趋磁细菌AMB-1对小鼠的生物相容性探究

目的在体外和体内条件下探究趋磁细菌AMB-1对BALB/c小鼠的生物相容性。方法透射电镜观察AMB-1形貌特征;显微镜拍摄AMB-1在血清中的运动,Image J计算运动速度;乳酸脱氢酶(lactate dehydrogenase,LDH)检测AMB-1对小鼠乳腺癌细胞4T1和成纤维细胞L929细胞毒性;流式细胞术评价AMB-1对BALB/c小鼠骨髓来源树突细胞成熟影响;改良寇氏法计算出AMB-1对BALB/c小鼠的半数致死剂量;普鲁士蓝染色BALB/c小鼠心、肝、脾、肺、肾脏器观察AMB-1在小鼠体内的分布情况;流式细胞术检测AMB-1对BALB/c小鼠脾脏树突细胞的影响;检测小鼠BALB/c血生化指标评估其安全性;苏木精-伊红染色BALB/c小鼠心、肝、脾、肺、肾脏器,观察其组织形态变化。结果37℃条件下,AMB-1在血清中可保持运动至少120 min;AMB-1菌量超过3.3×10^(6)个时,对小鼠乳腺癌细胞4T1和成纤维细胞L929具有毒性,随菌量增加,毒性越大;AMB-1可促进骨髓来源树突细胞CD86^(+)、CD80^(+)双阳细胞的比例增大。AMB-1对BALB/c小鼠半数致死剂量为2.59×10^(10)个。AMB-1对小鼠脾脏树突细胞成熟的影响随着时间延长逐渐减弱;血生化指标在正常范围内;小鼠主要脏器无明显组织形态学变化。结论趋磁细菌AMB-1具有良好生物相容性,在体内不会引发严重免疫炎症等不良反应,具有体内应用潜能。

Electroactivity of the magnetotactic bacteria Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1

Magnetotactic bacteria reside in sediments and stratified water columns.They are named after their ability to synthesize internal magnetic particles that allow them to align and swim along the Earth’s magnetic field lines.Here,we show that two magnetotactic species,Magnetospirillum magneticum strain AMB-1 and Magnetospirillum gryphiswaldense strain MSR-1,are electroactive.Both M.magneticum and M.gryphiswaldense were able to generate current in microbial fuel cells with maximum power densities of 27 and 11μW/m^(2),respectively.In the presence of the electron shuttle resazurin both species were able to reduce the crystalline iron oxide hematite(Fe_(2)O_(3)).In addition,M.magneticum could reduce poorly crystalline iron oxide(FeOOH).Our study adds M.magneticum and M.gryphiswaldense to the growing list of known electroactive bacteria,and implies that electroactivity might be common for bacteria within the Magnetospirillum genus.

Biosorption Equilibrium and Kinetics of Au（Ⅲ） and Cu（Ⅱ） on Magnetotactic Bacteria

Magnetotactic bacteria （MTB） as biosorbents for the adsorption of Au（Ⅲ） and Cu（Ⅱ） ions from aqueous solution have been investigated. The optimum adsorption conditions for both metal ions were the initial pH scope of 1-5.5 for Au（Ⅲ） and 2.0-4.5 for Cu（Ⅱ）, room temperature, biomass concentration of 10.0g.L^-1 and sorotion du-ration more than 10 min. When the initial metal concentration were within 500mg.L^-1, the maximum biosorption capacity of 1.0g of MTB （dry mass basis） for Au（Ⅲ） and Cu（Ⅱ） were calculated as 505.2mg of Au（Ⅲ） and 493.1mg of.Cu（Ⅱ） by Langmuir model in single system, respectively. The isotherm equilibrium of Au（Ⅲ） and Cu（Ⅱ） ions in the Au-Cu binary system reflected a unique phenomenon that the adsorption of Au（Ⅲ） was rein-forced and that of Cu（Ⅱ） prohibited, compared respectively-with their performances in the single metal system.When the,concentration of-Au（Ⅲ） and Cu（Ⅱ）. were below 80mg.L^-1, the waste waterafter MTB treating, wasbelow 1.0mg.L^-1, which is in conformity with Environmental Performance Standards （EPS） of Canada. Besides, all the kinetic data were fitted well to the pseudo second-order kinetic model with a high correlation coefficient （R^2〉0.999）.

