Preparation of luciferase-bacterial magnetic particle complex by artificial integration of MagA-luciferase fusion protein into the bacterial magnetic particle membrane

Improved methods for mass production of magnetosomes and applications: a review

Magnetotactic bacteria have the unique ability to synthesize magnetosomes (nano-sized magnetite or greigite crystals arranged in chain-like structures) in a variety of shapes and sizes. The chain alignment of magnetosomes enables magnetotactic bacteria to sense and orient themselves along geomagnetic fields. There is steadily increasing demand for magnetosomes in the areas of biotechnology, biomedicine, and environmental protection. Practical difficulties in cultivating magnetotactic bacteria and achieving consistent, high-yield magnetosome production under artificial environmental conditions have presented an obstacle to successful development of magnetosome applications in commercial areas. Here, we review information on magnetosome biosynthesis and strategies for enhancement of bacterial cell growth and magnetosome formation, and implications for improvement of magnetosome yield on a laboratory scale and mass-production (commercial or industrial) scale.

Magnetotactic bacteria: nanodrivers of the future

Magnetotactic bacteria (MTB) represent a heterogeneous group of Gram-negative aquatic prokaryotes with a broad range of morphological types, including vibrioid, coccoid, rod and spirillum. MTBs possess the virtuosity to passively align and actively swim along the magnetic field. Magnetosomes are the trademark nano-ranged intracellular structures of MTB, which comprise magnetic iron-bearing inorganic crystals enveloped by an organic membrane, and are dedicated organelles for their magnetotactic lifestyle. Magnetosomes endue high and even dispersion in aqueous solutions compared with artificial magnetites, claiming them as paragon nanomaterials. MTB and magnetosomes offer high technological potential in modern science, technology and medicines. This review focuses on the applicability of MTB and magnetosomes in various areas of modern benefits.

Optimized method for preparation of IgG-binding bacterial magnetic nanoparticles

In this study, the optimized method for designing IgG-binding magnetosomes based on integration of IgG-binding fusion proteins into magnetosome membrane in vitro is presented. Fusion proteins Mbb and Mistbb consisting of magnetosome membrane protein MamC and membrane associating protein Mistic from Bacillus subtilis as anchors and BB-domains of Staphylococcus aureus protein A as IgG-binding region were used. With Response Surface Methodology (RSM) the highest level of proteins integration into magnetosome membrane was achieved under the following parameters: pH 8.78, without adding NaCl and 55 s of vortexing for Mbb; pH 9.48, 323 mM NaCl and 55 s of vortexing for Mistbb. Modified magnetosomes with Mbb and Mistbb displayed on their surface demonstrated comparable levels of IgG-binding activity, suggesting that both proteins could be efficiently used as anchor molecules. We also demonstrated that such modified magnetosomes are stable in PBS buffer during at least two weeks. IgG-binding magnetosomes obtained by this approach could serve as a multifunctional platform for displaying various types of antibodies.

Bacterial Magnetosome: A Novel Biogenetic Magnetic Targeted Drug Carrier with Potential Multifunctions

Bacterial magnetosomes (BMs) synthesized by magnetotactic bacteria have recently drawn great interest due to their unique features. BMs are used experimentally as carriers for antibodies, enzymes, ligands, nucleic acids, and chemotherapeutic drugs. In addition to the common attractive properties of magnetic carriers, BMs also show superiority as targeting nanoscale drug carriers, which is hardly matched by artificial magnetic particles. We are presenting the potential applications of BMs as drug carriers by introducing the drug-loading methods and strategies and the recent research progress of BMs which has contributed to the application of BMs as drug carriers.

In vivo display of a multisubunit enzyme complex on biogenic magnetic nanoparticles

Magnetosomes are unique bacterial organelles comprising membrane-enveloped magnetic crystals produced by magnetotactic bacteria. Because of several desirable chemical and physical properties, magnetosomes would be ideal scaffolds on which to display highly complicated biological complexes artificially. As a model experiment for the functional expression of a multisubunit complex on magnetosomes, we examined the display of a chimeric bacterial RNase P enzyme composed of the protein subunit (C5) of Escherichia coli RNase P and the endogenous RNA subunit by expressing a translational fusion of C5 with MamC, a known magnetosome protein, in the magnetotactic bacterium Magnetospirillum gryphiswaldense. As intended, the purified C5 fusion magnetosomes, but not wild-type magnetosomes, showed apparent RNase P activity and the association of a typical bacterial RNase P RNA. Our results demonstrate for the first time that magnetosomes can be employed as scaffolds for the display of multisubunit complexes.

