Fangchinoline inhibits growth and biofilm of Candida albicans by inducing ROS overproduction.

Infections caused by Candida species, especially Candida albicans, threaten the public health and create economic burden. Shortage of antifungals and emergence of drug resistance call for new antifungal therapies while natural products were attractive sources for developing new drugs. In our study, fangchinoline, a bis-benzylisoquinoline alkaloid from Chinese herb Stephania tetrandra S. Moore, exerted antifungal effects on planktonic growth of several Candida species including C. albicans, with MIC no more than 50 µg/mL. In addition, results from microscopic, MTT and XTT reduction assays showed that fangchinoline had inhibitory activities against the multiple virulence factors of C. albicans, such as adhesion, hyphal growth and biofilm formation. Furthermore, this compound could also suppress the metabolic activity of preformed C. albicans biofilms. PI staining, followed by confocal laser scanning microscope (CLSM) analysis showed that fangchinoline can elevate permeability of cell membrane. DCFH-DA staining suggested its anti-Candida mechanism also involved overproduction of intracellular ROS, which was further confirmed by N-acetyl-cysteine rescue tests. Moreover, fangchinoline showed synergy with three antifungal drugs (amphotericin B, fluconazole and caspofungin), further indicating its potential use in treating C. albicans infections. Therefore, these results indicated that fangchinoline could be a potential candidate for developing anti-Candida therapies.

The hyphal-specific toxin candidalysin promotes fungal gut commensalism.

The fungus Candida albicans frequently colonizes the human gastrointestinal tract, from which it can disseminate to cause systemic disease. This polymorphic species can transition between growing as single-celled yeast and as multicellular hyphae to adapt to its environment. The current dogma of C. albicans commensalism is that the yeast form is optimal for gut colonization, whereas hyphal cells are detrimental to colonization but critical for virulence1-3. Here, we reveal that this paradigm does not apply to multi-kingdom communities in which a complex interplay between fungal morphology and bacteria dictates C. albicans fitness. Thus, whereas yeast-locked cells outcompete wild-type cells when gut bacteria are absent or depleted by antibiotics, hyphae-competent wild-type cells outcompete yeast-locked cells in hosts with replete bacterial populations. This increased fitness of wild-type cells involves the production of hyphal-specific factors including the toxin candidalysin4,5, which promotes the establishment of colonization. At later time points, adaptive immunity is engaged, and intestinal immunoglobulin A preferentially selects against hyphal cells1,6. Hyphal morphotypes are thus under both positive and negative selective pressures in the gut. Our study further shows that candidalysin has a direct inhibitory effect on bacterial species, including limiting their metabolic output. We therefore propose that C. albicans has evolved hyphal-specific factors, including candidalysin, to better compete with bacterial species in the intestinal niche.

Functional Portrait of Irf1 (Orf19.217), a Regulator of Morphogenesis and Iron Homeostasis in Candida albicans.

The alternate growth of Candida albicans between a unicellular yeast form and a multicellular hyphal form is crucial for its ability to cause disease. Interestingly, both morphological forms support distinct functions during proliferation in the human host. We previously identified ORF19.217 (C2_08890W_A), encoding a zinc-finger transcription factor of the C2H2 family, in a systematic screen of genes whose overexpression contributes to C. albicans' morphological changes. Conditional overexpression of ORF19.217 with the strong tetracycline-inducible promoter (P TET ) resulted in a hyperfilamentous phenotype. We examined growth of the orf19.217 knockout-mutant in different hypha-inducing conditions and found that the mutant still formed hyphae under standard hypha-inducing conditions. To further investigate the function of Orf19.217 in C. albicans, we combined genome-wide expression (RNA-Seq) and location (ChIP-Seq) analyses. We found that Orf19.217 is involved in regulatory processes comprising hyphal morphogenesis and iron acquisition. Comparative analysis with existing C. albicans hyphal transcriptomes indicates that Orf19.217-mediated filamentation is distinct from a true hyphal program. Further, the orf19.217 knockout-mutant did not show increased sensitivity to iron deprivation, but ORF19.217 overexpression was able to rescue the growth of a hap5-mutant, defective in a subunit of the CCAAT-complex, which is essential for iron acquisition. This suggested that Orf19.217 is involved in regulation of iron acquisition genes during iron deprivation and acts in a parallel pathway to the established CCAAT-complex. Interestingly, the orf19.217-mutant turned out to be defective in its ability to form filaments under iron-deficiency. Taken together our findings propose that the transcription factor Orf19.217 stimulates expression of the hyphal regulators EFG1 and BRG1 to promote filamentous growth under iron deprivation conditions, allowing the fungus to escape these iron-depleted conditions. The transcription factor therefore appears to be particularly important for adaptation of C. albicans to diverse environmental conditions in the human host. In regard to the newly identified functions, we have given the regulator the name Irf1, Iron-dependent Regulator of Filamentation.

