Magnetotactic bacteria

About: Magnetotactic bacteria is a research topic. Over the lifetime, 1118 publications have been published within this topic receiving 43741 citations.

Design and application of the method for isolating magnetotactic bacteria

Abstract: 一台简单仪器被设计有效地基于他们的 magnetotaxis.Through 从土壤或沉积孤立磁电机策略细菌包括样品孵化，收获的鱼雷快艇，隔离，纯化和鉴定的一系列过程，细菌的几紧张成功地从样品被孤立。由传播电子显微镜学( TEM )andEnergy散的X光检查分析( EDXA )，这些细菌被认证是 magnetotacticbacteria.The 在孤立的磁性的紧张之间的种系发生的关系和一些 knownmagnetotactic 细菌被种系发生的树的构造基于 .This 仪器被证明了有的优点是便宜的 16SrDNAsequences 推断，对assemble 简单，对容易表现并且对高度有效孤立新奇磁电机策略细菌。研究显示由自制仪器和板殖民地隔离的方法收获鱼雷快艇的联合途径能有效地净化并且孤立磁电机策略细菌。

Defining Local Chemical Conditions in Magnetosomes of Magnetotactic Bacteria.

Abstract: Defining chemical properties of intracellular organelles is necessary to determine their function(s) as well as understand and mimic the reactions they host. However, the small size of bacterial and archaeal microorganisms often prevents defining local intracellular chemical conditions in a similar way to what has been established for eukaryotic organelles. This work proposes to use magnetite (Fe3O4) nanocrystals contained in magnetosome organelles of magnetotactic bacteria as reporters of elemental composition, pH, and redox potential of a hypothetical environment at the site of formation of intracellular magnetite. This methodology requires combining recent single-cell mass spectrometry measurements together with elemental composition of magnetite in trace and minor elements. It enables a quantitative characterization of chemical disequilibria of 30 chemical elements between the intracellular and external media of magnetotactic bacteria, revealing strong transfers of elements with active influx or efflux processes that translate into elemental accumulation (Mo, Se, and Sn) or depletion (Sr and Bi) in the bacterial internal medium of up to seven orders of magnitude relative to the extracellular medium. Using this concept, we show that chemical conditions in magnetosomes are compatible with a pH of 7.5-9.5 and a redox potential of -0.25 to -0.6 V.

Biomimetic synthesis of iron oxide nanoparticles from Bacillus megaterium to be used in hyperthermia therapy

Abstract: The suitable structural characteristics of magnetic nanoparticles have resulted in their widespread use in magnetic hyperthermia therapy. Moreover, they are considered a proper and operational choice for pharmaceutical nanocarriers. Using the biomimetic method, we were able to produce iron oxide magnetic nanoparticles from the bacterial source of PTCC1250, Bacillus megaterium, for therangostic diagnosis systems and targeted drug delivery. Some of the benefits of this method include mitigated environmental and biological dangers, low toxicity, high biocompatibility, cheap and short-term mass production possibilities in each synthesis round compared to other biological sources, simple equipment required for the synthesis; and the possibility of industrial-scale production. Bacillus megaterium is a magnetotactic bacteria (MTB) that has a magnetosome organelle capable of orienting based on external magnetic fields, caused by the mineralization of magnetic nanocrystals. Utilizing this capability and adding an iron nitrate solution to the bacterial suspension, we synthesized iron oxide nanoparticles. The extent of synthesis was measured using UV-visible spectrophotometry. The morphology was evaluated using FESEM. The crystallized structure was characterized using RAMAN and XRD. The size and distribution of the nanoparticles were assessed using DLS. The surface charge of the nanoparticles was measured using zeta potential. The synthesis of iron oxide nanoparticles was confirmed using FT-IR, and the magnetic property was measured using VSM. This study is continued to identify industrial and clinical applications.