Formation of magnetite by bacteria and its application

Magnetic particles offer high technological potential since they can be conveniently collected with an external magnetic field. Magnetotactic bacteria synthesize bacterial magnetic particles (BacMPs) with well-controlled size and morphology. BacMPs are individually covered with thin organic membrane, which confers high and even dispersion in aqueous solutions compared with artificial magnetites, making them ideal biotechnological materials. Recent molecular studies including genome sequence, mutagenesis, gene expression and proteome analyses indicated a number of genes and proteins which play important roles for BacMP biomineralization. Some of the genes and proteins identified from these studies have allowed us to express functional proteins efficiently onto BacMPs, through genetic engineering, permitting the preservation of the protein activity, leading to a simple preparation of functional protein-magnetic particle complexes. They were applicable to high-sensitivity immunoassay, drug screening and cell separation. Furthermore, fully automated single nucleotide polymorphism discrimination and DNA recovery systems have been developed to use these functionalized BacMPs. The nano-sized fine magnetic particles offer vast potential in new nano-techniques.

Molecular analysis of magnetotactic bacteria and development of functional bacterial magnetic particles for nano-biotechnology

Biomineralization is an elaborate process that produces complex nano-structures consisting of organic and inorganic components of uniform size and highly ordered morphology that self-assemble into structures in a hierarchical manner. Magnetotactic bacteria synthesize nano-sized magnetite crystals that are highly consistent in size and morphology within bacterial species; each particle is surrounded by a thin organic membrane, which facilitates their use for various biotechnological applications. Recent molecular studies, including mutagenesis, whole genome, transcriptome and comprehensive proteome analyses, have elucidated the processes important to bacterial magnetite formation. Some of the genes and proteins identified from these studies have enabled us, through genetic engineering, to express proteins efficiently, with their activity preserved, onto bacterial magnetic particles, leading to the simple preparation of functional protein-magnetic particle complexes. This review describes the recent advances in the fundamental analysis of bacterial magnetic particles and the development of surface-protein-modified magnetic particles for biotechnological applications.

Magnetic cell separation using antibody binding with protein a expressed on bacterial magnetic particles

Bacterial magnetic particles (BacMPs) are efficient platforms of proteins for surface display systems. In this study, mononuclear cells from peripheral blood were separated using BacMPs expressing protein A on the BacMP membrane surface (protein A-BacMPs), which were complexed with the Fc fragment of anti-mouse IgG antibody. The procedure of positive selection involves incubation of mononuclear cells and mouse monoclonal antibodies against different cell surface antigens (CD8, CD14, CD19, CD20) prior to treatment with protein A-BacMP binding with rabbit anti-mouse IgG secondary antibodies. Flow cytometric analysis showed that approximately 97.5 +/- 1.7% of CD19(+) and CD20(+) cells were involved in the positive fraction after magnetic separation. The ratio of the negative cells in the negative fraction was approximately 97.6 +/-1.4%. This indicates that CD19(+) and CD20(+) cells can be efficiently separated from mononuclear cells. Stem cell marker (CD34) positive cells were also separated using protein A-BacMP binding with antibody. May-Grunwald Giemsa stain showed a high nuclear/cytoplasm ratio, which indicates a typical staining pattern of stem cells. The separated cells had the capability of colony formation as hematopoietic stem cells. Furthermore, the inhibitory effect of magnetic cell separation on CD14(+) cells was evaluated by measurement of cytokine in the culture supernatant by ELISA when the cells were cultured with or without lipopolysaccharide (LPS). The induction of IL1-beta, TNFalpha, and IL6 was observed in the presence of 1 ng/mL LPS in all fractions. On the other hand, in the absence of LPS, BacMPs had little immunopotentiation to CD14(+) cells as well as that of artificial magnetic particles, although TNFalpha and IL6 were slightly induced in the absence of LPS in the positive fraction.

Spontaneous integration of transmembrane peptides into a bacterial magnetic particle membrane and its application to display of useful proteins

An antimicrobial peptide, temporin L, and its derivative (TL-A2) were employed as anchor peptides and displayed streptavidin on a bacterial magnetic particle (BMP) membrane. The ribotoxin L3 loop (L3) and the arginine-chain peptide (R(12)), which are carrier peptides permeable to eukaryotic cell membranes, were also used. The peptides were labeled with a fluorescent dye, 4-fluoro-7-nitrobenzofurazan (NBD), at the N-terminal region (NBD-peptides) and mixed with BMPs. A specific integration of NBD-temporin L into a BMP membrane was observed. The basic amino acids in temporin L played an important role in the integration into BMPs. Biotin conjugated to the N-terminus of temporin L was integrated into a BMP membrane. The C-terminus of temporin L was incorporated into a BMP membrane, and the N-terminus was located on the BMP membrane surface. The present study shows that temporin L is a stable molecular anchor on BMPs by the binding of soluble protein to the N-terminus.

Single nucleotide mismatch analysis using oligonucleotide probes synthesized on bacterial magnetic particle

An approach to analyze mismatches using short and specific oligonucleotide probes directly synthesized on bacterial magnetic particles (BMPs) by phosphoramidite methods was exploited. Approximately 126 molecules of 4-mer oligonucleotides/particle were synthesized on BMPs with high reaction efficiencies. Hybridization between FITC-labeled oligonucleotides and chemically synthesized oligonucleotides on BMPs was performed. Perfect matched and mismatched hybridizations were successfully discriminated by using the oligonucleotide probes on BMPs.