scholarly journals Chemical and Morphological Studies of Bacterial Spore Formation

1959 ◽  
Vol 6 (3) ◽  
pp. 467-482 ◽  
Author(s):  
I. Elizabeth Young ◽  
Philip C. Fitz-James
Keyword(s):  
Deoxyribonucleic Acid ◽  
Growth Cycle ◽  
Dark Phase ◽  
Experimental Conditions ◽  
Radioactive Phosphorus ◽  
Thin Sections ◽  
Morphological Studies ◽  
Segregation Process ◽  
A Cell ◽  
Bright Field Microscopy

Experimental conditions were developed whereby a culture of Bacillus cereus formed spores with reasonable synchrony following a growth cycle of some 8 hours. The cytology of this metamorphosis was studied by dark phase contrast, bright-field microscopy and electron microscopy of thin sections. Particular attention has been paid to the changes in chromatin patterns and these have been correlated with quantitative chemical estimations of the nucleic acids. The cell commencing sporulation contains two compact chromatin bodies and twice the spore amount of deoxyribonucleic acid. Following fusion of the two chromatin bodies, one-half of this chromatin becomes located at a cell end. A transverse septum growing inwards from, and remaining attached to, the inner surface of the cell wall separates this end-piece of chromatin and some associated cytoplasm from the rest of the cell to form the primordial spore. Although the synthesis of deoxyribonucleic acid ceases during the segregation process, it recommences in this organism and continues at a linear rate as the spore develops. Tracer studies with radioactive phosphorus indicated that this further synthesis is confined to the non-spore portion of the sporangium. Although the net synthesis of ribonucleic acid ceased prior to the onset of sporogenesis, some evidence of a turnover of this fraction during the sporulation process was found.

scholarly journals CHEMICAL AND MORPHOLOGICAL STUDIES OF BACTERIAL SPORE FORMATION

1962 ◽  
Vol 12 (1) ◽  
pp. 115-133 ◽  
Author(s):  
I. Elizabeth Young ◽  
Philip C. Fitz-James
Keyword(s):  
Phase Contrast ◽  
Calcium Uptake ◽  
Dipicolinic Acid ◽  
Double Layers ◽  
Dark Phase ◽  
Chemical Methods ◽  
Thin Sections ◽  
Morphological Studies ◽  
Water Suspensions ◽  
Free Spore

From the stage of a completed membranous forespore to that of a fully ripened free spore, synchronously sporulating cells of a variant Bacillus cereus were studied by cytological and chemical methods. Particular attention was paid to the development of the three spore layers—cortex, coat, and exosporium—in relation to the forespore membrane. First, the cortex is laid down between the recently described (5) double layers of the forespore membrane. Then when the cortex is ⅓ fully formed, the spore coat and exosporium are laid down peripheral to the outer membrane layer covering the cortex. As these latter layers appear, the spores, previously dense by dark phase contrast, gradually "whiten" or show an increase in refractive index. With this whitening, calcium uptake commences, closely followed by the synthesis of dipicolinic acid and the process is terminated, an hour later, with the formation of a fully refractile spore. In calcium-deficient media, final refractility is lessened and dipicolinic acid is formed only in amounts proportional to the available calcium. If calcium is withheld during the period of uptake beyond a critical point, sporulating cells lose the ability to assimilate calcium and to form normal amounts of dipicolinic acid. The resulting deficient spores are liberated from the sporangia but are unstable in water suspensions. Unlike ripe spores, they do not react violently to acid hydrolysis and, in thin sections, their cytoplasmic granules continue to stain with lead solutions.

Observations of Frozen-Hydrated Microtubules

1990 ◽  
Vol 48 (1) ◽  
pp. 504-505
Author(s):  
D. Chrétien ◽  
D. Job ◽  
R.H. Wade
Keyword(s):  
Fourier Transforms ◽  
Structural Complexity ◽  
Image Contrast ◽  
Phase Behaviour ◽  
Experimental Conditions ◽  
Thin Sections ◽  
Surface Lattice ◽  
Cilia And Flagella ◽  
Outstanding Question

