Biomineralization In Bacteria Research Articles

Interplay between arsenic and selenium biomineralization in Shewanella sp. O23S

Bacteria play crucial roles in the biogeochemical cycle of arsenic (As) and selenium (Se) as these elements are metabolized via detoxification, energy generation (anaerobic respiration) and biosynthesis (e.g. selenocysteine) strategies. To date, arsenic and selenium biomineralization in bacteria were studied separately. In this study, the anaerobic metabolism of As and Se in Shewanella sp. O23S was investigated separately and mixed, with an emphasis put on the biomineralization products of this process. Multiple analytical techniques including ICP-MS, TEM-EDS, XRD, Micro-Raman, spectrophotometry and surface charge (zeta potential) were employed. Shewanella sp. O23S is capable of reducing selenate (SeO42−) and selenite (SeO32−) to red Se(-S)0, and arsenate (AsO43−) to arsenite (AsO33−). The release of H2S from cysteine led to the precipitation of AsS minerals: nanorod AsS and granular As2S3. When As and Se oxyanions were mixed, both As–S and Se(-S)0 biominerals were synthesized. All biominerals were extracellular, amorphous and presented a negative surface charge (−24 to −38 mV). Kinetic analysis indicated the following reduction yields: SeO32− (90%), AsO43− (60%), and SeO42− (<10%). The mix of SeO32− with AsO43− led to a decrease in As removal to 30%, while Se reduction yield was unaffected (88%). Interestingly, SeO42− incubated with AsO43− boosted the Se removal (71%). The exclusive extracellular formation of As and Se biominerals might indicate an extracellular respiratory process characteristic of various Shewanella species and strains. This is the first study documenting a complex interplay between As and Se oxyanions: selenite decreased arsenate reduction, whereas arsenate stimulated selenate reduction. Further investigation needs to clarify whether Shewanella sp. O23S employs multi-substrate respiratory enzymes or separate, high affinity enzymes for As and Se oxyanion respiration.

MagCluster: a Tool for Identification, Annotation, and Visualization of Magnetosome Gene Clusters.

ABSTRACTMagnetosome gene clusters (MGCs), which are responsible for magnetosome biosynthesis and organization in magnetotactic bacteria (MTB), are the key to deciphering the mechanisms and evolutionary origin of magnetoreception, organelle biogenesis, and intracellular biomineralization in bacteria. Here, we report the development of MagCluster, a Python stand-alone tool for efficient exploration of MGCs from large-scale (meta)genomic data.

Biomineralized Bacteria: Biomineralization of Bacteria by a Metal–Organic Framework for Therapeutic Delivery (Adv. Healthcare Mater. 12/2020)

In article number 2000046, Shuangqian Yan and co-workers show a biomineralized bacteria that delivers multiple therapeutics to tumor sites for synergistic therapy. The report demonstrates that the metal-organic framework (MOF)-biomineralized bacteria maintains its viability and tumor-selectivity after loading with therapeutics. The as-prepared bacteria@MOF modality exhibits significant therapeutic efficacy, broadening the application field of living organism-based biomineralization.

Biomineralization of Bacteria by a Metal-Organic Framework for Therapeutic Delivery.

Biomimetic mineralization of live organisms shows extraordinary promise in biotechnology. However, their therapeutic applications have been insufficiently explored. Herein, it is demonstrated that metal-organic framework (MOF)-engineered bacteria are powerful carriers for tumor-targeted therapeutic delivery. Specifically, Escherichia coli (MG1655) is coated with a zeolitic imidazolate framework-8 layer coloaded with a photosensitizer and chemical drug through a one-step in situ method. The as-prepared bacteria@MOF hybrid preserves its viability and tumor selectivity. It exhibits high therapeutic efficacy both in vitro and in vivo in a combined chemo-photodynamic manner. To the best of knowledge, this is the first report of engineered bacteria@MOFs for in vivo tumor treatment. This study opens a new horizon for the bioapplications of biomineralized organisms and may provide novel strategies against tumors.

