Cell compensatory responses of fungi to damage of the cell wall induced by Calcofluor White and Congo Red with emphasis on Sporothrix schenckii and Sporothrix globosa. A review.

The cell wall (CW) of fungi exhibits a complex structure and a characteristic chemical composition consisting almost entirely of interacting crystalline and amorphous polysaccharides. These are synthesized by a number of sugar polymerases and depolymerases encoded by a high proportion of the fungal genome (for instance, 20% in Saccharomyces cerevisiae). These enzymes act in an exquisitely coordinated process to assemble the tridimensional and the functional structure of the wall. Apart from playing a critical role in morphogenesis, cell protection, viability and pathogenesis, the CW represents a potential target for antifungals as most of its constituents do not exist in humans. Chitin, ß-glucans and cellulose are the most frequent crystalline polymers found in the fungal CW. The hexosamine biosynthesis pathway (HBP) is critical for CW elaboration. Also known as the Leloir pathway, this pathway ends with the formation of UDP-N-GlcNAc after four enzymatic steps that start with fructose-6-phosphate and L-glutamine in a short deviation of glycolysis. This activated aminosugar is used for the synthesis of a large variety of biomacromolecules in a vast number of organisms including bacteria, fungi, insects, crustaceans and mammalian cells. The first reaction of the HBP is catalyzed by GlcN-6-P synthase (L-glutamine:D-fructose-6-phosphate amidotransferase; EC 2.6.1.16), a critical enzyme that has been considered as a potential target for antifungals. The enzyme regulates the amount of cell UDP-N-GlcNAc and in eukaryotes is feedback inhibited by the activated aminosugar and other factors. The native and recombinant forms of GlcN-6-P synthase has been purified and characterized from both prokaryotic and eukaryotic organisms and demonstrated its critical role in CW remodeling and morphogenesis after exposure of some fungi to agents that stress the cell surface by interacting with wall polymers. This review deals with some of the cell compensatory responses of fungi to wall damage induced by Congo Red and Calcofluor White.

Sporothrix schenckii regulates macrophage inflammatory responses via the c-JUN-induced Dab2 transcription.

Macrophages, which serve as a bridge between innate and adaptive immunity, play an important role in sporotrichosis. Sporothrix schenckii infections can produce immune responses such as macrophage polarization and inflammatory factor secretion. In the early stages of inflammation, the expression of DAB2 in macrophages is increased, which controls the secretion of inflammatory factors and affects the polarization of macrophages. However, the expressions and mechanisms of DAB2 in sporotrichosis are not clear. In this study, we examined the expression of DAB2 and its regulation of inflammatory factors under conditions of Sporothrix schenckii infection. Our results indicated that the Sporothrix schenckii infection increased the expression of DAB2 and revealed a mixed M1/M2-like type of gene expression in BMDMs with the inhibited Il-6, Il1-ß and Arg-1 and induced Tnf-α, Il-10 and Mgl-1. The deficiency of Dab2 gene suspended the changes of cytokines. In addition, JNK activity in BMDMs was inhibited by Sporothrix schenckii infection, leading to an increase in c-JUN. We also identified c-JUN as a transcription factor for Dab2 through chromatin immunoprecipitation and luciferase reporter assays. In an in vivo mouse model, sporotrichosis-induced skin lesions were accompanied with an upregulation of c-JUN and inhibition of JNK activity, which were in accord with findings from in vitro experiments. Taken together, these findings indicate that in the early stages of Sporothrix schenckii infection there is a promotion of DAB2 expression through the JNK/c-JUN pathway, effects that can then control the expression of inflammatory factors.

Map of dimorphic switching­related signaling pathways in Sporothrix schenckii based on its transcriptome.

