Biogenic Magnetic Nanoparticles Research Articles

Transformation Cycle of Magnetosomes in Human Stem Cells: From Degradation to Biosynthesis of Magnetic Nanoparticles Anew.

The nanoparticles produced by magnetotactic bacteria, called magnetosomes, are made of a magnetite core with high levels of crystallinity surrounded by a lipid bilayer. This organized structure has been developed during the course of evolution of these organisms to adapt to their specific habitat and is assumed to resist degradation and to be able to withstand the demanding biological environment. Herein, we investigated magnetosomes' structural fate upon internalization in human stem cells using magnetic and photothermal measurements, electron microscopy, and X-ray absorption spectroscopy. All measurements first converge to the demonstration that intracellular magnetosomes can experience an important biodegradation, with up to 70% of their initial content degraded, which is associated with the progressive storage of the released iron in the ferritin protein. It correlates with an extensive magnetite to ferrihydrite phase transition. The ionic species delivered by this degradation could then be used by the cells to biosynthesize magnetic nanoparticles anew. In this case, cell magnetism first decreased with magnetosomes being dissolved, but then cells remagnetized entirely, evidencing the neo-synthesis of biogenic magnetic nanoparticles. Bacteria-made biogenic magnetosomes can thus be totally remodeled by human stem cells, into human cells-made magnetic nanoparticles.

MAGNETIC HYPERTHERMIA OF MICROORGANISMS WITH NATURAL FERRIMAGNETIC PROPERTIES

Мета: Зазвичай у практиці знешкодження мікроорганізмів магнітною гіпертермією не враховують наявність у останніх власних біогенних магнітних наночастинок. Мета дослідження виявити мікроорганізми, для яких врахування характеристик їх власних біогенних магнітних наночастинок може привести до помітного зростання ефективності магнітної гіпертермії.Методи: У дослідженні використано методи порівняльної геноміки, зокрема, попарне вирівнювання з використанням бази даних Genbank. Проведено вирівнювання протеомівмагнітотаксисної бактерії Magnetospirillumgryphiswaldense MSR-1 з протеомами патогенних мікроорганізмів, які були класифіковані за місцем локалізації і типом внутрішньої будови їх біогенних магнітних наночастинок.Результати: Проаналізовано геноми 24 штамів патогенних мікроорганізмів, які належать до таких родів: Staphylococcus, Pseudomonas, Bacillus, Shigella, Clostridioides, Streptococcus, Peptostreptococcus. Показано, що 2 із них мають кристалічні внутрішньоклітинні біогенні магнітні наночастинки, зовнішньоклітинні кристалічні – 11 штамів, внутрішньоклітинні аморфні – 8 штамів, зовнішньоклітинні аморфні – 3 штами. Також в роботі представлені розрахунки сил диполь-дипольних взаємодій між аморфними біогенними наночастинками Staphylococcusaureus та штучними магнітними наночастинками. Обговорення: Ми рекомендуємо використовувати методи порівняльної геноміки для поділу мікроорганізмів за магнітними властивостями для підбору більш ефективного способу знешкодження магнітною гіпертермією. Так 3 штами, що продукують кристалічні внутрішньоклітинні біогенні магнітні наночастинки, можна знешкодити методом магнітної гіпертермії, використовуючи у якості магнітного матеріалу їх власні наночастинки. 21 штам із зовнішньоклітинними кристалічними, внутрішньоклітинними аморфними та зовнішньоклітинними аморфними біогенними магнітними наночастинками, можна знешкодити магнітною гіпертермією, використовуючи методи штучного магнітомічення. Показано, що сил диполь-дипольних взаємодій між аморфними магнітними наночастинками та штучними магнітними наночастинками достатньо для того, щоб магнітомітити S. aureus і в подальшому знешкоджувати їх за допомогою магнітної гіпертермії. Висновки: Отже, врахування природних феримагнітних властивостей мікроорганізмів підвищить ефективність знешкодження магнітною гіпертермією.

