Tropicalis Cells Research Articles

CGA-N12, a peptide derived from chromogranin A, promotes apoptosis of Candida tropicalis by attenuating mitochondrial functions.

CGA-N12 (the amino acid sequence from the 65th to the 76th residue of the N-terminus of chromagranin A) is an antifungal peptide derived from human chromogranin A (CGA). In our previous investigation, CGA-N12 was found to have specific anti-candidal activity, though the mechanism of action remained unclear. Here, we investigated the effects of CGA-N12 on mitochondria. We found that CGA-N12 induced an over-generation of intracellular reactive oxygen species and dissipation in mitochondrial membrane potential, in which the former plays key roles in the initiation of apoptosis and the latter is a sign of the cell apoptosis. Accordingly, we assessed the apoptosis features of Candida tropicalis cells after treatment with CGA-N12 and found the following: leakage of cytochrome c and uptake of calcium ions into mitochondria and the cytosol; metacaspase activation; and apoptotic phenotypes, such as chromatin condensation and DNA degradation. In conclusion, CGA-N12 is capable of inducing apoptosis in C. tropicalis cells through mitochondrial dysfunction and metacaspase activation. Antifungal peptide CGA-N12 from human CGA exhibits a novel apoptotic mechanism as an antifungal agent.

Candida tropicalis affects the virulence profile of Candida albicans: an in vitro and in vivo study.

Candida albicans and Candida tropicalis are commensal microorganisms occurring in the oral cavity of approximately 50%-70% of healthy individuals. However, these microbes can become pathogenic through changes in the environment or weakened host immune system. Thus, the aim of this investigation was to evaluate the interaction between species of the genus Candida in the biofilm formation, filamentation, gene expression and virulence in Galleria mellonella. Coincubation of C. albicans with C. tropicalis cells after 48 h resulted in significant reduction of biofilm formation by decreasing viable cell counts, metabolic activity and hyphal growth. The C. albicans genes (BCR1, CPH1, EFG1, UME6, HWP1, ALS3, SAP5 and PLB2) were quantified by quantitative real-time polymerase chain reaction and most of genes were downregulated. Regarding in vivo assay, the groups that the larvae received C. albicans and C. tropicalis had a significant survival increase compared to the control group of C. albicans (P=0.0001) in agreement with the in vitro results. In conclusion, C. tropicalis colonization was associated with a decrease in the growth of C. albicans, suggesting an antagonistic relation between these two species. Therefore, C. tropicalis by reducing C. albicans virulence profile may limit the ability of this pathogenic fungus to cause infection.

γ-irradiation from radiotherapy improves the virulence potential of Candida tropicalis.

To evaluate if radiation used in radiotherapy can cause changes in the virulence potential of Candida tropicalis ATCC 750. C. tropicalis was exposed in vitro to identical dose and scheme of irradiation would be used in patients with head and neck cancer. Some virulence parameters were analyzed before and after irradiation. Colony morphologies were irreversibly affected by irradiation. Increase in growth rate, filamentation, adhesion on cell lines and phagocytosis process were also observed. Overall the irradiated C. tropicalis cells became more efficient at causing systemic infection in mice. γ-radiation induced important changes in C. tropicalis increasing its virulence profile, which could directly affect the relationship between yeasts and hosts.

Xylitol production from non-detoxified and non-sterile lignocellulosic hydrolysate using low-cost industrial media components.

Immobilized Candida tropicalis cells in freeze dried calcium alginate beads were used for production of xylitol from lignocellulosic waste like corn cob hydrolysate without any detoxification and sterilization of media. Media components for xylitol fermentation were screened by statistical methods. Urea, KH2PO4 and initial pH were identified as significant variables by Plackett-Burman (PB) design. Significant medium components were optimized by response surface methodology (RSM). Predicted xylitol yield by RSM model and experimental yield was 0.87 and 0.79g/g, respectively. Optimized conditions (urea 1.5g/L, KH2PO4 1.9g/L, xylose 55g/L, pH 6.7) enhanced xylitol yield by 32% and xylose consumption by twofold over those of basal media. In addition, the immobilized cells were reused five times at shake flask level with optimized medium without affecting the xylitol productivity and yield. Xylitol production was successfully scaled up to 7.5L stirred tank reactor using optimized media. Thus, the optimized condition with non-detoxified pentose hydrolysate from corn cob lignocellulosic waste with minimal nutrients without any sterilization opens up the scope for commercialization of the process.

