Binding of mutagenic pyrolyzates to fractions of intestinal bacterial cells

1992 ◽  
Vol 38 (7) ◽  
pp. 614-617 ◽  
Author(s):  
Xue Bin Zhang ◽  
Yoshiyuki Ohta
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Outer Membrane ◽  
Bacterial Strain ◽  
Cytoplasmic Membrane ◽  
Intestinal Bacteria ◽  
Bacterial Cells ◽  
Gram Negative ◽  
Membrane Bound ◽  
Cell Fractions

The binding of mutagenic pyrolyzates to cell fractions from some gram-negative intestinal bacteria and to thermally treated bacterial cells was investigated. 3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) were effectively bound by several of the bacterial cells. The cell wall skeletons of all bacteria effectively bound Trp-P-1 and Trp-P-2. Their cytoplasmic fractions retained Trp-P-1 and Trp-P-2, but to a lesser extent than the cell wall skeletons. 2-Amino-3-methylimidazo [4,5-f]quinoline (IQ) was not found in their cytoplasmic fractions. These cell wall skeletons also bound 2-amino-6-methyldipyrido[1,2-a:3′2′-d] imidazole (Glu-P-1), 2-amino-5-phenylpyridine (Phe-P-1), IQ, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQX). The amount of each mutagen bound differed with the type of mutagen and the bacterial strain used. The outer membrane of Escherichia coli IFO 14249 showed binding of about 123.7 μg/mg of Trp-P-2, and its cytoplasmic membrane bound 57.14 μg/mg. Trp-P-2 bound to the bacterial cells was extracted with ammonia (5%), methanol, and ethanol but not with water. Key words: cell wall skeletons, outer membrane, cytoplasmic membrane, binding of mutagenic pyrolyzates.

scholarly journals Novel Antibacterial Targets and Compounds Revealed by a High-Throughput Cell Wall Reporter Assay

2015 ◽  
Vol 197 (10) ◽  
pp. 1726-1734 ◽  
Author(s):  
Asha S. Nayar ◽  
Thomas J. Dougherty ◽  
Keith E. Ferguson ◽  
Brett A. Granger ◽  
Lisa McWilliams ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Outer Membrane ◽  
High Throughput ◽  
Cell Envelope ◽  
Mechanisms Of Action ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Phenotypic Screen

ABSTRACTA high-throughput phenotypic screen based on aCitrobacter freundiiAmpC reporter expressed inEscherichia coliwas executed to discover novel inhibitors of bacterial cell wall synthesis, an attractive, well-validated target for antibiotic intervention. Here we describe the discovery and characterization of sulfonyl piperazine and pyrazole compounds, each with novel mechanisms of action.E. colimutants resistant to these compounds display no cross-resistance to antibiotics of other classes. Resistance to the sulfonyl piperazine maps to LpxH, which catalyzes the fourth step in the synthesis of lipid A, the outer membrane anchor of lipopolysaccharide (LPS). To our knowledge, this compound is the first reported inhibitor of LpxH. Resistance to the pyrazole compound mapped to mutations in either LolC or LolE, components of the essential LolCDE transporter complex, which is required for trafficking of lipoproteins to the outer membrane. Biochemical experiments withE. colispheroplasts showed that the pyrazole compound is capable of inhibiting the release of lipoproteins from the inner membrane. Both of these compounds have significant promise as chemical probes to further interrogate the potential of these novel cell wall components for antimicrobial therapy.IMPORTANCEThe prevalence of antibacterial resistance, particularly among Gram-negative organisms, signals a need for novel antibacterial agents. A phenotypic screen using AmpC as a sensor for compounds that inhibit processes involved in Gram-negative envelope biogenesis led to the identification of two novel inhibitors with unique mechanisms of action targetingEscherichia coliouter membrane biogenesis. One compound inhibits the transport system for lipoprotein transport to the outer membrane, while the other compound inhibits synthesis of lipopolysaccharide. These results indicate that it is still possible to uncover new compounds with intrinsic antibacterial activity that inhibit novel targets related to the cell envelope, suggesting that the Gram-negative cell envelope still has untapped potential for therapeutic intervention.

