Magnetotactic bacteria

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

Effects of static magnetic field on magnetosome formation and expression of mamA, mms13, mms6 and magA in Magnetospirillum magneticum AMB-1

Abstract: Magnetotactic bacteria produce nanometer-size intracellular magnetic crystals. The superior crystalline and magnetic properties of magnetosomes have been attracting much interest in medical applications. To investigate effects of intense static magnetic field on magnetosome formation in Magnetospirillum magneticum AMB-1, cultures inoculated with either magnetic or non-magnetic pre-cultures were incubated under 0.2 T static magnetic field or geomagnetic field. The results showed that static magnetic field could impair the cellular growth and raise C(mag) values of the cultures, which means that the percentage of magnetosome-containing bacteria was increased. Static magnetic field exposure also caused an increased number of magnetic particles per cell, which could contribute to the increased cellular magnetism. The iron depletion in medium was slightly increased after static magnetic field exposure. The linearity of magnetosome chain was also affected by static magnetic field. Moreover, the applied intense magnetic field up-regulated mamA, mms13, magA expression when cultures were inoculated with magnetic cells, and mms13 expression in cultures inoculated with non-magnetic cells. The results implied that the interaction of the magnetic field created by magnetosomes in AMB-1 was affected by the imposed magnetic field. The applied static magnetic field could affect the formation of magnetic crystals and the arrangement of the neighboring magnetosome.

Elemental analysis of uncultured magnetotactic bacteria exposed to heavy metals.

Abstract: Natural enrichments of magnetotactic bacteria were used to study the sites where heavy metals accumulate in uncultured bacteria. Most bacteria obtained by magnetic concentration from these enrichments contained, in addition to the magnetosomes, large phosphorus-rich granules in the cytoplasm. Metal (Zn, Mn, Sr, Cd, Al, Cr, and Pb) chlorides were added independently to the enrichments, and after 24 h, the elemental composition of the phosphorus-rich granules, magnetosomes, and "soft parts" (cytoplasm plus cell envelope) of whole bacteria was analyzed by energy-dispersive X-ray analysis on a transmission electron microscope. All bacteria contained Mn and Sr in the phosphorus-rich granules; some of them presented Mn peaks also in the soft parts. Zinc accumulation was variable and was found mainly in the phosphorus-rich granules, but also in the soft part of some bacteria. Some analyzed bacteria presented Zn peaks only in the soft parts, and some of them did not present Zn in any structure. Cadmium and Al were found only in the granules of some bacteria. Chromium was found in the soft parts of some bacteria. Lead was not detected in any bacteria. We concluded that the phosphorus-rich granules are major sites for metal accumulation by these bacteria. No conclusive results for magnetosomes were obtained because of the limitations of the analytical techniques particularly when used for whole cell analysis.

Crystal habits and magnetic microstructures of magnetosomes in coccoid magnetotactic bacteria

Abstract: We report on the application of off-axis electron holography and high-resolution TEM to study the crystal habits of magnetosomes and magnetic microstructure in two coccoid morphotypes of magnetotactic bacteria collected from a brackish lagoon at Itaipu, Brazil. Itaipu-1, the larger coccoid organism, contains two separated chains of unusually large magnetosomes; the magnetosome crystals have roughly square projections, lengths up to 250 nm and are slightly elongated along [111] (width/length ratio of about 0.9). Itaipu-3 magnetosome crystals have lengths up to 120 nm, greater elongation along [111] (width/length ∼ 0.6), and prominent corner facets. The results show that Itaipu-1 and Itaipu-3 magnetosome crystal habits are related, differing only in the relative sizes of their crystal facets. In both cases, the crystals are aligned with their [111] elongation axes parallel to the chain direction. In Itaipu-1, but not Itaipu-3, crystallographic positioning perpendicular to [111] of successive crystals in the magnetosome chain appears to be under biological control. Whereas the large magnetosomes in Itaipu-1 are metastable, single-magnetic domains, magnetosomes in Itaipu-3 are permanent, single-magnetic domains, as in most magnetotactic bacteria.

Generation of nanomagnetic biocomposites by genetic engineering of bacterial magnetosomes

Abstract: Magnetosomes are magnetic nanoparticles biomineralized by magnetotactic bacteria. They consist of a monocrystalline magnetite core enveloped by the magnetosome membrane, which harbors a set of spec...

Iron Uptake Kinetics and Magnetosome Formation by Magnetospirillum gryphiswaldense as a Function of pH, Temperature and Dissolved Iron Availability

Abstract: The dynamics of iron uptake and magnetosome formation by the magnetotactic bacteria (MTB) Magnetospirillum gryphiswaldense was investigated at a broad range of pH, temperature and iron availability to evaluate the role of MTB in the iron biogeochemical cycle. Except at pH 5.0, all incubations have shown significant bacterial growth. However, magnetosome formation was limited at pH 8.0 and 9.0 as well as at 4°C, 10°C and 35°C. At optimal conditions (i.e., pH 7 and 28°C), the uptake rates of dissolved Fe(III) as a function of initial Fe concentration can be described by a Michaelis-Menten-type kinetic model with a maximum iron uptake rate, Vmax ,, of 11 × 10−12 μmoles cell−1 h−1 and an affinity constant, Ks of 26 μM Fe. High resolution imaging of magnetosomes synthesized at the different pH values, revealed a large range of morphologies and sizes, which illustrate the impact of environmental conditions on the formation of magnetite crystals by MTB.