RGD-functionalized magnetosomes are efficient tumor radioenhancers for X-rays and protons

Although chemically synthesized ferro/ferrimagnetic nanoparticles have attracted great attention in cancer theranostics, they lack radio-enhancement efficacy due to low targeting and internalization ability. Herein, we investigated the potential of RGD-tagged magnetosomes, bacterial biogenic magnetic nanoparticles naturally coated with a biological membrane and genetically engineered to express an RGD peptide, as tumor radioenhancers for conventional radiotherapy and proton therapy. Although native and RGD-magnetosomes similarly enhanced radiation-induced damage to plasmid DNA, RGD-magnetoprobes were able to boost the efficacy of radiotherapy to a much larger extent than native magnetosomes both on cancer cells and in tumors. Combined to magnetosomes@RGD, proton therapy exceeded the efficacy of X-rays at equivalent doses. Also, increased secondary emissions were measured after irradiation of magnetosomes with protons versus photons. Our results indicate the therapeutic advantage of using functionalized magnetoparticles to sensitize tumors to both X-rays and protons and strengthen the case for developing biogenic magnetoparticles for multimodal nanomedicine in cancer therapy.

Radiolabeling of Biogenic Magnetic Nanoparticles with Rhenium-188 as a Novel Agent for Targeted Radiotherapy.

Use of nanoparticles as carriers of anticancer drugs is a suitable way for targeted drug delivery and reduction of the side effects. This research focuses on a novel drug carrier for therapeutic goals by the bacterial magnetic nanoparticles (magnetosomes). The unique characteristics of magnetosomes make them ideal nanobiotechnological materials. In this study, magnetic nanoparticles of Alphaproteobacterium MTB-KTN90 were labeled with the radioisotope rhenium-188 and optimized the factors affecting the labeling efficiency. The results showed that the labeling efficiency of magnetosomes with rhenium-188 was more than 96%. The optimum concentration of bacterial nanoparticles was 133mg/ml and the best time for maximum efficiency labeling was 60min. The labeling stability showed that the 188Re-nanoparticle complexes have good stability in 29h. The results of magnetic nanoparticles bacterial cytotoxicity on cancer cells AsPC1 did not show significant toxicity to concentration of 100μg/μl. Finally, the biogenic magnetic nanoparticles labeled with rhenium-188 can be introduced as a valuable candidate for the targeted therapy of tumor with reducing radiation to surrounding healthy tissues.

Prospects of Using Biological Test-Systems for Evaluation of Effects of Electromagnetic Fields

Electromagnetic fields (EMF) can occur both naturally and due to human activity. Nowadays, through the innovative communication technologies, the new sources of artificial EMFs are widely disseminated. Therefore, one needs to study the artificial EMFs and mechanisms of their influence on biosystems. The paper deals with the issues of the influence of artificial EMFs on human health, environment and biological objects. The experimental and theoretical investigations concerning an action of EMF are analyzed. The description of principles of standardization of non-specific EMFs and protection from the influence of man-made fields is presented. Possible mechanisms of EMF and electromagnetic radiation (EMR) action on biological objects, including those due to the accumulation of biogenic magnetic nanoparticles in an organism, are discussed. The aim of the research is to review state-of-the-art methods for detecting the biological effects of non-thermal non-ionizing EMF and EMR and to determine the prospects of using biological test-systems for evaluation of effects of EMFs. Hereby, the main attention is drawn to EMF sensors based on the cultures of microorganisms. The classification of existing test-systems is proposed according to criteria: 1) vitality of cells; 2) motor activity of cells; 3) bioluminescence and color changes under the influence of EMF. The need to develop simple and reliable biological indicators for various types of EMFs, especially for ultrahigh-frequency radiation in connection with the introduction of 5G communications technology, is substantiated. The necessity of standardized test-protocols for comparison of research results is emphasized. It is shown that the description of corresponding experiments should be accompanied by the following features: 1) name of the cell culture; native or modified cells; 2) physical characteristics of EMF or EMR (frequency, power, modulation, source type); 3) exposure duration of; 4) list of parameters to be investigated; 5) research methods; 6) absolute measurements, results and the relative magnitude of an effect; 7) what does the influence depend on (temperature, age of cell culture, composition of the nutrient medium); 8) inheritance of changes in cells; 9) relaxation time of the effect.

