Inhibition of Distinct Proline- or N-Acetylglucosamine-Induced Hyphal Formation Pathways by Proline Analogs in Candida albicans

Biochemical Characterization of Recombinant Enterococcus faecalis EntV Peptide to Elucidate Its Antihyphal and Antifungal Mechanisms against Candida albicans

Candida albicans is a common opportunistic fungus in humans, whose morphological switch between yeast and hyphae forms represents a key virulence trait. Developing strategies to inhibit C. albicans hyphal growth may provide insights into designs of novel antivirulent therapeutics. Importantly, the gut commensal bacterium, Enterococcus faecalis, secretes a bacteriocin EntV which has potent antivirulent and antifungal effects against C. albicans in infection models; however, hampered by the challenges to access large quantities of bioactive EntV, the detailed understanding of its mechanisms on C. albicans has remained elusive. In this work, we biochemically reconstituted the proteolytic cleavage reaction to obtain recombinant EntV88-His6 on a large preparative scale, providing facile access to the C-terminal EntV construct. Under in vitro C. albicans hyphal assay with specific inducers, we demonstrated that EntV88-His6 exhibits potent bioactivity against GlcNAc-triggered hyphal growth. Moreover, with fluorescent FITC-EntV88-His6, we revealed that EntV88-His6 enters C. albicans via endocytosis and perturbs the proper localization of the polarisome scaffolding Spa2 protein. Our findings provide important clues on EntV's mechanism of action. Surprisingly, we showed that EntV88-His6 does not affect C. albicans yeast cell growth but potently exerts cytotoxicity against C. albicans under hyphal-inducing conditions in vitro. The combination of EntV88-His6 and GlcNAc displays rapid killing of C. albicans, rendering it a promising antivirulent and antifungal agent.

Four-Arm δ-Ornithine-Based Polypeptoids Resensitize Voriconazole against Azole-Resistant C. albicans

Worldwide Candida albicans infections cause a huge burden in healthcare and the efficacy of traditional antifungals is diminished because of the rapid development of antifungal resistance. It is necessary to develop new antifungals or new strategies to make multidrug-resistant (MDR) C. albicans to resensitize to existing antifungal drugs. In this work, a series of 4-arm polypeptoids (FAPs) were synthesized through grafting linear ε-l-lysine or δ-ornithine-based oligopeptides to a trimeric lysine core. The most potent 4R-O7 exhibited excellent activities toward three sensitive and two MDR C. albicans strains with MIC values as low as 24-48 μg/mL (vs 375 μg/mL for ε-polylysine, ε-PL). The mechanism studies revealed that 4R-O7 penetrated the cell membrane and generated ROS to kill cells. 4R-O7 exhibited a synergistic effect (FICI < 0.5) with voriconazole (VOR) and also assisted VOR to restore its efficacy to MDR C. albicans. In addition, the combined use of 4R-O7 and VOR significantly improved the elimination efficacy of mature C. albicans biofilms and enhanced the potency in a mouse subcutaneous C. albicans infection model.

The Mechanism of Transcription Factor Swi6 in Regulating Growth and Pathogenicity of Ceratocystis fimbriata: Insights from Non-Targeted Metabolomics

