scholarly journals Magnetosomes could be protective shields against metal stress in magnetotactic bacteria

2020 ◽  
Author(s):  
D. Muñoz ◽  
L. Marcano ◽  
R. Martín-Rodríguez ◽  
L. Simonelli ◽  
A. Serrano ◽  
...  
Keyword(s):  
Magnetotactic Bacteria ◽  
Resistance Mechanisms ◽  
Metal Stress ◽  
Bacterial Populations ◽  
Cell Compartments ◽  
Aquatic Microorganisms ◽  
Field Lines ◽  
A Chain ◽  
X Ray Absorption

AbstractMagnetotactic bacteria are aquatic microorganisms with the ability to biomineralise membrane-enclosed magnetic nanoparticles, called magnetosomes. These magnetosomes are arranged into a chain that behaves as a magnetic compass, allowing the bacteria to align in and navigate along the Earth’s magnetic field lines. According to the magneto-aerotactic hypothesis, the purpose of producing magnetosomes is to provide the bacteria with a more efficient movement within the stratified water column, in search of the optimal positions that satisfy their nutritional requirements. However, magnetosomes could have other physiological roles, as proposed in this work. Here we analyse the role of magnetosomes in the tolerance of Magnetospirillum gryphiswaldense MSR-1 to transition metals (Co, Mn, Ni, Zn, Cu). By exposing bacterial populations with and without magnetosomes to increasing concentrations of metals in the growth medium, we observe that the tolerance is significantly higher when bacteria have magnetosomes. The resistance mechanisms triggered in magnetosome-bearing bacteria under metal stress have been investigated by means of x-ray absorption near edge spectroscopy (XANES). XANES experiments were performed both on magnetosomes isolated from the bacteria and on the whole bacteria, aimed to assess whether bacteria use magnetosomes as metal storages, or whether they incorporate the excess metal in other cell compartments. Our findings reveal that the tolerance mechanisms are metal-specific: Mn, Zn and Cu are incorporated in both the magnetosomes and other cell compartments; Co is only incorporated in the magnetosomes, and Ni is incorporated in other cell compartments. In the case of Co, Zn and Mn, the metal is integrated in the magnetosome magnetite mineral core.

scholarly journals Magnetotaxis as a Means for Nanofabrication

2014 ◽  
Vol 23 (01n02) ◽  
pp. 1450008
Author(s):  
Isaac Macwan ◽  
Zihe Zhao ◽  
Omar Sobh ◽  
Jinnque Rho ◽  
Ausif Mahmood ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Field ◽  
Semiconductor Manufacturing ◽  
Magnetic Field Intensity ◽  
Magnetotactic Bacteria ◽  
Semiconductor Substrate ◽  
Field Lines ◽  
A Chain ◽  
Magnetospirillum Magneticum ◽  
The Magnetic Field

Magnetotactic bacteria (MTB), discovered in early 1970s contain single-domain crystals of magnetite ( Fe 3 O 4) called magnetosomes that tend to form a chain like structure from the proximal to the distal pole along the long axis of the cell. The ability of these bacteria to sense the magnetic field for displacement, also called magnetotaxis, arises from the magnetic dipole moment of this chain of magnetosomes. In aquatic habitats, these organisms sense the geomagnetic field and traverse the oxic-anoxic interface for optimal oxygen concentration along the field lines. Here we report an elegant use of MTB where magnetotaxis of Magnetospirillum magneticum (classified as AMB-1) could be utilized for controlled navigation over a semiconductor substrate for selective deposition. We examined 50mm long coils made out of 18AWG and 20AWG copper conductors having diameters of 5mm, 10mm and 20mm for magnetic field intensity and heat generation. Based on the COMSOL simulations and experimental data, it is recognized that a compound semiconductor manufacturing technology involving bacterial carriers and carbon-based materials such as graphene and carbon nanotubes would be a desirable choice in the future.

scholarly journals Effect of equatorial ionization anomaly on the occurrence of spread-F

1997 ◽  
Vol 15 (2) ◽  
pp. 255-262 ◽  
Author(s):  
P. T. Jayachandran ◽  
P. Sri Ram ◽  
V. V. Somayajulu ◽  
P. V. S. Rama Rao
Keyword(s):  
Electric Field ◽  
Geomagnetic Field ◽  
Critical Frequency ◽  
Equatorial Ionosphere ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
Field Lines ◽  
A Chain ◽  
Indian Sector

