Simple homemade apparatus for harvesting uncultured magnetotactic microorganisms

Lins, Ulysses; Freitas, Flavia D'Albergaria; Keim, Carolina N.; Barros, Henrique Lins de; Esquivel, Darci M. S.; Farina, Marcos

doi:10.1590/s1517-83822003000200004

Cited by 54 publications

(33 citation statements)

References 18 publications

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“…M. multicellularis has not been cultured, DNA samples were prepared according to a modified magnetic enrichment procedure (Lins et al, 2003) which is based on capillary racetrack principle (Wolfe et al, 1987). Water and sediment were collected from Araruama Lagoon, Rio de Janeiro, Brazil (221 50 0 S, 421 13 0 W) and magnetic enrichment was carried out with additional washing steps using lagoon sterile autoclaved water.…”

Section: Methodsmentioning

confidence: 99%

Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria

et al. 2011

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Magnetosomes are prokaryotic organelles produced by magnetotactic bacteria that consist of nanometer-sized magnetite (Fe 3 O 4 ) or/and greigite (Fe 3 S 4 ) magnetic crystals enveloped by a lipid bilayer membrane. In magnetite-producing magnetotactic bacteria, proteins present in the magnetosome membrane modulate biomineralization of the magnetite crystal. In these microorganisms, genes that encode for magnetosome membrane proteins as well as genes involved in the construction of the magnetite magnetosome chain, the mam and mms genes, are organized within a genomic island. However, partially because there are presently no greigite-producing magnetotactic bacteria in pure culture, little is known regarding the greigite biomineralization process in these organisms including whether similar genes are involved in the process. Here using cultureindependent techniques, we now show that mam genes involved in the production of magnetite magnetosomes are also present in greigite-producing magnetotactic bacteria. This finding suggest that the biomineralization of magnetite and greigite did not have evolve independently (that is, magnetotaxis is polyphyletic) as once suggested. Instead, results presented here are consistent with a model in which the ability to biomineralize magnetosomes and the possession of the mam genes was acquired by bacteria from a common ancestor, that is, the magnetotactic trait is monophyletic.

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Section: Methodsmentioning

confidence: 99%

Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria

et al. 2011

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“…Samples were pooled from about 20 microcosms and subsequently transferred to an "MTB trap" (Fig. 1B), which is a modified version of a collection vessel for harvesting uncultured magnetotactic microorganisms (29). This homemade device consists of a reservoir with two opposite funnels pointing toward a collecting tube in parallel to the applied magnetic field of two square ferrite magnets (5 by 7.5 cm) as indicated in Fig.…”

Section: Methodsmentioning

confidence: 99%

Toward Cloning of the Magnetotactic Metagenome: Identification of Magnetosome Island Gene Clusters in Uncultivated Magnetotactic Bacteria from Different Aquatic Sediments

Jogler

Lin

Meyerdierks

et al. 2009

Appl Environ Microbiol

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In this report, we describe the selective cloning of large DNA fragments from magnetotactic metagenomes from various aquatic habitats. This was achieved by a two-step magnetic enrichment which allowed the mass collection of environmental magnetotactic bacteria (MTB) virtually free of nonmagnetic contaminants. Four fosmid libraries were constructed and screened by end sequencing and hybridization analysis using heterologous magnetosome gene probes. A total of 14 fosmids were fully sequenced. We identified and characterized two fosmids, most likely originating from two different alphaproteobacterial strains of MTB that contain several putative operons with homology to the magnetosome island (MAI) of cultivated MTB. This is the first evidence that uncultivated MTB exhibit similar yet differing organizations of the MAI, which may account for the diversity in biomineralization and magnetotaxis observed in MTB from various environments.

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“…Cells were isolated from sediment and water samples by using glass chambers with capillary ends positioned inside magnetic coils (8). Whole cells, or magnetosomes extracted from disrupted cells (see reference 9 for details), were deposited on holey-carbon TEM grids.…”

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Habits of Magnetosome Crystals in Coccoid Magnetotactic Bacteria

Lins

McCartney

Farina

et al. 2005

Appl Environ Microbiol

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High-resolution transmission electron microscopy and electron holography were used to study the habits of exceptionally large magnetite crystals in coccoid magnetotactic bacteria. In addition to the crystal habits, the crystallographic positioning of successive crystals in the magnetosome chain appears to be under strict biological control.Magnetotactic bacteria (MB) contain magnetosomes comprising nanoscale magnetic iron mineral crystals in membrane vesicles (1). A striking feature of magnetosome magnetite crystals is that they have different, but consistent, projected shapes in different bacterial species or strains when observed by transmission electron microscopy (TEM) (3). The overall sizes of the crystals, the width/length ratios, and the relative sizes of putative corner faces can vary from one bacterial species or strain to another, resulting in the distinctive projected shapes.Off-axis electron holography can be used to obtain both magnetic and structural information about nanometer-sized magnetic crystals (4). We report here on the application of electron holography and high-resolution TEM to study the crystal habits of magnetosomes in two coccoid morphotypes of MB collected from a brackish lagoon at Itaipu, Brazil, which is located on the coast north of Rio de Janeiro (10). Itaipu-1 and Itaipu-3 bacteria predominated in the lagoon at the time the samples for the present study were collected. Itaipu-1, the largest coccoid organism, contains two chains of magnetosomes (Fig. 1); the magnetosome crystals have roughly square projections, lengths up to 250 nm, and width/length ratios of ca. 0.9 (10). These are the largest-volume magnetosome crystals yet reported. Itaipu-3 has magnetosome crystals that are elongated (width/length ratio of ϳ0.6) along [111], with lengths up to 120 nm and prominent corner facets. Whereas magnetosomes in most MB, including Itaipu-3, are permanent singlemagnetic domains, we previously reported that the large magnetosomes in Itaipu-1 are metastable, single-magnetic domains (9).Cells were isolated from sediment and water samples by using glass chambers with capillary ends positioned inside magnetic coils (8). Whole cells, or magnetosomes extracted from disrupted cells (see reference 9 for details), were deposited on holey-carbon TEM grids. Water drops containing the crystals were spread over the grids. Grids were then air dried and observed under a transmission electron microscope. In some cases the crystal suspension was sonicated prior to deposition on the grids. The disruption process resulted in Itaipu-1 and Itaipu-3 magnetosomes mixed together on the TEM grid (Fig. 2). High-resolution TEM, selected-area electron diffraction measurements, and off-axis electron holography were made with a Phillips CM200 FEG TEM operated at 200 kV. For details on the application of electron holography to MB, see references 4 and 9. Figure 2 shows a chain of magnetosomes from Itaipu-1, together with some smaller, more elongated, crystals from Itaipu-3. The inset in Fig. 2A

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Simple homemade apparatus for harvesting uncultured magnetotactic microorganisms

Cited by 54 publications

References 18 publications

Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria

Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria

Toward Cloning of the Magnetotactic Metagenome: Identification of Magnetosome Island Gene Clusters in Uncultivated Magnetotactic Bacteria from Different Aquatic Sediments

Habits of Magnetosome Crystals in Coccoid Magnetotactic Bacteria

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