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Magnetotactic bacteria as potential sources of bioproducts.

Araujo AC, Abreu F, Silva KT, Bazylinski DA, Lins U - Mar Drugs (2015)

Bottom Line: As a result of this control, magnetosomes have narrow and uniform size ranges, relatively specific magnetic and crystalline properties, and an enveloping biological membrane.Most currently described MTB have been isolated from saline or brackish environments and the availability of their genomes has contributed to a better understanding and culturing of these fastidious microorganisms.More specifically, we discovered that the genome of the cultured MTB Magnetovibrio blakemorei, among other MTB, contains several metabolic pathways for the synthesis of secondary metabolites and other compounds, thereby raising the possibility of the co-production of new bioactive molecules along with magnetosomes by this species.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, 373, CCS, UFRJ, Rio de Janeiro, RJ 21941-902, Brazil. acvaraujo@gmail.com.

ABSTRACT
Magnetotactic bacteria (MTB) produce intracellular organelles called magnetosomes which are magnetic nanoparticles composed of magnetite (Fe3O4) or greigite (Fe3S4) enveloped by a lipid bilayer. The synthesis of a magnetosome is through a genetically controlled process in which the bacterium has control over the composition, direction of crystal growth, and the size and shape of the mineral crystal. As a result of this control, magnetosomes have narrow and uniform size ranges, relatively specific magnetic and crystalline properties, and an enveloping biological membrane. These features are not observed in magnetic particles produced abiotically and thus magnetosomes are of great interest in biotechnology. Most currently described MTB have been isolated from saline or brackish environments and the availability of their genomes has contributed to a better understanding and culturing of these fastidious microorganisms. Moreover, genome sequences have allowed researchers to study genes related to magnetosome production for the synthesis of magnetic particles for use in future commercial and medical applications. Here, we review the current information on the biology of MTB and apply, for the first time, a genome mining strategy on these microorganisms to search for secondary metabolite synthesis genes. More specifically, we discovered that the genome of the cultured MTB Magnetovibrio blakemorei, among other MTB, contains several metabolic pathways for the synthesis of secondary metabolites and other compounds, thereby raising the possibility of the co-production of new bioactive molecules along with magnetosomes by this species.

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Proposed mechanism of magnetosome biomineralization in Magnetovibrio blakemorei strain MV-1. The putative magnetosome island (MAI) of Mv. blakemorei (A) [5] and the putative function of each encoded protein during magnetosome formation (B) based on their similarities to proteins described for Magnetospirillum species. The color of each ORF is used to identify the localization of encoded proteins. Unidentified genes in grey encode hypothetical proteins. The mamL, J, U, G, and F genes, although present in Magnetospirillum species, are not present in the MAI of Mv. blakemorei.
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marinedrugs-13-00389-f004: Proposed mechanism of magnetosome biomineralization in Magnetovibrio blakemorei strain MV-1. The putative magnetosome island (MAI) of Mv. blakemorei (A) [5] and the putative function of each encoded protein during magnetosome formation (B) based on their similarities to proteins described for Magnetospirillum species. The color of each ORF is used to identify the localization of encoded proteins. Unidentified genes in grey encode hypothetical proteins. The mamL, J, U, G, and F genes, although present in Magnetospirillum species, are not present in the MAI of Mv. blakemorei.

Mentions: Magnetosome biomineralization is a genetically controlled process that involves approximately 28 proteins encoded by the so-called mam and mms genes. In Magnetospirillum gryphiswaldense, these genes are organized in four operons: the mamAB, mamGFDC, mamXY and mms6 operons [5,76]. In Ms. gryphiswaldense, only the mamAB operon is essential for magnetosome synthesis while the absence of the other operons does not lead to the absence of magnetosomes but to differences in magnetite crystal morphology and the production of particles not clearly organized in chains [77]. The operons, localized in a larger cluster in the genome of Ms. gryphiswaldense and of some other MTB, represent a genomic island referred to as the MAI standing for Magnetosome Island [76]. This genomic region contains genes responsible for iron transport, magnetite crystal nucleation and growth, magnetite crystal morphology, and magnetosome organization within the cell (Figure 4). Comparative studies based on cultured and uncultured magnetite- and greigite-producing MTB show that the mamABEIKMOPQ genes are strongly conserved among different species [73,74,75,76,77]. Although the function of many of these genes has not yet been elucidated, they have been inferred from similarities to other known proteins. One of the more conserved proteins is MamK, a homolog of the prokaryotic cytoskeleton protein MreB [78]. MamK is an actin-like protein that forms interconnected filaments along the cell. Magnetosomes are linked to this long structure by another protein called MamJ, although the gene coding for this protein is absent from the genomes of many MTB including Magnetovibrio blakemorei, Magnetofaba australis, and Magnetococcus marinus. In these bacteria, a hypothetical protein is encoded by a gene adjacent to mamK but it is not clear whether this protein functions similarly to MamJ. The fixed organization of magnetosomes into chains and its connection to the cell membrane enable the cells to orient along magnetic field lines since the torque exerted by magnetosomes chain is transferred to the whole cell [41].


Magnetotactic bacteria as potential sources of bioproducts.