Sporothrix schenckii (S. schenckii) induces sporotrichosis, which has gained attention in recent years due to its worldwide prevalence. The dimorphic switching process is essential for the pathogenesis of S. schenckii. Previously, overexpression of several signal transduction genes, including SsDRK1 and SsSte20, was observed during the mycelium­to­yeast transition; these were necessary for asexual development, yeast­phase cell formation, cell wall integrity and melanin synthesis. However, the mechanisms of the signaling pathways during dimorphic switching of S. schenckii remain unclear. In the present study, transcriptome sequencing of the 48­h induced yeast forms and mycelium of S. schenckii was performed. In total, 24,904,510 high­quality clean reads were obtained from mycelium samples and 22,814,406 from 48­h induced yeast form samples. Following assembly, 31,779 unigene sequences were obtained with 52.98% GC content (The proportion of guanine G and cytosine C to all bases in nucleic acid). The results demonstrated that 12,217 genes, including genes involved in signal transduction and chitin synthesis, were expressed differentially between the two stages. According to these results, a map of the signaling pathways, including two­component and heterotrimeric G­protein signaling systems, Ras and MAPK cascades associated with the dimorphic switch, was drawn. Taken together, the transcriptome data and analysis performed in the present study lay the foundation for further research into the molecular mechanisms controlling the dimorphic switch of S. schenckii and support the development of anti­S. schenckii strategies targeting genes associated with signaling pathways.

Anti-Sporothrix activity of ibuprofen combined with antifungal.

The in vitro activity of ibuprofen, a nonsteroidal anti-inflammatory drug, was evaluated against Sporothrix brasiliensis and S. schenckii, either alone or in combination with amphotericin B, itraconazole, or terbinafine. The inhibitory activity of ibuprofen as a single agent was determined according to minimum inhibitory concentration (MIC) values, while the effect of ibuprofen combined with amphotericin B, itraconazole, or terbinafine was estimated by microdilution checkerboard methodology. The ultrastructural alterations of S. schenckii after exposure to the combination of ibuprofen and amphotericin B were evaluated by scanning electron microscopy (SEM) and flow cytometry analysis. As a single agent, ibuprofen inhibited Sporothrix growth with a MIC median of 256 µg/mL, while the MIC medians of ibuprofen in combination with antifungals were 16 µg/mL and 128 µg/mL. The MIC values of amphotericin B, itraconazole, and terbinafine were reduced when isolates were co-incubated with ibuprofen, mainly the polyene. The major alteration after treatment with the ibuprofen/amphotericin B combination was the increase in the presence of filamentous forms and high membrane damage with loss of plasma membrane integrity. In summary, we demonstrated that ibuprofen increases the in vitro activity of antifungals, mainly amphotericin B, against S. brasiliensis and S. schenckii. Future in vivo studies exploring combination therapy with ibuprofen and antifungals in animal models are needed to confirm its efficacy.

Comparative proteomics in the three major human pathogenic species of the genus Sporothrix.

Sporotrichosis is a subcutaneous mycosis of humans and other mammals, caused by dimorphic species of the genus Sporothrix. In Brazil, human disease is broadly linked to transmission by infected cats and is mainly caused by Sporothrix brasiliensis, Sporothrix schenckii and Sporothrix globosa. In this study, we used a nanoscale liquid chromatography coupled with tandem mass spectrometry approach to provide the yeast proteomic profiles of S. brasiliensis, S. schenckii and S. globosa. From a total of 247 identified proteins, 137 were found as differentially expressed. Functional classification revealed that most are related to carbohydrate and amino acid metabolism as well as stress response. Our data indicate that S. brasiliensis metabolism is distinct of that of S. schenckii and S. globosa, mainly regarding amino acid metabolism and cell wall remodeling, which are induced in the former. Enzymes belonging to glycolytic pathway are, on the other hand, up-regulated in S. schenckii and S. globosa. These findings may explain the previously described more virulent character of S. brasiliensis. Besides complementing genomic comparisons already published, this first comparative proteomic study provided information that indicates new aspects of Sporothrix species metabolism as well as offers information that may be useful in the development of prospective functional studies.

Evolution of virulence-related phenotypes of Sporothrix brasiliensis isolates from patients with chronic sporotrichosis and acquired immunodeficiency syndrome.

