scholarly journals The Gas Vesicle Gene Cluster from Microcystis aeruginosa and DNA Rearrangements That Lead to Loss of Cell Buoyancy

2004 ◽  
Vol 186 (8) ◽  
pp. 2355-2365 ◽  
Author(s):  
Alyssa Mlouka ◽  
Katia Comte ◽  
Anne-Marie Castets ◽  
Christiane Bouchier ◽  
Nicole Tandeau de Marsac
Keyword(s):  
Electron Microscopy ◽  
Gene Cluster ◽  
Microcystis Aeruginosa ◽  
Gas Vesicles ◽  
Structural Protein ◽  
Dna Rearrangements ◽  
Unicellular Cyanobacterium ◽  
Laboratory Cultures ◽  
Insertion Elements ◽  
Freshwater Environments

ABSTRACT Microcystis aeruginosa is a planktonic unicellular cyanobacterium often responsible for seasonal mass occurrences at the surface of freshwater environments. An abundant production of intracellular structures, the gas vesicles, provides cells with buoyancy. A 8.7-kb gene cluster that comprises twelve genes involved in gas vesicle synthesis was identified. Ten of these are organized in two operons, gvpAI AII AIII CNJX and gvpKFG, and two, gvpV and gvpW, are individually expressed. In an attempt to elucidate the basis for the frequent occurrence of nonbuoyant mutants in laboratory cultures, four gas vesicle-deficient mutants from two strains of M. aeruginosa, PCC 7806 and PCC 9354, were isolated and characterized. Their molecular analysis unveiled DNA rearrangements due to four different insertion elements that interrupted gvpN, gvpV, or gvpW or led to the deletion of the gvpAI -AIII region. While gvpA, encoding the major gas vesicle structural protein, was expressed in the gvpN, gvpV, and gvpW mutants, immunodetection revealed no corresponding GvpA protein. Moreover, the absence of a gas vesicle structure was confirmed by electron microscopy. This study brings out clues concerning the process driving loss of buoyancy in M. aeruginosa and reveals the requirement for gas vesicle synthesis of two newly described genes, gvpV and gvpW.

Structure of the gas vesicle protein GvpF from the cyanobacteriumMicrocystis aeruginosa

2014 ◽  
Vol 70 (11) ◽  
pp. 3013-3022 ◽  
Author(s):  
Bo-Ying Xu ◽  
Ya-Nan Dai ◽  
Kang Zhou ◽  
Yun-Tao Liu ◽  
Qianqian Sun ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Gene Cluster ◽  
Microcystis Aeruginosa ◽  
Immunogold Labelling ◽  
Gas Vesicles ◽  
Structural Protein ◽  
Apparent Variation ◽  
Vesicle Protein

Gas vesicles are gas-filled proteinaceous organelles that provide buoyancy for bacteria and archaea. A gene cluster that is highly conserved in various species encodes about 8–14 proteins (Gvp proteins) that are involved in the formation of gas vesicles. Here, the first crystal structure of the gas vesicle protein GvpF fromMicrocystis aeruginosaPCC 7806 is reported at 2.7 Å resolution. GvpF is composed of two structurally distinct domains (the N-domain and C-domain), both of which display an α+β class overall structure. The N-domain adopts a novel fold, whereas the C-domain has a modified ferredoxin fold with an apparent variation owing to an extension region consisting of three sequential helices. The two domains pack against each otherviainteractions with a C-terminal tail that is conserved among cyanobacteria. Taken together, it is concluded that the overall architecture of GvpF presents a novel fold. Moreover, it is shown that GvpF is most likely to be a structural protein that is localized at the gas-facing surface of the gas vesicle by immunoblotting and immunogold labelling-based tomography.

scholarly journals The mcyF gene of the microcystin biosynthetic gene cluster from Microcystis aeruginosa encodes an aspartate racemase

2003 ◽  
Vol 373 (3) ◽  
pp. 909-916 ◽  
Author(s):  
Heike SIELAFF ◽  
Elke DITTMANN ◽  
Nicole TANDEAU de MARSAC ◽  
Christiane BOUCHIER ◽  
Hans von DÖHREN ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Microcystis Aeruginosa ◽  
Biosynthetic Gene Cluster ◽  
Sequence Motifs ◽  
Independent Manner ◽  
Unicellular Cyanobacterium ◽  
Reading Frame ◽  
Glutamate Racemase ◽  
Aspartate Racemase ◽  
Mcy Gene

