have been used as both past terrestrial and potential Martian life biosignature. However, until recently, the general belief was that the morphology of mature magnetite crystals formed by MTB was largely unaffected by environmental conditions. Here we review a series of studies that showed how changes in environmental factors such as temperature, pH, external Fe concentration, external magnetic fields, static or dynamic fluid conditions, and nutrient availability or concentrations can all affect the biomineralization of magnetite magnetosomes in MTB. The resulting variations in magnetic nanocrystals characteristics can have consequence both for their commercial value but also for their use as indicators for ancient life.In this paper we will review the recent findings regarding the influence of variable chemical and physical environmental control factors on the synthesis of magnetosome by MTB, and address the role of MTB in the global biogeochemical cycling of iron.