Sporotrichosis in immunocompromised patients has a high morbidity and may cause deaths. Particularly, patients with acquired immunodeficiency syndrome (AIDS) with low T CD4 counts develop a chronic disease, with severe and widespread forms. Recently, the ability of Sporothrix brasiliensis, the main agent of zoonotic sporotrichosis, to increase its virulence in a diabetic patient without HIV infection was described. Since it was a unique finding, it is not known how often this occurs in patients with chronic and refractory sporotrichosis. The aim of this study is to compare sequential Sporothrix isolates obtained from patients with sporotrichosis and AIDS in order to detect changes in virulence-related phenotypes and acquisition of antifungal resistance during the evolution of the disease. Fungal growth in different substrates, antifungal susceptibility, thermotolerance, resistance to oxidative stress, and production of hydrolytic enzymes were evaluated. Correlations were assessed between clinical and phenotypic variables. Sixteen isolates, all identified as S. brasiliensis, obtained from five patients were studied. They grew well on glucose and N-acetyl-D-glucosamine, but poorly on lactate. Except from isolates collected from two patients, which were non-wild type for terbinafine, they were considered wild type for the antifungal drugs tested. Thermotolerance of the isolates was moderate to high. Except for phytase and phospholipase, isolates were able to produce virulence-related enzymes on different levels. Changes in all studied phenotypes were observed during the course of the disease in some patients. The results show that the HIV-driven immunosuppression is more relevant than fungal phenotypes on the unfavorable outcomes of disseminated sporotrichosis.

Influence of iron on growth and on susceptibility to itraconazole in Sporothrix spp.

We evaluated the growth and the susceptibility to oxidative stress of Sporothrix spp., exposed to different iron concentrations in culture medium, and the susceptibility of Sporothrix spp. to itraconazole, alone and in combination with to the iron chelator deferasirox. The results showed that the growth of S. brasiliensis isolates was more affected by iron availability in comparison to S. schenckii, but both fungal species conidia became more prone to oxidative stress when iron was added to culture medium. Conversely, the combination of itraconazole and deferasirox only resulted in synergism against a minority of S. schenckii isolates.

Serological tests using Sporothrix species antigens for the accurate diagnosis of sporotrichosis: a meta-analysis.

Some species of the fungus Sporothrix cause a chronic granulomatous infection in humans and animals called sporotrichosis. In the last decades, some research into serological tests has been carried out by different groups for the rapid detection of this infection. We performed a systematic review of the literature with meta-analysis to evaluate studies using Sporothrix spp. antigens and to evaluate their accuracy for sporotrichosis diagnostic. We searched Scopus, MEDLINE, Web of Science, GALE, Technology Research Database, DOA, Elsevier, SciELO, and Google Scholar Databases. The united results of sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio with their corresponding 95% confidence intervals (CI) were assessed. A total of 15 assays from 8 studies using 7 different serological methods and 8 different antigens were analyzed. The studies were performed in the USA, Brazil, and Venezuela from 1973 until 2015 and presented good quality. A high heterogeneity for sensitivity [I2 = 90.7%; 87% CI = (84-89), P < 0.001] and specificity [I2 = 89.2%; 93% CI = (92-95), P < 0.001] was observed. The performance of diagnostic tests was 0.93. Enzyme-linked immunosorbent assay was the main tool used, and the ConA-binding fraction antigen of the strain 1099-18 appears as a promising diagnostic biomarker candidate.

Proteomic analysis of Sporothrix schenckii cell wall reveals proteins involved in oxidative stress response induced by menadione.

