Antifungal resistance has become a very serious concern, and
is considered one of the most opportunistic fungal pathogens responsible for several human infections. In this context, the use of new ...antifungal agents such as zinc-based layered double hydroxides to fight such fungal pathogens is considered one possible means to help limit the problem of antifungal resistance. In this study, we show that ZnAl LDH nanoparticles exhibit remarkable antifungal properties against
and cause serious cell wall damage, as revealed by growth tests and atomic force microscopy (AFM) imaging. To further link the antifungal activity of ZnAl LDHs to their adhesive behaviors toward
cells, AFM-based single-cell spectroscopy and single-particle force spectroscopy were used to probe the nanoscale adhesive interactions. The force spectroscopy analysis revealed that antimicrobial ZnAl LDHs exhibit specific surface interactions with
cells, demonstrating remarkable force magnitudes and adhesion frequencies in comparison with non-antifungal negative controls,
, Al-coated substrates and MgAl LDHs, which showed limited interactions with
cells. Force signatures suggest that such adhesive interactions may be attributed to the presence of agglutinin-like sequence (Als) adhesive proteins at the cell wall surface of
cells. Our findings propose the presence of a strong correlation between the antifungal effect provided by ZnAl LDHs and their nanoscale adhesive interactions with
cells at both the single-cell and single-particle levels. Therefore, ZnAl LDHs could interact with
fungal pathogens by specific adhesive interactions through which they adhere to fungal cells, leading to their damage and subsequent growth inhibition.
Series of force-distance profiles obtained by stretching adhesins from various microbial species (see text for details): single adhesion peaks reflecting specific recognition (A), sawtooth patterns ...with multiple force peaks corresponding to the force-induced unfolding of protein secondary structures (B), constant force plateaus originating from the mechanical unzipping of amyloid interactions formed between multiple adhesins (C), and single large adhesion force peaks with linear shapes obtained by pulling on Gram-positive bacterial pili (D). AFM imaging enables microbiologists to decipher the nanoscale architecture of cell surfaces and its remodelling upon growth or interaction with drugs. ...force spectroscopy allows us to understand how cell surface receptors are spatially organized (e.g. clustering) and respond to force (e.g. single specific bonds, sequential unfolding, zipper-like adhesion, and spring-like properties).
We fabricated an electrochemical molecularly imprinted polymer (MIP) chemosensor for rapid identification and quantification of E. coli strain using 2-aminophenyl boronic acid as the functional ...monomer. This strain is a modified Gram-negative strain of Escherichia coli bacterium, an ordinary human gut component. The E. coli strongly interacts with a boronic acid because of porous and flexible polymers of the cell wall. The SEM imaging showed that the bacteria template was partially entrapped within the polymeric matrix in a single step. Moreover, this imaging confirmed E. coli K-12 cell template extraction effectiveness. The prepared MIP determined the E. coli K-12 strain up to 2.9 × 104 cells mL−1. The interference study performed in the presence of E. coli variants expressing different surface appendages (type 1 fimbriae or Antigen 43 protein) or Shewanella oneidensis MR1, another Gram-negative bacteria, demonstrated that the bacterial surface composition notably impacts sensing properties of the bacteria imprinted polymer.
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•E. coli E2152 was successfully imprinted in a polymer by 2-aminophenylboronic acid and aniline co-electropolymerization.•The bacteria template was entrapped in the resulting molecularly imprinted polymer in a single step.•Thus prepared MIP film-based electrochemical chemosensor determined E. coli E2152 up to 2.9 × 104 cells/mL.•E. coli E2152 determination was selective versus bacteria of other surface properties.
Up to recent years, bacterial adhesion has mostly been evaluated at the population level. Single cell level has improved in the past few years allowing a better comprehension of the implication of ...individual behaviors as compared to the one of a whole community. A new approach using atomic force microscopy (AFM) to measure adhesion forces between a live bacterium attached via a silica microbead to the AFM tipless cantilever and the surface has been recently developed. The objectives of this study is to examine the bacterial adhesion to a surface dedicated to ship hulls at the population and the cellular level to understand to what extent these two levels could be correlated. Adhesion of marine bacteria on inert surfaces are poorly studied in particular when substrata are dedicated to ship hulls. Studying these interactions in this context are worthwhile as they may involve different adhesion behaviors, taking place in salty conditions, using different surfaces than the ones usually utilized in the literacy. FRC (fouling release coatings)-SPC (self-polishing coatings) hybrids antifouling coatings have been used as substrata and are of particular interest for designing environmentally friendly surfaces, combining progressive surface erosion and low adhesion properties. In this study, a hybrid coating has been synthetized and used to study the adhesion of three marine bacteria, displaying different surface characteristics, using microplate assays associated with confocal scanning laser microscopy (CSLM) and AFM. This study shows that the bacterial strain that appeared to have the weakest adhesion and biofilm formation abilities when evaluated at the population level using microplates assays and CSLM, displayed stronger adhesion forces on the same surfaces at the single cell level using AFM. In addition, one of the strains tested which presented a strong ability to adhere and to form biofilm at the population level, displayed a heterogeneous phenotypic behavior at the single cell level. Therefore, these results suggest that the evaluation of adhesion at the population level cannot always be correlated with adhesion forces measured individually by AFM and that some bacteria are prone to phenotypic heterogeneity among their population.
