Quantitative proteomic reveals gallium maltolate induces an iron-limited stress response and reduced quorum-sensing in Pseudomonas aeruginosa

Gallium-based drugs have been repurposed as antibacterial therapeutic candidates and have shown significant potential as an alternative treatment option against drug resistant pathogens. The activity of gallium (Ga3+) is a result of its chemical similarity to ferric iron (Fe3+) and substitution into iron-dependent pathways. Ga3+ is redox inactive in typical physiological environments and therefore perturbs iron metabolism vital for bacterial growth. Gallium maltolate (GaM) is a well-known water-soluble formulation of gallium, consisting of a central gallium cation coordinated to three maltolate ligands, [Ga(Maltol-1H)3]. This study implemented a label-free quantitative proteomic approach to observe the effect of GaM on the bacterial pathogen, Pseudomonas aeruginosa. The replacement of iron for gallium mimics an iron-limitation response, as shown by increased abundance of proteins associated with iron acquisition and storage. A decreased abundance of proteins associated with quorum-sensing and swarming motility was also identified. These processes are a fundamental component of bacterial virulence and dissemination and hence suggest a potential role for GaM in the treatment of P. aeruginosa infection. </p

Additional file 2: of Characterisation of the cellular and proteomic response of Galleria mellonella larvae to the development of invasive aspergillosis

Figure S2. The acute ex vivo cellular response of G. mellonella hemocytes to A. fumigatus. Hemocytes were extracted from G. mellonella washed 3 times with PBS and mixed for 20 min at a 2: 1 ratio with live A. fumigatus conidia. Bright field images suggest the phagocytosis (white arrow) and accumulation and lysis (Blue arrow) of hemocytes around conidia as well as viable hemocytes attached to the outer perimeter (red arrow), (Scale bar corresponds to 20 μm). (TIF 4357 kb

Additional file 1: Figure S1. of Evaluation of Galleria mellonella larvae for studying the virulence of Streptococcus suis

LD50s of tested strains. Figure S2. Infection with S. suis triggers melanisation in G. mellonella larvae. Figure S3. Effect of cell-free supernatant and heat-inactivated inocula on G. mellonella larvae survivial. Table S1. LD50s of tested strains. (DOC 2250 kb)

Additional file 3: of Characterisation of the cellular and proteomic response of Galleria mellonella larvae to the development of invasive aspergillosis

Figure S3. Principal component analysis (PCA) and hierarchical clustering of G. mellonella hemolymph proteomic profiles following infection with viable A. fumigatus conidia for 0, 6 and 24 h. (A) PCA of four replicates of each treatment included in LFQ analysis with a clear distinction between each time point. (B) Two-way unsupervised hierarchical clustering of the median protein expression values of all statistically significant differentially abundant proteins. Hierarchical clustering (columns) identified 2 distinct clusters comprising the four replicates from their original sample groups. (TIF 4138 kb

Additional file 1: of Characterisation of the cellular and proteomic response of Galleria mellonella larvae to the development of invasive aspergillosis

Figure S1. Visualization of development of A. fumigatus conidia and hyphae in fungal nodules/granulomas in G. mellonella larvae inoculated with 1 × 106 viable conidia. Fungal nodules were dissected from larvae and stained with Calcofluor white. Confocal laser scanning microscopy using Calcofluor white fluorescence revealed germinated conidia (germ tube) and germinating conidia (oval shaped) at 6 h and dense hyphal infiltration at 24 h post infection within nodules/granulomas (Black arrow; germinated conidia, white arrows; hyphae), (Scale bar corresponds to 10 μm). (TIF 1660 kb

Silver(I) complexes of 9-anthracenecarboxylic acid and imidazoles: synthesis, structure and antimicrobial activity

[Ag2(9-aca)2] (1) (9-acaH = 9-anthracenecarboxylic acid) reacts with a series of imidazoles to give [Ag(imidH)2.3(CH3CN)0.7](9-aca) (3), [Ag6(imidH)4(9-aca)6(MeOH)2] (4), {[Ag(1-Me-imid)2]2[Ag4(9- aca)6]} (5), {[Ag(1-Bu-imid)2]2[Ag4(9-aca)6]} (6) and [Ag(apim)](9-aca)·H2O (7) (imidH = imidazole; 1-Me-imid = 1-methylimidazole; 1-Bu-imid = 1-butylimidazole; apim = 1-(3-aminopropyl)imidazole). The mononuclear complex 3, hexanuclear 4–6, and polymeric 7, were all characterised using X-ray crystallography. While many of the complexes possess excellent in vitro antifungal and antibacterial activities they are, unanimously, more effective against fungal cells. The insect, Galleria mellonella, can survive high doses of the Ag(I) complexes administered in vivo, and a number of the complexes offer significant protection to larvae infected with a lethal dose of pathogenic Candida albicans cells

Natural Product-Based 1,2,3-Triazole/Sulfonate Analogues as Potential Chemotherapeutic Agents for Bacterial Infections

Despite the vast availability of antibiotics, bacterial infections remain a leading cause of death worldwide. In an effort to enhance the armamentarium against resistant bacterial strains, 1,2,3-triazole (<b>5a–x</b>) and sulfonate (<b>7a–j</b>) analogues of natural bioactive precursors were designed and synthesized. Preliminary screening against two Gram-positive (Streptococcus pneumoniae and Enterococcus faecalis) and four Gram-negative bacterial strains (Pseudomonas aeruginosa, Salmonella enterica, Klebsiella pneumoniae, and Escherichia coli) was performed to assess the potency of these analogues as antibacterial agents. Among all triazole analogues, <b>5e</b> (derived from carvacrol) and <b>5u</b> (derived from 2-hydroxy 1,4-naphthoquinone) bearing carboxylic acid functionality emerged as potent antibacterial agents against S. pneumoniae (IC₅₀: 62.53 and 39.33 μg/mL), E. faecalis (IC₅₀: 36.66 and 61.09 μg/mL), and E. coli (IC₅₀: 15.28 and 22.57 μg/mL). Furthermore, <b>5e</b> and <b>5u</b> also demonstrated moderate efficacy against multidrug-resistant E. coli strains and were therefore selected for further biological studies. Compound <b>5e</b> in combination with ciprofloxacin displayed a synergistic effect on multidrug-resistant E. coli MRA11 and MRC17 strains, whereas compound <b>5u</b> was selective against E. coli MRA11 strain. Growth kinetic studies on S. pneumoniae and E. coli treated with <b>5e</b> and <b>5u</b> showed an extended lag phase. <b>5e</b> and <b>5u</b> did not show significant cytotoxicity up to 100 μg/mL concentration on human embryonic kidney (HEK293) cells. Transmission electron microscopic (TEM) analysis of bacterial cells (S. pneumoniae and E. coli) exposed to <b>5e</b> and <b>5u</b> clearly showed morphological changes and damaged cell walls. Moreover, these compounds also significantly inhibited biofilm formation in S. pneumoniae and E. coli strains, which was visualized by scanning electron microscopic (SEM) analysis. Treatment of larvae of Galleria mellonella (an in vivo model for antimicrobial studies) with <b>5e</b> and <b>5u</b> did not cause an alteration in the hemocyte density, thereby indicating lack of an immune response, and were nontoxic up to a concentration of 2.5 mg/mL