Chemical Composition and In Vitro Antioxidant and Antimicrobial Activities of the Marine Cyanolichen Lichina pygmaea Volatile Compounds.

Volatile compounds from the marine cyanolichen Lichina pygmaea, collected from the Moroccan Atlantic coast, were extracted by hydrodistillation and their putative chemical composition was investigated by gas chromatography coupled to mass spectrometry (GC/MS). Based on the obtained results, Lichina pygmaea volatile compounds (LPVCs) were mainly dominated by sesquiterpenes compounds, where γ-himachalene, ß-himachalene, (2E,4E)-2,4 decadienal and α-himachalene were assumed to be the most abundant constituents, with percentage of 37.51%, 11.71%, 8.59% and 7.62%, respectively. LPVCs depicted significant antimicrobial activity against all tested strains (Staphylococcus aureus CCMM B3, Pseudomonas aeruginosa DSM 50090, Escherichia coli ATCC 8739 and Candida albicans CCMM-L4) with minimum inhibitory concentration (MIC) values within the range of 1.69-13.5 mg/mL. Moreover, this LPVC showed interesting scavenging effects on the 2,2-diphenyl-1-picrylhydrazyl radical with an IC50 of 0.21 mg/mL. LPVCs could be an approving resource with moderate antimicrobial potential and interesting antioxidant activity for cosmetics and pharmaceutical applications.

Rare ß-Resorcylic Acid Derivatives from a Halophyte-Associated Fungus Colletotrichum gloeosporioides JS0419 and Their Antifungal Activities.

Six new ß-resorcylic acid derivatives (1-5 and 7) were isolated from a halophyte-associated fungus, Colletotrichum gloeosporioides JS0419, together with four previously reported ß-resorcylic acid lactones (RALs). The relative and absolute stereochemistry of 1 was completely established by a combination of spectroscopic data and chemical reactions. The structures of the isolated compounds were elucidated by analysis of HRMS and NMR data. Notably, compounds 1-3 had a ß-resorcylic acid harboring a long unesterified aliphatic side chain, whereas the long aliphatic chains were esterified to form macrolactones in 4-9. Among the isolated compounds, monocillin I and radicicol showed potent antifungal activities against Cryptococcus neoformans, comparable to clinically available antifungal agents and radicicol showed weak antifungal activity against Candida albicans. These findings provide insight into the chemical diversity of fungal RAL-type compounds and their pharmacological potential.

Unique Cyclized Thiolopyrrolones from the Marine-Derived Streptomyces sp. BTBU20218885.

Two new cyclized thiolopyrrolone derivatives, namely, thiolopyrrolone A (1) and 2,2-dioxidothiolutin (2), together with the kn own compound, thiolutin (3) were identified from a marine-derived Streptomyces sp. BTBU20218885, which was isolated from a mud sample collected from the coastal region of Xiamen, China. Their chemical structures were determined using spectroscopic data, including HRESIMS, 1D and 2D NMR techniques. 1 possessed a unique unsymmetrical sulfur-containing thiolopyrrolone structure. All the compounds were tested for bioactivities against Staphylococcus aureus, Escherichia coli, Bacille Calmette-Guérin (BCG), Mycobacterium tuberculosis, and Candida albicans. 1 displayed antibacterial activities against BCG, M. tuberculosis, and S. aureus with minimum inhibitory concentration (MIC) values of 10, 10, and 100 µg/mL, respectively. Thiolutin (3) showed antibacterial activities against E. coli, BCG, M. tuberculosis, and S. aureus with MIC values of 6.25, 0.3125, 0.625, and 3.125 µg/mL, respectively.