Characterization of Mediterranean Magnetotactic Bacteria

Magnetotactic bacteria are a diverse group of motile prokaryotes that are ubiquitous in aquatic habitats and cosmopolitan in distribution. In this study, we collected magnetotactic bacteria from the Mediterranean Sea. A remarkable diversity of morphotypes was observed, including multicellular types that seemed to differ from those previously found in North and South America. Another interesting organism was one with magnetosomes arranged in a six-stranded bundle which occupied one third of the cell width. The magnetosome bundle was evident even under optic microscopy. These cells were connected together and swam as a linear entire unit. Magnetosomes did not always align up to form a straight linear chain. A chain composed of rectangle magnetosomes bent at a posi- tion with an oval crystal. High resolution transmission electron microscopy analysis of the crystal at the pivotal position suggested uncompleted formation of the crystal. This is the first report of Mediterranean magnetotactic bacteria, which should be useful for studies of biogeochemical cycling and geohistory of the Mediterranean Sea.

Characterization of uncultivated magnetotactic bacteria from the sediments of Yuehu Lake, China

Marine magnetotactic bacteria were collected from the intertidal sediments of Yuehu Lake（China）, where their abundance reached 103–104 ind./cm3. Diverse morphotypes of magnetotactic bacteria were observed, including cocci and oval, vibrio-, spirillum-, rod-, elliptical-, handle- and bar-shaped forms. The magnetococci were the most abundant, and had flagella arranged in parallel within a bundle. The majority of magnetosomes were arranged in one, two or multiple chains, although irregular arrangements were also evident. All the results of high-resolution transmission electron microscopy（HRTEM） analysis show that magnetosome crystals were composed of Fe3O4, and their morphology was specific to particular cell morphotypes. By the 16 S r RNA gene sequence analysis, we found fourteen operational taxonomic units（OTUs） which were related to magnetotactic bacteria. Among these, thirteen belonged to the Alphaproteobacteria and one to the Gammaproteobacteria.Compared with known axenic and uncultured marine magnetotactic bacteria, the 16 S r RNA gene sequences of most magnetotactic bacteria collected from the Yuehu Lake exhibited sequence identities ranging from 90.1% to96.2%（〈97%）. The results indicate that microbial communities containing previously unidentified magnetotactic bacteria occur in the Yuehu Lake.

Characterization and diversity of magnetotactic bacteria from sediments of Caroline Seamount in the Western Pacific Ocean

Magnetotactic bacteria(MTB)are a group of microorganisms capable of orientating and swimming along magnetic fields because they contain intracellular biomineralized magnetosomes composed of magnetite(Fe 3 O 4)or/and greigite(Fe_(3)S_(4)).They are ubiquitous in freshwater,brackish,and marine habitats,and are cosmopolitan in distribution.However,knowledge of their occurrence and distribution in seamount ecosystems is limited.We investigated the diversity and distribution of MTB in the Caroline Seamount(CM4).The abundance of living MTB in 12 stations in depth varying from 90 to 1545 m was 1.1×10^(3)-43.7×10^(3) inds./dm 3.Despite diverse shapes of MTB observed,magnetotactic cocci were the dominant morphotype and could be categorized into two types:1)typical cocci that appeared to have peritrichous fl agella;and 2)those characterized by having a drop-shaped form and one bundle of fl agella located at the thin/narrow end of the cell.Transmission electron microscopy(TEM)analysis revealed that the magnetosomes formed by those magnetotactic cocci are magnetite(Fe 3 O 4)with octahedral crystal habit.A total of 41 operational taxonomic units(OTUs)of putative MTB(2702 reads)were acquired from nine stations,based on high-throughput sequencing.Of these,40 OTUs belonged to the Proteobacteria phylum and one belonged to the Nitrospirae phylum.We found apparent connectivity between the MTB populations on the Caroline and Kexue(Science in Chinese)seamounts,although the diversity of MTB on Caroline was much richer than on the Kexue Seamount.Our results imply that the unique topography of seamounts and other as-yet unclear environmental factors could lead to evolution of different fl agella arrangements in magnetotactic cocci,and the occurrence of octahedral magnetite magnetosomes.

Observations on a magnetotactic bacteria-grazing ciliate in sediment from the intertidal zone of Huiquan Bay,China

