Study of the mechanism of ε-poly-l-lysine as an antifungal on Candida albicans and Saccharomyces cerevisiae

The antimicrobial activity of ε-poly-l-lysine (EPL) has been documented, but its antifungal activity on yeast is not well defined and its mechanism of action has been vaguely explained. Our studies revealed that on both, Candida albicans and Saccharomyces cerevisiae, the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) were 250 μg·mL^?1; EPL produced a K⁺ and Ca²⁺ efflux, and at higher concentrations also an efflux of material absorbing at 260 nm, small peptides, and phosphate is produced, along with the inhibition of fermentation and extracellular acidification and respiration. Moreover, growth was inhibited, reactive oxygen species (ROS) production increased, and cell viability decreased. The polycation also produced plasma membrane potential hyperpolarization. The effects were dependent both on the cell quantity and polycation concentration, as well as the media used. The plasma membrane disruption was confirmed by TEM and PI staining.     

Enhancement of ε-poly-l-lysine synthesis in Streptomyces by exogenous glutathione

Bioprocess and Biosystems Engineering - Our previous work indicated that the vigor of Streptomyces decreased at the later stage of ε-poly-l-lysine (ε-PL) fermentation. In this study, we...     

Promotion of ε-poly-l-lysine production by iron in Kitasatospora kifunense

Kitasatospora kifunense, belonging to the Streptomycetaceae family, produces a basic homopolymer, ε-poly-l-lysine, which is used as a food preservative. We showed that ε-poly-l-lysine production in this bacterium on agar plates with iron started two or three days earlier than that on plates without iron. We also showed that iron added to a liquid culture medium increased ε-poly-l-lysine production by K. kifunense. Similarly, manganese and cobalt also promoted ε-poly-l-lysine production on agar plates. Moreover, cobalt promoted ε-poly-l-lysine production in liquid culture media. These results indicate that iron, manganese and cobalt are involved in regulating the ε-poly-l-lysine biosynthesis system in K. kifunense.     

Enhanced ε-poly-l-lysine production by inducing double antibiotic-resistant mutations in Streptomyces albulus

Bioprocess and Biosystems Engineering - ε-Poly-l-lysine (ε-PL), as a food additive, has been widely used in many countries. However, its production still needs to be improved. We...     

Candida albicans Elicits Pro-Inflammatory Differential Gene Expression in Intestinal Peyer’s Patches

The details of how gut-associated lymphoid tissues such as Peyer’s patches (PPs) in the small intestine play a role in immune surveillance, microbial differentiation and the mucosal barrier protection in response to fungal organisms such as Candida albicans are still unclear. We particularly focus on PPs as they are the immune sensors and inductive sites of the gut that influence inflammation and tolerance. We have previously demonstrated that CD11c⁺ phagocytes that include dendritic cells and macrophages are located in the sub-epithelial dome within PPs sample C. albicans. To gain insight on how specific cells within PPs sense and respond to the sampling of fungi, we gavaged naïve mice with C. albicans strains ATCC 18804 and SC5314 as well as Saccharomyces cerevisiae. We measured the differential gene expression of sorted CD45⁺ B220⁺ B-cells, CD3⁺ T-cells and CD11c⁺ DCs within the first 24 h post-gavage using nanostring nCounter^® technology. The results reveal that at 24 h, PP phagocytes were the cell type that displayed differential gene expression. These phagocytes were able to sample C. albicans and discriminate between strains. In particular, strain ATCC 18804 upregulated fungal-specific pro-inflammatory genes pertaining to innate and adaptive immune responses. Interestingly, PP CD11c⁺ phagocytes also differentially expressed genes in response to C. albicans that were important in the protection of the mucosal barrier. These results highlight that the mucosal barrier not only responds to C. albicans, but also aids in the protection of the host.