The Anticancer Agent 3,3'-Diindolylmethane Inhibits Multispecies Biofilm Formation by Acne-Causing Bacteria and Candida albicans.

The Gram-positive anaerobic bacterium Cutibacterium acnes is a major inhabitant of human skin and has been implicated in acne vulgaris formation and in the formation of multispecies biofilms with other skin-inhabiting organisms like Staphylococcus aureus and Candida albicans. Indoles are widespread in nature (even in human skin) and function as important signaling molecules in diverse prokaryotes and eukaryotes. In the present study, we investigated the antibacterial and antibiofilm activities of 20 indoles against C. acnes. Of the indoles tested, indole-3-carbinol at 0.1 mM significantly inhibited biofilm formation by C. acnes without affecting planktonic cell growth, and the anticancer drug 3,3'-diindolylmethane (DIM) at 0.1 mM (32 µg/mL) also significantly inhibited planktonic cell growth and biofilm formation by C. acnes, whereas the other indoles and indole itself were less effective. Also, DIM at 0.1 mM successfully inhibited multispecies biofilm formation by C. acnes, S. aureus, and C. albicans. Transcriptional analyses showed that DIM inhibited the expressions of several biofilm-related genes in C. acnes, and at 0.05 mM, DIM inhibited hyphal formation and cell aggregation by C. albicans. These results suggest that DIM and other indoles inhibit biofilm formation by C. acnes and have potential use for treating C. acnes associated diseases. IMPORTANCE Since indoles are widespread in nature (even in human skin), we hypothesized that indole and its derivatives might control biofilm formation of acne-causing bacteria (Cutibacterium acnes and Staphylococcus aureus) and fungal Candida albicans. The present study reports for the first time the antibiofilm and antimicrobial activities of several indoles on C. acnes. Of the indoles tested, two anticancer agents, indole-3-carbinol and 3,3'-diindolylmethane found in cruciferous vegetables, significantly inhibited biofilm formation by C. acnes. Furthermore, the most active 3,3'-diindolylmethane successfully inhibited multispecies biofilm formation by C. acnes, S. aureus, and C. albicans. Transcriptional analyses showed that 3,3'-diindolylmethane inhibited the expressions of several biofilm-related genes including lipase, hyaluronate lyase, and virulence-related genes in C. acnes, and 3,3'-diindolylmethane inhibited hyphal formation and cell aggregation by C. albicans. Our findings show that 3,3'-diindolylmethane offers a potential means of controlling acne vulgaris and multispecies biofilm-associated infections due to its antibiofilm and antibiotic properties.

K143R Amino Acid Substitution in 14-α-Demethylase (Erg11p) Changes Plasma Membrane and Cell Wall Structure of Candida albicans.

The opportunistic pathogen Candida albicans is responsible for life-threating infections in immunocompromised individuals. Azoles and polyenes are two of the most commonly used antifungals and target the ergosterol biosynthesis pathway or ergosterol itself. A limited number of clinically employed antifungals correspond to the development of resistance mechanisms. One resistance mechanism observed in clinical isolates of azole-resistant C. albicans is the introduction of point mutations in the ERG11 gene, which encodes a key enzyme (lanosterol 14-α-demethylase) on the ergosterol biosynthesis pathway. Here, we demonstrate that a point mutation K143R in ERG11 (C. albicans ERG11K143R/K143R) contributes not only to azole resistance, but causes increased gene expression. Overexpression of ERG11 results in increased ergosterol content and a significant reduction in plasma membrane fluidity. Simultaneously, the same point mutation caused cell wall remodeling. This could be facilitated by the unmasking of chitin and ß-glucan on the fungal cell surface, which can lead to recognition of the highly immunogenic ß-glucan, triggering a stronger immunological reaction. For the first time, we report that a frequently occurring azole-resistance strategy makes C. albicans less susceptible to azole treatment while, at the same time, affects its cell wall architecture, potentially leading to exposure of the pathogen to a more effective host immune response.