Magnetotactic bacteria(MTB)are a group of prokaryotes having the ability to orient and swim along geomagnetic field lines because they contain intracellular magnetosomes that are synthesized through a biomineralization process.Magnetosomes have recently also been found in unicellular eukaryotes,which are referred to as magnetically responsive protists(MRPs).The magnetosomes have three origins in MRPs.In this study,we characterized a MTB-grazing ciliated MRP that was magnetically collected from intertidal sediment of Huiquan Bay,Qingdao,China.Based on 18S rRNA gene sequence analysis,the ciliated MRP was tentatively identified as Uronemella parafi lificum HQ.Using transmission electron microscopy,we observed that magnetosomes having 2-3 shapes were randomly distributed within this ciliate.Energydispersive X-ray spectroscopy and high-resolution transmission electron microscopy images of the magnetosomes were consistent with them being composed of magnetite.Magnetosomes having the same shape and mineral composition were also detected in MTB that occurred in the same environment as the ciliated MRP.Statistical analysis showed that the size and shape of the magnetosomes in the ciliated MRP were similar to those in MTB.The results suggest that this ciliated MRP can graze,ingest,and digest various types of MTB.It is certainly worth noting that this is the first record of MRPs in Asian aquatic sediment and suggesting they might be widely distributed.These results also support the assertion that MRPs probably contribute to the ecological cycles of iron,and expand possibilities for research into the mechanism of magnetoreception in eukaryotes.

Magnetotactic bacteria from the human gut microbiome associated with orientation and navigation regions of the brain

Magnetotactic bacteria(MTB),ubiquitous in soil and fresh and saltwater sources have been identified in the microbiome of humans and many animals.MTB endogenously produce magnetic nanocrystals enabling them to orient and navigate along geomagnetic fields.Similar magnetite deposits have been found throughout the tissues of the human brain,including brain regions associated with orientation such as the cerebellum and hippocampus,the origins of which remain unknown.Speculation over the role and source of MTB in humans,as well as any association with the brain,remain unanswered.We performed a metagenomic analysis of the gut microbiome of 34 healthy females as well as grey matter volume analysis in magnetite-rich brain regions associated with orientation and navigation with the goal of identifying specific MTB that could be associated with brain structure in orientation and navigation regions.We identified seven MTB in the human gut microbiome:Magnetococcus marinus,Magnetospira sp.QH-2,Magnetospirillum magneticum,Magnetospirillum sp.ME-1,Magnetospirillum sp.XM-1,Magnetospirillum gryphiswaldense,and Desulfovibrio magneticus.Our preliminary results show significant negative associations between multiple MTB with bilateral flocculonodular lobes of the cerebellum and hippocampus(adjusted for total intracranial volume,uncorrected P<0.05).These findings indicate that MTB in the gut are associated with grey matter volume in magnetite-rich brain regions related to orientation and navigation.These preliminary findings support MTB as a potential biogenic source for brain magnetite in humans.Further studies will be necessary to validate and elucidate the relationship between these bacteria,magnetite concentrations,and brain function.

Release the iron: does the infection of magnetotactic bacteria by phages play a role in making iron available in aquatic environments?

Magnetotactic bacteria(MTB)are ubiquitous prokaryotes that orient along magnetic field lines due to magnetosomes’biomineralization within the cell.These structures are ferrimagnetic organelles that impart a magnetic moment to the cell.To succeed in producing magnetosomes,MTB accumulate iron in(i)cytoplasm;(ⅱ)magnetosomes;and(ⅲ)nearby the organelle.It has already been estimated that a single MTB has an iron content of 10 to 100-fold higher than Escherichia coli.Phages are the most abundant entity in oceans and are known for controlling nutrient flow such as carbon and nitrogen by viral shunt and pump.The current work addresses the putative role of phages that infect MTB on the iron biogeochemical cycle.Can phage infection in MTB hosts cause a biogenic iron fertilization-like event in localized microenvironments?Are phages critical players in driving magnetosome biomineralization genes(BGs)horizontal transfer?Further investigation of those events,including frequency of occurrence,is necessary to fully comprehend MTB’s effect on iron cycling in aqueous environments.

Determination of the heating efficiency of magnetotactic bacteria in alternating magnetic field

Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring equipment.The specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field amplitude.In this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/m.The measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain range.In combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and coercivity.Thus when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.

Morphological and phylogenetic diversity of magnetotactic bacteria and multicellular magnetotactic prokaryotes from a mangrove ecosystem in the Sanya River,South China

Magnetotactic bacteria(MTB)are morphologically and phylogenetically diverse prokaryotes commonly able to produce magnetic nanocrystals within intracellular membrane-bound organelles(i.e.,magnetosomes)and to swim along geomagnetic field lines.We studied the diversity of MTB in the samples collected from a mangrove area in the Sanya River,Hainan,South China,using microscopic and microbial phylogenetic methods.Results of microanalysis and observation in microscopy and energy dispersive X-ray spectroscopy(EDXS)reveal a highly morphological diversity of MTB including unicellular cocci,vibrios,rod-shaped bacteria,and three morphotypes of multicellular magnetotactic prokaryotes(MMPs).In addition,analysis of the 16S rRNA gene showed that these MTB were clustered into 16 operational taxonomic units affi liated to the Alpha-,Delta-,and Gamma-proteobacteria classes within the Proteobacteria phylum.Meanwhile,by using the coupled fluorescence and transmission electron microscopy analysis,rodshaped bacteria,vibrio,and cocci were phylogenetically and structurally identified at the single-cell level.This study demonstrated highly diverse MTB communities in the mangrove ecosystem and provide a new insight into the overall diversity of MTB.

