Flowering poration – a synergistic multi-mode antibacterial mechanism by a bacteriocin fold

Bacteriocins are a distinct family of antimicrobial proteins postulated to porate bacterial membranes. However, direct experimental evidence of pore formation by these proteins is lacking. Here we report a multi-mode poration mechanism induced by four-helix bacteriocins, epidermicin NI01 and aureocin A53. Using a combination of crystallography, spectroscopy, bioassays and nanoscale imaging, we established that individual two-helix segments of epidermicin retain antibacterial activity but each of these segments adopts a particular poration mode. In the intact protein these segments act synergistically to balance out antibacterial and hemolytic activities. The study sets a precedent of multi-mode membrane disruption advancing the current understanding of structure-activity relationships in pore-forming proteins

Silver nanoparticle embedded copper oxide as an efficient core–shell for the catalytic reduction of 4-nitrophenol and antibacterial activity improvement

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Different Dose-Dependent Modes of Action of C-Type Natriuretic Peptide on Pseudomonas aeruginosa Biofilm Formation.

We have previously shown that the C-type Natriuretic Peptide (CNP), a peptide produced by lungs, is able to impact Pseudomonasaeruginosa physiology. In the present work, the effect of CNP at different concentrations on P. aeruginosa biofilm formation was studied and the mechanisms of action of this human hormone on P. aeruginosa were deciphered. CNP was shown to inhibit dynamic biofilm formation in a dose-dependent manner without affecting the bacterial growth at any tested concentrations. The most effective concentrations were 1 and 0.1 µM. At 0.1 µM, the biofilm formation inhibition was fully dependent on the CNP sensor protein AmiC, whereas it was only partially AmiC-dependent at 1 µM, revealing the existence of a second AmiC-independent mode of action of CNP on P. aeruginosa. At 1 µM, CNP reduced both P. aeruginosa adhesion on glass and di-rhamnolipid production and also increased the bacterial membrane fluidity. The various effects of CNP at 1 µM and 0.1 µM on P. aeruginosa shown here should have major consequences to design drugs for biofilm treatment or prevention

Pseudomonas aeruginosa Biofilm Dispersion by the Human Atrial Natriuretic Peptide

This is the final version. Available on open access from Wiley via the DOI in this recordData Availability Statement: The data that support the findings of this study are available from the corresponding author upon reasonable request.Pseudomonas aeruginosa biofilms cause chronic, antibiotic tolerant infections in wounds and lungs. Numerous recent studies demonstrate that bacteria can detect human communication compounds through specific sensor/receptor tools that modulate bacterial physiology. Consequently, interfering with these mechanisms offers an exciting opportunity to directly affect the infection process. It is shown that the human hormone Atrial Natriuretic Peptide (hANP) both prevents the formation of P. aeruginosa biofilms and strongly disperses established P. aeruginosa biofilms. This hANP action is dose-dependent with a strong effect at low nanomolar concentrations and takes effect in 30-120 min. Furthermore, although hANP has no antimicrobial effect, it acts as an antibiotic adjuvant. hANP enhances the antibiofilm action of antibiotics with diverse modes of action, allowing almost full biofilm eradication. The hANP effect requires the presence of the P. aeruginosa sensor AmiC and the AmiR antiterminator regulator, indicating a specific mode of action. These data establish the activation of the ami pathway as a potential mechanism for P. aeruginosa biofilm dispersion. hANP appears to be devoid of toxicity, does not enhance bacterial pathogenicity, and acts synergistically with antibiotics. These data show that hANP is a promising powerful antibiofilm weapon against established P. aeruginosa biofilms in chronic infections.Normandy RegionFrench Ministry of Research (MRE

Prediction of Bacillus weihenstephanensis acid resistance: The use of gene expression patterns to select potential biomarkers

Exposure to mild stress conditions can activate stress adaptation mechanisms and provide cross-resistance towards otherwise lethal stresses. In this study, an approach was followed to select molecular biomarkers (quantitative gene expressions) to predict induced acid resistance after exposure to various mild stresses, i.e. exposure to sublethal concentrations of salt, acid and hydrogen peroxide during 5 min to 60 min. Gene expression patterns of unstressed and mildly stressed cells of Bacillus weihenstephanensis were correlated to their acid resistance (3D value) which was estimated after exposure to lethal acid conditions. Among the twenty-nine candidate biomarkers, 12 genes showed expression patterns that were correlated either linearly or non-linearly to acid resistance, while for the 17 other genes the correlation remains to be determined. The selected genes represented two types of biomarkers, (i) four direct biomarker genes (lexA, spxA, narL, bkdR) for which expression patterns upon mild stress treatment were linearly correlated to induced acid resistance; and (ii) nine long-acting biomarker genes (spxA, BcerKBAB4_0325, katA, trxB, codY, lacI, BcerKBAB4_1716, BcerKBAB4_2108, relA) which were transiently up-regulated during mild stress exposure and correlated to increased acid resistance over time. Our results highlight that mild stress induced transcripts can be linearly or non-linearly correlated to induced acid resistance and both approaches can be used to find relevant biomarkers. This quantitative and systematic approach opens avenues to select cellular biomarkers that could be incremented in mathematical models to predict microbial behaviour. Keywords: Bacillus; Acid resistance; Gene expression; Modelling; Biomarker; Food safet

The hormone C-type natriuretic peptide (CNP) effects on P. aeruginosa: a new natural weapon against biofilm formation

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The lung hormone C-type natriuretic peptide (CNP) modifies Pseudomonas aeruginosa virulence and biofilm formation: Mechanism of action and involvement of the ami operon.