Vacuole and mitochondria patch (vCLAMP) and ER-mitochondria encounter structure (ERMES) maintain cell survival by protecting mitochondrial functions in Candida albicans.

Candida albicans is an important opportunistic fungus in the clinic. In recent years, with the widespread use of antibiotics, drug-resistant strains have been isolated in the clinic, so finding new drug targets has become an urgent problem to be solved. The vacuole and mitochondria patch (vCLAMP) and the ER-mitochondria encounter structure (ERMES) are new types of inner membrane junction systems in Saccharomyces cerevisiae. However, the functions in maintaining cell survival of the two structures have not yet been elucidated in C. albicans. In this study, VAM6 and MDM34 knockout mutants (vam6Δ/Δmet-MDM34) were constructed using an induction system regulated by the MET3 promoter. PI-positive assays showed that deletion of vCLAMP and ERMES led to abnormal growth of C. albicans. Furthermore, the vam6Δ/Δmet-MDM34 mutant exhibited obvious mitochondrial fragmentation, mtDNA damage, reduced ATP levels, and abnormal mitochondrial membrane potential, indicating its important role in maintaining the structures and functions of mitochondria. Moreover, deletion of vCLAMP and ERMES inhibited filamentous growth. Overall This study shows that vCLAMP and ERMES play important roles in maintaining the survival of C. albicans cells.

Target-based drug repurposing against Candida albicans-A computational modeling, docking, and molecular dynamic simulations study.

The emergence of multidrug-resistant strains of Candida albicans has become a global threat mostly due to co-infection with immune-compromised patients leading to invasive candidiasis. The life-threatening form of the disease can be managed quickly and effectively by drug repurposing. Thus, the study used in silico approaches to evaluate Food and Drug Administration (FDA) approved drugs against three drug targets-TRR1, TOM40, and YHB1. The tertiary structures of three drug targets were modeled, refined, and evaluated for their structural integrity based on PROCHECK, ERRAT, and PROSA. High-throughput virtual screening of FDA-approved drugs (8815), interaction analysis, and energy profiles had revealed that DB01102 (Arbutamine), DB01611 (Hydroxychloroquine), and DB09319 (Carindacillin) exhibited better binding affinity with TRR1, TOM40, and YHB1, respectively. Notably, the molecular dynamic simulation explored that Gln45, Thr119, and Asp288 of TRR1; Thr107 and Ser121 of TOM40; Arg193, Glu213, and Ser228 of YHB1 are crucial residues for stable drug-target interaction. Additionally, it also prioritized Arbutamine-TRR1 as the best drug-target complex based on MM-PBSA (-52.72 kcal/mol), RMSD (2.43 Å), and radius of gyration (-21.49 Å) analysis. In-depth, PCA results supported the findings of molecular dynamic simulations. Interestingly, the conserved region (>70%) among the TRR1 sequences from pathogenic Candida species indicated the effectiveness of Arbutamine against multiple species of Candida as well. Thus, the study dispenses new insight and enriches the understanding of developing an advanced technique to consider potential antifungals against C. albicans. Nonetheless, a detailed experimental validation is needed to investigate the efficacy of Arbutamin against life-threatening candidiasis.

Prevention of the proliferation of oral pathogens due to prolonged mask use based on α-cyclodextrin and hydroxytyrosol mouthwash.

