Molecular organization of the outer membrane of Salmonella typhimurium different release of lipopolysaccharide from wild type and lipopolysaccharide mutant cells by EDTA treatment

1980 ◽  
Vol 124 (1) ◽  
pp. 69-71 ◽  
Author(s):  
Jobst Gmeiner ◽  
Hildegard Bergmann ◽  
Siegfried Schlecht
Keyword(s):  
Salmonella Typhimurium ◽  
Outer Membrane ◽  
Molecular Organization ◽  
Wild Type ◽  
Edta Treatment ◽  
Mutant Cells

scholarly journals Extracellular Reduction of Hexavalent Chromium by Cytochromes MtrC and OmcA of Shewanella oneidensis MR-1

2011 ◽  
Vol 77 (12) ◽  
pp. 4035-4041 ◽  
Author(s):  
Sara M. Belchik ◽  
David W. Kennedy ◽  
Alice C. Dohnalkova ◽  
Yuanmin Wang ◽  
Papatya C. Sevinc ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Extracellular Matrix ◽  
Outer Membrane ◽  
Initial Rate ◽  
Mutant Cell ◽  
Shewanella Oneidensis ◽  
Wild Type ◽  
Content Type ◽  
Transmission Electron ◽  
Mutant Cells

ABSTRACTTo characterize the roles of cytochromes MtrC and OmcA ofShewanella oneidensisMR-1 in Cr(VI) reduction, the effects of deleting themtrCand/oromcAgene on Cr(VI) reduction and the cellular locations of reduced Cr(III) precipitates were investigated. Compared to the rate of reduction of Cr(VI) by the wild type (wt), the deletion ofmtrCdecreased the initial rate of Cr(VI) reduction by 43.5%, while the deletion ofomcAor bothmtrCandomcAlowered the rate by 53.4% and 68.9%, respectively. In wt cells, Cr(III) precipitates were detected by transmission electron microscopy in the extracellular matrix between the cells, in association with the outer membrane, and inside the cytoplasm. No extracellular matrix-associated Cr(III) precipitates, however, were found in the cytochrome mutant cell suspension. In mutant cells without either MtrC or OmcA, most Cr(III) precipitates were found in association with the outer membrane, while in mutant cells lacking both MtrC and OmcA, most Cr(III) precipitates were found inside the cytoplasm. Cr(III) precipitates were also detected by scanning election microscopy on the surfaces of the wt and mutants without MtrC or OmcA but not on the mutant cells lacking both MtrC and OmcA, demonstrating that the deletion ofmtrCandomcAdiminishes the extracellular formation of Cr(III) precipitates. Furthermore, purified MtrC and OmcA reduced Cr(VI) with apparentkcatvalues of 1.2 ± 0.2 (mean ± standard deviation) and 10.2 ± 1 s−1andKmvalues of 34.1 ± 4.5 and 41.3 ± 7.9 μM, respectively. Together, these results consistently demonstrate that MtrC and OmcA are the terminal reductases used byS. oneidensisMR-1 for extracellular Cr(VI) reduction where OmcA is a predominant Cr(VI) reductase.

Permeability of lipopolysaccharide-deficient (rough) mutants of Salmonella typhimurium to antibiotics, lysozyme, and other agents

1974 ◽  
Vol 20 (8) ◽  
pp. 1135-1145 ◽  
Author(s):  
K. E. Sanderson ◽  
T. MacAlister ◽  
J. W. Costerton ◽  
K.-J. Cheng
Keyword(s):  
Salmonella Typhimurium ◽  
Outer Membrane ◽  
Major Part ◽  
Actinomycin D ◽  
Cell Envelope ◽  
Inhibitory Effects ◽  
Large Molecules ◽  
Edta Treatment ◽  
Growth Inhibitory ◽  
Toxic Agents

Six mutants of Salmonella typhimurium LT2 with defects in the heptose region of the lipopolysaccharide (LPS) ("rough" mutants) were more sensitive to the growth-inhibitory effects of erythromycin, bacitracin, vancomycin, novobiocin, kanamycin, and cloxacillin and of deoxycholate than smooth strains, but less sensitive to tetracycline and ampicillin. In general, growth of the three rough mutants of chemotype Rd2, which lack the distal but not the proximal heptose unit in the LPS, was less inhibited than the three mutants of chemotype Re, which are heptose-deficient. In addition, inhibition of uracil-1-14C incorporation in the presence of actinomycin D and spheroplast formation in the presence of lysozyme occurred in the rough mutants without ethylenediaminetetraacetate (EDTA) treatment of the cells, while actinomycin D and lysozyme were effective on smooth strains only after EDTA treatment. Since the major part of the LPS is in the outer membrane of the cell envelope, and since the target of the toxic agents used is located inside this layer, these data indicate that the carbohydrate part of the LPS component of the outer membrane is an essential part of a barrier layer preventing penetration of large molecules.

scholarly journals Regulation of mitochondrial morphology and inheritance by Mdm10p, a protein of the mitochondrial outer membrane.