Microtubules are filamentary structures found in the cytoplasm of eukaryotic cells, where, together with actin and intermediate filaments, they form the components of the cytoskeleton. They have many functions and show various levels of structural complexity as witnessed by the singlet, doublet and triplet structures involved in the architecture of centrioles, basal bodies, cilia and flagella. The accepted microtubule model consists of a 25 nm diameter hollow tube with a wall made up of 13 paraxial protofilaments (pf). Each pf is a string of aligned tubulin dimers. Some results have suggested that the pfs follow a superhelix. To understand how microtubules function in the cell an accurate model of the surface lattice is one of the requirements. For example the 9x2 architecture of the axoneme will depend on the organisation of its component microtubules. We should also note that microtubules with different numbers of pfs have been observed in thin sections of cellular and of in-vitro material. An outstanding question is how does the surface lattice adjust to these different pf numbers?We have been using cryo-electron microscopy of frozen-hydrated samples to study in-vitro assembled microtubules. The experimental conditions are described in detail in this reference. The results obtained in conjunction with thin sections of similar specimens and with axoneme outer doublet fragments have already allowed us to characterise the image contrast of 13, 14 and 15 pf microtubules on the basis of the measured image widths, of the the image contrast symmetry and of the amplitude and phase behaviour along the equator in the computed Fourier transforms. The contrast variations along individual microtubule images can be interpreted in terms of the geometry of the microtubule surface lattice. We can extend these results and make some reasonable predictions about the probable surface lattices in the case of other pf numbers, see Table 1. Figure 1 shows observed images with which these predictions can be compared.

scholarly journals Detecting Single Molecule Deoxyribonucleic Acid in a Cell Using a Three‐Dimensionally Integrated Nanopore (Small Methods 9/2021)

Small Methods ◽  
2021 ◽  
Vol 5 (9) ◽  
pp. 2170043
Author(s):  
Makusu Tsutsui ◽  
Kazumichi Yokota ◽  
Akihide Arima ◽  
Takashi Washio ◽  
Yoshinobu Baba ◽  
...  
Keyword(s):  
Single Molecule ◽  
Deoxyribonucleic Acid ◽  
A Cell

INCORPORATION OF RADIOACTIVE PURINE AND PYRIMIDINE BASES AND OF THYMIDINE INTO THE DEOXYRIBONUCLEIC ACID OF SALMON MILTS

1964 ◽  
Vol 42 (1) ◽  
pp. 51-57 ◽  
Author(s):  
H. L. A. Tarr
Keyword(s):  
Orotic Acid ◽  
Deoxyribonucleic Acid ◽  
Tritiated Thymidine ◽  
Experimental Conditions ◽  
Live Fish ◽  
Pyrimidine Bases

C14-labeled adenine, guanine and cytosine, and tritiated thymidine were incorporated into the deoxyribonucleic acid of salmon milts, either by injection into the milts of live fish or into excised milts. The amount incorporated was very small. Under the experimental conditions radioactive nucleosides, deoxyuridine, adenosine 5′-mono- and tri-phosphates, orotic acid, uracil, ribose 1-phosphate, and ribose 5-phosphate were not incorporated. It is suggested that these results may be due to the comparative impermeability of the cells to the various compounds.

scholarly journals Catatropis pakistanensis n. sp. (Trematoda: Notocotylidae) from Northern shovelers, Anas clypeata (Anatidae: Aves) from Pakistan with some remarks on the history of Catatropis species

2012 ◽  
Vol 49 (1) ◽  
pp. 43-48 ◽  
Author(s):  
R. Schuster ◽  
G. Wibbelt
Keyword(s):  
Electron Microscopy ◽  
Histological Evaluation ◽  
Thin Sections ◽  
Genital Opening ◽  
Morphological Studies ◽  
Anas Clypeata ◽  
History Of ◽  
Free Ranging ◽  
A New Species ◽  
Scanning Electron

AbstractFive out of 15 free-ranging Northern shovelers (Anas clypeata Linneus) caught in Pakistan were infected with notocotylid trematodes. Out of the 31 flukes, 10 specimens were used morphological studies, 4 others were also examined by scanning electron microscopy and one remaining trematode was cut in serial semi-thin sections for histological evaluation in order to describe a new species. Like all species of this genus, Catatropis pakistanensis n. sp has a median ridge starting posterior to the basis of the cirrus sac and extends posterior to the ovary. Bilateral to this ridge there are two rows of 9–10 ventral papillae each. Metraterm and cirrus sac are equally in length. In contrast to most other Catatropis spp. the genital opening in C. pakistanensis is situated between the oral sucker and bifurcation of the caeca.