Sporotrichosis is an emergent subcutaneous mycosis that is a threat to both humans and other animals. Sporotrichosis is acquired by the traumatic implantation of species of the Sporothrix genus. Added to the detoxification systems, pathogenic fungi possess different mechanisms that allow them to survive within the phagocytic cells of their human host during the oxidative burst. These mechanisms greatly depend from the cell wall (CW) since phagocytic cells recognize pathogens through specific receptors associated to the structure. To date, there are no studies addressing the modulation of the expression of S. schenckii CW proteins (CWP) in response to reactive oxygen species (ROS). Therefore, in this work, a proteomic analysis of the CW of S. schenckii in response to the oxidative agent menadione (O2•-) was performed. Proteins that modulate their expression were identified which can be related to the fungal survival mechanisms within the phagocyte. Among the up-regulated CWP in response to the oxidative agent, 13 proteins that could be involved in the mechanisms of oxidative stress response in S. schenckii were identified. The proteins identified were thioredoxin1 (Trx1), superoxide dismutase (Sod), GPI-anchored cell wall protein, ß-1,3-endoglucanase EglC, glycoside hydrolase (Gh), chitinase, CFEM domain protein, glycosidase crf1, covalently-linked cell wall protein (Ccw), 30 kDa heat shock protein (Hsp30), lipase, trehalase (Treh), fructose-bisphosphate aldolase (Fba1) and citrate synthase (Cs). The identification of CWP that modulates their expression in response to superoxide ion (O2•-) in S. schenckii is a useful approach to understand how the fungus defends itself against ROS, in order to evade the phagocytic cells from the host and cause the infection.

Antifungal activity of silver salts of Keggin-type heteropolyacids against Sporothrix spp.

Sporotrichosis is a chronic and subacute mycosis causing epidemiological outbreaks involving sick cats and humans in southeastern Brazil. The systemic disease prevails in cats, and in humans, the symptoms are restricted to skin in immunocompetent individuals. Under these conditions, the prolonged treatment of animals and cases of recurrence justify the discovery of new treatments for sporotrichosis. This work addresses the antifungal activity of silver salts of Keggin-type heteropolyacid salts (Ag-HPA salts) such as Ag3[PW12O40], Ag6[SiW10V2O40], Ag4[SiW12O40] and Ag3[PMo12O40] and interactions with the antifungal drugs itraconazole (ITC), terbinafine (TBF) and amphotericin B (AMB) on the yeast and mycelia forms of Sporothrix spp. Sporothrix spp. yeast cells were susceptible to Ag-HPA salts at minimum inhibitory concentration (MIC) values ranging from 8 to 128 µg/mL. Interactions between Ag3[PW12O40] and Ag3[PMo12O40] with itraconazole and amphotericin B resulted in higher antifungal activity with a reduction in growth and melanization. Treated cells showed changes in cell membrane integrity, vacuolization, cytoplasm disorder, and membrane detachment. Promising antifungal activity for treating sporotrichosis was observed for the Ag-HPA salts Ag3[PMo12O40] and Ag3[PW12O40], which have a low cost, high yield and activity at low concentrations. However, further evaluation of in vivo tests is still required.

Virulence Factors in Sporothrix schenckii, One of the Causative Agents of Sporotrichosis.

Sporothrix schenckii is one of the etiological agents of sporotrichosis, a fungal infection distributed worldwide. Both, the causative organism and the disease have currently received limited attention by the medical mycology community, most likely because of the low mortality rates associated with it. Nonetheless, morbidity is high in endemic regions and the versatility of S. schenckii to cause zoonosis and sapronosis has attracted attention. Thus far, virulence factors associated with this organism are poorly described. Here, comparing the S. schenckii genome sequence with other medically relevant fungi, genes involved in morphological change, cell wall synthesis, immune evasion, thermotolerance, adhesion, biofilm formation, melanin production, nutrient uptake, response to stress, extracellular vesicle formation, and toxin production are predicted and discussed as putative virulence factors in S. schenckii.

Interaction with Pantoea agglomerans Modulates Growth and Melanization of Sporothrix brasiliensis and Sporothrix schenckii.

Sporothrix brasiliensis and Sporothrix schenckii stand as the most virulent agents of sporotrichosis, a worldwide-distributed subcutaneous mycosis. The origin of Sporothrix virulence seems to be associated with fungal interactions with organisms living in the same environment. To assess this hypothesis, the growth of these two species in association with Pantoea agglomerans, a bacterium with a habitat similar to Sporothrix spp., was evaluated. Growth, melanization, and gene expression of the fungus were compared in the presence or absence of the bacterium in the same culture medium. Both S. brasiliensis and S. schenckii grew in contact with P. agglomerans yielding heavily melanized conidia after 5 days of incubation at 30 °C in Sabouraud agar. This increased melanin production occurred around bacterial colonies, suggesting that fungal melanization is triggered by a diffusible bacterial product, which is also supported by a similar pattern of melanin production during Sporothrix spp. growth in contact with heat-killed P. agglomerans. Growth of P. agglomerans was similar in the presence or absence of the fungus. However, the growth of S. brasiliensis and S. schenckii was initially inhibited, but further enhanced when these species were co-cultured with P. agglomerans. Moreover, fungi were able to use killed bacteria as both carbon and nitrogen sources for growth. Representational difference analysis identified overexpressed genes related to membrane transport when S. brasiliensis was co-cultured with the bacteria. The down-regulation of metabolism-related genes appears to be related to nutrient availability during bacterial exploitation. These findings can lead to a better knowledge on Sporothrix ecology and virulence.