OBJECTIVE: Face masks help contain the aerosol-mediated transmission of infectious viral particles released from individuals via cough and sneezes. However, the prolonged use of face masks has raised concerns regarding oral hygiene. Here, we present a mouthwash formulation based on α-cyclodextrin and hydroxytyrosol that can maintain healthy oral microbiota. MATERIALS AND METHODS: We isolated and cultured Candida albicans, Staphylococcus aureus, and a mix of Streptococcus sp., Staphylococcus sp. and Neisseria sp. from oral and throat swabs. The microorganisms were cultured in a standard medium with or without the mouthwash. To evaluate the effect of the mouthwash on the oral microbiota, the DNA from the saliva of 3 volunteers that used the mouthwash was extracted. Then, the DNA was amplified using primer pairs specific for bacterial and fungal DNA. Twelve further volunteers were offered to use the mouthwash and a questionnaire was submitted to them to assess the possible beneficial effects of mouthwash on halitosis and other oral disturbances. RESULTS: The bacteria and fungi cultured in media containing the mouthwash showed a growth reduction ranging from 20 to 80%. The PCR amplification of fungal and bacterial DNA extracted from volunteers that used the mouthwash showed a reduction of both bacteria and fungi. Volunteers that used the mouthwash reported a tendency towards a reduction of halitosis, gingival and mouth inflammation, and dry mouth. CONCLUSIONS: The use of a mouthwash containing α-cyclodextrin and hydroxytyrosol is not aggressive against oral mucosa; it is safe and effective to reduce the bacterial and fungal load due to the continuous use of face masks.

Ozone ultrafine bubble water inhibits the early formation of Candida albicans biofilms.

This study aimed to investigate the effect of ozone ultrafine bubble water (OUFBW) on the formation and growth of Candida albicans (C. albicans) biofilms and surface properties of denture base resins. OUFBWs were prepared under concentrations of 6 (OUFBW6), 9 (OUFBW9), and 11 ppm (OUFBW11). Phosphate buffered saline and ozone-free electrolyte aqueous solutions (OFEAS) were used as controls. Acrylic resin discs were made according to manufacturer instructions, and C. albicans was initially cultured on the discs for 1.5 h. A colony forming unit (CFU) assay was performed by soaking the discs in OUFBW for 5 min after forming a 24-h C. albicans biofilm. The discs after initial attachment for 1.5 h were immersed in OUFBW and then cultured for 0, 3, and 5 h. CFUs were subsequently evaluated at each time point. Moreover, a viability assay, scanning electron microscopy (SEM), Alamar Blue assay, and quantitative real-time polymerase chain reaction (qRT-PCR) test were performed. To investigate the long-term effects of OUFBW on acrylic resin surface properties, Vickers hardness (VH) and surface roughness (Ra) were measured. We found that OUFBW9 and OUFBW11 significantly degraded the formed 24-h biofilm. The time point CFU assay showed that C. albicans biofilm formation was significantly inhibited due to OUFBW11 exposure. Interestingly, fluorescence microscopy revealed that almost living cells were observed in all groups. In SEM images, the OUFBW group had lesser number of fungi and the amount of non-three-dimensional biofilm than the control group. In the Alamar Blue assay, OUFBW11 was found to suppress Candida metabolic function. The qRT-PCR test showed that OUFBW down-regulated ALS1 and ALS3 expression regarding cell-cell, cell-material adhesion, and biofilm formation. Additionally, VH and Ra were not significantly different between the two groups. Overall, our data suggest that OUFBW suppressed C. albicans growth and biofilm formation on polymethyl methacrylate without impairing surface properties.

Chlovalicin B, a Chlorinated Sesquiterpene Isolated from the Marine Mushroom Digitatispora marina.

As part of our search for bioactive metabolites from understudied marine microorganisms, the new chlorinated metabolite chlovalicin B (1) was isolated from liquid cultures of the marine basidiomycete Digitatispora marina, which was collected and isolated from driftwood found at Vannøya, Norway. The structure of the novel compound was elucidated by spectroscopic methods including 1D and 2D NMR and analysis of HRMS data, revealing that 1 shares its molecular scaffold with a previously isolated compound, chlovalicin. This represents the first compound isolated from the Digitatispora genus, and the first reported fumagillin/ovalicin-like compound isolated from Basidiomycota. Compound 1 was evaluated for antibacterial activities against a panel of five bacteria, its ability to inhibit bacterial biofilm formation, for antifungal activity against Candida albicans, and for cytotoxic activities against malignant and non-malignant human cell lines. Compound 1 displayed weak cytotoxic activity against the human melanoma cell line A2058 (~50% survival at 50 µM). No activity was detected against biofilm formation or C. albicans at 50 µM, or against bacterial growth at 100 µM nor against the production of cytokines by the human acute monocytic leukemia cell line THP-1 at 50 µM.