Propolis: a potential natural product to fight Candida species infections.

To evaluate the effect of propolis against Candida species planktonic cells and its counterpart's biofilms. The MIC values, time-kill curves and filamentation form inhibition were determined in Candida planktonic cells. The effect of propolis on Candida biofilms was assessed through quantification of CFUs. MIC values, ranging from 220 to 880 µg/ml, demonstrated higher efficiency on C. albicans and C. parapsilosis than on C. tropicalis cells. In addition, propolis was able to prevent Candida species biofilm's formation and eradicate their mature biofilms, coupled with a significant reduction on C. tropicalis and C. albicans filamentation. Propolis is an inhibitor of Candida virulence factors and represents an innovative alternative to fight candidiasis.

Copper(II) and Phenol Adsorption by Cell Surface Treated Candida tropicalis Cells in Aqueous Suspension

An experimental study was performed to determine the feasibility of using physically treated Candida tropicalis cells for sorption of Cu(II) and phenol, the role of competition between phenol molecules and Cu(II). The yeast cells were lyophilized (LC), heat-treated at 65 °C for 24 h (HT1), at 90 °C for 24 h (HT2), and 72 h (HT3), inactivated at 120 °C and 104 kPa for 20 min (PC). The adsorption isotherms were determined in batch system. Experimental equilibrium data were evaluated using Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models by linear and non-linear regression. The adsorbed Cu(II) and phenol amounts by yeast cells were decreased due to the physical treatments of cells. With the increase of biomass dosage from 1 to 10 g L−1, the adsorption efficiency was increased. The Cu(II) adsorption capacity was also determined in the presence of phenol at various initial concentrations, and in these systems, phenol adsorption isotherms were determined. In the presence of phenol, the Cu(II) sorption capacity by lyophilized cells and carbon particles was decreased. The most commonly used sorbent in water treatment is activated carbon with large specific surface; therefore, the results were compared with the experimental data obtained by using activated carbon (AC).

Surfaceome of pathogenic yeasts, Candida parapsilosis and Candida tropicalis, revealed with the use of cell surface shaving method and shotgun proteomic approach.

In the course of infections caused by pathogenic yeasts from the genus Candida, the fungal cell surface is the first line of contact with the human host. As the surface-exposed proteins are the key players in these interactions, their identification can significantly contribute to discovering the mechanisms of pathogenesis of two emerging pathogens from this genus, C. parapsilosis and C. tropicalis. Therefore, the aim of the present study was to identify the cell wall-attached proteins of these two species with the use of cell surface shaving and a shotgun proteomic approach. Different morphological forms of C. parapsilosis and C. tropicalis cells obtained after growth under various conditions were subjected to this treatment. This allowed to indicate the most abundant cell surface proteins on the basis of the normalized spectral abundance factors. In case of yeast-like forms these were, among others, proteins similar to a chitinase, glyceraldehyde-3-phosphate dehydrogenase and an inducible acid phosphatase for C. parapsilosis, and a constitutive acid phosphatase, pyruvate decarboxylase and glyceraldehyde-3-phosphate dehydrogenase for C. tropicalis. In case of pseudohyphal forms, proteins similar to a cell surface mannoprotein Mp65, chitinase and glycosylphosphatidylinositol-anchored transglycosylase Crh11 were identified at the cell surface of C. parapsilosis. The Rbt1 cell wall protein, a hyphally regulated cell wall protein and proteins from agglutinin-like sequence protein family were found as the most abundant on C. tropicalis pseudohyphae. Apart from the abovementioned proteins, several additional covalently bound and atypical cell wall proteins were also identified. These results extend the current knowledge regarding the molecular basis of virulence of these two non-albicans Candida species.

