Mean [C<i>_n</i>mim]Cl minimum inhibitory concentration (MIC) values for Gram positive and Gram-negative marine-derived bacterial isolates.

<p>Mean [C<i>_n</i>mim]Cl minimum inhibitory concentration (MIC) values for Gram positive and Gram-negative marine-derived bacterial isolates.</p

Biodegradation of (a) [C₂mim]Cl, and (b) [C₄mim]Cl by cell suspensions of <i>B. sanguinis, R. erythropolis</i>, and <i>K. palustris</i> after 7, 21, and 28 days.

<p>Plotted values are the mean of duplicate measurements; error bars represent one standard deviation.</p

General structure of 1-alkyl-3-methylimidazolium chloride ionic liquids.

<p>General structure of 1-alkyl-3-methylimidazolium chloride ionic liquids.</p

Bacterial isolates obtained in this study on isolation media containing [C_nmim]Cl.

<p>G+, Gram positive; G-, Gram negative; C, cocci; R, rods.</p

Biodegradation analysis of [C₄mim]Cl in M9 minimal salts medium by selected isolates after 7 days.

<p>Chromatograms presented show (a) uninoculated control medium, (b) <i>B. sanguinis</i>, and (c) <i>R. erythropolis</i>.</p

Growth characteristics of marine-derived bacterial isolates on plates containing M9 minimal salts medium containing [C<i>_n</i>mim]Cl as the sole carbon source.

<p>Slight growth (+), moderate growth (++), dense growth (+++).</p

A summary of previously-reported microbial biodegradation efficiencies of methylimidazolium-based ionic liquids.

<p>A summary of previously-reported microbial biodegradation efficiencies of methylimidazolium-based ionic liquids.</p

Ultrashort Cationic Naphthalene-Derived Self-Assembled Peptides as Antimicrobial Nanomaterials

Self-assembling dipeptides conjugated to naphthalene show considerable promise as nanomaterial structures, biomaterials, and drug delivery devices. Biomaterial infections are responsible for high rates of patient mortality and morbidity. The presence of biofilm bacteria, which thrive on implant surfaces, are a huge burden on healthcare budgets, as they are highly resistant to current therapeutic strategies. Ultrashort cationic self-assembled peptides represent a highly innovative and cost-effective strategy to form antibacterial nanomaterials. Lysine conjugated variants display the greatest potency with 2% w/v NapFFKK hydrogels significantly reducing the viable <i>Staphylococcus epidermidis</i> biofilm by 94%. Reducing the size of the R-group methylene chain on cationic moieties resulted in reduction of antibiofilm activity. The primary amine of the protruding R-group tail may not be as readily available to interact with negatively charged bacterial membranes. Cryo-SEM, FTIR, CD spectroscopy, and oscillatory rheology provided evidence of supramolecular hydrogel formation at physiological pH (pH 7.4). Cytotoxicity assays against murine fibroblast (NCTC 929) cell lines confirmed the gels possessed reduced cytotoxicity relative to bacterial cells, with limited hemolysis upon exposure to equine erythrocytes. The results presented in this paper highlight the significant potential of ultrashort cationic naphthalene peptides as future biomaterials

Exiguolysin, a novel thermolysin (M4) peptidase from exiguobacterium oxidotolerans

This study details a comprehensive biochemical and structural characterization of exiguolysin, a novel thermolysin-like, caseinolytic peptidase secreted by a marine isolate of Exiguobacterium oxidotolerans strain BW26. Exiguolysin demonstrated optimal proteolytic activity at 37 ◦C and pH 3, retaining 85% activity at 50 ◦C, highlighting its potential stability under broad reaction conditions. SDS-PAGE and LC-MS analysis identified the enzyme as a 32 kDa M4-family metalloprotease. Exiguolysin activity was inhibited by 1,10-phenanthroline, confirming its dependence on metal ions for activity. Zymographic analysis and substrate specificity assays revealed selective hydrolysis of matrix metalloproteinase (MMP) substrates but no activity against elastase substrates. Analysis of the predicted gene sequence and structural predictions using AlphaFold identified the presence and position of HEXXH and Glu-Xaa-Xaa-Xaa-Asp motifs, crucial for zinc binding and catalytic activity, characteristic of ‘Glu-zincins’ and members of the M4 peptidase family. High-throughput screening of a 20 × 20 N-alpha mercaptoamide dipeptide inhibitor library against exiguolysin identified SH-CH2 -CO-Met-Tyr-NH2 as the most potent inhibitor, with a Ki of 1.95 µM. Notably, exiguolysin selectively inhibited thrombin-induced PAR-1 activation in PC-3 cells, potentially indicating a potential mechanism of virulence in modulating PAR-1 signalling during infection by disarming PARs. This is the first detailed characterization of a peptidase of the M4 (thermolysin) family in the genus Exiguobacterium which may have industrial application potential and relevance as a putative virulence factor.</p

The plasma jet used in this study.

<p>(A) Schematic diagram of the plasma jet. (B) Photograph of the plasma jet interacting with a biofilm sample.</p