scholarly journals Algae-Assisted Microbial Desalination Cell: Analysis of Cathode Performance and Desalination Efficiency Assessment

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2011
Author(s):  
David Ewusi-Mensah ◽  
Jingyu Huang ◽  
Laura Katherin Chaparro ◽  
Pau Rodenas ◽  
Marina Ramírez-Moreno ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Chlorella Vulgaris ◽  
Coulombic Efficiency ◽  
Geobacter Sulfurreducens ◽  
Dark Phase ◽  
Water Production ◽  
Light Phase ◽  
Experimental Conditions ◽  
Residual Concentration ◽  
Microbial Desalination Cell

Algae-assisted microbial desalination cells represent a sustainable technology for low-energy fresh water production in which microalgae culture is integrated into the system to enhance oxygen reduction reaction in the cathode chamber. However, the water production (desalination rate) is low compared to conventional technologies (i.e., reverse osmosis and/or electrodialysis), as biocathodes provide low current generation to sustain the desalination process. In this sense, more research efforts on this topic are necessary to address this bottleneck. Thus, this study provides analysis, from the electrochemical point of view, on the cathode performance of an algae-assisted microbial desalination cell (MDC) using Chlorella vulgaris. Firstly, the system was run with a pure culture of Chlorella vulgaris suspension in the cathode under conditions of an abiotic anode to assess the cathodic behavior (i.e., cathode polarization curves in light-dark conditions and oxygen depletion). Secondly, Geobacter sulfurreducens was inoculated in the anode compartment of the MDC, and the desalination cycle was carried out. The results showed that microalgae could generate an average of 9–11.5 mg/L of dissolved oxygen during the light phase, providing enough dissolved oxygen to drive the migration of ions (i.e., desalination) in the MDC system. Moreover, during the dark phase, a residual concentration of oxygen (ca. 5.5–8 mg/L) was measured, indicating that oxygen was not wholly depleted under our experimental conditions. Interestingly, the oxygen concentration was restored (after complete depletion of dissolved oxygen by flushing with N2) as soon as microalgae were exposed to the light phase again. After a 31 h desalination cycle, the cell generated a current density of 0.12 mA/cm2 at an efficiency of 60.15%, 77.37% salt was removed at a nominal desalination rate of 0.63 L/m2/h, coulombic efficiency was 9%, and 0.11 kWh/m3 of electric power was generated. The microalgae-assisted biocathode has an advantage over the air diffusion and bubbling as it can self-sustain a steady and higher concentration of oxygen, cost-effectively regenerate or recover from loss and sustainably retain the system’s performance under naturally occurring conditions. Thus, our study provides insights into implementing the algae-assisted cathode for sustainable desalination using MDC technology and subsequent optimization.

scholarly journals Influences of CO2 on the Microstructure in Sheared Olivine Aggregates

2021 ◽  
Author(s):  
Huihui Zhang ◽  
Ningli Zhao ◽  
Chao Qi ◽  
Xiaoge Huang ◽  
Greg Hirth
Keyword(s):  
Olivine Basalt ◽  
Fluid Phase ◽  
Shear Plane ◽  
Formation Model ◽  
Two Phase ◽  
Experimental Conditions ◽  
Crystallographic Preferred Orientation ◽  
Segregation Process ◽  
Basaltic Melt ◽  
Carbonate Melt

Shear deformation of a solid-fluid, two-phase material induces a fluid segregation process that produces fluid-enriched bands and fluid-depleted regions, and crystallographic preferred orientation (CPO) characterized by girdles of [100] and [001] axes sub-parallel to the shear plane and a cluster of [010] axes sub-normal to the shear plane, namely the AG-type fabric. Based on experiments of two-phase aggregates of olivine + basalt, a two-phase flow theory and a CPO-formation model were established to explain these microstructures. Here, we investigate the microstructure in a two-phase aggregate with supercritical CO2 as the fluid phase and examine the theory and model, as CO2 is different from basaltic melt in rheological properties. We conducted high‐temperature and high-pressure shear deformed experiments at 1 GPa and 1100ºC in a Griggs-type apparatus on samples made of olivine + dolomite, which decomposed into carbonate melt and CO2 at experimental conditions. After deformation, CO2 segregation and an AG-type fabric occurred in these CO2-bearing samples, inconsistency with basaltic melt-bearing samples. The SPO-induce CPO model was used to explain the formation of the fabric. Our results suggest that the influences of CO2 as a fluid phase on the microstructure of a two-phase olivine aggregate is similar to that of basaltic melt and can be explained by the CPO-formation model for the solid-fluid system.