Effects of Electromagnetic Fields Exposure on the Production of Nanosized Magnetosome, Elimination of Free Radicals and Antioxidant Defense Systems in <i>Magnetospirillum gryphiswaldense</i> MSR-1

Magnetotactic bacteria integrated magnetosomes, which are unique organelles that contain nanosized crystals of biogenic magnetic iron minerals with the ability to respond to the external magnetic fields. The biogenic magnetic nanoparticles (magnetosomes) show high biocompatibility in medical applications especially as scavengers to eliminate intracellular reactive oxygen species. The aim of this study was to highlight the impact of magnetosome formation and antioxidant systems in the suppression of oxidative stress on the magnetotactic bacteria cells. To assess the changes in ROS levels under different magnetic field intensity conditions, cells were cultured under the microaerobic condition in medium containing the high and low intensity of magnetic field. Treatment of magnetic field with an intensity of 500 mT during 50 hours bionormalization process of magnetotactic bacteria increased the antioxidant enzyme activity for eliminating of free radicals by 64%. We concluded that magnetosomes production plays an important role in decreasing or eliminating ROS. This is the first study to demonstrate that the magnetic field assisted magnetosome formation and antioxidants defense systems inMagnetospirillum gryphiswaldenseMSR-1.

Bacterial intracellular nanoparticles exhibiting antioxidant properties and the significance of their formation in ROS detoxification.

Biogenic magnetic nanoparticles (BMNPs) can be formed by numerous microorganisms. However, the significance of their formation and their possible functions have not been explored in detail. To explore a possible function of Fe3 O4 NPs in Burkholderia sp. strain YN01, we investigated their catalytic abilities in the elimination of intracellular reactive oxygen species (ROS). Changes in ROS content under different conditions were assessed and showed that low oxygen and high iron concentrations in the growth medium promoted ROS production. However, the levels of ROS gradually decreased with BMNP formation, suggesting that these particles possess intrinsic superoxide dismutase (SOD)-like activity and catalase (CAT)-like activity, as proven in this study. To ensure that the observed ROS decrease was not due to antioxidase overexpression caused by the oxidative stress response, SOD and CAT were inhibited in vivo to analyse the ROS variation and BMNP yield under microoxic and high-iron conditions respectively. The results demonstrated that the formation of these intracellular iron nanoparticles was required for the efficient scavenging of excess ROS, which was dependent on their antioxidase-like properties. This result reveals a novel physiological function of biogenic intracellular Fe3 O4 nanoparticles.

Determination of Potential Producers of Biogenic Magnetic Nanoparticles Among the Fungi Representatives of Ascomycota and Basidiomycota Divisions