The operons and genes related to magnetosome biogenesis in magnetotactic bacteria

Magnetosomes are natural magnetic nanoparticles with special properties that are synthesized by magnetotactic bacteria. Bacterial magnetosomes have become increasingly attractive for researchers in biology, medicine, geology and other fields of scientific researches. It is significant to explore a promising nanomaterial for multiple applications in science and industry. Magnetosomes contains magnetic particles that are enclosed by intracellular membrane. These particles can be either ferrimagnetic crystal of magnetite (Fe3O4) or the iron sulfide greigite (Fe3S4). Three crystal morphologies including roughly cuboidal, roughly rectangular, bullet-shaped have been found in magnetotactic bacteria. Magnetosomes are organized as well-ordered chains which orient magnetotactic bacteria in geomagnetic fields. The question ‘what and how is genetic material responsible for magnetosome genesis and following diversity’ was raised when biologists tried to understand the formation mechanism of magnetosome in the last century. Now almost two decades have passed since 2000, magnetosome biogenesis still remains one of the hotspots in scientific researches. Both bioinformatic analyses and gene deletion experiments are extensively carried out in the study of magnetosome biogenesis. Consequently, multiple operons and genes are found to be involved in the process of magnetosome formation. This article introduces important findings in the field of operons and genes as controllers of magnetosome biogenesis. The mamAB operon is found to be more critical than other operons to magnetosome biogenesis and it is necessary for rudimentary biomineralization in bacteria. Less than 10 genes within the mamAB operon are essential for the magnetosome formation. Moreover, other four small operons ( mamGFDC , mamXY , mms6 and feoAB1 ) play non-critical roles for magnetosome biogenesis. Non-essential genes can be found in both the mamAB operon and non-critical operons. In addition, several genes and genomic regions outside of magnetosome-related operons such as the mms16 gene in Magnetospirillum magneticum AMB1 or the mad gene clusters in Deltaproteobacteria are also related to magnetosome synthesis. These discoveries provide insights into the molecular mechanisms of magnetosome biogenesis. Some researchers have separated the whole process of magnetosome formation into three or five key steps, they proposed several hypothesized mechanisms of magnetosome formation in magnetotactic bacteria by summarizing functional genes and proteins in each of key steps. The Arakaki’s model in 2018 is a relatively comprehensive model of magnetosome formation and can offer detail information about molecular and cellular mechanisms. With rapid development of research on magnetotactic bacteria emerging in China in recent years, Chinese scientists have made various types of research achievements such as discoveries of novel magnetotactic bacteria, calculations of diversity of magnetotactic bacteria in specific water areas and evolutionary mechanism of microbial magnetoreception. It is expected that more valuable achievements would be obtained from bacterial research than ever before. Natural magnetic nanoparticles have potentials to bring many advancements in science and they can help overcome technical challenges in various scientific fields. To release the power within magnetosomes, biologists are required to reveal the genetic foundation of magnetosome biogenesis and help material scientists invent new technology using biological knowledge. Magnetosome researches are attracting more and more scientists from all areas of science. Interdisciplinary research has become an increasingly common method of study in magnetosome. How well the material scientists can cooperate with other scientists will be crucial for important discoveries in magnetosomes in the future.

Correlative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging

Magnetotactic bacteria biomineralize ordered chains of uniform, membrane-bound magnetite or greigite nanocrystals that exhibit nearly perfect crystal structures and species-specific morphologies. Transmission electron microscopy (TEM) is a critical technique for providing information regarding the organization of cellular and magnetite structures in these microorganisms. However, conventional TEM can only be used to image air-dried or vitrified bacteria removed from their natural environment. Here we present a correlative scanning TEM (STEM) and fluorescence microscopy technique for imaging viable cells of Magnetospirillum magneticum strain AMB-1 in liquid using an in situ fluid cell TEM holder. Fluorescently labeled cells were immobilized on microchip window surfaces and visualized in a fluid cell with STEM, followed by correlative fluorescence imaging to verify their membrane integrity. Notably, the post-STEM fluorescence imaging indicated that the bacterial cell wall membrane did not sustain radiation damage during STEM imaging at low electron dose conditions. We investigated the effects of radiation damage and sample preparation on the bacteria viability and found that approximately 50% of the bacterial membranes remained intact after an hour in the fluid cell, decreasing to ~30% after two hours. These results represent a first step toward in vivo studies of magnetite biomineralization in magnetotactic bacteria.

