Modification of Salmonella Lipopolysaccharides Prevents the Outer Membrane Penetration of Novobiocin

Nobre, Thatyane M.; Martynowycz, Michael W.; Andreev, Konstantin; Kuzmenko, Ivan; Nikaido, Hiroshi; Gidalevitz, David

doi:10.1016/j.bpj.2015.10.013

Cited by 30 publications

(35 citation statements)

References 38 publications

(54 reference statements)

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“…LPS and mLPS monolayers on Dulbecco's phosphate-buffered saline displayed structural characteristics similar to those detailed earlier in pure water (see the Supporting Information). 26 The limiting area per lipid was determined using the Langmuir isotherm as previously described and found to be 130 ± 5 Å 2 for LPS and 175 ± 5 Å 2 for mLPS. We created a simplified model of the LPS mololayer based on the electron density we derived from our specular X-ray reflectivity measurements ( Figure 2).…”

Section: Lps Structurementioning

confidence: 99%

Salmonella Membrane Structural Remodeling Increases Resistance to Antimicrobial Peptide LL-37

et al. 2019

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Gram-negative bacteria are protected from their environment by an outer membrane that is primarily composed of lipopolysaccharides (LPSs). Under stress, pathogenic serotypes of Salmonella enterica remodel their LPSs through the PhoPQ two-component regulatory system that increases resistance to both conventional antibiotics and antimicrobial peptides (AMPs). Acquired resistance to AMPs is contrary to the established narrative that AMPs circumvent bacterial resistance by targeting the general chemical properties of membrane lipids. However, the specific mechanisms underlying AMP resistance remain elusive. Here we report a 2-fold increase in bacteriostatic concentrations of human AMP LL-37 for S. enterica with modified LPSs. LPSs with and without chemical modifications were isolated and investigated by Langmuir films coupled with grazing-incidence X-ray diffraction (GIXD) and specular X-ray reflectivity (XR). The initial interactions between LL-37 and LPS bilayers were probed using all-atom molecular dynamics simulations. These simulations suggest that initial association is nonspecific to the type of LPS and governed by hydrogen bonding to the LPS outer carbohydrates. GIXD experiments indicate that the interactions of the peptide with monolayers reduce the number of crystalline domains but greatly increase the typical domain size in both LPS isoforms. Electron densities derived from XR experiments corroborate the bacteriostatic values found in vitro and indicate that peptide intercalation is reduced by LPS modification. We hypothesize that defects at the liquid-ordered boundary facilitate LL-37 intercalation into the outer membrane, whereas PhoPQ-mediated LPS modification protects against this process by having innately increased crystallinity. Since induced ordering has been observed with other AMPs and drugs, LPS modification may represent a general mechanism by which Gram-negative bacteria protect against host innate immunity.

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Section: Lps Structurementioning

confidence: 99%

Salmonella Membrane Structural Remodeling Increases Resistance to Antimicrobial Peptide LL-37

et al. 2019

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“…The charged TMCL head groups favor interacting with divalent calcium ions instead with the monovalent cesium ions. Therefore, a second set of experiments has been conducted with the addition of 0.1 mM ethylenediaminetetraacetic acid (EDTA) to the subphase containing 1 mM cesium ions in order to bind the competing calcium ions . In the calcium complex, EDTA is a tetradentate ligand, and chelation involves the two nitrogen atoms and two oxygen atoms in separate carboxyl groups.…”

Section: Resultsmentioning

confidence: 99%

The Influence of Calcium Traces in Ultrapure Water on the Lateral Organization in Tetramyristoyl Cardiolipin Monolayers

2019

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Cardiolipin (CL) plays an important role in administering the structural organization of biological membranes and therefore helps maintaining the integer membrane functionality. CL has a dimeric structure consisting of four acyl chains and two phosphate groups. With its unusual structure, the phospholipid is responsible for curvature formation in CL containing biological membranes. The acidic properties of the phosphate head groups are still not sufficiently investigated since there are controversial results in literature. The main aim of this work was to gain deeper insights into the influence of the pH on the ionization degree of CL. During the experiments, it became clear that the used ultrapure water contained traces of calcium. These unexpected calcium ions had a major impact on the behavior of CL monolayers. Therefore, the focus was put on the analysis of CL layers without and with EDTA in the subphase used to complex divalent calcium ions. For the analyses, traditional surface pressure (π) – molecular area (A) isotherm experiments combined with total reflection x‐ray fluorescence (TRXF) and grazing incidence x‐ray diffraction (GIXD) have been used.

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“…This approach has been recently applied for studying membrane interaction mechanisms by antimicrobial peptide mimics (41,(42)(43)(44), lipopolysaccharide permeability in Salmonella spp. (45,46), and surface catalysis (47).…”

Section: Methodsmentioning

confidence: 99%

Subphase Material Stabilizes Films of Pulmonary Surfactant

Andreev

Martynowycz

Kuzmenko

et al. 2020

Preprint

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When compressed by the shrinking alveolar surface area during exhalation, films of pulmonary surfactant in situ reduce surface tension to levels, at which surfactant monolayers collapse from the surface in vitro. Vesicles of pulmonary surfactant added below these monolayers slow collapse. X-ray scattering here determined the structural changes that improve stability. Grazing incidence X-ray diffraction on monolayers of extracted calf surfactant detected an ordered phase.Mixtures of dipalmitoyl phosphatidylcholine and cholesterol, but not the phospholipid alone, mimic that structure. At concentrations that stabilize the monolayers, vesicles in the subphase had no effect on the unit cell, and the film remained monomolecular. The added vesicles, however, produced a concentration-dependent increase in the diffracted intensity. These results suggest that the enhanced resistance to collapse results from components of an ordered interfacial phase which partition from subphase to the surface, increasing the area of the ordered structure. SIGNIFICANCELow alveolar surface tensions are essential for maintaining the integrity of the pulmonary air-sacks during normal breathing. Films of pulmonary surfactant cause the low tensions. The interfacial structures required for the low surface tensions remain uncertain. These studies used X-ray scattering to determine the initial structure of pulmonary surfactant monolayers, and to establish how vesicles of pulmonary surfactant enhance the ability of those initial monolayers to sustain low tensions. The initial monolayers contained ordered structures that differ from the crystalline forms widely speculated to occur in alveolar films. The added vesicles had no effect on the local structure of the initial monolayer, but substantially increased the area of the ordered regions. This structural change reasonably explains the functional improvement.

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Modification of Salmonella Lipopolysaccharides Prevents the Outer Membrane Penetration of Novobiocin

Cited by 30 publications

References 38 publications

Salmonella Membrane Structural Remodeling Increases Resistance to Antimicrobial Peptide LL-37

Salmonella Membrane Structural Remodeling Increases Resistance to Antimicrobial Peptide LL-37

The Influence of Calcium Traces in Ultrapure Water on the Lateral Organization in Tetramyristoyl Cardiolipin Monolayers

Subphase Material Stabilizes Films of Pulmonary Surfactant

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