Ultrastructure of the cell wall and the mechanism of cellular division of a Gram-variable coccus

1971 ◽  
Vol 17 (3) ◽  
pp. 421-424 ◽  
Author(s):  
H. E. Gilleland Jr. ◽  
I. L. Roth ◽  
R. G. Eagon
Keyword(s):  
Cell Wall ◽  
Outer Membrane ◽  
Ultrastructural Study ◽  
Cytoplasmic Membrane ◽  
Gram Positive ◽  
Cellular Division ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Isolated Cell ◽  
Peptidoglycan Layer

An ultrastructural study of a Gram-variable coccus was carried out. The cell wall of this microorganism was composed of an inner peptidoglycan layer, a middle electron-transparent compartment, and an undulating trilayered outer membrane. This microorganism also possessed numerous mesosomes which were simple bulb-like invaginations of the cytoplasmic membrane. The mechanism of cellular division involved the formation of a septum by the cytoplasmic membrane and the inner layer of the cell wall. Membranous structures were associated with the developing septum throughout the process. The outer membrane of the cell wall did not invaginate with the inner layer but reformed as the completed septum began to split. In isolated cell wall preparations, no 2-keto-3-deoxyoctonate or heptose could be detected. It is suggested that the Gram-variable cocci previously classified as micrococci may represent a group that is intermediate between true Gram-negative and Gram-positive bacteria.

scholarly journals MexAB-OprM Efflux Pump Interaction with the Peptidoglycan of Escherichia coli and Pseudomonas aeruginosa

2021 ◽  
Vol 22 (10) ◽  
pp. 5328
Author(s):  
Miao Ma ◽  
Margaux Lustig ◽  
Michèle Salem ◽  
Dominique Mengin-Lecreulx ◽  
Gilles Phan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Cell Division ◽  
Membrane Proteins ◽  
Outer Membrane ◽  
Efflux Pump ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Active Efflux

One of the major families of membrane proteins found in prokaryote genome corresponds to the transporters. Among them, the resistance-nodulation-cell division (RND) transporters are highly studied, as being responsible for one of the most problematic mechanisms used by bacteria to resist to antibiotics, i.e., the active efflux of drugs. In Gram-negative bacteria, these proteins are inserted in the inner membrane and form a tripartite assembly with an outer membrane factor and a periplasmic linker in order to cross the two membranes to expulse molecules outside of the cell. A lot of information has been collected to understand the functional mechanism of these pumps, especially with AcrAB-TolC from Escherichia coli, but one missing piece from all the suggested models is the role of peptidoglycan in the assembly. Here, by pull-down experiments with purified peptidoglycans, we precise the MexAB-OprM interaction with the peptidoglycan from Escherichia coli and Pseudomonas aeruginosa, highlighting a role of the peptidoglycan in stabilizing the MexA-OprM complex and also differences between the two Gram-negative bacteria peptidoglycans.

Sensitivity of normal and mutant strains of Escherichia coli to actinomycin-D

1972 ◽  
Vol 18 (6) ◽  
pp. 909-915 ◽  
Author(s):  
A. P. Singh ◽  
K.-J. Cheng ◽  
J. W. Costerton ◽  
E. S. Idziak ◽  
J. M. Ingram
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Wild Type Strain ◽  
Actinomycin D ◽  
Cytoplasmic Membrane ◽  
Cell Envelope ◽  
Coli Strain ◽  
Wild Type ◽  
Mutant Strains ◽  
In The Wild

The site of the cell barrier to actinomycin-D uptake was studied using a wild-type Escherichia coli strain P and its cell envelope-defective filamentous mutants, strains 6γ and 12γ, both of which 'leak' β-galactosidase and alkaline phosphatase into the medium during growth indicating both membrane and cell-wall defects. Actinomycin-D entered the cells of these two mutant strains as evidenced by the inhibition of both 14C-uracil incorporation and synthesis of the induced β-galactosidase system. Under similar conditions, no inhibition occurred in the wild-type strain and its sucrose-lysozyme prepared spheroplasts. Actinomycin-D did, however, inhibit the above-mentioned systems in the wild-type sucrose-lysozyme spheroplasts prepared in the presence of 2 mM EDTA. The experimental data indicate that although the cell wall may act as a primary barrier or sieve to actinomycin-D, the cytoplasmic membrane should be considered the final and determinative barrier to this antibiotic.

scholarly journals Membrane fusion during phage lysis

2015 ◽  
Vol 112 (17) ◽  
pp. 5497-5502 ◽  
Author(s):  
Manoj Rajaure ◽  
Joel Berry ◽  
Rohit Kongari ◽  
Jesse Cahill ◽  
Ry Young
Keyword(s):  
Membrane Fusion ◽  
Outer Membrane ◽  
Cytoplasmic Membrane ◽  
Bacterial Host ◽  
Inner Membrane ◽  
Gram Negative ◽  
Encoded Proteins ◽  
Coliphage Lambda ◽  
Necessary And Sufficient