1994 ◽  
Vol 126 (6) ◽  
pp. 1361-1373 ◽  
Author(s):  
L F Sogo ◽  
M P Yaffe
Keyword(s):  
Outer Membrane ◽  
Yeast Cells ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Morphology ◽  
Wild Type ◽  
Giant Mitochondria ◽  
Mitochondrial Distribution ◽  
Rapid Restoration ◽  
Mutant Phenotypes ◽  
Mutant Cells

Yeast cells with the mdm10 mutation possess giant spherical mitochondria and are defective for mitochondrial inheritance. The giant mitochondria display classical features of mitochondrial ultrastructure, yet they appear incapable of movement or division. Genetic analysis indicated that the mutant phenotypes resulted from a single nuclear mutation, and the isolated MDM10 gene restored wild-type mitochondrial distribution and morphology when introduced into mutant cells. MDM10 encodes a protein of 56.2 kD located in the mitochondrial outer membrane. Depletion of Mdm10p from cells led to a condensation of normally extended, tubular mitochondria into giant spheres, and reexpression of the protein resulted in a rapid restoration of normal mitochondrial morphology. These results demonstrate that Mdm10p can control mitochondrial morphology, and that it plays a role in the inheritance of mitochondria.

Isolation and characterization of hemin-permeable, envelope-defective mutants of Salmonella typhimurium

1981 ◽  
Vol 27 (2) ◽  
pp. 226-237 ◽  
Author(s):  
Janice J. Janzer ◽  
Helga Stan-Lotter ◽  
Kenneth E. Sanderson
Keyword(s):  
Salmonella Typhimurium ◽  
Outer Membrane ◽  
Aminolevulinic Acid ◽  
Gentian Violet ◽  
Protein Pattern ◽  
Outer Membrane Proteins ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Wild Type ◽  
Isolation And Characterization

From Salmonella typhimurium LT2 hemA (δ-aminolevulinic acid requiring) 15 mutants were isolated which grew on the hydrophobic compound hemin. All had increased sensitivity to antibiotics such as vancomycin, bacitracin, novobiocin, erythromycin, rifampin, and oleandomycin, and were considered to be envelope mutants (Env−). Half the mutants were rough, based on altered bacteriophage sensitivity and deoxycholate sensitivity, whereas the remainder were smooth; three of the smooth mutants were studied in detail. They gave increased uptake of gentian violet but no increase in leakage of a periplasmic protein, RNase I. The total membranes and fractions from sucrose gradient centrifugations representing inner and outer membranes of the wild type and three mutants were examined by sodium dodecyl sulfate – polyacrylamide gel electrophoresis (SDS–PAGE) and isoelectric focussing – PAGE (IEF–PAGE). The major outer membrane proteins (molecular weights (MW)33 000, 34 000, 35 000, and 36 000) showed no or very little alterations in the Env− mutants. In SA1926 (env-52) one protein spot at MW 48 000, proven to be an outer membrane protein, was missing, whereas a new spot appeared nearby, and other proteins in this area of the gel were reduced. An Env+ transductant selected from this strain had the wild-type protein pattern restored. The two other Env− mutants had similar but not identical changes in protein composition.

scholarly journals Outer membrane protein A (OmpA) deficient Salmonella Typhimurium displays enhanced susceptibility towards β-lactam antibiotics: third-generation cephalosporins (ceftazidime) and carbapenems (meropenem)

2022 ◽  
Author(s):  
Atish Roy Chowdhury ◽  
Debapriya Mukherjee ◽  
Ashish Kumar Singh ◽  
Dipshikha Chakravortty
Keyword(s):  
Antimicrobial Resistance ◽  
Salmonella Typhimurium ◽  
Outer Membrane ◽  
Relative Proportion ◽  
Protein A ◽  
Sub Saharan Africa ◽  
Wild Type ◽  
Severe Problem ◽  
Sub Saharan