Microcystins are hepatotoxic, non-ribosomal peptides produced by several genera of freshwater cyanobacteria. Among other enzymic activities, in particular those of peptide synthetases and polyketide synthases, microcystin biosynthesis requires racemases that provide d-aspartate and d-glutamate. Here, we report on the cloning, expression and characterization of an open reading frame, mcyF, that is part of the mcy gene cluster involved in microcystin biosynthesis in the Microcystis aeruginosa strain PCC 7806. Conserved amino acid sequence motifs suggest a function of the McyF protein as an aspartate racemase. Heterologous expression of mcyF in the unicellular cyanobacterium Synechocystis PCC 6803 yielded an active His6-tagged protein that was purified to homogeneity by Ni2+-nitriloacetate affinity chromatography. The purified recombinant protein racemized in a pyridoxal-5′-phosphate-independent manner l-aspartate, but not l-glutamate. Furthermore, we have identified a putative glutamate racemase gene that is located outside the mcy gene cluster in the M. aeruginosa PCC 7806 genome. Whereas homologues of this glutamate racemase gene are present in all the Microcystis strains examined, mcyF could only be detected in microcystin-producing strains.

Interrelationship of the cellular distribution and secretion of regular structure (RS) protein in Bacillus licheniformis nm 105

1992 ◽  
Vol 50 (1) ◽  
pp. 712-713
Author(s):  
Xiaorong Zhu ◽  
Richard McVeigh ◽  
Bijan K. Ghosh
Keyword(s):  
Alkaline Phosphatase ◽  
Bacillus Licheniformis ◽  
Self Assembly ◽  
Gel Electrophoresis ◽  
Culture Supernatant ◽  
Regular Structure ◽  
The Self ◽  
Cellular Distribution ◽  
Structural Protein ◽  
Laboratory Cultures

A mutant of Bacillus licheniformis 749/C, NM 105 exhibits some notable properties, e.g., arrest of alkaline phosphatase secretion and overexpression and hypersecretion of RS protein. Although RS is known to be widely distributed in many microbes, it is rarely found, with a few exceptions, in laboratory cultures of microorganisms. RS protein is a structural protein and has the unusual properties to form aggregate. This characteristic may have been responsible for the self assembly of RS into regular tetragonal structures. Another uncommon characteristic of RS is that enhanced synthesis and secretion which occurs when the cells cease to grow. Assembled RS protein with a tetragonal structure is not seen inside cells at any stage of cell growth including cells in the stationary phase of growth. Gel electrophoresis of the culture supernatant shows a very large amount of RS protein in the stationary culture of the B. licheniformis. It seems, Therefore, that the RS protein is cotranslationally secreted and self assembled on the envelope surface.

scholarly journals A Bacterial Microcompartment Is Used for Choline Fermentation byEscherichia coli536

2018 ◽  
Vol 200 (10) ◽  
Author(s):  
Taylor I. Herring ◽  
Tiffany N. Harris ◽  
Chiranjit Chowdhury ◽  
Sujit Kumar Mohanty ◽  
Thomas A. Bobik
Keyword(s):  
Electron Microscopy ◽  
Heart Disease ◽  
Gene Cluster ◽  
Transcriptional Regulator ◽  
Human Gut ◽  
Content Type ◽  
E Coli ◽  
Bacterial Microcompartment ◽  
New Type ◽  
Insight Into

ABSTRACTBacterial choline degradation in the human gut has been associated with cancer and heart disease. In addition, recent studies found that a bacterial microcompartment is involved in choline utilization byProteusandDesulfovibriospecies. However, many aspects of this process have not been fully defined. Here, we investigate choline degradation by the uropathogenEscherichia coli536. Growth studies indicatedE. coli536 degrades choline primarily by fermentation. Electron microscopy indicated that a bacterial microcompartment was used for this process. Bioinformatic analyses suggested that the choline utilization (cut) gene cluster ofE. coli536 includes two operons, one containing three genes and a main operon of 13 genes. Regulatory studies indicate that thecutXgene encodes a positive transcriptional regulator required for induction of the maincutoperon in response to choline supplementation. Each of the 16 genes in thecutcluster was individually deleted, and phenotypes were examined. ThecutX,cutY,cutF,cutO,cutC,cutD,cutU, andcutVgenes were required for choline degradation, but the remaining genes of thecutcluster were not essential under the conditions used. The reasons for these varied phenotypes are discussed.IMPORTANCEHere, we investigate choline degradation inE. coli536. These studies provide a basis for understanding a new type of bacterial microcompartment and may provide deeper insight into the link between choline degradation in the human gut and cancer and heart disease. These are also the first studies of choline degradation inE. coli536, an organism for which sophisticated genetic analysis methods are available. In addition, thecutgene cluster ofE. coli536 is located in pathogenicity island II (PAI-II536) and hence might contribute to pathogenesis.