Background. Biogenic magnetic nanoparticles (BMNs) were found in organisms that belong to all three domains: prokaryotes, archaea, and eukaryotes. And it was found that the mechanism of biomineralization of BMN is the same for all living organisms. BMNs have been experimentally detected in algae and protozoa, worms, сhitons, snails, ants and butterflies, honey bees, termites, lobsters, tritons, migratory and non-migratory fish, turtles, birds, bats, dolphins and whales, humans, plants and mushrooms. The study of the presence of BMNs in representatives of the kingdom of the Fungi is not numerous, as well as an idea of the functions they perform. In particular, a small amount of bioinformatic research was caused by the absence of decrypted fungi genomes in databases. In total, there are 10 divisions of the kingdom Fungi, of which not a single division has been analyzed completely. The study of fungi, which are representatives of different parts of the kingdom Fungi has fundamental and practical interest. From a fundamental point of view, identifying potential producers of BMNs among fungi can help find an answer to an open-ended question about the functional purpose of BMNs in various organisms. From a practical point of view, the identification of potential producers of BMNs among fungi is promising for the manufacture of magnetically controlled sorbent based on the biomass of fungi. Two of the most abundant sections of fungi – Ascomycetes (Ascomycota) and Basidiomycetes (Basidiomycota), which genomes are widely represented in bioinformatic databases were selected to the study.Objective. The aim of the is to identify potential producers of BMNs among the representatives of higher fungi by methods of comparative genomics and experimental research using atomic force microscopy (AFM) and magnetic force microscopy (MFM) of samples of higher fungi tissue for the presence of BMN in them.Methods. The method of pairwise alignment of the amino acid sequences of the fungi proteins with Magnetospirillum gryphiswaldense MSR-1 proteins by using BLAST program of National Center for Biotechnology Information (NCBI, USA). Methods for AFM and MFM were used to study the fruiting bodies of fungi for the presence of BMNs.Results. Bioinformatic analysis of 160 species of fungi of the Ascomycota division and 63 species of fungi of the Basidiomycota division was carried out and selected to analyze the alignment results for 15 representatives each, since their genome was deciphered by more than 50% in the database of the GenBank NCBI and functions of homologous proteins are known. For the analysis of the conducted research results, the following indicators were used: the value of the E-number (the number of alignments with the same or better alignment weight that can be found by chance in a database of a certain size), Іdent – the percentage of amino acid sequence overlapping within which the alignment is made, Length – the number of identical amino acid residues of the proteins, compared at optimal alignment and the function of the aligned proteins. When Ident > 18%, E-number ≤ 0.05, Length > 100, it can be argued that the sequences are homologous, and the fungus is a potential producer of BMN.Conclusions. Using the methods of comparative genomics, it is shown that among the studied representatives of higher fungi of the Ascomycota and Basidiomycota division, which genomes are decoded by more than 50% in the GenBank NCBI database, all species are potential producers of BMNs. At the same time, experimental studies of BMNs in A. bisporus and L. edodes fungi using the methods of AFM and MSM showed that BMNs in fungi form chains localized on the walls of the hyphae of the investigated fungi samples.

Activated Sludge Biomass as Magnetic Biosorbent

Background. Heavy metal pollution is a typical issue for a number of industries, and their removal is crucial for the environmental ecology. Biomass can be used as cheap and eco-friendly sorbent, for example excess activated sludge, because its utilization is a major expense in water treatment. Sorbents with magnetic properties can be extracted using fast and efficient magnetic separation method. Mechanism of biomineralization biogenic magnetic nanoparticles (BMN) is proved to be general for all three domains, so it is important to study what amount of activated sludge microorganisms are potential BMN producents. Objectives. The objective of this study is to determine potential BMN producents among microorganisms of activated sludge using methods of comparative genomics, to obtain magnetic biosorbent and investigate its efficiency in Fe 2+ removal from FeSO 4 solution (500 mg/L). Methods. For estimating homologies between biomineralization proteins of Μ agnetospirillum gryphiswaldense MSR-1 and microorga­nisms of activated sludge were used methods of pairwise and multiple genomic sequence alignment using free access tool BLAST (National Centre for Biotechnological Information, USA). For obtaining magnetic sorbent from activated sludge biomass high gradient magnetic separation was used. Results. Bioinformatic analysis showed, that among studied microorganisms of activated sludge, whose genomes are sequenced per 25% and more, all appeared to be potential BMN producers ( Stentor coeruleus , Bodo saltans , Sphaerotilus natans , Beggiatoa alba B18LD, Oscillatoria acuminata PCC 6304, Oscillatoria sp. PCC 10802, Oscillatoria nigro-viridis PCC 7112, Rivularia sp. PCC 7116, Anabaena sp. CRKS33, Anabaena sp. WA113, Anabaena sp. AL93, Anabaena sp. PCC7108, Anabaena MDT 14b, Thiothrix nivea DSM 5205, Duganella zoogloeoides ATCC 25935), 12 of them – potential producents of intracellular crystalline BMN. It was shown, that Fe 2+ removal efficiency isequal for non-separated activated sludge and both magnetic and non-magnetic fractions. Conclusions. Results show that excess sludge biomass can be used to obtain magnetic sorbent, which can be made without the use of extra magnetization with artificial magnetic nanoparticles. This allows extracting sorbent using methods of high gradient magnetic separation. Sorption results of Fe 2+ for magnetically labelled biosorbent on the base of activated sludge microorganisms experimentally proves equal efficiency of magnetically labelled, non-labelled fractions and biomass which was not exposed to HGMS and is higher than 97%.