Identification of proteins in Sporothrixschenckiisensu stricto in response to oxidative stress induced by hydrogen peroxide / Identificación de proteínas en Sporothrix schenckii sensu stricto en respuesta al estrés oxidativo inducido por peróxido de hidrógeno

Background: Sporotrichosis is a fungal infection caused by the Sporothrix schenckii complex. In order to colonize the host, the pathogen must neutralize the reactive oxygen species produced by the phagocytic cells during the respiratory burst. Little is known about these mechanisms in S. schenckii. Aims: To identify the proteins differentially expressed after the exposure of S. schenckiisensu stricto to different concentrations of H2O2. Methods: Yeast cells of S. schenckiisensu stricto were exposed to increasing concentrations of H2O2. Proteins differentially expressed in response to oxidative stress were analyzed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and identified by MALDI-MS/MS. RT-PCR assays were performed to evaluate the transcription of genes of the identified proteins. Results: Concentrations of H2O2 as high as 800 mM allowed cell growth, and 200 mM and 400mM were selected for comparative analysis by 2D-PAGE. This analysis revealed at least five differentially expressed proteins, which were identified as heat shock 70 kDa protein (Hsp70), chaperonin GroEL, elongation factor 1-β (EF1-β), a hypothetical protein, and mitochondrial peroxiredoxin (Prx1). RT-PCR revealed that the transcription of the genes coding for some of these proteins are differentially regulated. Conclusions: Based on these results, it is proposed that these proteins may be involved in the resistance of S. schenckii to oxidative stress, and play an important role in the fungus survival in the host

Antecedentes: La esporotricosis es una infección fúngica causada por el complejo Sporothrix schenckii. Para colonizar al huésped, los patógenos deben neutralizar las especies reactivas de oxígeno producidas por las células fagocíticas durante el estallido respiratorio. Poco se conoce sobre este mecanismo en S. schenckii. Objetivos: Identificar proteínas diferencialmente expresadas durante la exposición de S. schenckiisensu stricto a diferentes concentraciones de H2O2. Métodos: Levaduras de S. schenckiisensu stricto fueron expuestas a concentraciones crecientes de H2O2. Las proteínas diferencialmente expresadas en respuesta el estrés oxidativo fueron analizadas mediante electroforesis en geles de poliacrilamida en doble dimensión (2D-PAGE) e identificadas por MALDI-MS/MS. Se realizaron ensayos de RT-PCR para evaluar la transcripción de genes de las proteínas identificadas. Resultados: Concentraciones altas de H2O2 (800 mM) permitieron el crecimiento celular, y se seleccionaron las concentraciones de 200 y 400 mM para el análisis comparativo mediante 2D-PAGE. Este análisis reveló al menos cinco proteínas diferencialmente expresadas, identificadas como proteína de choque térmico de 70 kDa (Hsp70), chaperonina GroEL, factor de alargamiento 1-β (EF1-β), una proteína hipotética y peroxirredoxina mitocondrial (Prx1). La RT-PCR reveló que la transcripción de los genes que codifican para algunas de estas proteínas se regula diferencialmente. Conclusiones: Con estos resultados pensamos que estas proteínas podrían estar involucradas en la resistencia de S. schenckiisensu stricto al estrés oxidativo y jugar un papel importante en la supervivencia del hongo en el huésped

Identification of proteins in Sporothrixschenckiisensu stricto in response to oxidative stress induced by hydrogen peroxide.