Abstract. The unique geometry of the geomagnetic field lines over the equatorial ionosphere coupled with the E-W electric field causes the equatorial ionization anomaly (EIA) and equatorial spread-F (ESF). Ionosonde data obtained at a chain of four stations covering equator to anomaly crest region (0.3 to 33 °N dip) in the Indian sector are used to study the role of EIA and the associated processes on the occurrence of ESF. The study period pertains to the equinoctial months (March, April, September and October) of 1991. The ratios of critical frequency of F-layer (ƒ0F2) and electron densities at an altitude of 270 km between Ahmedabad (33 °N dip) and Waltair (20 °N dip) are found to shoot up in the afternoon hours on spread-F days showing strengthening of the EIA in the afternoon hours. The study confirms the earlier conclusions made by Raghava Rao et al. and Alex et al. that a well-developed EIA is one of the conditions conducive for the generation of ESF. This study also shows that the location of the crest is also important in addition to the strength of the anomaly.

scholarly journals Characterization of Bacterial Magnetotactic Behaviors by Using a Magnetospectrophotometry Assay

2009 ◽  
Vol 75 (12) ◽  
pp. 3835-3841 ◽  
Author(s):  
Christopher T. Lefèvre ◽  
Tao Song ◽  
Jean-Paul Yonnet ◽  
Long-Fei Wu
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Light Beam ◽  
Geomagnetic Field ◽  
Magnetic Particles ◽  
Magnetotactic Bacteria ◽  
Cell Alignment ◽  
The North ◽  
Field Lines ◽  
A Chain

ABSTRACT Magnetotactic bacteria have the unique capacity of synthesizing intracellular single-domain magnetic particles called magnetosomes. The magnetosomes are usually organized in a chain that allows the bacteria to align and swim along geomagnetic field lines, a behavior called magnetotaxis. Two mechanisms of magnetotaxis have been described. Axial magnetotactic cells swim in both directions along magnetic field lines. In contrast, polar magnetotactic cells swim either parallel to the geomagnetic field lines toward the North Pole (north seeking) or antiparallel toward the South Pole (south seeking). In this study, we used a magnetospectrophotometry (MSP) assay to characterize both the axial magnetotaxis of “Magnetospirillum magneticum” strain AMB-1 and the polar magnetotaxis of magneto-ovoid strain MO-1. Two pairs of Helmholtz coils were mounted onto the cuvette holder of a common laboratory spectrophotometer to generate two mutually perpendicular homogeneous magnetic fields parallel or perpendicular to the light beam. The application of magnetic fields allowed measurements of the change in light scattering resulting from cell alignment in a magnetic field or in absorbance due to bacteria swimming across the light beam. Our results showed that MSP is a powerful tool for the determination of bacterial magnetism and the analysis of alignment and swimming of magnetotactic bacteria in magnetic fields. Moreover, this assay allowed us to characterize south-seeking derivatives and non-magnetosome-bearing strains obtained from north-seeking MO-1 cultures. Our results suggest that oxygen is a determinant factor that controls magnetotactic behavior.

Ionic homeostasis and subcellular element compartmentation

1990 ◽  
Vol 48 (2) ◽  
pp. 150-151
Author(s):  
Ann LeFurgey ◽  
Peter Ingram ◽  
J.J. Blum ◽  
M.C. Carney ◽  
L.A. Hawkey ◽  
...  
Keyword(s):  
Leishmania Major ◽  
Ionic Homeostasis ◽  
X Ray ◽  
Functional Studies ◽  
Cell Compartments ◽  
X Ray Imaging ◽  
Resolution Electron ◽  
Multiple Cell ◽  
Role Of Zn

Subcellular compartments commonly identified and analyzed by high resolution electron probe x-ray microanalysis (EPXMA) include mitochondria, cytoplasm and endoplasmic or sarcoplasmic reticulum. These organelles and cell regions are of primary importance in regulation of cell ionic homeostasis. Correlative structural-functional studies, based on the static probe method of EPXMA combined with biochemical and electrophysiological techniques, have focused on the role of these organelles, for example, in maintaining cell calcium homeostasis or in control of excitation-contraction coupling. New methods of real time quantitative x-ray imaging permit simultaneous examination of multiple cell compartments, especially those areas for which both membrane transport properties and element content are less well defined, e.g. nuclei including euchromatin and heterochromatin, lysosomes, mucous granules, storage vacuoles, microvilli. Investigations currently in progress have examined the role of Zn-containing polyphosphate vacuoles in the metabolism of Leishmania major, the distribution of Na, K, S and other elements during anoxia in kidney cell nuclel and lysosomes; the content and distribution of S and Ca in mucous granules of cystic fibrosis (CF) nasal epithelia; the uptake of cationic probes by mltochondria in cultured heart ceils; and the junctional sarcoplasmic retlculum (JSR) in frog skeletal muscle.