A Sunflower Lectin with Antifungal Properties and Putative Medical Mycology Applications

Lectins are carbohydrate-binding proteins with a high specificity for a variety of glycoconjugate sugar motifs. The jacalin-related lectins (JRL) are considered to be a small sub-family composed of galactose- and mannose-specific members. Using a proteomics approach, we have detected a 16 kDa protein (Helja) in sunflower seedlings that were further purified by mannose-agarose affinity chromatography. The aim of this work was to characterize the biological activity of Helja and to explore potential applications for the antifungal activity of this plant lectin against medically important yeasts. To initially assess the agglutination properties of the lectin, Saccharomyces cerevisiae cells were incubated with increasing concentrations of the purified lectin. At a concentration of 120 μg/ml, Helja clearly agglutinated these cells. The ability of different sugars to inhibit S. cerevisiae cell agglutination determined its carbohydrate-specificity. Among the monosaccharides tested, D-mannose had the greatest inhibitory effect, with a minimal concentration of 1.5 mM required to prevent cell agglutination. The antifungal activity was evaluated using pathogenic fungi belonging to the Candida and Pichia genera. We demonstrate that 200 μg/ml of Helja inhibited the growth of all yeasts, and it induced morphological changes, particularly through pseudohyphae formation on Candida tropicalis. Helja alters the membrane permeability of the tested fungi and is also able to induce the production of reactive oxygen species in C. tropicalis cells. We concluded that Helja is a mannose-binding JRL with cell agglutination capabilities and antifungal activity against yeasts. The biological properties of Helja may have practical applications in the control of human pathogens.

Enhancement of biosorption of zinc ions from aqueous solution by immobilized Candida utilis and Candida tropicalis cells

The cells of Candida utilis and Candida tropicalis were immobilized by calcium alginate gel and used for the investigation of biosorption parameters for the removal of zinc ions from aqueous solution. The isotherms, kinetics and thermodynamics of biosorption were studied in batch system under optimum operating conditions. Experimental equilibrium data were analyzed using Langmuir, Freundlich and Dubinin–Raduskhkevich isotherm models by linear and non-linear regression. The functional groups responsible for the biosorption of zinc ions were identified using Fourier transform infrared spectra. Immobilized C. utilis exhibited the highest biosorption capacity of 181.7 mg g−1 at 45 °C for removal of zinc ions from aqueous solution. The kinetics analysis of the experimental data showed that the biosorption process followed the pseudo second order kinetic. Different desorbing agents were investigated for elution of adsorbed zinc ions from the immobilized biomass and regenerated biosorbent was reused without significant loss in its biosorption capacity. Thermodynamic parameters were calculated by using the biosorption equilibrium constant based on Langmuir isotherm.

The non-mammalian hostGalleria mellonellacan be used to study the virulence of the fungal pathogenCandida tropicalisand the efficacy of antifungal drugs during infection by this pathogenic yeast

Although Candida tropicalis is a frequent cause of invasive fungal diseases, its interaction with the host remains poorly studied. Galleria mellonella is a Lepidoptera model which offers a useful tool to study virulence of different microorganisms and drug efficacy. In this work we investigated the virulence of C. tropicalis in G. mellonella at different temperatures and the efficacy of antifungal drugs in this infection model. When larvae were infected with yeast inocula suspensions of different concentrations (4 × 10(6), 2 × 10(6), 10(6) and 5 × 10(5) cells/larva), we observed a dose-dependent effect on the killing of the insect (50% survival ranging from 1.4 ± 0.8 to 8.8 ± 1.2 days with the higher and lower inocula, respectively). Candida tropicalis killed G. mellonella larvae at both 30°C and 37°C, although at 37°C the virulence was more evident. Haemocytes phagocytosed C. tropicalis cells after 2 hours of infection, although the phagocytosis rate was lower when compared with other fungal pathogens, such as Cryptococcus neoformans. Moreover, the haemocyte density in the haemolymph decreased during infection and the yeast formed pseudohyphae in G. mellonella. The efficacy of amphotericin B, caspofungin, fluconazole and voriconazole was tested at different concentrations, and a protective effect was observed with all the drugs at concentrations equivalent to therapeutic dose. Fungal burden increased in infected larvae during time of infection and amphotericin B and fluconazole reduced the number of colony-forming units in the worms. Moreover, antifungal treatment was associated with the presence of cell aggregates around infected areas. We conclude that G. mellonella offers a simple and feasible model to study C. tropicalis virulence and drug efficacy.