Ceratocystis fimbriata (C. fimbriata) is a notorious pathogenic fungus that causes sweet potato black rot disease. The APSES transcription factor Swi6 in fungi is located downstream of the cell wall integrity (CWI)-mitogen-activated protein kinase (MAPK) signaling pathway and has been identified to be involved in cell wall integrity and virulence in several filamentous pathogenic fungi. However, the specific mechanisms by which Swi6 regulates the growth and pathogenicity of plant pathogenic fungi remain elusive. In this study, the SWI6 deletion mutants and complemented strains of C. fimbriata were generated. Deletion of Swi6 in C. fimbriata resulted in aberrant growth patterns. Pathogenicity assays on sweet potato storage roots revealed a significant decrease in virulence in the mutant. Non-targeted metabolomic analysis using LC-MS identified a total of 692 potential differentially accumulated metabolites (PDAMs) in the ∆Cfswi6 mutant compared to the wild type, and the results of KEGG enrichment analysis demonstrated significant enrichment of PDAMs within various metabolic pathways, including amino acid metabolism, lipid metabolism, nucleotide metabolism, GPI-anchored protein synthesis, and ABC transporter metabolism. These metabolic pathways were believed to play a crucial role in mediating the growth and pathogenicity of C. fimbriata through the regulation of CWI. Firstly, the deletion of the SWI6 gene led to abnormal amino acid and lipid metabolism, potentially exacerbating energy storage imbalance. Secondly, significant enrichment of metabolites related to GPI-anchored protein biosynthesis implied compromised cell wall integrity. Lastly, disruption of ABC transport protein metabolism may hinder intracellular transmembrane transport. Importantly, this study represents the first investigation into the potential regulatory mechanisms of SWI6 in plant filamentous pathogenic fungi from a metabolic perspective. The findings provide novel insights into the role of SWI6 in the growth and virulence of C. fimbriata, highlighting its potential as a target for controlling this pathogen.

Chiral secondary amino acids, their importance, and methods of analysis

Naturally occurring secondary amino acids, with proline as the main representative, contain an alpha-imino group in a cycle that is typically four-, five-, and six-membered. The unique ring structure exhibits exceptional properties-conformational rigidity, chemical stability, and specific roles in protein structure and folding. Many proline analogues have been used as valuable compounds for the study of metabolism of both prokaryotic and eukaryotic cells and for the synthesis of compounds with desired biological, pharmaceutical, or industrial properties. The D-forms of secondary amino acids play different roles in living organisms than the L-forms. They have different metabolic pathways, biological, physiological, and pharmacological effects, they can be indicators of changes and also serve as biomarkers of diseases. In the scientific literature, the number of articles examining D-amino acids in biological samples is increasing. The review summarises information on the occurrence and importance of D- and L-secondary amino acids-azetidic acid, proline, hydroxyprolines, pipecolic, nipecotic, hydroxypipecolic acids and related peptides containing these D-AAs, as well as the main analytical methods (mostly chromatographic) used for their enantiomeric determination in different matrices (biological samples, plants, food, water, and soil).

Phytolectin nanoconjugates in combination with standard antifungals curb multi-species biofilms and virulence of Vulvovaginal Candidiasis (VVC) causing Candida albicans and Non albicans Candida

Vulvovaginal Candidiasis (VVC) is commonly occurring yeast infection caused by Candida species in women. Among Candida species, C. albicans is the predominant member that causes vaginal candidiasis followed by Candida glabrata. Biofilm formation by Candida albicans on the vaginal mucosal tissue leads to VVC infection and is one of the factors for a commensal organism to get into virulent form leading to disease. In addition to that, morphological switching from yeast to hyphal form increases the risk of pathogenesis as it aids in tissue invasion. In this study, jacalin, a phyto-lectin complexed Copper sulfide nanoparticles (NPs) have been explored to eradicate the mono and mixed species biofilms formed by fluconazole resistant C. albicans and C. glabrata isolated from VVC patients. NPs along with standard antifungals like micafungin and amphotericin B have been evaluated to explore interaction behaviour and we observed synergistic interactions between them. Microscopic techniques like light microscopy, phase contrast microscopy, scanning electron microscopy, confocal laser scanning microscopy were used to visualize the inhibition of biofilm by NPs and in synergistic combinations with standard antifungals. Real time PCR analysis was carried out to study the expression pattern of the highly virulent genes which are responsible for yeast to hyphal switch, drug resistance and biofilm formation upon treatment with NPs in combination with standard antifungals. The current study shows that lectin conjugated NPs with standard antifungals might be a different means to disrupt the mixed species population of Candida spp. that causes VVC.