The Nature of S-N Bonding in Sulfonamides and Related Compounds: Insights into π-Bonding Contributions from Sulfur K-Edge XAS

2020 ◽  
Author(s):  
Tulin Okbinoglu ◽  
Pierre Kennepohl
Keyword(s):  
Density Functional ◽  
Chemical Properties ◽  
Functional Theory ◽  
Rotational Barriers ◽  
Td Dft ◽  
Nitrogen Bonds ◽  
X Ray Absorption ◽  
Related Compounds ◽  
And Chemical Properties

Molecules containing sulfur-nitrogen bonds, like sulfonamides, have long been of interest due to their many uses and chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet their continues to be controversy regarding the relevance of S-N π bonding in describing these species. In this paper, we use sulfur K-edge x-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to explore the role of S<sub>3p</sub> contributions to π-bonding in sulfonamides, sulfinamides and sulfenamides. We explore the nature of electron distribution of the sulfur atom and its nearest neighbors and extend the scope to explore the effects on rotational barriers along the sulfur-nitrogen axis. The experimental XAS data together with TD-DFT calculations confirm that sulfonamides, and the other sulfinated amides in this series, have essentially no S-N π bonding involving S<sub>3p</sub> contributions and that electron repulsion and is the dominant force that affect rotational barriers.

scholarly journals The MarR-Type Regulator PA3458 Is Involved in Osmoadaptation Control in Pseudomonas aeruginosa

2021 ◽  
Vol 22 (8) ◽  
pp. 3982
Author(s):  
Karolina Kotecka ◽  
Adam Kawalek ◽  
Kamil Kobylecki ◽  
Aneta Agnieszka Bartosik
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Binding Sites ◽  
Transcriptional Profiling ◽  
Mrna Level ◽  
Transcriptional Regulators ◽  
Resistance Mechanisms ◽  
Chronic Infections ◽  
Environmental Signals ◽  
Regulatory Systems

Pseudomonas aeruginosa is a facultative human pathogen, causing acute and chronic infections that are especially dangerous for immunocompromised patients. The eradication of P. aeruginosa is difficult due to its intrinsic antibiotic resistance mechanisms, high adaptability, and genetic plasticity. The bacterium possesses multilevel regulatory systems engaging a huge repertoire of transcriptional regulators (TRs). Among these, the MarR family encompasses a number of proteins, mainly acting as repressors, which are involved in response to various environmental signals. In this work, we aimed to decipher the role of PA3458, a putative MarR-type TR from P. aeruginosa. Transcriptional profiling of P. aeruginosa PAO1161 overexpressing PA3458 showed changes in the mRNA level of 133 genes; among them, 100 were down-regulated, suggesting the repressor function of PA3458. Concomitantly, ChIP-seq analysis identified more than 300 PA3458 binding sites in P. aeruginosa. The PA3458 regulon encompasses genes involved in stress response, including the PA3459–PA3461 operon, which is divergent to PA3458. This operon encodes an asparagine synthase, a GNAT-family acetyltransferase, and a glutamyl aminopeptidase engaged in the production of N-acetylglutaminylglutamine amide (NAGGN), which is a potent bacterial osmoprotectant. We showed that PA3458-mediated control of PA3459–PA3461 expression is required for the adaptation of P. aeruginosa growth in high osmolarity. Overall, our data indicate that PA3458 plays a role in osmoadaptation control in P. aeruginosa.

scholarly journals Cancer, Retrogenes, and Evolution

Life ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 72
Author(s):  
Klaudia Staszak ◽  
Izabela Makałowska
Keyword(s):  
Specific Resistance ◽  
Neoplastic Transformation ◽  
Resistance Mechanisms ◽  
Response To Therapy ◽  
Additional Gene ◽  
Cancer Subtypes ◽  
Gene Copies ◽  
Specific Cancer ◽  
Evolution Of Genomes

This review summarizes the knowledge about retrogenes in the context of cancer and evolution. The retroposition, in which the processed mRNA from parental genes undergoes reverse transcription and the resulting cDNA is integrated back into the genome, results in additional copies of existing genes. Despite the initial misconception, retroposition-derived copies can become functional, and due to their role in the molecular evolution of genomes, they have been named the “seeds of evolution”. It is convincing that retrogenes, as important elements involved in the evolution of species, also take part in the evolution of neoplastic tumors at the cell and species levels. The occurrence of specific “resistance mechanisms” to neoplastic transformation in some species has been noted. This phenomenon has been related to additional gene copies, including retrogenes. In addition, the role of retrogenes in the evolution of tumors has been described. Retrogene expression correlates with the occurrence of specific cancer subtypes, their stages, and their response to therapy. Phylogenetic insights into retrogenes show that most cancer-related retrocopies arose in the lineage of primates, and the number of identified cancer-related retrogenes demonstrates that these duplicates are quite important players in human carcinogenesis.

scholarly journals Antimicrobials and Food-Related Stresses as Selective Factors for Antibiotic Resistance along the Farm to Fork Continuum

