Iron Transport and Magnetite Crystal Formation of the Magnetic Bacterium Magnetospirillum gryphiswaldense

Abstract

Magnetic bacteria are found in various morphologies as cocci, vibrios, spirilli and rods in aquatic mud layers. Magnetite (Fe3O4) is stored in phospholipid vesicles as bullet-shaped. hexagonal or cubooctahydral crystals. S i z e and form of these crystals are species-specific and precisely controlled. The microaemphilic MagnetospirilIum gryphiswaldense forms in a near to linear chain up to 60 cubooctahedral, single domain magnetite crystals of 42-45nm diameter, which generates a magnetic dipole. Six proteins were detected in SDS-gels of the special phospholipid vesicles, which envelope the magnetite crystals These proteins are probably involved in iron transport (Fen orland Fem), in nucleation catalysis, in redox orland pH colhoL Iron uptake and dynamics of magnetite crystal formation were estimated simultaneously by change of light scattering of the cells within homogeneous magnetic fields. A very &cient, energy-dependent uptake of Fern in presence of spent, irondeficient growth medium was found. Iron uptake was tightly coupled to magnetite crystal formation and magnetisation. When FeIU was added to iron-starved cells under inducing conditions, Fern was immediately transpotted into the cells and superparamagnetic crystals of less than 20nm were formed first within 30 min.

Envelope ultrastructure of uncultured naturally occurring magnetotactic cocci

“…Primarily, they may influence the ability of the bacteria to overcome the viscous drag of the environment[23] during the swimming of the cells while they find a suitable place in the environment. The cultured species Magnetospirillum magnetotacticum has about 2% of its dry weight as iron[27], which is 100 times higher than the content of Escherichia coli cells[28]. No siderophores were identified in spent culture media of Magnetospirillum gryphiswaldense [28].…”

Characterization of a Spontaneous Nonmagnetic Mutant ofMagnetospirillum gryphiswaldenseReveals a Large Deletion Comprising a Putative Magnetosome Island

“…In contrast to most other magnetotactic bacteria, methods for mass culture and genetic manipulation of M. gryphiswaldense are available (17,38,44), which has facilitated its analysis in a number of studies (37,39,40,43).…”

Nanomicrobiology

“…All known species within the most deeply branching phylogenetic groups in the domain Bacteria containing magnetotactic bacteria which include the candidate division OP3, the Nitrospirae, and the Deltaproteobacteria biomineralize only bullet-shaped crystals of magnetite in their magnetosomes (Kolinko et al 2011;Lefèvre et al 2011a, b, c) although some species in the Deltaproteobacteria also produce greigite (Lefèvre et al 2011b;Lins et al 2007) or only greigite (Abreu et al 2007). Magnetotactic bacteria in the later diverging groups, the Alpha-and Gammaproteobacteria, biomineralize only cuboctahedral and elongated prismatic crystals of magnetite and never bullet-shaped crystals (Bazylinski and Williams 2007;Lefèvre et al 2012;Schüler and Baeuerlein 1997). This finding suggests, given this correlation and the large amount of variation and number of crystal flaws in bullet-shaped magnetite crystals in general, that the composition of the first magnetosome crystals was magnetite and the first magnetosome mineral morphology was bullet-shaped (Abreu et al 2011;Lefèvre et al 2013a).…”

“…Magnetite biomineralization has been mainly studied in Magnetospirillum species, a group of Alphaproteobacteria that produce cuboctahedral crystals of magnetite (Bazylinski and Frankel 2004;Lefèvre and Bazylinski 2013;Schüler and Baeuerlein 1997), because growing these organisms is relatively simple and because there are tractable and efficient genetic systems for species of this genus (Komeili et al 2004;Matsunaga et al 1992;Murat et al 2010;Schultheiss and Schüler 2004;Schultheiss et al 2004). A summary of the proteins believed to be involved in magnetite biomineralization and their putative function is shown in Table 3.1.…”