Detection of biogenic magnetic nanoparticles in ethmoid bones of migratory and non-migratory fishes

In this paper, the presence of biogenic magnetic nanoparticles, their localization, and quantity in the ethmoid bone and lateral ethmoid bone of Atlantic salmon, Salmo salar, northern pike, Esox lucius, and silver carp, Hypophthalmichthys molitrix, were studied using atomic force microscopy and magnetic force microscopy. It is shown that biogenic magnetic nanoparticles, grouped mainly in short or long chains, are contained in the ethmoid and lateral ethmoid bones of migratory (Atlantic salmon, Salmo salar) and non-migratory (northern pike, Esox lucius, and silver carp, Hypophthalmichthys molitrix) fishes. The number of biogenic magnetic nanoparticles in the ethmoid and lateral ethmoid bones of non-migratory fishes is of the same order of magnitude as in migratory fishes. The localization of biogenic magnetic nanoparticles in the ethmoid and lateral ethmoid bones of migratory and non-migratory fishes is similar. Thus, for the first time it was shown that the presence of biogenic magnetic nanoparticles in the ethmoid and lateral ethmoid bones of fishes is not related to their ability to navigate in the geomagnetic field.

Potential Producers of Biogenic Magnetic Nanoparticles among Pathogenic and Opportunistic Microorganisms

Проблематика. Ускладнені форми інфекції при запальних процесах характеризуються зростанням резистентності мікрофлори до антибіотиків, що змушує шукати нові способи лікування, які б запобігали розвитку патогенних мікроорганізмів, підвищували місцевий імунітет і тим самим прискорювали регенеративні процеси. Мета. Метою роботи є класифікація патогенних та умовно-патогенних мікроорганізмів, які можуть бути потенційними продуцентами біогенних магнітних наночастинок (БМН), на предмет локалізації та властивостей БМН за допомогою методів порів­няльної геноміки з перспективою їх подальшого використання як магнітокерованих векторів для цільової доставки лікарських препаратів. Це дасть змогу використовувати методи гіпертермії для знешкодження патогенних та умовно-патогенних мікроорганізмів, які здатні до біомінералізації БМН, застосовуючи для нагріву клітин безпосередньо внутрішньоклітинні БМН цих мікроорганізмів. Методика реалізації. У роботі застосовано методи попарного та множинного вирівнювання з використанням вільної в доступі програми “BLAST” Національного центру біотехнологічної інформації. Результати. Виявлено, що такі штами, як E. coli (541-15), K. pneumoniae 342, C. perfringens str. 13 , P. fluorescens , є потенційними продуцентами саме кристалічного магнетиту, а мікроорганізми S. aureus RF122, S. suis BM407 , E. aerogenes KCTC 2190 , K. pneumoniae RYC492 , P. aeruginosa M18 можуть бути продуцентами внутрішньоклітинних аморфних БМН. Сила магнітодипольної взаємодії між БМН бактерій і БМН пухлин становить 10 - 7 –10 - 8 Н. Висновки. Пояснюється ефект знешкодження патогенних мікроорганізмів за допомогою методу магнітної гіпертермії за рахунок наявності БМН. Запропоновано використовувати для лікування гнійно-запальних процесів не тільки антибіотичні препарати, але й електромагнітні поля для тих мікроорганізмів, які є продуцентами БМН. Показано, що як вектори для цільової доставки лікарських препаратів доцільно використовувати мікроорганізми з природними магнітними властивостями, що зробить метод цільової доставки препаратів надійнішим та більш ефективним і зменшить його вартість.