scholarly journals Optical, Structural and Electrical Properties of Electrochemical Synthesis of Thin Film of Polyaniline

2018 ◽  
Vol 15 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Baghdad Science Journal
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Morphological Studies ◽  
Atomic Force ◽  
Vis Spectroscopy ◽  
Structural And Electrical Properties ◽  
A Cell ◽  
Ft Ir ◽  
Ir And Raman

Polyaniline membranes of aniline were produced using an electrochemical method in a cell consisting of two poles. The effect of the vaccination was observed on the color of membranes of polyaniline, where analysis as of blue to olive green paints. The sanction of PANI was done by FT-IR and Raman techniques. The crystallinity of the models was studied by X-ray diffraction technique. The different electronic transitions of the PANI were determined by UV-VIS spectroscopy. The electrical conductivity of the manufactured samples was measured by using the four-probe technique at room temperature. Morphological studies have been determined by Atomic force microscopy (AFM). The structural studies have been measured by (SEM).

scholarly journals Rupture force of cell adhesion ligand tethers modulates biological activities of a cell-laden hydrogel

2016 ◽  
Vol 52 (26) ◽  
pp. 4757-4760 ◽  
Author(s):  
Min Kyung Lee ◽  
Jooyeon Park ◽  
Xuefeng Wang ◽  
Mehdi Roein-Peikar ◽  
Eunkyung Ko ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Adhesion ◽  
Deoxyribonucleic Acid ◽  
Biological Activities ◽  
Rupture Force ◽  
A Cell ◽  
Adhesion Ligand

Hydrogels coupled with integrin-binding deoxyribonucleic acid (DNA) tethers with pre-defined rupture forces can modulate phenotypic activities of stem cells.

F-actin as a functional target for retro-retinoids: a potential role in anhydroretinol-triggered cell death

1999 ◽  
Vol 112 (15) ◽  
pp. 2521-2528 ◽  
Author(s):  
I. Korichneva ◽  
U. Hammerling
Keyword(s):  
Cell Death ◽  
Early Event ◽  
Pattern Reversal ◽  
Cell Periphery ◽  
Growth And Survival ◽  
Signalling Molecules ◽  
Herbimycin A ◽  
Morphological Studies ◽  
A Cell ◽  
Survival Potential

The retro-retinoids, metabolites of vitamin A (retinol), belong to a family of lipophilic signalling molecules implicated in regulation of cell growth and survival. Growth-promoting properties have been ascribed to 14-hydroxy-retro-retinol (14HRR), while anhydroretinol (AR) was discovered to act as a natural antagonist triggering growth arrest and death by apoptosis. Based on morphological studies and inhibition of apoptosis by the kinase blocker, herbimycin A, it has been suggested that retro-retinoids exhibit their function in the cytosolic compartment. F-actin emerged as a functional target for retro-retinoid action. By FACS analysis and fluorescence microscopy of phalloidin-FITC labeled cells we demonstrated that F-actin reorganization was an early event in AR-triggered apoptosis. Fluorescence images of AR-treated fibroblasts displayed short, thick, stick-like and punctate structures, and membrane ruffles at the cell periphery along with an increased diffuse staining pattern. Reversal of the AR effect by 14HRR or retinol indicates that F-actin is a common site for regulation by retro-retinoids. Inhibition of both cell death and actin depolymerisation by bcl-2 implies that cytoskeleton reorganization is downstream of bcl-2-related processes. Furthermore, stabilization of microfilaments by jasplakinolide increased the survival potential of AR treated cells, while weakening the cytoskeleton by cytochalasin B abetted apoptosis. Thus the cytoskeleton is an important way station in a communication network that decides whether a cell should live or die.

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