The Effect of Conjugation with Octaarginine, a Cell-Penetrating Peptide on Antifungal Activity of Imidazoacridinone Derivative.

Acridine cell-penetrating peptide conjugates are an extremely important family of compounds in antitumor chemotherapy. These conjugates are not so widely analysed in antimicrobial therapy, although bioactive peptides could be used as nanocarriers to smuggle antimicrobial compounds. An octaarginine conjugate of an imidazoacridinone derivative (Compound 1-R8) synthetized by us exhibited high antifungal activity against reference and fluconazole-resistant clinical strains (MICs ≤ 4 µg mL-1). Our results clearly demonstrate the qualitative difference in accumulation of the mother compound and Compound 1-R8 conjugate into fungal cells. Only the latter was transported and accumulated effectively. Microscopic and flow cytometry analysis provide some evidence that the killing activity of Compound 1-R8 may be associated with a change in the permeability of the fungal cell membrane. The conjugate exhibited low cytotoxicity against human embryonic kidney (HEK-293) and human liver (HEPG2) cancer cell lines. Nevertheless, the selectivity index value of the conjugate for human pathogenic strains remained favourable and no hemolytic activity was observed. The inhibitory effect of the analysed compound on yeast topoisomerase II activity suggested its molecular target. In summary, conjugation with R8 effectively increased imidazoacridinone derivative ability to enter the fungal cell and achieve a concentration inside the cell that resulted in a high antifungal effect.

ZnO, TiO2 and Ag nanoparticles impact against some species of pathogenic bacteria and yeast.

The economic approaches for manufacturing the nanoparticles with physical and chemical effects and limited resistance to antibiotics have been progressed recently due to the rise of microbial resistance to antibiotics. This research aimed to study the antimicrobial efficacy of silver nanoparticles Ag, ZnO, and Tio2 nanoparticles against Salmonella typhimurium and Brucella abortus and Candida albicans. Two isolates of Salmonella and two isolates of Brucella abortus were isolated from food spastically meat and blood specimens, respectively. Candida albicans were isolated from the patient's mouth with oral candidiasis (oral thrush) and confirmed diagnosis by API 20C test. The antimicrobial susceptibility of Salmonella typhimurium and B. abortus isolates were performed against nine different antibiotics. Silver nanoparticles consisting of AgNPs size (90) nm, ZnO NPs size (20, 50) nm as well as TiO2 NPs size (10, 50) nm, were used. UV-Visible spectrophotometer was used to characterize silver nanoparticles. The highest resistance of Candida albicans was seen for fluconazole, Clotrimazole and Itraconazole. The results of the Minimum Inhibitory Concentration (MIC) of nanoparticles against Salmonella typhimurium showed the average MIC of Tio2-10nm and Tio2-50nm were 5000 and 2500 µg\ml for S1 and S2 isolates, respectively. The isolated Brucella abortus (B1 and B2) showed sensitivity to NPs with different MIC. The average MIC for Ag-90nm was 5000 and 2500 µg/ml for B1 and B2 isolates, respectively. The findings suggest NP solution has fungicidal and bactericidal impacts on the tested microorganisms so they can be suitable for multiple applications of the biomedical field such as developing new antimicrobial agents.

Synthesis, Structural Characterization, and In Vitro and In Silico Antifungal Evaluation of Azo-Azomethine Pyrazoles (PhN2(PhOH)CHN(C3N2(CH3)3)PhR, R = H or NO2).

The azo-azomethine imines, R1-N=N-R2-CH=N-R3, are a class of active pharmacological ligands that have been prominent antifungal, antibacterial, and antitumor agents. In this study, four new azo-azomethines, R1 = Ph, R2 = phenol, and R3 = pyrazol-Ph-R' (R = H or NO2), have been synthesized, structurally characterized using X-ray, IR, NMR and UV-Vis techniques, and their antifungal activity evaluated against certified strains of Candida albicans and Cryptococcus neoformans. The antifungal tests revealed a high to moderate inhibitory activity towards both strains, which is regulated as a function of both the presence and the location of the nitro group in the aromatic ring of the series. These biological assays were further complemented with molecular docking studies against three different molecular targets from each fungus strain. Molecular dynamics simulations and binding free energy calculations were performed on the two best molecular docking results for each fungus strain. Better affinity for active sites for nitro compounds at the "meta" and "para" positions was found, making them promising building blocks for the development of new Schiff bases with high antifungal activity.

