Quantifying the Magnetic Advantage in Magnetotaxis

Smith, Moira J.; Sheehan, Paul E.; Perry, Lynda; O’Connor, Kevin E.; Csonka, L N; Applegate, Bruce; Whitman, L. J.

doi:10.1529/biophysj.106.085167

Cited by 62 publications

(69 citation statements)

References 28 publications

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“…The magnetic phenotypes of the MSR-1 and AMB-1 magA mutants constructed during this study, together with the magA localization outside the MAI, its poor conservation among MTB, and the affiliation of MagA with the CPA2 subfamily, clearly contradict the results of previous studies (24,36). However, as mentioned above, all previous genetic studies were lacking appropriate experimental controls, i.e., they failed to demonstrate that wildtype-like phenotypes could be restored by the reintroduction of magA (24,36).…”

Section: Resultscontrasting

confidence: 99%

“…A more recent study by a different laboratory, in which the targeted deletion of magA in AMB-1 supposedly resulted in the loss of the ability to form magnetosomes, seemed to confirm the reported essential function of magA (36). However, there still is a lack of evidence for the suggestion that the observed nonmagnetic phenotypes were caused by the loss of magA function, since neither this mutant nor the original transposon mutant (24) were shown to be complemented by a wild-type copy of magA.…”

mentioning

confidence: 68%

“…However, as mentioned above, all previous genetic studies were lacking appropriate experimental controls, i.e., they failed to demonstrate that wildtype-like phenotypes could be restored by the reintroduction of magA (24,36). Thus, it can be speculated that the previously observed nonmagnetic phenotypes likely were due to the accidental isolation of clones coincidentally harboring an undetected spontaneous second-site mutation, leading to the wrongful conclusion of a role of MagA in magnetosome formation.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

The MagA Protein of Magnetospirilla Is Not Involved in Bacterial Magnetite Biomineralization

Uebe

Henn

Schüler

2011

Journal of Bacteriology

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Magnetotactic bacteria have the ability to orient along geomagnetic field lines based on the formation of magnetosomes, which are intracellular nanometer-sized, membrane-enclosed magnetic iron minerals. The formation of these unique bacterial organelles involves several processes, such as cytoplasmic membrane invagination and magnetosome vesicle formation, the accumulation of iron in the vesicles, and the crystallization of magnetite. Previous studies suggested that the magA gene encodes a magnetosome-directed ferrous iron transporter with a supposedly essential function for magnetosome formation in Magnetospirillum magneticum AMB-1 that may cause magnetite biomineralization if expressed in mammalian cells. However, more recent studies failed to detect the MagA protein among polypeptides associated with the magnetosome membrane and did not identify magA within the magnetosome island, a conserved genomic region that is essential for magnetosome formation in magnetotactic bacteria. This raised increasing doubts about the presumptive role of magA in bacterial magnetosome formation, which prompted us to reassess MagA function by targeted deletion in Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1. Contrary to previous reports, magA mutants of both strains still were able to form wild-type-like magnetosomes and had no obvious growth defects. This unambiguously shows that magA is not involved in magnetosome formation in magnetotactic bacteria.

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Section: Resultscontrasting

confidence: 99%

mentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

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The MagA Protein of Magnetospirilla Is Not Involved in Bacterial Magnetite Biomineralization

Uebe

Henn

Schüler

2011

Journal of Bacteriology

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“…[46,47] for introductions to chemotaxis). In the simplest case, the bacteria in the capillary can be described by one-dimensional dynamics [41,48,49], so that only two densities of bacteria, those swimming to the left and to the right, ρ L (x, t) and ρ R (x, t), respectively, need to be considered. This description is valid for magnetotaxis when the magnetic field is parallel or antiparallel to the capillary axis (it can be used for other cases by considering the projection of the velocity).…”

Section: Modeling Magneto-aerotaxismentioning

confidence: 99%

Magnetotactic bacteria

Klumpp

Faivre

2016

Eur. Phys. J. Spec. Top.

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Abstract. Magnetotactic bacteria are aquatic microorganisms with the ability to swim along the field lines of a magnetic field, which in their natural environment is provided by the magnetic field of the Earth. They do so with the help of specialized magnetic organelles called magnetosomes, vesicles containing magnetic crystals. Magnetosomes are aligned along cytoskeletal filaments to give linear structures that can function as intracellular compass needles. The predominant viewpoint is that the cells passively align with an external magnetic field, just like a macroscopic compass needle, but swim actively along the field lines, propelled by their flagella. In this minireview, we give an introduction to this intriguing bacterial behavior and discuss recent advances in understanding it, with a focus on the swimming directionality, which is not only affected by magnetic fields, but also by gradients of the oxygen concentration.

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“…The magnetosome organelle is a lipidbounded invagination of the cytoplasmic membrane that directs the biomineralization of a single, highly ordered magnetic crystal of magnetite (Fe 3 O 4 ) or greigite (Fe 3 S 4 ). Individual magnetosomes are aligned in one or more chains that allow MTB to orient in geomagnetic field lines, which in turn facilitates their search for low-oxygen environments (3,4). Magnetosomes have been largely used as a model to study biomineralization, the process by which living organisms build highly ordered three-dimensional structures out of inorganic molecules.…”

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confidence: 99%

Comprehensive genetic dissection of the magnetosome gene island reveals the step-wise assembly of a prokaryotic organelle

Murat¹,

Quinlan

Vali

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

293

559

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Although membrane-bounded compartments are commonly considered a unique eukaryotic characteristic, many species of bacteria have organelles. Compartmentalization is well studied in eukaryotes; however, the molecular factors and processes leading to organelle formation in bacteria are poorly understood. We use the magnetosome compartments of magnetotactic bacteria as a model system to investigate organelle biogenesis in a prokaryotic system. The magnetosome is an invagination of the cell membrane that contains a specific set of proteins able to direct the synthesis of a nanometer-sized magnetite crystal. A well-conserved region called the magnetosome island (MAI) is known to be essential for magnetosome formation and contains most of the genes previously implicated in magnetosome formation. Here, we present a comprehensive functional analysis of the MAI genes in a magnetotactic bacterium, Magnetospirillum magneticum AMB-1. By characterizing MAI deletion mutants, we show that parts of its conserved core are not essential for magnetosome biogenesis and that nonconserved genes are important for crystal formation. Most importantly, we show that the mamAB gene cluster encodes for factors important for magnetosome membrane biogenesis, for targeting of proteins to this compartment and for several steps during magnetite production. Altogether, this genetic analysis defines the function of more than a dozen factors participating in magnetosome formation and shows that magnetosomes are assembled in a step-wise manner in which membrane biogenesis, magnetosome protein localization, and biomineralization are placed under discrete genetic control.bacterial organelle | biomineralization | compartmentalization | magnetosome | magnetotactic bacteria

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Quantifying the Magnetic Advantage in Magnetotaxis

Cited by 62 publications

References 28 publications

The MagA Protein of Magnetospirilla Is Not Involved in Bacterial Magnetite Biomineralization

The MagA Protein of Magnetospirilla Is Not Involved in Bacterial Magnetite Biomineralization

Magnetotactic bacteria

Comprehensive genetic dissection of the magnetosome gene island reveals the step-wise assembly of a prokaryotic organelle

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