In general, phages cause lysis of the bacterial host to effect release of the progeny virions. Until recently, it was thought that degradation of the peptidoglycan (PG) was necessary and sufficient for osmotic bursting of the cell. Recently, we have shown that in Gram-negative hosts, phage lysis also requires the disruption of the outer membrane (OM). This is accomplished by spanins, which are phage-encoded proteins that connect the cytoplasmic membrane (inner membrane, IM) and the OM. The mechanism by which the spanins destroy the OM is unknown. Here we show that the spanins of the paradigm coliphage lambda mediate efficient membrane fusion. This supports the notion that the last step of lysis is the fusion of the IM and OM. Moreover, data are provided indicating that spanin-mediated fusion is regulated by the meshwork of the PG, thus coupling fusion to murein degradation by the phage endolysin. Because endolysin function requires the formation of μm-scale holes by the phage holin, the lysis pathway is seen to require dramatic dynamics on the part of the OM and IM, as well as destruction of the PG.

scholarly journals Endotoxins and the importance of procalcitonin

2019 ◽  
Vol 67 (1) ◽  
pp. 169-170
Author(s):  
Paola Andrea Yasnó-Navia ◽  
Luisa Fernanda Zuñiga-Ceron ◽  
Jhan Sebastián Saavedra-Torres ◽  
María Virginia Pinzón-Fernández
Keyword(s):  
Septic Shock ◽  
Immune Response ◽  
Cell Wall ◽  
Outer Membrane ◽  
Inflammatory Mediators ◽  
Platelet Activating Factor ◽  
Cellular Level ◽  
Lipid Mediators ◽  
The State ◽  
Gram Negative

Gram-negative bacilli and cocci bacteria produce and release endotoxins, which are lipopolysaccharides found in the outer membrane of the cell wall. These endotoxins are responsible for releasing a series of inflammatory mediators such as IL1, TNFα and proteases, as well as lipid mediators such as prostaglandins, leukotrienes, thromboxanes and platelet-activating factor, ultimately activitating immune response cells like leukocytes, macrophages and platelets. These cells amplify the response to shock, generate a procoagulant state and produce alterations at the cellular level, for example, damage to the endothelium, which in the end benefit and worsen the state of septic shock (Figure 1).

scholarly journals Plasticity in Escherichia coli cell wall metabolism promotes fitness and mediates intrinsic antibiotic resistance across environmental conditions

2018 ◽  
Author(s):  
Elizabeth A Mueller ◽  
Petra Anne Levin
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Growth Parameter ◽  
Culture Conditions ◽  
Cell Wall Integrity ◽  
Bacterial Cells ◽  
Intrinsic Resistance ◽  
Wide Range ◽  
Peptidoglycan Cell Wall ◽  
Wide Ph Range

ABSTRACTAlthough the peptidoglycan cell wall is an essential structural and morphological feature of most bacterial cells, the extracytoplasmic enzymes involved in its synthesis are frequently dispensable under standard culture conditions. By modulating a single growth parameter—extracellular pH—we discovered a subset of these so-called “redundant” enzymes in Escherichia coli are required for maximal fitness across pH environments. Among these pH specialists are the class A penicillin binding proteins PBP1 a and PBP1 b; defects in these enzymes attenuate growth in alkaline and acidic conditions, respectively. Genetic, biochemical, and cytological studies demonstrate that synthase activity is required for cell wall integrity across a wide pH range, and differential activity across pH environments significantly alters intrinsic resistance to cell wall active antibiotics. Together, our findings reveal previously thought to be redundant enzymes are instead specialized for distinct environmental niches, thereby ensuring robust growth and cell wall integrity in a wide range of conditions.

scholarly journals The effects of anions on fumarate reductase isolated from the cytoplasmic membrane of Escherichia coli

1981 ◽  
Vol 199 (3) ◽  
pp. 473-477 ◽  
Author(s):  
J J Robinson ◽  
J H Weiner
Keyword(s):  
Escherichia Coli ◽  
Cytoplasmic Membrane ◽  
Chemical Properties ◽  
Fumarate Reductase ◽  
Maximal Velocity ◽  
Nitrobenzoic Acid ◽  
Thiol Reagent ◽  
Membrane Bound ◽  
Physical And Chemical ◽  
And Chemical Properties

A broad range of anions was shown to stimulate the maximal velocity of purified fumarate reductase isolated from the cytoplasmic membrane of Escherichia coli, while leaving the Km for fumarate unaffected. Reducing agents potentiate the effects of anions on the activity, but have no effect by themselves. Thermal stability, conformation as monitored by circular dichroism and susceptibility to the thiol reagent 5,5′-dithiobis-(2-nitrobenzoic acid) are also altered by anions. The apparent Km for succinate in the reverse reaction (succinate dehydrogenase activity) varies as a function of anion concentration, but the maximal velocity is not affected. The membrane-bound activity is not stimulated by anions and its properties closely resemble those of the purified enzyme in the presence of anions. Thus it appears that anions alter the physical and chemical properties of fumarate reductase, so that it more closely resembles the membrane-bound form.

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