BACKGROUND: Sporotrichosis is a fungal infection caused by the Sporothrix schenckii complex. In order to colonize the host, the pathogen must neutralize the reactive oxygen species produced by the phagocytic cells during the respiratory burst. Little is known about these mechanisms in S. schenckii. AIMS: To identify the proteins differentially expressed after the exposure of S. schenckiisensu stricto to different concentrations of H2O2. METHODS: Yeast cells of S. schenckiisensu stricto were exposed to increasing concentrations of H2O2. Proteins differentially expressed in response to oxidative stress were analyzed using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and identified by MALDI-MS/MS. RT-PCR assays were performed to evaluate the transcription of genes of the identified proteins. RESULTS: Concentrations of H2O2 as high as 800mM allowed cell growth, and 200mM and 400mM were selected for comparative analysis by 2D-PAGE. This analysis revealed at least five differentially expressed proteins, which were identified as heat shock 70kDa protein (Hsp70), chaperonin GroEL, elongation factor 1-ß (EF1-ß), a hypothetical protein, and mitochondrial peroxiredoxin (Prx1). RT-PCR revealed that the transcription of the genes coding for some of these proteins are differentially regulated. CONCLUSIONS: Based on these results, it is proposed that these proteins may be involved in the resistance of S. schenckii to oxidative stress, and play an important role in the fungus survival in the host.

Congo Red affects the growth, morphology and activity of glucosamine-6-phosphate synthase in the human pathogenic fungus Sporothrix schenckii.

Sporothrix schenckii is the etiological agent of sporotrichosis, a mycosis of humans and other mammals. Little is known about the responses of this thermodimorphic pathogen to perturbations in the cell wall (CW) by different stress conditions. Here we describe the effect of Congo Red (CR) on the fungal growth, morphogenesis and activity of glucosamine-6-phosphate (GlcN-6-P) synthase. Under conditions of yeast development, 15 µM CR abolished conidia (CN) germination, but when yeast cells were first obtained in the absence of the dye and then post-incubated in its presence, yeasts rapidly differentiated into mycelial cells. On the other hand, under conditions of mycelium development, 150 µM CR did not affect CN germination, but filamentous cells underwent structural changes characterized by a distorted CW contour, the loss of polarity and the formation of red-pigmented, hyphal globose structures. Under these conditions, CR also induced a significant and transient increase in the activity of GlcN-6-P synthase, an essential enzyme in CW biogenesis.

Evaluation of melanin production by Sporothrix luriei

There is a paucity of studies on the cell biology of Sporothrix luriei, the less common of the pathogenic Sporothrix species worldwide. The production of DHN-melanin, eumelanin, and pyomelanin were evaluated on the mycelial and yeast forms of the S. luriei ATCC 18616 strain. The mycelial form of this species produced only pyomelanin, which protected the fungus against environmental stressors such as ultraviolet light, heat, and cold. The yeast form was unable to produce any of the tested melanin types. The lack of melanin in the parasitic form of S. luriei may be an explanation for its low frequency in human infections.

Evaluation of melanin production by Sporothrix luriei.

There is a paucity of studies on the cell biology of Sporothrix luriei, the less common of the pathogenic Sporothrix species worldwide. The production of DHN-melanin, eumelanin, and pyomelanin were evaluated on the mycelial and yeast forms of the S. luriei ATCC 18616 strain. The mycelial form of this species produced only pyomelanin, which protected the fungus against environmental stressors such as ultraviolet light, heat, and cold. The yeast form was unable to produce any of the tested melanin types. The lack of melanin in the parasitic form of S. luriei may be an explanation for its low frequency in human infections.

Functional diversity for biomass deconstruction in family 5 subfamily 5 (GH5_5) of fungal endo-ß1,4-glucanases.