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The involvement of the ami operon in Pseudomonas aeruginosa virulence regulation and biofilm formation reveals new functions for the amidase AmiE

International audienceWe have previously shown that the C-type Natriuretic Peptide (CNP), a peptide produced by the lung, prevents Pseudomonas aeruginosa biofilm formation. In the present study, we identified AmiC as the bacterial target explaining CNP effects, and we studied the involvement of the aliphatic amidase AmiE in these effects. Comparison of 3D structures of human natriuretic peptide receptors and Pseudomonas proteins revealed that the bacterial protein AmiC shows significant similarity with the human C-type natriuretic peptide receptor (hNPR-C). Recombinant protein AmiC was purified and protein/peptide interactions assessed using MicroScale Thermophoresis. Results showed that both CNP and hNPR-C agonists bind the AmiC protein. The amiC gene belongs to the ami operon. This operon also encodes the aliphatic amidase AmiE which hydrolyses short-chain aliphatic amides to their corresponding organic acids. We investigated AmiE potential alternative functions in P. aeruginosa. We observed that over expression of AmiE protein altered biofilm formation, bacterial motilities and quorum sensing molecules production. Using several infection models, we demonstrated that AmiE overproduction led to a strong decrease in P. aeruginosa virulence both in vitro and in vivo, suggesting that in addition to its carbon-nitrogen metabolic process activities, AmiE would have multiple other functions. We demonstrate that the bacterial protein AmiC is an ortholog of the eukaryotic receptor hNPR-C, acting as a CNP sensor in P. aeruginosa. Our data show that the whole ami operon has new functions in bacteria, allowing to modulate the switch between chronic and acute infection depending on exposition to host factors

The involvement of the ami operon in Pseudomonas aeruginosa virulence regulation and biofilm formation reveals new functions for the amidase AmiE

International audienceWe have previously shown that the C-type Natriuretic Peptide (CNP), a peptide produced by the lung, prevents Pseudomonas aeruginosa biofilm formation. In the present study, we identified AmiC as the bacterial target explaining CNP effects, and we studied the involvement of the aliphatic amidase AmiE in these effects. Comparison of 3D structures of human natriuretic peptide receptors and Pseudomonas proteins revealed that the bacterial protein AmiC shows significant similarity with the human C-type natriuretic peptide receptor (hNPR-C). Recombinant protein AmiC was purified and protein/peptide interactions assessed using MicroScale Thermophoresis. Results showed that both CNP and hNPR-C agonists bind the AmiC protein. The amiC gene belongs to the ami operon. This operon also encodes the aliphatic amidase AmiE which hydrolyses short-chain aliphatic amides to their corresponding organic acids. We investigated AmiE potential alternative functions in P. aeruginosa. We observed that over expression of AmiE protein altered biofilm formation, bacterial motilities and quorum sensing molecules production. Using several infection models, we demonstrated that AmiE overproduction led to a strong decrease in P. aeruginosa virulence both in vitro and in vivo, suggesting that in addition to its carbon-nitrogen metabolic process activities, AmiE would have multiple other functions. We demonstrate that the bacterial protein AmiC is an ortholog of the eukaryotic receptor hNPR-C, acting as a CNP sensor in P. aeruginosa. Our data show that the whole ami operon has new functions in bacteria, allowing to modulate the switch between chronic and acute infection depending on exposition to host factors

Fraction volumique de la phase dispersée, acides organiques et Tween80 dans une émulsion modèle: effet sur la germination et la croissance de spores de bactéries weihenstephanensis KBAB4

International audienceIn foodstuffs, physico-chemical interactions and/or physical constraints between spores, inhibitors and food components may exist. Thus, the objective of this study was to investigate such interactions using a model emulsion as a microbial medium in order to improve bacterial spore control with better knowledge of the interactions in the formulation.Emulsions were prepared with hexadecane mixed with nutrient broth using sonication and were stabilized by Tween 80 and Span 80. The hexadecane ratio was either 35% (v/v) or 50% (v/v) and each emulsion was studied in the presence of organic acid (acetic, lactic or hexanoic) at two pH levels (5.5 and 6). Self-diffusion coefficients of emulsion components and the organic acids were measured by Pulsed Field Gradient-Nuclear Magnetic Resonance (PFG-NMR). The inhibition effect on the spore germination and cell growth of Bacillus weihenstephanensis KBAB4 was characterized by the measure of the probability of growth using the most probable number methodology, and the measure of the time taken for the cells to germinate and grow using a single cell Bioscreen® method and using flow cytometry. The inhibition of spore germination and growth in the model emulsion depended on the dispersed phase volume fraction and the pH value. The effect of the dispersed phase volume fraction was due to a combination of (i) the lipophilicity of the biocide, hexanoic acid, that may have had an impact on the distribution of organic acid between hexadecane and the aqueous phases and (ii) the antimicrobial activity of the emulsifier Tween 80 detected at the acidic pH value. The interface phenomena seemed to have a major influence. Future work will focus on the exploration of these phenomena at the interface