scholarly journals Ultrastructure of Lobosphaera reniformis (Watanabe) Komárek et Fott (Chlorellales) from King George Island, South Shetland Islands, Antarctica

2014 ◽  
Vol 63 (2) ◽  
pp. 205-210 ◽  
Author(s):  
A. Massalski ◽  
T. Mrozińska ◽  
M. Olech
Keyword(s):  
Electron Microscopy ◽  
Life Cycle ◽  
South Shetland Islands ◽  
King George Island ◽  
Vegetative Cells ◽  
Shetland Islands ◽  
Complete Life Cycle ◽  
Laboratory Cultures ◽  
First Time

<i>Lobosphaera reniformis</i> (Wat.) Kom. et Fott (=<i>Chlorella reniformis</i> Wat.) so far known only from Japan, and Papua Island, was for the first time found in Antarctica (King George Island, South Shetland Islands). In laboratory cultures a complete life cycle was obtained, and most of its stages were followed by the electron microscopy. Reproduction is by morphologically different autospores. In some large vegetative cells two Golgi apparatuses lying side by side were observed.

scholarly journals Identification of Pilus-Like Structures and Genes in Microcystis aeruginosa PCC7806

2005 ◽  
Vol 71 (11) ◽  
pp. 7621-7625 ◽  
Author(s):  
Kenlee Nakasugi ◽  
Brett A. Neilan
Keyword(s):  
Electron Microscopy ◽  
Microcystis Aeruginosa ◽  
Type Iv Pilus ◽  
Type Iv

ABSTRACT Four putative type IV pilus genes from the toxic, naturally transformable Microcystis aeruginosa PCC7806 were identified. Three of these genes were clustered in an arrangement which is identical to that from other cyanobacterial genomes. Type IV pilus-like appendages were also observed by electron microscopy.

Hydrogenase from the unicellular cyanobacterium, Microcystis aeruginosa

1987 ◽  
Vol 26 (3) ◽  
pp. 637-640 ◽  
Author(s):  
Yasuo Asada ◽  
Sugio Kawamura ◽  
Kwok-Ki Ho
Keyword(s):  
Microcystis Aeruginosa ◽  
Unicellular Cyanobacterium

scholarly journals Immunocytochemical localization of actin in epithelial cells of rat small intestine by light and electron microscopy.

1988 ◽  
Vol 36 (7) ◽  
pp. 717-727 ◽  
Author(s):  
S J Hagen ◽  
J S Trier
Keyword(s):  
Electron Microscopy ◽  
Small Intestine ◽  
Epithelial Cells ◽  
Light And Electron Microscopy ◽  
Basal Membrane ◽  
Ground Substance ◽  
Structural Protein ◽  
Thin Sections ◽  
Filament Bundles ◽  
Lowicryl K4m

We used post-embedding immunocytochemical techniques and affinity-purified anti-actin antibody to evaluate localization of actin in epithelial cells of small intestine by fluorescence and electron microscopy. Small intestine was fixed with 2% formaldehyde-0.1% glutaraldehyde and embedded in Lowicryl K4M. One-micron or thin sections were stained with antibody followed by rhodamine- or colloidal gold-labeled goat anti-rabbit IgG, respectively. Label was present overlying microvilli, the apical terminal web, and the cytoplasm directly adjacent to occluding and intermediate junctions. Label was associated with outer mitochondrial membranes of all cells and the supranuclear Golgi region of goblet cells. Lateral cytoplasmic interdigitations between mature cells and subplasmalemmal filaments next to intrusive cells were densely labeled. The cytoplasm adjacent to unplicated domains of lateral membrane was focally labeled. Label was prominent over organized filament bundles within the subplasmalemmal web at the base of mature cells, whereas there was focal labeling of the cytoplasm adjacent to the basal membrane of undifferentiated cells. Basolateral epithelial cell processes were labeled. Label was focally present overlying the cellular ground substance. Our results demonstrate that actin is distributed in a distinctive fashion within intestinal epithelial cells. This distribution suggests that in addition to its function as a structural protein, actin may participate in regulation of epithelial tight junction permeability, in motile processes including migration of cells from the crypt to the villus tip, in accommodation of intrusive intraepithelial cells and in adhesion of cells to one another and to their substratum.

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