Candida tropicalis biofilms: Effect on urinary epithelial cells

Candida tropicalis infection is strongly associated with the presence of biofilms in urinary catheters. Thus, the aim of this work was to study the behaviour of C. tropicalis in biofilms of different ages (24–120 h) formed in artificial urine (AU) and their effect in human urinary bladder cells (TCC-SUP). Reference strain ATCC 750 and two isolates from patients with candiduria (U69 and U75) were used in this study. The adhesion to human cells was evaluated after 2 h of contact with Candida biofilms, using the Crystal violet staining method, and the human cells response was evaluated in terms of activity inhibition and cell damage. Candida tropicalis aspartyl proteinase (SAPT) gene expression was determined by real-time PCR. Candida tropicalis biofilm cells were able to adhere to TCC-SUP cells. The highest extent of yeast attachment was obtained for the 72 h old biofilm cells. Yeasts affected TCC-SUP cells, with 120 h-biofilm cells causing the highest levels of cell injury. Generally, SAPT3 was highly expressed and SAPT4 was only detected in the reference strain. Overall, it is important to highlight that C. tropicalis cells detached from biofilms are able to colonize human cells and cause some injury and reduction of metabolic activity.

Capsicum annuum L. trypsin inhibitor as a template scaffold for new drug development against pathogenic yeast

A 6,000Da peptide, named CaTI, was isolated from Capsicum annuum L. seeds and showed potent inhibitory activity against trypsin and chymotrypsin. The aim of this study was to determine the effect of CaTI on Saccharomyces cerevisiae, Candida albicans, Candida tropicalis and Kluyveromyces marxiannus cells. We observed that CaTI inhibited the growth of S. cerevisiae, K. marxiannus as well as C. albicans and induced cellular agglomeration and the release of cytoplasmic content. No effect on growth was observed in C. tropicalis but morphological changes were noted. In the spot assay, different degrees of sensitivity were shown among the strains and concentrations tested. Scanning electron microscopy showed that S. cerevisiae, K. marxiannus and C. albicans, in the presence of CaTI, exhibited morphological alterations, such as the formation of pseudohyphae, cellular aggregates and elongated forms. We also show that CaTI induces the generation of nitric oxide and interferes in a dose-dependent manner with glucose-stimulated acidification of the medium mediated by H(+)-ATPase of S. cerevisiae cells.

Two families of Xenopus tropicalis skeletal genes display well‐conserved expression patterns with mammals in spite of their highly divergent regulatory regions

The origin of bone and cartilage, and their subsequent diversification in specific vertebrate lineages, is intimately linked to the precise transcriptional control of genes involved in matrix mineralization. It is not yet clear, however, to which extent the osteoblasts, osteocytes, and chondrocytes of each of the major vertebrate groups express similar sets of genes. In this study we have focused on the evolution of two independent families of genes that code for extracellular matrix components of the skeleton and that include secreted protein, acidic, cysteine-rich (SPARC), bone sialoprotein (BSP) and dentin matrix protein 1 (DMP1) paralogues, and the osteocalcin (OC) and matrix gla protein (MGP) paralogues. Analyzing developing Xenopus tropicalis skeletal elements, we show that the expression patterns of these genes are well conserved with mammals. The fact that only a few osteoblasts express DMP1, while only some osteocytes express SPARC and BSP, reveals a significant degree of molecular heterogeneity for these two populations of X. tropicalis cells, similarly to what has been described in mouse. Although the cis-regulatory modules (CRM) of the mammalian OC, DMP1, and BSP orthologs have been functionally characterized, we found no evidence of sequence similarity between these regions and the X. tropicalis genome. Furthermore, these regulatory elements evolve rapidly, as they are only poorly conserved between human and rodents. Therefore, the SPARC/DMP1/BSP and the OC/MGP families provide a good paradigm to study how transcriptional output can be maintained in skeletal cells despite extensive sequence divergence of CRM.