Detection of Biogenic Magnetic Nanoparticles in Human Aortic Aneurysms

Detection of Biogenic Magnetic Nanoparticles in Human Aortic Aneurysms

Magnetogenetics for Drosophila

Magnetically sensitive genetically encoded channels enable remote activation of specific neural networks deep within the brain of freely moving animals. Recent progress coupling various TRP channels and the biogenic magnetic nanoparticle ferritin in mammalian cells shows significant promise for creating such “magnetogenetic” technology, but this approach relies on ferritin assembly by endogenously expressed subunits. This reliance on endogenously expressed ferritin subunits makes it difficult to study the efficacy of ferritin formation and iron loading and prevents transfer of the technology developed with mammalian ferritin to species like Drosophila that express divergent ferritin proteins. In addition, magnetogenetics in Drosophila provides two key advantages for optimizing the magnetic sensitivity of the proteins: 1) because Drosophila ferritin is secreted and circulates throughout the animal within hemolymph, the particles can be more easily isolated for characterization, 2) once isolated, we can bind these ferritin nanoparticles to other proteins with minimal reduction of iron loading. By developing magnetogenetic channels for Drosophila with an extracellular binding site for functionalized ferritin or superparamagnetic nanoparticles, we can study the responses of the channels to low frequency magnetic stimulation with fewer unknowns and create driver lines expressing functionalized magnetogenetic ferritin nanoparticles. Drosophila also enable this technology to be rapidly tested in various cell types by taking advantage of large depositories of UAS/Gal4 drosophila lines. We believe developing these magnetogenetic channels and functionalized biogenic magnetic nanoparticles will create a testbed for behavioral studies in drosophila and enable researchers to rapidly test responses to stimuli throughout the animal while gaining a deeper understanding of the physics behind magnetogenetics.

Роль патогенних мікроорганізмів у накопиченні біогенних магнітних наночастинок у тканинах легень

Мета: У цій роботі досліджується роль патогенних мікроорганізмів у накопиченні біогенних магнітних наночастинок у тканинах легень. Основна мета даного дослідження – довести, що біогенні магнітні наночастинки можуть потрапляти у тканини легень разом з патогенними мікроорганізмами та накопичуватись там при відповідних захворюваннях. Методи дослідження: Попарне та множинне вирівнювання амінокислотних послідовностей, електронний парамагнітний резонанс. Результати: Продуценти біогенних магнітних наночастинок були знайдені серед патогенних мікроорганізмів, що є збудниками захворювань легень. Біогенні магнітні наночастинки можуть потрапляти у тканини легень разом з патогенними мікроорганізмами та накопичуватись там при відповідних захворюваннях. Наявність біогенних магнітних наночастинок у тканинах легень була експериментально доведена в ході аналізу спектра електронного парамагнітного резонансу. Обговорення: Результати даного дослідження можуть бути використані для запобігання та розуміння можливих причин токсичного, алергічного впливу і закупорки судин під час неконтрольованого накопичення магнітних наночастинок в різних органах та тканинах через їх магнітні диполь-дипольні взаємодії з біогенними магнітними наночастинками на клітинних мембранах.

Ferromagnetic resonance in the ethmoid bones of salmon and silver carp

The detection of biogenic magnetic nanoparticles (BMN) with different magnetic properties in biological material was done using magnetic resonance (MR) spectroscopy. MR spectra of biological material of ethmoid bone of salmon (containing ferritin and BMN), bacteria E. coli K13 (containing ferritin and without BMN), yeast S. cerevisiae (without ferritin or BMN) and ethmoid bone of silver carp (containing ferritin and not investigated for the presence of BMN) were investigated. The analysis of MR spectra shows that S. cerevisiae cells produce much lower signal MR than samples of ethmoid bones of salmon and silver carp which is confirming conclusions about the presence of BMN and ferritin in the ethmoid bones of fishes. The narrow MR linewidth indicates that the magnetic particles in the ethmoid bones of salmon and silver carp are in monodisperse state. The presence of a broad line and the absence of a narrow peak in MR spectrum of E. coli K13 cells are typical for ferritin.