The invasive non-typhoidal serovar of Salmonella enterica, namely Salmonella Typhimurium ST313, causes bloodstream infection in sub-Saharan Africa. Like other bacterial pathogens, the development of antimicrobial resistance is a severe problem in curing non-typhoidal Salmonella infection. In this work, we have investigated the role of four prominent outer membrane porins of S. Typhimurium, namely OmpA, OmpC, OmpD, and OmpF, in resistance against broad-spectrum β-lactam antibiotics- ceftazidime and meropenem. We found that deleting OmpA from Salmonella makes the bacteria susceptible to β-lactam drugs. The MIC for both the antibiotics reduced significantly for STM ΔompA compared to the wild-type and the ompA complemented strains. Despite the presence of antibiotics, the uninterrupted growth of STM ΔompC, ΔompD, and ΔompF endorsed the dispensability of these three porins in antimicrobial resistance. The β-lactam antibiotics caused massive depolarization in the outer membrane of the bacteria in the absence of OmpA. We have proved that none of the extracellular loops but the complete structure of perfectly folded OmpA is required by the bacteria for developing antimicrobial resistance. Our data revealed that STM ΔompA consumed more antibiotics than the wild-type and the complemented strain, resulting in severe damage of the bacterial outer membrane and subsequent killing of the pathogen by antibiotic-mediated oxidative stress. Upon deleting ompA, the steady decrease in the relative proportion of antibiotic-resistant persisters and the clearance of the STM ΔompA from the liver and spleen of C57BL/6 mice upon treatment with ceftazidime proved the role of OmpA in rendering protection against β-lactam antibiotics.

Ultrastructure and Morphology of the Neurospora Crassa Cell Wall Mutants, Slime And Slime X, Using Tem and Sem

1976 ◽  
Vol 34 ◽  
pp. 54-55
Author(s):  
Karen S. Howard ◽  
H. D. Braymer ◽  
M. D. Socolofsky ◽  
S. A. Milligan
Keyword(s):  
Cell Wall ◽  
Neurospora Crassa ◽  
Wild Type ◽  
Morphological Comparison ◽  
Small Areas ◽  
Solid Media ◽  
Thin Sectioning ◽  
X Cells ◽  
Mutant Cells ◽  
Isolated Cell

The recently isolated cell wall mutant slime X of Neurospora crassa was prepared for ultrastructural and morphological comparison with the cell wall mutant slime. The purpose of this article is to discuss the methods of preparation for TEM and SEM observations, as well as to make a preliminary comparison of the two mutants.TEM: Cells of the slime mutant were prepared for thin sectioning by the method of Bigger, et al. Slime X cells were prepared in the same manner with the following two exceptions: the cells were embedded in 3% agar prior to fixation and the buffered solutions contained 5% sucrose throughout the procedure.SEM: Two methods were used to prepare mutant and wild type Neurospora for the SEM. First, single colonies of mutant cells and small areas of wild type hyphae were cut from solid media and fixed with OSO4 vapors similar to the procedure used by Harris, et al. with one alteration. The cell-containing agar blocks were dehydrated by immersion in 2,2-dimethoxypropane (DMP).

scholarly journals The role of Zur-regulated lipoprotein A in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles in Acinetobacter baumannii

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nayeong Kim ◽  
Hyo Jeong Kim ◽  
Man Hwan Oh ◽  
Se Yeon Kim ◽  
Mi Hyun Kim ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Mutant Strain ◽  
Antimicrobial Susceptibility ◽  
Type Strain ◽  
Wild Type Strain ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Wild Type ◽  
Bacterial Morphology

Abstract Background Zinc uptake-regulator (Zur)-regulated lipoprotein A (ZrlA) plays a role in bacterial fitness and overcoming antimicrobial exposure in Acinetobacter baumannii. This study further characterized the zrlA gene and its encoded protein and investigated the roles of the zrlA gene in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles (OMVs) in A. baumannii ATCC 17978. Results In silico and polymerase chain reaction analyses showed that the zrlA gene was conserved among A. baumannii strains with 97–100% sequence homology. Recombinant ZrlA protein exhibited a specific enzymatic activity of D-alanine-D-alanine carboxypeptidase. Wild-type A. baumannii exhibited more morphological heterogeneity than a ΔzrlA mutant strain during stationary phase. The ΔzrlA mutant strain was more susceptible to gentamicin than the wild-type strain. Sizes and protein profiles of OMVs were similar between the wild-type and ΔzrlA mutant strains, but the ΔzrlA mutant strain produced 9.7 times more OMV particles than the wild-type strain. OMVs from the ΔzrlA mutant were more cytotoxic in cultured epithelial cells than OMVs from the wild-type strain. Conclusions The present study demonstrated that A. baumannii ZrlA contributes to bacterial morphogenesis and antimicrobial resistance, but its deletion increases OMV production and OMV-mediated host cell cytotoxicity.

scholarly journals EPHA2-dependent outcompetition of KRASG12D mutant cells by wild-type neighbors in the adult pancreas

2021 ◽  
Author(s):  
William Hill ◽  
Andreas Zaragkoulias ◽  
Beatriz Salvador-Barbero ◽  
Geraint J. Parfitt ◽  
Markella Alatsatianos ◽  
...  
Keyword(s):  
Wild Type ◽  
Mutant Cells
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