Improving the lipid accumulation properties of the yeast cells for biodiesel production using molasses

In this article the high lipid accumulation potential of Candida lipolytica, Candida tropicalis and Rhodotorula mucilaginosa cells were shown in molasses medium. Four different pH values were examined (4–7) to discover the optimum lipid accumulation medium. Varied concentrations of (NH 4) 2SO 4 (0.5, 1.0, 1.5 g/L) and molasses (6%, 8%, 10%) were tested to find the optimum carbon and nitrogen amounts for the highest cellular lipid production. It is shown that the maximum lipid content could be achieved in the medium containing 8% molasses solution and 1.0 g/L (NH 4) 2SO 4 at pH 5 after four days of incubation time. The maximum lipid contents and methyl ester yields were measured as 59.9% and 84.9% for C. lipolytica, 46.8% and 93.2% for C. tropicalis, 69.5% and 92.3% for R. mucilaginosa. Because of the dominant fatty acids were C16 and C18 in the lipids of yeast cells, these crude lipids could be promising feedstock for biodiesel production.

Enhanced ethanol production via fermentation of rice straw with hydrolysate-adapted Candida tropicalis ATCC 13803

Neutralized hydrolysate and pretreated rice straw obtained from a 2% (w/v) sulfuric acid pretreatment were mixed at 10% (w/v) and subjected to simultaneous saccharification and co-fermentation (SSCF), with cellulase, β-glucosidase, and Candida tropicalis cells at 15 FPU/g-ds, 15 IU/g-ds and 1 × 10 9 cells/ml, respectively. A 36-h SSCF with adapted cells resulted in YP/S and ethanol volumetric productivity of 0.36 g/g and 0.57 g/l/h, respectively. In addition to ethanol, insignificant amounts of glycerol and xylitol were also produced. Adapted C. tropicalis cells produced nearly 1.6 times more ethanol than non-adapted cells. Ethanol yield (Yp/s), ethanol volumetric productivity and a xylitol concentration of 0.48 g/g, 0.33 g/l/h and 0.89 g/l, respectively, were produced from fermentation of remaining hydrolysate with adapted C. tropicalis cells. The 0.20 g/g ethanol yield and 77% production efficiency from SSCF of pretreated rice straw indicate scale-up potential for the process. This study demonstrated that C. tropicalis produced ethanol and xylitol from a mixed-sugar stream, although cell adaptation affected ethanol and xylitol yields. Scanning electron microscopy indicated agglomeration of cellulose microfibrils and globular deposition of lignin in acid-pretreated rice straw.

Production of ethanol from starch by free and immobilized Candida tropicalis in the presence of α-amylase

Candida tropicalis is a potentially useful organism for the commercial production of ethanol as it is capable of fermenting starch at a low rate. To enhance this carbon source utilization and increase the rate of alcohol production, we pretreated corn soluble starch with α-amylase. Starch liquefaction was sufficient to drive the fermentation and to convert 96% substrate to ethanol. Indeed, in the presence of exogenous α-amylase, 9% (w/v) soluble starch was converted to 43.1 g ethanol/l in 65 h with a productivity of 0.65 g/l h. Thus, bio-ethanol production using free and calcium alginate-immobilized C. tropicalis does not require the saccharification step. Furthermore, fed-batch fermentation by free C. tropicalis cells increased the final concentration to 56 g ethanol/l, reaching published values for Saccharomyces cerevisiae recombinant strains expressing both α-amylase and glucoamylase.

Kinetic study of phenol hydroxylase and catechol 1,2-dioxygenase biosynthesis by Candida tropicalis cells grown on different phenolic substrates

When Candida tropicalis was grown on phenol, catechol or resorcinol, the highest levels of specific activity of phenol hydroxylase (EC. 1.14.13.7) and catechol 1,2-dioxygenase (EC. 1.13.11.1) were attained with phenol. With the three aromatic compounds tested, the yeast cells exhibited sharp peaks of specific activity of both enzymes at particular incubation times. Phenol-induced cells containing high levels of both enzymes were capable of degrading rapidly and without delay 4-chlorophenol and 2,6-dichlorophenol, and to a lesser extend pentachlorophenol. However, the yeast could not grow on chlorophenols as major carbon and energy source.