Design and application of the method for isolating magnetotactic bacteria

A simple apparatus was designed to effectively isolate magnetotactic bacteria from soils or sediments based on their magnetotaxis. Through a series of processes including sample incubation, MTB harvesting, isolation, purification and identification, several strains of bacteria were isolated from the samples successfully. By Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray Analysis (EDXA), these bacteria were certificated to be magnetotactic bacteria. The phylogenetic relationship between the isolated magnetic strains and some known magnetotactic bacteria was inferred by the construction of phylogenetic tree based on 16SrDNA sequences. This apparatus has been proven to have the advantages of being inexpensive, simple to assemble, easy to perform and highly efficient to isolate novel magnetotactic bacteria. The research indicated that the combined approach of harvesting MTB by home-made apparatus and the method of plate colony isolation could purify and isolate magnetotactic bacteria effectively.

Characterization of dominant giant rod-shaped magnetotactic bacteria from a low tide zone of the China Sea

Magnetotactic bacteria are a group of Gram-negative bacteria that synthesize magnetic crystals, enabling them to navigate in relation to magnetic field lines. Morphologies of magnetotactic bacteria include spirillum, coccoid, rod, vibrio, and multicellular morphotypes. The coccid shape is generally the most abundant morphotype among magnetotactic bacteria. Here we describe a species of giant rod-shaped magnetotactic bacteria(designated QR-1) collected from sediment in the low tide zone of Huiquan Bay(Yellow Sea, China). This morphotype accounted for 90% of the magnetotactic bacteria collected, and the only taxonomic group which was detected in the sampling site. Microscopy analysis revealed that QR-1 cells averaged(6.71±1.03)×(1.54±0.20) m m in size, and contained in each cell 42–146 magnetosomes that are arranged in a bundle formed one to four chains along the long axis of the cell. The QR-1 cells displayed axial magnetotaxis with an average velocity of 70±28 mm/s. Transmission electron microscopy based analysis showed that QR-1 cells had two tufts of fl agella at each end. Phylogenetic analysis of the 16 S r RNA genes revealed that QR-1 together with three other rod-shaped uncultivated magnetotactic bacteria are clustered into a deep branch of A lphaproteobacteria.

Performance Research on Magnetotactic Bacteria Optimization Algorithm with the Best Individual-Guided Differential Interaction Energy

Magnetotactic bacteria optimization algorithm (MBOA) is a new optimization algorithm inspired by the characteristics of magnetotactic bacteria, which is a kind of polyphyletic group of prokaryotes with the characteristics of magnetotaxis that make them orient and swim along geomagnetic field lines. The original Magnetotactic Bacteria Optimization Algorithm (MBOA) and several new variants of MBOA mimics the interaction energy between magnetosomes chains to obtain moments for solving problems. In this paper, Magnetotactic Bacteria Optimization Algorithm with the Best Individual-guided Differential Interaction Energy (MBOA-BIDE) is proposed. We improved interaction energy calculation by using the best individual-guided?differential interaction energy formation. We focus on analyzing the performance of different parameters settings. The experiment results show that the proposed algorithm is sensitive to parameters settings on some functions.

Statistical approach for the culture conditions optimization of magnetotactic bacteria for magnetic cells production

The culture of Magnetospirillum magneticum WM-1 depends on several control factors that have great effect on the magnetic cells concentration. Investigation into the optimal culture conditions needs a large number of experiments So it is desirable to minimize the number of experiments and maximize the information gained from them. The orthogonal design of experiments and mathematical statistical method are considered as effective methods to optimize the culture condition of magnetotactic bacteria WMol for high magnetic cells concentration. The effects of the four factors, such as pH value of medium, oxygen concentration of gas phase in the serum bottle, C：C （mtartaric acid： m=succinic acid） ratio and NaNO3 concentration, are simultaneously investigated by only sixteen experiments through the orthogonal design L16（44） method. The optimal culture condition is obtained. At the optimal culture condition （ pH 7.0, an oxygen concentration 4.0%, C：C （mtartaric acid： m=succinic acid） ratio 1：2 and NaNO3 100 mg 1^-1）, the magnetic cells concentration is promoted tO 6.5×10^7 cells ml^-1, approximately 8.3% higher than that under the initial conditions. The pH value of medium is a very important factor for magnetic cells concentration. It can be Proved that the orthogonal design of experiment is of 90% confidence. Ferric iron uptake follows MichaelisoMenten kinetics with a Km of 2.5 pM and a Vmax of 0.83 min^-1.