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 671
Author(s):  
Federica Giacometti ◽  
Hesamaddin Shirzad-Aski ◽  
Susana Ferreira
Keyword(s):  
Antibiotic Resistance ◽  
Food Safety ◽  
Antimicrobial Resistance ◽  
Food Processing ◽  
Resistance Mechanisms ◽  
Human Environment ◽  
Real Risk ◽  
Cross Adaptation ◽  
Novel Approaches

Antimicrobial resistance (AMR) is a global problem and there has been growing concern associated with its widespread along the animal–human–environment interface. The farm-to-fork continuum was highlighted as a possible reservoir of AMR, and a hotspot for the emergence and spread of AMR. However, the extent of the role of non-antibiotic antimicrobials and other food-related stresses as selective factors is still in need of clarification. This review addresses the use of non-antibiotic stressors, such as antimicrobials, food-processing treatments, or even novel approaches to ensure food safety, as potential drivers for resistance to clinically relevant antibiotics. The co-selection and cross-adaptation events are covered, which may induce a decreased susceptibility of foodborne bacteria to antibiotics. Although the available studies address the complexity involved in these phenomena, further studies are needed to help better understand the real risk of using food-chain-related stressors, and possibly to allow the establishment of early warnings of potential resistance mechanisms.

scholarly journals Stoichiometric Analysis of Shifting in Subcellular Compartmentalization of HSP70 within Ischemic Penumbra

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3578
Author(s):  
Federica Mastroiacovo ◽  
Francesca Biagioni ◽  
Paola Lenzi ◽  
Larisa Ryskalin ◽  
Stefano Puglisi-Allegra ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Neuronal Survival ◽  
Hsp 70 ◽  
Preclinical Models ◽  
Brain Areas ◽  
Cell Compartments ◽  
Control Brain ◽  
Disease Modifier ◽  
Subcellular Compartmentalization

The heat shock protein (HSP) 70 is considered the main hallmark in preclinical studies to stain the peri-infarct region defined area penumbra in preclinical models of brain ischemia. This protein is also considered as a potential disease modifier, which may improve the outcome of ischemic damage. In fact, the molecule HSP70 acts as a chaperonine being able to impact at several level the homeostasis of neurons. Despite being used routinely to stain area penumbra in light microscopy, the subcellular placement of this protein within area penumbra neurons, to our knowledge, remains undefined. This is key mostly when considering studies aimed at deciphering the functional role of this protein as a determinant of neuronal survival. The general subcellular placement of HSP70 was grossly reported in studies using confocal microscopy, although no direct visualization of this molecule at electron microscopy was carried out. The present study aims to provide a direct evidence of HSP70 within various subcellular compartments. In detail, by using ultrastructural morphometry to quantify HSP70 stoichiometrically detected by immuno-gold within specific organelles we could compare the compartmentalization of the molecule within area penumbra compared with control brain areas. The study indicates that two cell compartments in control conditions own a high density of HSP70, cytosolic vacuoles and mitochondria. In these organelles, HSP70 is present in amount exceeding several-fold the presence in the cytosol. Remarkably, within area penumbra a loss of such a specific polarization is documented. This leads to the depletion of HSP70 from mitochondria and mostly cell vacuoles. Such an effect is expected to lead to significant variations in the ability of HSP70 to exert its physiological roles. The present findings, beyond defining the neuronal compartmentalization of HSP70 within area penumbra may lead to a better comprehension of its beneficial/detrimental role in promoting neuronal survival.

scholarly journals Recapitulation of the Function and Role of ROS Generated in Response to Heat Stress in Plants

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 371
Author(s):  
Emily Medina ◽  
Su-Hwa Kim ◽  
Miriam Yun ◽  
Won-Gyu Choi
Keyword(s):  
Heat Stress ◽  
Plant Growth ◽  
Intracellular Signaling ◽  
Oxygen Species ◽  
Natural Ecosystems ◽  
Signaling Molecule ◽  
Signaling Systems ◽  
Cell Compartments ◽  
Tropical Area

In natural ecosystems, plants are constantly exposed to changes in their surroundings as they grow, caused by a lifestyle that requires them to live where their seeds fall. Thus, plants strive to adapt and respond to changes in their exposed environment that change every moment. Heat stress that naturally occurs when plants grow in the summer or a tropical area adversely affects plants’ growth and poses a risk to plant development. When plants are subjected to heat stress, they recognize heat stress and respond using highly complex intracellular signaling systems such as reactive oxygen species (ROS). ROS was previously considered a byproduct that impairs plant growth. However, in recent studies, ROS gained attention for its function as a signaling molecule when plants respond to environmental stresses such as heat stress. In particular, ROS, produced in response to heat stress in various plant cell compartments such as mitochondria and chloroplasts, plays a crucial role as a signaling molecule that promotes plant growth and triggers subsequent downstream reactions. Therefore, this review aims to address the latest research trends and understandings, focusing on the function and role of ROS in responding and adapting plants to heat stress.

Sign in / Sign up

Export Citation Format

Share Document