Correlative electron and fluorescence microscopy of magnetotactic bacteria in liquid: toward in vivo imaging.

Magnetotactic bacteria biomineralize ordered chains of uniform, membrane-bound magnetite or greigite nanocrystals that exhibit nearly perfect crystal structures and species-specific morphologies. Transmission electron microscopy (TEM) is a critical technique for providing information regarding the organization of cellular and magnetite structures in these microorganisms. However, conventional TEM can only be used to image air-dried or vitrified bacteria removed from their natural environment. Here we present a correlative scanning TEM (STEM) and fluorescence microscopy technique for imaging viable cells of Magnetospirillum magneticum strain AMB-1 in liquid using an in situ fluid cell TEM holder. Fluorescently labeled cells were immobilized on microchip window surfaces and visualized in a fluid cell with STEM, followed by correlative fluorescence imaging to verify their membrane integrity. Notably, the post-STEM fluorescence imaging indicated that the bacterial cell wall membrane did not sustain radiation damage during STEM imaging at low electron dose conditions. We investigated the effects of radiation damage and sample preparation on the bacteria viability and found that approximately 50% of the bacterial membranes remained intact after an hour in the fluid cell, decreasing to ~30% after two hours. These results represent a first step toward in vivo studies of magnetite biomineralization in magnetotactic bacteria.

Intracellular biomineralization in bacteria

Microorganisms have populated the Earth for billions of years and their activities are important forces shaping our planetary environments through biogeochemical cycles. In particular, microbial biomineralization that selectively take up environmental elements and deposit minerals either intracellularly or extracellularly is of great interest, because these processes play vital roles in the global cycles of numerous elements, such as Fe, Mn, Ca, As, O, S, and P, etc. Biominerals, the products of biomineralization, not only serve as important biosignatures for the search of traces of past life and the reconstruction of ancient environments but also have many important commercial applications.

The magnetosome model: insights into the mechanisms of bacterial biomineralization

Though the most ready example of biomineralization is the calcium phosphate of vertebrate bones and teeth, many bacteria are capable of creating biominerals inside their cells. Because of the diversity of these organisms and the minerals they produce, their study may reveal aspects of the fundamental mechanisms of biomineralization in more complex organisms. The best-studied case of intracellular biomineralization in bacteria is the magnetosome, an organelle produced by a diverse group of aquatic bacteria that contains single-domain crystals of the iron oxide magnetite (Fe3O4) or the iron sulfide greigite (Fe3S4). Here, recent advances in our understanding of the mechanisms of bacterial magnetite biomineralization are discussed and used as a framework for understanding less-well studied examples, including the bacterial intracellular biomineralization of cadmium, selenium, silver, nickel, uranium, and calcium carbonate. Understanding the molecular mechanisms underlying the biological formation of these minerals will have important implications for technologies such as the fabrication of nanomaterials and the bioremediation of toxic compounds.

Giant magnetofossils and hyperthermal events

Magnetotactic bacteria biomineralize magnetic minerals with precisely controlled size, morphology, and stoichiometry. These cosmopolitan bacteria are widely observed in aquatic environments. If preserved after burial, the inorganic remains of magnetotactic bacteria act as magnetofossils that record ancient geomagnetic field variations. They also have potential to provide paleoenvironmental information. In contrast to conventional magnetofossils, giant magnetofossils (most likely produced by eukaryotic organisms) have only been reported once before from Paleocene-Eocene Thermal Maximum (PETM; 55.8Ma) sediments on the New Jersey coastal plain. Here, using transmission electron microscopic observations, we present evidence for abundant giant magnetofossils, including previously reported elongated prisms and spindles, and new giant bullet-shaped magnetite crystals, in the Southern Ocean near Antarctica, not only during the PETM, but also shortly before and after the PETM. Moreover, we have discovered giant bullet-shaped magnetite crystals from the equatorial Indian Ocean during the Mid-Eocene Climatic Optimum (∼40Ma). Our results indicate a more widespread geographic, environmental, and temporal distribution of giant magnetofossils in the geological record with a link to “hyperthermal” events. Enhanced global weathering during hyperthermals, and expanded suboxic diagenetic environments, probably provided more bioavailable iron that enabled biomineralization of giant magnetofossils. Our micromagnetic modelling indicates the presence of magnetic multi-domain (i.e., not ideal for navigation) and single domain (i.e., ideal for navigation) structures in the giant magnetite particles depending on their size, morphology and spatial arrangement. Different giant magnetite crystal morphologies appear to have had different biological functions, including magnetotaxis and other non-navigational purposes. Our observations suggest that hyperthermals provided ideal conditions for giant magnetofossils, and that these organisms were globally distributed. Much more work is needed to understand the interplay between magnetofossil morphology, climate, nutrient availability, and environmental variability.