Properties of Magnetite Nanoparticles Produced by Magnetotactic Bacteria

The magnetic nanoparticles（magnetite） were prepared through the fermentation of the Magnetospirillum strain WM-1 newly isolated by our group. The samples were characterized by TEM, SAED, XRD, rock magnetic analysis, and Mossbauer spectroscopy. TEM and SAED measurements showed that the magnetosomes formed by strain WM-1 were single crystallites of high perfection with a cubic spinel structure of magnetite. X-ray measurements also fitted very well with standard Fe3O4 reflections with an inverse spinel structure of the magnetite core. The size of crystal as calculated by the Debye-Scherrer’s equation was approximately 55 nm. Rock magnetic analysis showed WM-1 synthesized single-domain magnetite magnetosomes, which were arranged in the form of linear chain. The high delta ratio（（δFC / δZFC = 4） supported the criteria of Moskowitz test that there were intact magnetosomes chains in cells. The Verwey transition occurred at 105 K that closed to stoochiometric magnetite in composition. These observations provided useful insights into the biomineralization of magnetosomes and properties of M. WM-1 and potential application of biogenic magnetite in biomaterials and biomagnetism.

Magnetotactic Bacteria Algorithm for Function Optimization

Magnetotactic bacteria is a kind of polyphyletic group of prokaryotes with the characteristics of magnetotaxis that make them orient and swim along geomagnetic field lines. A magnetotactic bacteria optimization algorithm(MBOA) inspired by the characteristics of magnetotactic bacteria is researched in the paper. Experiment results show that the MBOA is effective in function optimization problems and has good and competitive performance compared with the other classical optimization algorithms.

脉冲磁场对趋磁螺细菌AMB-1磁小体形成及相关基因表达的影响

本文利用Cmag测量、透射电镜观察等技术研究了脉冲磁场对不同初始状态的趋磁螺细菌AMB-1（Magnetospirillum magneticum AMB-1）磁小体形成的影响,并对其相关蛋白MamA、Mms13、Mms6和MagA编码基因的表达情况做了荧光实时定量反转录聚合酶链式反应（qRT-PCR）。结果表明：同自然地磁场相比,50Hz、1mT脉冲磁场可促进AMB-1磁小体形成;当初始菌种为含有磁小体的AMB-1时,脉冲磁场促进指数期菌体magA基因的表达;而当初始菌种为不含磁小体的AMB-1时,则促进指数期菌体magA和mamA基因的表达。脉冲磁场虽然导致指数期细胞磁颗粒不均匀,但使磁小体链加长,含磁小体菌的平均磁颗粒数也较地磁场明显增加。实验结果为应用磁场干预磁小体形成,提高磁小体产率的研究提供了实验和理论依据,也有助于进一步了解磁场的生物学效应。

五大连池月牙泡沉积物中趋磁细菌群落对季节变化的响应

为了解五大连池月牙泡样品中趋磁细菌(Magnetotactic Bacteria,MTB)多样性对季节动态的响应。采用高通量测序手段,分别考察不同季节月牙泡中MTB的Alpha多样性、群落组成、群落功能及多样性与理化的相关性。结果显示,MTB菌群丰度在夏季和秋季较高,春季和秋季较低。春季样品中仅有Magnetospirillum,Magnetospirillum在秋季(73.42%)和冬季(98.36%)是优势菌属,Magnetovibrio为夏季(29.76%)的优势菌属。RDA表明,大部分MTB分布与Fe(Ⅱ)、S和Sulfate呈正相关。研究结果为火山湖泊中MTB对季节动态响应提供了依据。

Magnetospirillum sp.AMB-1菌株培养及磁小体形成条件的研究

本文通过改变基础螺菌培养基中琥珀酸添加量、氮源、铁源种类及含量以及培养条件,观察各因素对Magnetospirillum sp.AMB-1生长量及磁小体形成量的影响.单因素实验结果表明:其最适生长温度为30℃,pH为6.9,250mL锥形瓶中装液量为70%,在添加0.80g琥珀酸、并以0.12g NaNO3为氮源、2.0μmol/L奎尼酸铁为铁源的基础螺菌培养基中按2%的接种量,静置培养4d后,趋磁细菌的吸光度可达0.853,磁小体的形成量Cmag值为1.673.