Magnetosome-specific expression of chimeric proteins in Magnetospirillum gryphiswaldense for applications in cell biology and biotechnology

Abstract: Magnetosomes are magnetic nanoparticles that are formed by magnetotactic bacteria (MTB) by a complex, genetically controlled biomineralization process Magnetosomes from the model organism Magnetospirillum gryphiswaldense consist of single-magnetic-domain sized nanocrystals of chemically pure magnetite, which are formed intracellularly within specialized membranous compartments The natural coating by the biological membrane and the defined physico-chemical properties designate magnetosomes as a biogenic material with high bio- and nanotechnological potential In addition, there is a great interest in the cell biology of magnetosome formation in MTB The development of these true bacterial organelles involves the invagination of distinctly sized membrane vesicles and the assembly of magnetosome vesicles in chain-like arrangements along novel cytoskeletal structures The first part of this thesis focussed on the development of genetic tools for the functionalization and expression of modified magnetosome proteins The identification of proteins that are specifically and efficiently inserted into the magnetosome membrane (MM) was facilitated by analysis of green fluorescent protein (GFP) fusions of different magnetosome membrane proteins (MMP) After optimization of cultivation conditions for the utilization of GFP in MTB, it has been demonstrated that fusions of the proteins MamC, MamF and MamG are specifically targeted to the MM In particular, the MamC-GFP fusion protein was stably integrated and highly abundant in the MM Therefore, MamC represents an ideal anchor protein for the immobilization of functional proteins in the MM To address the question, if a specific signal sequence determines the magnetosome specific targeting of MamC-GFP, the localization of truncated MamC derivatives was studied These experiments have shown that, except for the last nine C-terminal amino acids, the entire sequence is required for the correct targeting and membrane insertion of MamC Stability of MamC-GFP is greatly reduced if larger parts are missing or if the N-terminus is deleted MamC-GFP localized at the expected position of the magnetosome chain irrespective of cultivation conditions that impeded magnetite formation This shows that MMP targeting, magnetosome vesicle formation and magnetosome chain assembly are not dependent on the prevalence of magnetite inducing conditions or the presence of magnetite crystals In contrast, the localization of MamC-GFP was altered in the magnetic mamK as well as in the non-magnetic MSR-1B, mamB, mamM, mamJKL mutants in comparison to the wild type This indicates that the interaction with specific proteins in the magnetosome vesicle is required for the correct localization of MamC The spotted MamC-GFP signals in the mamJ mutant, which are congruent with the position of magnetosomes in this strain, indicate that MamJ is not required for the magnetosome-specific targeting of MamC-GFP It has also been demonstrated that the native MamC protein and other proteins encoded by the mamGFDC operon are not required for the magnetosome-directed targeting of MamC, as the localization patterns of MamC-GFP in the mamC and mamGFDC mutants were similar to the localization of MamC-GFP in the wild type and congruent with the position of the magnetosomes The comparison of different promoters from E coli and M gryphiswaldense by fluorometry and flow cytometry with a GFP-reporter system revealed that the magnetosomal promoter, PmamDC, is highly efficient in M gryphiswaldense The applicability of this promoter for the functionalization of magnetosomes has been demonstrated by expression of a fusion protein of MamC and the antibody binding ‘ZZ’ protein in the MM to generate antibody-binding magnetosomes In addition, the E coli Ptet promoter has been identified as the first inducible promoter for regulated gene expression in MTB The expression was tightly regulated in the absence of an inducer and a ten-fold increase of the proportion of fluorescent cells was observed in the presence of the inducer anhydrotetracycline Therefore, the Ptet promoter is an important addition to the M gryphiswaldense genetic toolbox In the second part of this thesis, magnetosomes were tested for their use in biomedical and biotechnological applications To this end, large scale procedures for the purification of intact magnetosomes were developed In collaboration with the groups of Prof Dr C M Niemeyer (Universitat Dortmund) and Dr R Wacker (Chimera Biotec), streptavidin-biotin chemistry was employed to develop a modular system for the production of DNA- and antibody-coated magnetosomes The modified magnetosomes were used in DNA- and protein detection systems, and an automatable magnetosome-based Magneto-Immuno-PCR procedure was developed for the sensitive detection of antigens With collaborators from the groups of Dr T Hieronymus (RWTH Aachen) and Dr I Hilger (Universitat Jena), it has been shown that magnetosomes can be used as specific magnetic resonance imaging (MRI) contrast agents for phagocytotic cells such as macrophages and dendritic cells to study cell migration Fluorescently labelled magnetosomes were successfully used as bimodal contrast agents for the visualization of labelled cells by MRI and fluorescence imaging