The prediction of biogenic magnetic nanoparticles biomineralization in human tissues and organs

In this study, human homologs of magnetosome island proteins basing on pairwise and multiple alignment of amino acid sequences were found. The expression levels of genes, which encode magnetosome island proteins of M. gryphiswaldense MSR-1, that were cultured under oxygen deficiency conditions and also under microaerobic conditions were compared to the expression levels of genes that encode the relevant homologs in human organism. The possibility of BMN biomineralization in human tissues and organs, in which BMN were not experimentally found before, was predicted.

Potential producers of biogenic magnetic nanoparticles among disease-producing microorganisms of the brain

Potential producers of biogenic magnetic nanoparticles among disease-producing microorganisms of the brain

Physiological origin of biogenic magnetic nanoparticles in health and disease: from bacteria to humans.

The discovery of biogenic magnetic nanoparticles (BMNPs) in the human brain gives a strong impulse to study and understand their origin. Although knowledge of the subject is increasing continuously, much remains to be done for further development to help our society fight a number of pathologies related to BMNPs. This review provides an insight into the puzzle of the physiological origin of BMNPs in organisms of all three domains of life: prokaryotes, archaea, and eukaryotes, including humans. Predictions based on comparative genomic studies are presented along with experimental data obtained by physical methods. State-of-the-art understanding of the genetic control of biomineralization of BMNPs and their properties are discussed in detail. We present data on the differences in BMNP levels in health and disease (cancer, neurodegenerative disorders, and atherosclerosis), and discuss the existing hypotheses on the biological functions of BMNPs, with special attention paid to the role of the ferritin core and apoferritin.

Overproduction of Magnetosomes by Genomic Amplification of Biosynthesis-Related Gene Clusters in a Magnetotactic Bacterium.

Magnetotactic bacteria biosynthesize specific organelles, the magnetosomes, which are membrane-enclosed crystals of a magnetic iron mineral that are aligned in a linear chain. The number and size of magnetosome particles have to be critically controlled to build a sensor sufficiently strong to ensure the efficient alignment of cells within Earth's weak magnetic field while at the same time minimizing the metabolic costs imposed by excessive magnetosome biosynthesis. Apart from their biological function, bacterial magnetosomes have gained considerable interest since they provide a highly useful model for prokaryotic organelle formation and represent biogenic magnetic nanoparticles with exceptional properties. However, potential applications have been hampered by the difficult cultivation of these fastidious bacteria and their poor yields of magnetosomes. In this study, we found that the size and number of magnetosomes within the cell are controlled by many different Mam and Mms proteins. We present a strategy for the overexpression of magnetosome biosynthesis genes in the alphaproteobacterium Magnetospirillum gryphiswaldense by chromosomal multiplication of individual and multiple magnetosome gene clusters via transposition. While stepwise amplification of the mms6 operon resulted in the formation of increasingly larger crystals (increase of ∼35%), the duplication of all major magnetosome operons (mamGFDC, mamAB, mms6, and mamXY, comprising 29 genes in total) yielded an overproducing strain in which magnetosome numbers were 2.2-fold increased. We demonstrate that the tuned expression of the mam and mms clusters provides a powerful strategy for the control of magnetosome size and number, thereby setting the stage for high-yield production of tailored magnetic nanoparticles by synthetic biology approaches. Before our study, it had remained unknown how the upper sizes and numbers of magnetosomes are genetically regulated, and overproduction of magnetosome biosynthesis had not been achieved, owing to the difficulties of large-scale genome engineering in the recalcitrant magnetotactic bacteria. In this study, we established and systematically explored a strategy for the overexpression of magnetosome biosynthesis genes by genomic amplification of single and multiple magnetosome gene clusters via sequential chromosomal insertion by transposition. Our findings also indicate that the expression levels of magnetosome proteins together limit the upper size and number of magnetosomes within the cell. We demonstrate that tuned overexpression of magnetosome gene clusters provides a powerful strategy for the precise control of magnetosome size and number.

Biomineralization and synthesis of biogenic magnetic nanoparticles and magnetosensitive inclusions in microorganisms and fungi

Biomineralization and synthesis of biogenic magnetic nanoparticles and magnetosensitive inclusions in microorganisms and fungi