Molecular mechanisms of compartmentalization and biomineralization in magnetotactic bacteria

Magnetotactic bacteria (MB) are remarkable organisms with the ability to exploit the earth's magnetic field for navigational purposes. To do this, they build specialized compartments called magnetosomes that consist of a lipid membrane and a crystalline magnetic mineral. These organisms have the potential to serve as models for the study of compartmentalization as well as biomineralization in bacteria. Additionally, they offer the opportunity to design applications that take advantage of the particular properties of magnetosomes. In recent years, a sustained effort to identify the molecular basis of this process has resulted in a clearer understanding of the magnetosome formation and biomineralization. Here, I present an overview of MB and explore the possible molecular mechanisms of membrane remodeling, protein sorting, cytoskeletal organization, iron transport, and biomineralization that lead to the formation of a functional magnetosome organelle.

Controlled cobalt doping of magnetosomes in vivo

Magnetotactic bacteria biomineralize iron into magnetite (Fe3O4) nanoparticles that are surrounded by lipid vesicles. These 'magnetosomes' have considerable potential for use in bio- and nanotechnological applications because of their narrow size and shape distribution and inherent biocompatibility. The ability to tailor the magnetic properties of magnetosomes by chemical doping would greatly expand these applications; however, the controlled doping of magnetosomes has so far not been achieved. Here, we report controlled in vivo cobalt doping of magnetosomes in three strains of the bacterium Magnetospirillum. The presence of cobalt increases the coercive field of the magnetosomes--that is, the field necessary to reverse their magnetization--by 36-45%, depending on the strain and the cobalt content. With elemental analysis, X-ray absorption and magnetic circular dichroism, we estimate the cobalt content to be between 0.2 and 1.4%. These findings provide an important advance in designing biologically synthesized nanoparticles with useful highly tuned magnetic properties.

Intracellular Magnetite Biomineralization in Bacteria Proceeds by a Distinct Pathway Involving Membrane‐Bound Ferritin and an Iron(II) Species

Intracellular Magnetite Biomineralization in Bacteria Proceeds by a Distinct Pathway Involving Membrane‐Bound Ferritin and an Iron(II) Species

Biogenic nanoparticles: production, characterization, and application of bacterialmagnetosomes

The ability of magnetotactic bacteria (MTB) to navigate along magnetic field lines is basedon unique nanosized organelles (magnetosomes), which are membrane-enclosed intracellularcrystals of a magnetic iron mineral that assemble into highly ordered chain-like structures.The biomineralization of magnetosomes is a process with genetic control over theaccumulation of iron, the deposition of the magnetic crystal within a specific compartment,as well as the assembly, alignment and intracellular organization of particle chains.Magnetite crystals produced by MTB have uniform species-specific morphologies and sizes,which are mostly unknown from inorganic systems. The unusual characteristics ofmagnetosome particles have attracted a great interdisciplinary interest and inspirednumerous ideas for their biotechnological application. In this article, we summarize thecurrent knowledge of magnetosome biomineralization in bacteria. In addition, we willpresent results on the mass production, as well as the biochemical and physico-chemicalanalysis and functionalization of bacterial magnetosomes, with emphasis on theircharacterization as a novel class of magnetic nanoparticles. Finally, we describe thepotential of magnetosomes in various biomedical and technological applications.