An amperometric microbial biosensor development based on Candida tropicalis yeast cells for sensitive determination of ethanol

Different branchs of industry need to use ethanol in their production and some progress and not only the industry also to determine ethanol sensitively, accurately, fast and economical is very important. For the sensitive determination of ethanol a new amperometric biosensor based on Candida tropicalis cells, which contains alcohol oxidase enzyme, immobilized in gelatin by using glutaraldehyde was developed. In the study, before the microbial biosensor construction C. tropicalis cells were activated and cultured in a culture medium. By using gelatine and glutaraldehyde (0.1%) C. tropicalis cells obtained in logarithmic phase were immobilized and fixed on a pretreated teflon membrane of a dissolved oxygen probe. Ethanol determination is based on the assay of the differences on the respiration activity of the cells on the oxygenmeter in the absence and the presence of ethanol. The microbial biosensor response was depend linearly on ethanol concentration between 0.5 and 7.5 mM with 2 min response time. In the optimization studies of the microbial biosensor the most suitable microorganism amount were found as 4.42 mg cm −2 and also phosphate buffer (pH:7.5; 50 mM) and 30 °C were obtained as the optimum working conditions. In the characterization studies of the microbial biosensor some parameters such as substrate specificity, interference effects of some substances on the biosensor response, operational and storage stability were carried out.

A combination of alpha-tocopherol, vitamin C and N-acetyl cysteine increases unsaturated fatty acid levels in hydrogen peroxide-induced Candida tropicalis (ATCC 13803).

This research was aimed at evaluating the antioxidant effects of combinations of alpha lipoic acid (LA), vitamin C (VC), N-acetyl cysteine (NAC) and alpha-tocopherol (TOC) on lipid level and fatty acid composition of C. tropicalis (ATCC 13803) against hydrogen peroxide toxicity. According to the experimental results, the cell density of C. tropicalis increased significantly in NAC+LA+H2O2, NAC+TOC+ H2O2 and NAC+VC+H2O2 groups (p<0.001) at the end of 48 and 72 h incubation times. The total lipid level in H2O2 and H2O2 + antioxidant-supplemented groups was lower than that of the control group. In the fatty acid composition of C. tropicalis, the palmitic acid level was raised in the NAC group (p<0.05), whereas its level was reduced in the other supplemented groups. While the oleic acid level increased in NAC+TOC+H2O2 and NAC+VC+H2O2 (p<0.001) groups, its level slightly decreased in the H2O2 group. The linolenic acid level was low in all the supplemented groups, but linoleic acid and total mono-unsaturated fatty acid (MUFA) levels were high in these groups compared with the control group. Total polyunsaturated fatty acid level (PUFA) decreased in NAC and H2O2 groups (p<0.01), but its level increased in NAC+LA+H2O2 and NAC+TOC+H2O2 groups (respectively, p<0.01, p<0.001). Total saturated fatty acid level decreased significantly in NAC+TOC+H2O2, NAC+H2O2 and NAC+VC+H2O2 (p<0.001) groups (p<0.01), whereas total unsaturated fatty acid level increased in NAC, NAC+H2O2, NAC+LA+H2O2, NAC+TOC+H2O2 and NAC+VC+H2O2 groups. In conclusion, our data showed that the levels of total unsaturated fatty acid, MUFA and PUFA were raised with the combinations of NAC and TOC, LA and VC in C. tropicalis cells subjected to hydrogen peroxide toxicity.

Physiological difference during ethanol fermentation between calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae

Calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae are compared for glucose fermentation. Immobilized C. tropicalis cells showed a slight morphological alteration during ethanol production at 40°C, but their fermentation capacity was reduced by 25%. Under immobilization conditions, the two species demonstrated two different mathematical patterns when the relationship between growth rate, respiration rate, and ethanol tolerance was assessed. The interspecific difference in behavior of immobilized yeast cells is mainly due to their natural metabolic preference. The production of CO2 by calcium alginate-immobilized C. tropicalis, as well as the lower supply of oxygen to the cells, are the major factors that reduce ethanol production.