Endo-ß1,4-glucanases in glycosyl hydrolase family 5 (GH5) are ubiquitous enzymes in the multicellular fungi and are common components of enzyme cocktails for biomass conversion. We recently showed that an endo-glucanase of subfamily 5 of GH5 (GH5_5) from Sporotrichum thermophile (StCel5A) was more effective at releasing glucose from pretreated corn stover, when part of an eight-component synthetic enzyme mixture, compared to its closely related counterpart from Trichoderma reesei, TrCel5A. StCel5A and TrCel5A belong to different clades of GH5_5 (GH5_5_1 and GH5_5_2, respectively). To test whether the superior activity of StCel5A was a general property of all enzymes in the GH5_5_2 clade, StCel5A, TrCel5A, and two additional members of each subfamily were expressed in a common host that had been engineered to suppress its native cellulases (T. reesei Δxyr1) and compared against each other alone on pure substrates, in synthetic mixtures on pure substrates, and against each other in synthetic mixtures on real biomass. The results indicated that superiority is a unique property of StCel5A and not of GH5_5_2 generally. The six Cel5A enzymes had significant differences in relative activities on different substrates, in specific activities, and in sensitivities to mannan inhibition. Importantly, the behavior of the six endo-glucanases on pure cellulose substrates did not predict their behavior in combination with other cellulolytic enzymes on a real lignocellulosic biomass substrate.

Melanins Protect Sporothrix brasiliensis and Sporothrix schenckii from the Antifungal Effects of Terbinafine.

Terbinafine is a recommended therapeutic alternative for patients with sporotrichosis who cannot use itraconazole due to drug interactions or side effects. Melanins are involved in resistance to antifungal drugs and Sporothrix species produce three different types of melanin. Therefore, in this study we evaluated whether Sporothrix melanins impact the efficacy of antifungal drugs. Minimal inhibitory concentrations (MIC) and minimal fungicidal concentrations (MFC) of two Sporothrix brasiliensis and four Sporothrix schenckii strains grown in the presence of the melanin precursors L-DOPA and L-tyrosine were similar to the MIC determined by the CLSI standard protocol for S. schenckii susceptibility to amphotericin B, ketoconazole, itraconazole or terbinafine. When MICs were determined in the presence of inhibitors to three pathways of melanin synthesis, we observed, in four strains, an increase in terbinafine susceptibility in the presence of tricyclazole, a DHN-melanin inhibitor. In addition, one S. schenckii strain grown in the presence of L-DOPA had a higher MFC value when compared to the control. Growth curves in presence of 2×MIC concentrations of terbinafine showed that pyomelanin and, to a lesser extent, eumelanin were able to protect the fungi against the fungicidal effect of this antifungal drug. Our results suggest that melanin protects the major pathogenic species of the Sporothrix complex from the effects of terbinafine and that the development of new antifungal drugs targeting melanin synthesis may improve sporotrichosis therapies.

Identification of a type III polyketide synthase involved in the biosynthesis of spirolaxine.

Spirolaxine is a natural product isolated from Sporotrichum laxum ATCC 15155, which has shown a variety of biological activities including promising anti-Helicobacter pylori property. To understand how this compound is biosynthesized, the genome of S. laxum was sequenced. Analysis of the genome sequence revealed two putative type III polyketide synthase (PKS) genes in this strain, Sl-pks1 and Sl-pks2, which are located adjacent to each other (~2.0 kb apart) in a tail-to-tail arrangement. Disruption of these two genes revealed that Sl-PKS2 is the dedicated PKS involved in the biosynthesis of spirolaxine. The intron-free Sl-pks2 gene was amplified from the cDNA of S. laxum and ligated into the expression vector pET28a for expression in Escherichia coli BL21-CodonPlus (DE3)-RIL. The major products of Sl-PKS2 in E. coli were characterized as alkylresorcinols that contain a C13-C17 saturated or unsaturated hydrocarbon side chain based on the spectral data. This enzyme was purified and reacted with malonyl-CoA and a series of fatty acyl-SNACs (C6-C10). Corresponding alkylresorcinols were formed from the decarboxylation of the synthesized tetraketide resorcylic acids, together with fatty acyl-primed triketide and tetraketide pyrones as byproducts. This work provides important information about the PKS involved in the biosynthesis of spirolaxine, which will facilitate further understanding and engineering of the biosynthetic pathway of this medicinally important molecule.