Characterization of the mechanism of action of the Enterococcus faecalis bacteriocin EntV on Candida albicans

Candida albicans shares communal niches with multiple bacterial species. Previous work from our group demonstrated that the Gram-positive bacterium Enterococcus faecalis, a normal constituent of the oral and gut microbiome that is often co-isolated with C. albicans, antagonizes hyphal morphogenesis, biofilm formation, and virulence in C. albicans. These effects are mediated by EntV, a bacteriocin and antimicrobial peptide produced by E. faecalis. The main aim of this work is to unveil the molecular mechanism behind the activity of EntV on C. albicans. Using fluorescence microscopy, we determined that EntV binds to the cell walls of several Candida species, including both yeast and hyphae of C. albicans. Contrary to other antimicrobial peptides, it does not cause cell lysis and does not synergize with cell wall damaging agents. Moreover, we screened a library of C. albicans mutants for strains with altered susceptibility to the peptide; most of the positive hits had functions related to cell wall maintenance and were further screened to ascertain changes in the staining patterns. Furthermore, to identify the target layer on the cell wall, pull-down assays were performed. Mannan was identified as the major wall component able to bind the peptide. Finally, live imaging of macrophages incubated with Candida was carried out in order to assess any change in the phagocytic behaviour in presence of the peptide. Identifying the molecular target of EntV in regard to the anti-virulence mechanisms of C. albicans is an important step in its further development as a therapeutic addition to the classical antifungal agents.

Proteomic profiling of the endogenous peptides of MRSA and MSSA

Staphylococcus aureus is a Gram-positive bacterium that can cause diverse skin and soft tissue infections. Methicillin-resistant Staphylococcus aureus (MRSA) can cause more severe infections than methicillin-susceptible Staphylococcus aureus (MSSA). Nevertheless, the physiological and metabolic regulation of MSSA and MRSA has not been well studied. In light of the increased interest in endogenous peptides and recognition of the important roles that they play, we studied the endogenous peptidome of MSSA and MRSA. We identified 1,065 endogenous peptides, among which 435 were differentially expressed (DE), with 292 MSSA-abundant endogenous peptides and 35 MRSA-abundant endogenous peptides. MSSA-abundant endogenous peptides have significantly enriched “VXXXK” motif of at the C-terminus. MSSA-abundant endogenous peptides are involved in penicillin-binding and immune responses, whereas MRSA-abundant endogenous peptides are associated with antibiotic resistance and increased toxicity. Our characterization of the peptidome of MSSA and MRSA provides a rich resource for future studies to explore the functional regulation of drug resistance in S. aureus and may also help elucidate the mechanisms of its pathogenicity and the development of treatments.

The Effect of Raw Materials on the Properties of Oxidized Cellulose Nanofibers from Bacterial Cellulose

In the present study, nanofibers of oxidized cellulose (OC) were prepared from dried bacterial cellulose using a mixture of nitric acid/phosphoric acid and sodium nitrite. Three types of dried bacterial cellulose were used as raw materials. The results revealed that dried sheet bacterial cellulose (DSBC) yielded 86.8% oxidized cellulose with 19.4% carboxyl content, whereas squeeze-dried bacterial cellulose (SDBC) yielded 53.3% OC with 28.6% carboxyl content, and freeze-dried bacterial cellulose (FDBC) yielded 55.6% of OC with 27.6% carboxyl content. The results revealed that OC neutralized with sodium hydroxide from SDBC showed the best swelling property among all types of OC. SDBC indicated the reduction of CFU exceeds 99.99% for gram-negative bacterium Escherichia coli ATCC 25922 and gram-positive bacterium Staphylococcus aureus ATCC 6538.

Stabilization of Ribosomal RNA of the Small Subunit by Spermidine in Staphylococcus aureus

Cryo-electron microscopy is now used as a method of choice in structural biology for studying protein synthesis, a process mediated by the ribosome machinery. In order to achieve high-resolution structures using this approach, one needs to obtain homogeneous and stable samples, which requires optimization of ribosome purification in a species-dependent manner. This is especially critical for the bacterial small ribosomal subunit that tends to be unstable in the absence of ligands. Here, we report a protocol for purification of stable 30 S from the Gram-positive bacterium Staphylococcus aureus and its cryo-EM structures: in presence of spermidine at a resolution ranging between 3.4 and 3.6 Å and in its absence at 5.3 Å. Using biochemical characterization and cryo-EM, we demonstrate the importance of spermidine for stabilization of the 30 S via preserving favorable conformation of the helix 44.

Complete Genome Sequence of the Methicillin-Resistant Staphylococcus aureus Strain SQL1/USA300, Used for Testing the Antimicrobial Properties of Clay Phyllosilicates and Customized Aluminosilicates

Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive bacterium that causes community-acquired and health care-acquired infections. We previously demonstrated that clay phyllosilicates and customized aluminosilicates display antimicrobial activity against the MRSA strain SQL1. The SQL1 annotated genome reveals a USA300 lineage and contributes critical knowledge of the MRSA virulence factors associated with tissue infection.

Antimicrobial Activity and Synergy Investigation of Hypericum scabrum Essential Oil with Antifungal Drugs

The chemical composition of Lebanese Hypericum scabrum essential oil (EO) was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GG-MS). Its antimicrobial activity was evaluated by determining its minimal inhibitory concentrations (MICs) against a Gram-negative and a Gram-positive bacterium, one yeast, and five dermatophytes. H. scabrum EO was most active on filamentous fungi (MIC values of 32–64 µg/mL). Synergy within the oil was investigated by testing each of the following major components on Trichophyton rubrum: α-pinene, limonene, myrcene, β-pinene and nonane, as well as a reconstructed EO. The antifungal activity of the natural oil could not be reached, meaning that its activity might be due, in part, to minor constituent(s). The interactions between H. scabrum EO and commercially available antifungals were assessed by the checkerboard test. A synergistic effect was revealed in the combination of the EO with amphotericin B.

Phytochemical, antibacterial and antioxidant screening of Artemisia santolinifolia various parts

The current study was carried out to explore the phytochemical, antioxidant potential and antibacterial activities of the crude methanolic extract of A. santolinifolia Turcz. Ex Besser. The antioxidant activity was carried out by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) assay, while methanolic extract displayed the highest scavenging activity (DPPH) was 61.31µg/ml on Artemisia santolinifolia root and the lowest (51.05µg/ml) was record for their leaves. Similarly, in (ABTS) the highest activity (89.16µg/ml) was recorded for roots of A. santolinifolia followed by leaves (68.14µg/ml). In low inhibitory concentration assay, the crude methanolic extracts showed significant inhibition against all tested microbes on different concentrations like 25 µg/ml, 50 µg/ml, and 100 µg/ml. The leaves extract of A. santolinifolia AsL showed MIC of 12.5µg/ml for B. subtilis, a gram-positive bacterium, 50µg/ml for gram positive bacteria S. aureus and 37.5 µg/ml for gram negative bacteria P. aeruginosa that is almost equal to the response of standard ciprofloxacin. Our current study revealed that Artemisia santolinifolia root (AsR) exhibited a significant antioxidant potential while AsL showed good antibacterial effect which is suggested to be used for treatment and management of different infectious diseases.

Streptococcus pyogenes Forms Serotype- and Local Environment-Dependent Interspecies Protein Complexes

Streptococcus pyogenes (group A Streptococcus [GAS]), is a human-specific Gram-positive bacterium. Each year, the bacterium affects 700 million people globally, leading to 160,000 deaths.