Magnetotactic Bacteria and Magnetosomes

The development of eco-friendly technologies in material synthesis is of considerable importance to expand their biological applications. Nowadays, a variety of inorganic nanoparticles with well-defined chemical composition, size, and morphology have been synthesized by using different microorganisms, and their applications in many cutting-edge technological areas have been explored. This paper highlights the recent developments of the biosynthesis of inorganic nanoparticles including metallic nanoparticles, oxide nanoparticles, sulfide nanoparticles, and other typical nanoparticles. Different formation mechanisms of these nanoparticles will be discussed as well. The conditions to control the size/shape and stability of particles are summarized. The applications of these biosynthesized nanoparticles in a wide spectrum of potential areas are presented including targeted drug delivery, cancer treatment, gene therapy and DNA analysis, antibacterial agents, biosensors, enhancing reaction rates, separation science, and magnetic resonance imaging (MRI). The current limitations and future prospects for the synthesis of inorganic nanoparticles by microorganisms are discussed.

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Biosynthesis of nanoparticles by microorganisms and their applications

SUMMARY Magnetotactic bacteria (MTB) are widespread, motile, diverse prokaryotes that biomineralize a unique organelle called the magnetosome. Magnetosomes consist of a nano-sized crystal of a magnetic iron mineral that is enveloped by a lipid bilayer membrane. In cells of almost all MTB, magnetosomes are organized as a well-ordered chain. The magnetosome chain causes the cell to behave like a motile, miniature compass needle where the cell aligns and swims parallel to magnetic field lines. MTB are found in almost all types of aquatic environments, where they can account for an important part of the bacterial biomass. The genes responsible for magnetosome biomineralization are organized as clusters in the genomes of MTB, in some as a magnetosome genomic island. The functions of a number of magnetosome genes and their associated proteins in magnetosome synthesis and construction of the magnetosome chain have now been elucidated. The origin of magnetotaxis appears to be monophyletic; that is, it developed in a common ancestor to all MTB, although horizontal gene transfer of magnetosome genes also appears to play a role in their distribution. The purpose of this review, based on recent progress in this field, is focused on the diversity and the ecology of the MTB and also the evolution and transfer of the molecular determinants involved in magnetosome formation.

Ecology, Diversity, and Evolution of Magnetotactic Bacteria

Magnetotactic bacteria, magnetosomes and their application

Advancements in nanoparticle fabrication by hazard free eco-friendly green routes

Isolation and characterization of a marine magnetotactic spirillum axenic culture QH-2 from an intertidal zone of the China Sea.

Magnetotactic bacteria are a heterologous group of motile prokaryotes, ubiquitous in aquatic habitats and cosmopolitan in distribution. Here, we studied the diversity of magnetotactic bacteria in a seawater pond within an intertidal zone at Huiquan Bay in the China Sea. The pond is composed of a permanently submerged part and a low tide subregion. The magnetotactic bacteria collected from the permanently submerged part display diversity in morphology and taxonomy. In contrast, we found a virtually homogenous population of ovoid-coccoid magnetotactic bacteria in the low tide subregion of the pond. They were bilophotrichously flagellated and exhibited polar magnetotactic behaviour. Almost all cells contained two chains of magnetosomes composed of magnetite crystals. Intriguingly, the combination of restriction fragment length polymorphism analysis (RFLP) and sequencing of cloned 16S rDNA genes from the low tide subregion samples as well as fluorescence in situ hybridization (FISH) revealed the presence of a homogenous population. Moreover, phylogenetic analysis indicated that the Qingdao Huiquan low tide magnetotactic bacteria belong to a new genus affiliated with the alpha-subclass of Proteobacteria. This finding suggests the adaptation of the magnetotactic bacterial population to the marine tide.

Characterization of a homogeneous taxonomic group of marine magnetotactic cocci within a low tide zone in the China Sea.

Bacterial community composition and predominant bacteria were analyzed by PCR-denaturing gradient gel electrophoresis(DGGE) in the Yellow Sea Cold Water Mass(YSCWM).The results analysed by Glyko Bandscan software showed that samples from all stations in April and stations in the YSCWM area in October had almost the same number of different DNA bands(17 and 16 respectively) with high diversity.However,samples from the stations out of YSCWM area had fewer DNA bands(about 12) with lower diversity.24 DGGE bands reflecting varying phylotypes were excised,cloned and sequenced.Phylogenetic analysis of 24 cloned bands showed that bacterial phylotypes were made up of two phyla bacteria,Proteobacteria and Bacteroides.Among these sequences,16 were related to γ-Proteobacteria and δ-Proteobacteria and 5 were related to Bacteroides.It indicated that bacterial community composition,as well as the predominant bacterial groups,from all sampling stations in April(the temperature of seawater was around 7～12℃) and the inter of YSCWM in October(≤10℃) was the same,different from the exterior of YSCWM(≥19℃).By comparing,from samples of exterior of YSCWM,the predominant bacteria groups were different with the different sampling stations.So it suggested that bacterial community composition and the characteristic of predominant bacteria of the YSCWM may have something to do with the development of the YSCWM.

Kailing Zhu

Papers

Isolation and characterization of a marine magnetotactic spirillum axenic culture QH-2 from an intertidal zone of the China Sea.

Characterization of a homogeneous taxonomic group of marine magnetotactic cocci within a low tide zone in the China Sea.

[Bacterial community composition of the Yellow Sea Cold Water Mass studied by PCR-denaturing gradient gel electrophoresis].