Araujo AC, Abreu F, Silva KT, Bazylinski DA, Lins U - Mar Drugs (2015)

Proposed mechanism of magnetosome biomineralization in Magnetovibrio blakemorei strain MV-1. The putative magnetosome island (MAI) of Mv. blakemorei (A) [5] and the putative function of each encoded protein during magnetosome formation (B) based on their similarities to proteins described for Magnetospirillum species. The color of each ORF is used to identify the localization of encoded proteins. Unidentified genes in grey encode hypothetical proteins. The mamL, J, U, G, and F genes, although present in Magnetospirillum species, are not present in the MAI of Mv. blakemorei.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306944&req=5

marinedrugs-13-00389-f004: Proposed mechanism of magnetosome biomineralization in Magnetovibrio blakemorei strain MV-1. The putative magnetosome island (MAI) of Mv. blakemorei (A) [5] and the putative function of each encoded protein during magnetosome formation (B) based on their similarities to proteins described for Magnetospirillum species. The color of each ORF is used to identify the localization of encoded proteins. Unidentified genes in grey encode hypothetical proteins. The mamL, J, U, G, and F genes, although present in Magnetospirillum species, are not present in the MAI of Mv. blakemorei.
Mentions: Magnetosome biomineralization is a genetically controlled process that involves approximately 28 proteins encoded by the so-called mam and mms genes. In Magnetospirillum gryphiswaldense, these genes are organized in four operons: the mamAB, mamGFDC, mamXY and mms6 operons [5,76]. In Ms. gryphiswaldense, only the mamAB operon is essential for magnetosome synthesis while the absence of the other operons does not lead to the absence of magnetosomes but to differences in magnetite crystal morphology and the production of particles not clearly organized in chains [77]. The operons, localized in a larger cluster in the genome of Ms. gryphiswaldense and of some other MTB, represent a genomic island referred to as the MAI standing for Magnetosome Island [76]. This genomic region contains genes responsible for iron transport, magnetite crystal nucleation and growth, magnetite crystal morphology, and magnetosome organization within the cell (Figure 4). Comparative studies based on cultured and uncultured magnetite- and greigite-producing MTB show that the mamABEIKMOPQ genes are strongly conserved among different species [73,74,75,76,77]. Although the function of many of these genes has not yet been elucidated, they have been inferred from similarities to other known proteins. One of the more conserved proteins is MamK, a homolog of the prokaryotic cytoskeleton protein MreB [78]. MamK is an actin-like protein that forms interconnected filaments along the cell. Magnetosomes are linked to this long structure by another protein called MamJ, although the gene coding for this protein is absent from the genomes of many MTB including Magnetovibrio blakemorei, Magnetofaba australis, and Magnetococcus marinus. In these bacteria, a hypothetical protein is encoded by a gene adjacent to mamK but it is not clear whether this protein functions similarly to MamJ. The fixed organization of magnetosomes into chains and its connection to the cell membrane enable the cells to orient along magnetic field lines since the torque exerted by magnetosomes chain is transferred to the whole cell [41].

Bottom Line: As a result of this control, magnetosomes have narrow and uniform size ranges, relatively specific magnetic and crystalline properties, and an enveloping biological membrane.Most currently described MTB have been isolated from saline or brackish environments and the availability of their genomes has contributed to a better understanding and culturing of these fastidious microorganisms.More specifically, we discovered that the genome of the cultured MTB Magnetovibrio blakemorei, among other MTB, contains several metabolic pathways for the synthesis of secondary metabolites and other compounds, thereby raising the possibility of the co-production of new bioactive molecules along with magnetosomes by this species.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Avenida Carlos Chagas Filho, 373, CCS, UFRJ, Rio de Janeiro, RJ 21941-902, Brazil. acvaraujo@gmail.com.

ABSTRACT
Magnetotactic bacteria (MTB) produce intracellular organelles called magnetosomes which are magnetic nanoparticles composed of magnetite (Fe3O4) or greigite (Fe3S4) enveloped by a lipid bilayer. The synthesis of a magnetosome is through a genetically controlled process in which the bacterium has control over the composition, direction of crystal growth, and the size and shape of the mineral crystal. As a result of this control, magnetosomes have narrow and uniform size ranges, relatively specific magnetic and crystalline properties, and an enveloping biological membrane. These features are not observed in magnetic particles produced abiotically and thus magnetosomes are of great interest in biotechnology. Most currently described MTB have been isolated from saline or brackish environments and the availability of their genomes has contributed to a better understanding and culturing of these fastidious microorganisms. Moreover, genome sequences have allowed researchers to study genes related to magnetosome production for the synthesis of magnetic particles for use in future commercial and medical applications. Here, we review the current information on the biology of MTB and apply, for the first time, a genome mining strategy on these microorganisms to search for secondary metabolite synthesis genes. More specifically, we discovered that the genome of the cultured MTB Magnetovibrio blakemorei, among other MTB, contains several metabolic pathways for the synthesis of secondary metabolites and other compounds, thereby raising the possibility of the co-production of new bioactive molecules along with magnetosomes by this species.

Show MeSH
Related in: MedlinePlus