Resistance to antimicrobial agents is responsible for major social and economic losses. The World Health Organization estimated 700,000 global deaths a year due to antimicrobial resistance. The use ...of layered double hydroxides (LDHs) as antibacterial materials could present a way to reduce the risk of bacterial infections and antibacterial resistance, by partial release of metallic ions in aqueous dispersion. The partial dissolution of different synthetic LDHs MII-AlIII (M = Zn, Cu, Ni, Co, Mg) was studied in Lysogeny Broth (LB) and Tryptic Soy Broth (TSB), growth media of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, respectively. The influence of several parameters (crystallinity, MII:AlIII ratio, type of intercalated anion {CO32−, Cl−, NO3−, ClO4−} and nature of MII cations) was investigated. In the absence of any post-synthetic hydrothermal treatment, ZnII-AlIII LDH showed a release of ZnII ions 6 times enhanced. Upon increasing ZnII:AlIII molar ratio to 3: 1 and exchanging carbonate anions with other anions having lower intercalating affinities, a similar effect was observed. The dissolution properties of MII-AlIII LDHs were correlated with the thermodynamic stability of their MII(OH)2 hydroxide counterparts with the exception of CuII-based LDH, which showed an amplified release of CuII due to its irregular structure presenting defects. Finally, the antibacterial activity was only noted for ZnII and CuII-based LDHs. The antimicrobial effect of the studied LDHs was linked in the first place to the nature of divalent metal itself, and to the amount of released MII ions into the culture media in the second place. This effect was more easily identified in ZnII-AlIII LDHs whose minimum inhibitory concentration was decreased significantly from 12 to 0.375 mg.mL−1 when higher amounts of ZnII ions were released.
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•LDHs with low crystallinity and many defects release more ions into broth media.•LDHs having intercalating anions with low affinity are more soluble.•Copper LDHs release amplified amounts of CuII due to its defected structure.•The antimicrobial activity of LDHs is primary related to nature of divalent metal.•The antimicrobial effect of Zn LDHs is dependent on the amount of ZnII released.
Freshwater biofilms play an essential ecological role, but they also adversely affect human activities through undesirable biofouling of artificial submerged structures. They form complex aggregates ...of microorganisms that colonize any type of substratum. In phototrophic biofilms, diatoms dominate in biomass and produce copious amount of extracellular polymeric substances (EPSs), making them efficient early colonizers. Therefore, a better understanding of diatoms adhesive properties is essential to develop new anti-biofouling strategies. In this context, we used atomic force microscopy (AFM) to decipher the topography and adhesive mechanisms of the common freshwater diatom Nitzschia palea. Images taken in physiological conditions revealed typical ultrastructural features with a few nanometers resolution. Using single-cell force spectroscopy, we showed that N. palea strongly adheres to hydrophobic surfaces as compared to hydrophilic ones. Chemical force spectroscopy with hydrophobic tips further confirmed that the adhesion is governed by surface-associated hydrophobic EPS distributed in clusters at the frustule surface, and mostly composed of (glyco)-lipids as revealed by Raman spectroscopy. Collectively, our results demonstrate that AFM-based nanoscopy, combined with Raman spectroscopy, is a powerful tool to provide new insights into the adhesion mechanisms of diatoms.
As phages are extensively investigated as novel therapy tools but also as transfer agents for antibiotic resistance genes, thorough understanding of phage—host interactions becomes crucial. ...Prerequisite for phage infection is its adhesion to the host surface. Herein, we used atomic force microscopy-based single-particle force spectroscopy with phage-decorated tips to decipher the adhesion of phage 187 on living
Staphylococcus aureus
cells. We found that addition of free
N
-acetyl-
D
-glucosamine was able to decrease phage adhesion, suggesting that this monosaccharide plays major role in phage 187 infection of
S. aureus
. Moreover, phage 187 adhesion on monosaccharide-coated model surfaces combined with plaque forming unit counts suggested that a direct link can be established between the propensity to bind to a saccharide and the capability of the latter to inhibit phage infection. On a nanoscale level, single-particle force spectroscopy was successfully used to identify a major receptor required for phage 187 infection of
S. aureus
but also evidenced that this receptor was responsible for phage adhesion on host-cells. Our work demonstrates that single-particle force spectroscopy is a powerful platform to screen and predict the molecular target of phages on their host surfaces.
Whey protein concentrate powders can be strongly affected by storage conditions inducing both chemical and structural protein modifications. In the present work, a combination of different storage ...conditions were evaluated, leading to the evaluation of 6 different batches that were chosen in order to evaluate the impact of the following parameters: storage temperature, storage duration and storage heat load (°C.days). In each set the relative humidity was maintained at 70%. To estimate the impact of the three parameters, whey protein lactosylation, denaturation and aggregation were followed. It was shown that the highest temperatures (60 vs 55.5 °C and 41 vs 36 °C) led to greater protein modification, whereas the duration (17 vs 14 days and 33 vs 30 days) and the total heat load (low vs high C°.days) did not affect protein modification. Lactose content is known to be an important parameter for powder browning. Here, we show that if lactose content is crucial for the level of initial process induced browning of the powder, the additional browning that occurs during storage is mostly independent of lactose content. In addition, during storage, detected lactosylated proteins were found to be inversely proportional to powder browning indicating the occurrence of advanced Maillard reaction steps (e.g. dicarbonyl and AGEs formation and production of melanoidins). Protein aggregates contained both β-lactoglobulin and α-lactalbumin and were mostly formed by non-disulphide covalent bonds. Interestingly, despite protein structure being strongly impacted, good powder rehydration properties were obtained for the studied conditions.
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•Whey powder functionality is not impacted by storage.•Maillard-induced protein modification is repeatable between powder productions.•Initial protein lactosylation content drives powder aging.•Browning during storage is not related to lactose content.
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