Phytochemical and proximate content of Carapa procera bark and its antimicrobial potential against selected pathogens.

Medicinal plants represent a great source of antimicrobial and phytochemical constituents which are increasingly used to treat microbial infections and other ailments such as tuberculosis, anemia, and trachoma. Despite the use of antibiotics, antimicrobial resistance continues to be a world issue, in as much as nutrition. This study investigated the presence of phytochemicals, proximate compositions, and antimicrobial activity of methanolic extract of Carapa procera bark. The bark of Carapa procera was collected, cleaned and air dried for 72 h. The powder obtained was treated with diethyl ether and soaked in methanol (99%) for 72 h to obtain crude extract. The extract was used to test for the presence of phytochemicals and antimicrobial activities. The raw bark was used for proximate analysis. The result showed presence of steroids, tannins and saponins, but no alkaloids present. The 100 mg/mL extract had the highest inhibition zone on all tested organisms from 24.00 ± 0.94 to 26.67 ± 1.18, and 50 mg/mL showed the least (16.67 ± 1.24) on Candida albicans. Staphylococcus aureus showed the lowest minimum inhibition concentration (MIC) of 3.12 mg/mL, whereas the Gram-negative bacteria exhibited variations in their sensitivity with E. coli having the highest MIC of 25 mg/mL. The extract had high MIC (6.25 mg/mL) on Candida albicans than clotrimazole (50 mg/mL). The proximate compositions of Carapa procera were moisture (6.07 ± 0.07%), ash (12.46 ± 0.46%), crude protein (9.54 ± 0.12%), crude fat (1.42 ± 0.06%) and carbohydrate (70.50 ± 0.35%). The energy value was 1413.17 kj. Thus, Carapa procera possesses both antimicrobial and nutritional potentials worth exploring and domesticating for sustainable management and conservation.

Candida albicans Isolates 529L and CHN1 Exhibit Stable Colonization of the Murine Gastrointestinal Tract.

Candida albicans is a pathobiont that colonizes multiple niches in the body including the gastrointestinal (GI) tract but is also responsible for both mucosal and systemic infections. Despite its prevalence as a human commensal, the murine GI tract is generally refractory to colonization with the C. albicans reference isolate SC5314. Here, we identify two C. albicans isolates, 529L and CHN1, that stably colonize the murine GI tract in three different animal facilities under conditions where SC5314 is lost from this niche. Analysis of the bacterial microbiota did not show notable differences among mice colonized with the three C. albicans strains. We compared the genotypes and phenotypes of these three strains and identified thousands of single nucleotide polymorphisms (SNPs) and multiple phenotypic differences, including their ability to grow and filament in response to nutritional cues. Despite striking filamentation differences under laboratory conditions, however, analysis of cell morphology in the GI tract revealed that the three isolates exhibited similar filamentation properties in this in vivo niche. Notably, we found that SC5314 is more sensitive to the antimicrobial peptide CRAMP, and the use of CRAMP-deficient mice modestly increased the ability of SC5314 to colonize the GI tract relative to CHN1 and 529L. These studies provide new insights into how strain-specific differences impact C. albicans traits in the host and advance CHN1 and 529L as relevant strains to study C. albicans pathobiology in its natural host niche. IMPORTANCE Understanding how fungi colonize the GI tract is increasingly recognized as highly relevant to human health. The animal models used to study Candida albicans commensalism commonly rely on altering the host microbiome (via antibiotic treatment or defined diets) to establish successful GI colonization by the C. albicans reference isolate SC5314. Here, we characterize two C. albicans isolates that can colonize the murine GI tract without antibiotic treatment and can therefore be used as tools for studying fungal commensalism. Importantly, experiments were replicated in three different animal facilities and utilized three different mouse strains. Differential colonization between fungal isolates was not associated with alterations in the bacterial microbiome but rather with distinct responses to CRAMP, a host antimicrobial peptide. This work emphasizes the importance of C. albicans intraspecies variation as well as host antimicrobial defense mechanisms in defining the outcome of commensal interactions.