     

β-Glucan Induces Reactive Oxygen Species Production in Human Neutrophils to Improve the Killing of Candida albicans and Candida glabrata Isolates from Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) is among the most prevalent vaginal diseases. Candida albicans is still the most prevalent species associated with this pathology, however, the prevalence of other Candida species, such as C. glabrata, is increasing. The pathogenesis of these infections has been intensely studied, nevertheless, no consensus has been reached on the pathogenicity of VVC. In addition, inappropriate treatment or the presence of resistant strains can lead to RVVC (vulvovaginal candidiasis recurrent). Immunomodulation therapy studies have become increasingly promising, including with the β-glucans. Thus, in the present study, we evaluated microbicidal activity, phagocytosis, intracellular oxidant species production, oxygen consumption, myeloperoxidase (MPO) activity, and the release of tumor necrosis factor α (TNF-α), interleukin-8 (IL-8), IL-1β, and IL-1Ra in neutrophils previously treated or not with β-glucan. In all of the assays, human neutrophils were challenged with C. albicans and C. glabrata isolated from vulvovaginal candidiasis. β-glucan significantly increased oxidant species production, suggesting that β-glucan may be an efficient immunomodulator that triggers an increase in the microbicidal response of neutrophils for both of the species isolated from vulvovaginal candidiasis. The effects of β-glucan appeared to be mainly related to the activation of reactive oxygen species and modulation of cytokine release.     

Candida albicans hyphal invasion: thigmotropism or chemotropism?

Hyphae of the human pathogenic fungus Candida albicans exhibit thigmotropic behaviour in vitro, in common with phytopathogenic and saprotrophic fungi. An examination of the literature on C. albicans hyphal penetration of epithelial and endothelial membranes does not support the premise that hyphal thigmotropism plays a major role in tissue invasion. Further experimentation is now required to assess thigmotropic behaviour on host membranes and vaginal epithelial cells are suggested as a test model. It is proposed that while thigmotropism may and invasion of tissue invaginations, chemotropism can explain C. albicans hyphal invasion patterns of both endothelium and epithelium.     

Genetically Compromising Phospholipid Metabolism Limits Candida albicans’ Virulence

Mycopathologia - Perturbing ergosterol synthesis has been previously shown to reduce the virulence of Candida albicans. We tested the hypothesis that further altering cell membrane composition by...     

Effective vitrification of human induced pluripotent stem cells using carboxylated ε-poly-l-lysine

Derivation of human induced pluripotent stem (iPS) cells could enable their widespread application in future. Establishment of highly efficient and reliable methods for their preservation is a prerequisite for these applications. In this study, we developed a vitrification solution comprising ethylene glycol (EG) and sucrose as well as carboxylated ε-poly-l-lysine (PLL); this solution inhibited devitrification. Human iPS cells were vitrified in 200-μL vitrification solutions comprised 6.5 M EG, 0.75 M sucrose and 0 or 10% w/v carboxylated PLL with 65 mol% of the amino groups converted to carboxyl groups [PLL (0.65)] in a cryovial by directly immersing in liquid nitrogen. After warming, attached colony and recovery rates of human iPS cells vitrified by adding PLL (0.65) were significantly higher than those for cells without PLL (0.65) and vitrification solution (DAP213: 2 M dimethyl sulfoxide, 1 M acetamide and 3 M propylene glycol). Furthermore, even after warming at room temperature, attached colony and recovery rates of iPS cells vitrified with PLL (0.65) were reduced to a lesser extent than those vitrified with either DAP213 or EG and sucrose without PLL (0.65). This could be attributed to inhibition of devitrification by PLL (0.65), as differential scanning calorimetry indicated less damage after vitrification with PLL (0.65). In addition, human iPS cells vitrified in the solution with PLL (0.65) had normal karyotypes and maintained undifferentiated states and pluripotency as determined by immunohistochemistry and teratoma formation. Addition of PLL (0.65) successfully vitrified human iPS cells with high efficiency. We believe that this method could aid future applications and increase utility of human iPS cells.     

Antibiotic tetaine — a selective inhibitor of chitin and mannoprotein biosynthesis in Candida albicans

The antibiotic tetaine inhibits in Candida albicans the biosynthesis of two important cell wall constituents, chitin and mannoprotein. This effect is a consequence of inactivation of the enzyme glucosamine-6-phosphate synthetase. Due to the lack of glucosamine-6-phosphate the effective secretion of mannoprotein enzymes, acid phosphatase and invertase, by Candida albicans spheroplasts is inhibited. In the presence of tetaine, probably a modified mannoprotein, lacking a branched polymannan, is synthesized. The antibiotic action decreases the viability of Candida albicans cells, especially that of mycelial forms of this fungus.Abbreviations GlcNAc N-acetyl-d-glucosamine - GlcN-6-P d-glucosamine-6-phosphate - ManNAc N-acetyl-d-mannosamine - -MM -methylmannoside - EGTA 1,2 di/2-aminoethoxy/ethane - N,N,N,N tetra-acetic acid