The Effects of Tormentic Acid and Extracts from Callistemon citrinus on Candida albicans and Candida tropicalis Growth and Inhibition of Ergosterol Biosynthesis in Candida albicans.

Candida albicans and Candida tropicalis are the leading causes of human fungal infections worldwide. There is an increase in resistance of Candida pathogens to existing antifungal drugs leading to a need to find new sources of antifungal agents. Tormentic acid has been isolated from different plants including Callistemon citrinus and has been found to possess antimicrobial properties, including antifungal activity. The study aimed to determine the effects of tormentic and extracts from C. citrinus on C. albicans and C. tropicalis and a possible mode of action. The extracts and tormentic acid were screened for antifungal activity using the broth microdilution method. The growth of both species was inhibited by the extracts, and C. albicans was more susceptible to the extract compared to C. tropicalis. The growth of C. albicans was inhibited by 80% at 100 µg/ml of both the DCM: methanol extract and the ethanol: water extract. Tormentic acid reduced the growth of C. albicans by 72% at 100 µg/ml. The effects of the extracts and tormentic acid on ergosterol content in C. albicans were determined using a UV/Vis scanning spectrophotometer. At concentrations of tormentic acid of 25 µg/ml, 50 µg/ml, 100 µg/ml, and 200 µg/ml, the content of ergosterol was decreased by 22%, 36%, 48%, and 78%, respectively. Similarly, the DCM: methanol extract at 100 µg/ml and 200 µg/ml decreased the content by 78% and 88%, respectively. A dose-dependent decrease in ergosterol content was observed in cells exposed to miconazole with a 25 µg/ml concentration causing a 100% decrease in ergosterol content. Therefore, tormentic acid inhibits the synthesis of ergosterol in C. albicans. Modifications of the structure of tormentic acid to increase its antifungal potency may be explored in further studies.

A Myosin Light Chain Is Critical for Fungal Growth Robustness in Candida albicans.

In a number of elongated cells, such as fungal hyphae, a vesicle cluster is observed at the growing tip. This cluster, called a Spitzenkörper, has been suggested to act as a vesicle supply center, yet analysis of its function is challenging, as a majority of components identified thus far are essential for growth. Here, we probe the function of the Spitzenkörper in the human fungal pathogen Candida albicans, using genetics and synthetic physical interactions (SPI). We show that the C. albicans Spitzenkörper is comprised principally of secretory vesicles. Mutant strains lacking the Spitzenkörper component myosin light chain 1 (Mlc1) or having a SPI between Mlc1 and either another Spitzenkörper component, the Rab GTPase Sec4, or prenylated green fluorescent protein (GFP), are viable and still exhibit a Spitzenkörper during filamentous growth. Strikingly, all of these mutants formed filaments with increased diameters and extension rates, indicating that Mlc1 negatively regulates myosin V, Myo2, activity. The results of our quantitative studies reveal a strong correlation between filament diameter and extension rate, which is consistent with the vesicle supply center model for fungal tip growth. Together, our results indicate that the Spitzenkörper protein Mlc1 is important for growth robustness and reveal a critical link between filament morphology and extension rate. IMPORTANCE Hyphal tip growth is critical in a range of fungal pathogens, in particular for invasion into animal and plant tissues. In Candida albicans, as in many filamentous fungi, a cluster of vesicles, called a Spitzenkörper, is observed at the tip of growing hyphae that is thought to function as a vesicle supply center. A central prediction of the vesicle supply center model is that the filament diameter is proportional to the extension rate. Here, we show that mutants lacking the Spitzenkörper component myosin light chain 1 (Mlc1) or having synthetic physical interactions between Mlc1 and either another Spitzenkörper component or prenylated GFP, are defective in filamentous growth regulation, exhibiting a range of growth rates and sizes, with a strong correlation between diameter and extension rate. These results suggest that the Spitzenkörper is important for growth robustness and reveal a critical link between filament morphology and extension rate.