Purification and characterization of a 43.5 kDa keratinolytic metalloprotease from Microsporum canis

Dermatophyte infection: from fungal pathogenicity to host immune responses

Dermatophytosis is a common superficial infection caused by dermatophytes, a group of pathogenic keratinophilic fungi. Apart from invasion against skin barrier, host immune responses to dermatophytes could also lead to pathologic inflammation and tissue damage to some extent. Therefore, it is of great help to understand the pathogenesis of dermatophytes, including fungal virulence factors and anti-pathogen immune responses. This review aims to summarize the recent advances in host-fungal interactions, focusing on the mechanisms of anti-fungal immunity and the relationship between immune deficiency and chronic dermatophytosis, in order to facilitate novel diagnostic and therapeutic approaches to improve the outcomes of these patients.

Chicken Feather Waste Hydrolysate as a Superior Biofertilizer in Agroindustry

Billions of tons of keratinous waste in the form of feathers, antlers, bristles, claws, hair, hoofs, horns, and wool are generated by different industries and their demolition causes environmental deterioration. Chicken feathers have 92% keratin that can be a good source of peptides, amino acids, and minerals. Traditional methods of feather hydrolysis require large energy inputs, and also reduce the content of amino acids and net protein utilization values. Biological treatment of feathers with keratinolytic microbes is a feasible and environmental favorable preference for the formulation of hydrolysate that can be used as bioactive peptides, protein supplement, livestock feed, biofertilizer, etc. The presence of amino acids, soluble proteins, and peptides in hydrolysate facilitates the growth of microbes in rhizosphere that promotes the uptake and utilization of nutrients from soil. Application of hydrolysate enhances water holding capacity, C/N ratio, and mineral content of soil. The plant growth promoting activities of hydrolysate potentiates its possible use in organic farming, and improves soil ecosystem and microbiota. This paper reviews the current scenario on the methods available for management of keratinous waste, nutritional quality of hydrolysate generated using keratinolytic microbes, and its possible application as plant growth promoter in agroindustry.

Microbial keratinase and the bio-economy: a three-decade meta-analysis of research exploit

Microbial keratinase research has been on an upward trajectory due to the robustness and efficiency of the enzyme toward various green technological processes that promote economic development and environmental sustainability. A compendium of research progression and advancement within the domain was achieved through a bibliometric study to understand the trend of research productivity, scientific impacts, authors' involvement, collaboration networks, and the advancement of knowledge gaps for future research endeavours. A three-decade (1990 to 2019) scholarly published articles were retrieved from the web of science database using a combination of terms "keratinas* or keratinolytic proteas* or keratinolytic enzym*", and subsequently analyzed for bibliometric indicators. A collection of 330 peer-reviewed, research, articles were retrieved for the survey period and authored by 1063 researchers with collaboration index of 3.27. Research productivity was most in 2013 with total research output of 28 articles. The top three authors' keywords were keratinase, keratin and protease with a respective frequency of 188, 26 and 22. India, China and Brazil ranked top in terms of keratinase research outputs and total citation with respective article productivity (total citations) of 85 (1533), 57 (826), and 36 (764). This study evaluated the trend of keratinase research outputs, scientific impact, collaboration networks and biotechnology innovations. It has the potentials to influence positively decision making on future research direction, collaborations and development of products for the bio-economy.

Microbial Keratinase: Next Generation Green Catalyst and Prospective Applications

The search for novel renewable products over synthetics hallmarked this decade and those of the recent past. Most economies that are prospecting on biodiversity for improved bio-economy favor renewable resources over synthetics for the potential opportunity they hold. However, this field is still nascent as the bulk of the available resources are non-renewable based. Microbial metabolites, emphasis on secondary metabolites, are viable alternatives; nonetheless, vast microbial resources remain under-exploited; thus, the need for a continuum in the search for new products or bio-modifying existing products for novel functions through an efficient approach. Environmental distress syndrome has been identified as a factor that influences the emergence of genetic diversity in prokaryotes. Still, the process of how the change comes about is poorly understood. The emergence of new traits may present a high prospect for the industrially viable organism. Microbial enzymes have prominence in the bio-economic space, and proteases account for about sixty percent of all enzyme market. Microbial keratinases are versatile proteases which are continuously gaining momentum in biotechnology owing to their effective bio-conversion of recalcitrant keratin-rich wastes and sustainable implementation of cleaner production. Keratinase-assisted biodegradation of keratinous materials has revitalized the prospects for the utilization of cost-effective agro-industrial wastes, as readily available substrates, for the production of high-value products including amino acids and bioactive peptides. This review presented an overview of keratin structural complexity, the potential mechanism of keratin biodegradation, and the environmental impact of keratinous wastes. Equally, it discussed microbial keratinase; vis-à-vis sources, production, and functional properties with considerable emphasis on the ecological implication of microbial producers and catalytic tendency improvement strategies. Keratinase applications and prospective high-end use, including animal hide processing, detergent formulation, cosmetics, livestock feed, and organic fertilizer production, were also articulated.

Bacillus sp. FPF-1 Produced Keratinase with High Potential for Chicken Feather Degradation

Chicken feathers are predominantly composed of keratin; hence, valorizing the wastes becomes an imperative. In view of this, we isolated keratinase-producing bacteria and identified them through the 16S rDNA sequence. The process condition for keratinase activity was optimized, and electron micrography of the degradation timelines was determined. Keratinolytic bacteria were isolated and identified as Bacillus sp. FPF-1, Chryseobacterium sp. FPF-8, Brevibacillus sp. Nnolim-K2, Brevibacillus sp. FPF-12 and Brevibacillus sp. FSS-1; and their respective nucleotide sequences were deposited in GenBank, with the accession numbers MG214993, MG214994, MG214995, MG214996 and MG214999. The degree of feather degradation and keratinase concentration among the isolates ranged from 62.5 ± 2.12 to 86.0 ± 1.41(%) and 214.55 ± 5.14 to 440.01 ± 20.57 (U/mL), respectively. In the same vein, 0.1% (w/v) xylose, 0.5% (w/v) chicken feather, an initial fermentation pH of 5.0, fermentation temperature of 25 °C and an agitation speed of 150 rpm, respectively, served as the optimal physicochemical conditions for keratinase activity by Bacillus sp. FPF-1. The time course showed that Bacillus sp. FPF-1 yielded a keratinase concentration of 1698.18 ± 53.99(U/mL) at 120 h. The electron microscopic imaging showed completely structural dismemberment of intact chicken feather. Bacillus sp. FPF-1 holds great potential in the valorization of recalcitrant keratinous biomass from the agro sector into useful products.

Keratin hydrolysis by dermatophytes

Dermatophytes are the most common cause of superficial fungal infections (tinea infections) and are a specialized group of filamentous fungi capable of infecting and degrading keratinised tissues, including skin, hair, and nail. Essential to their pathogenicity and virulence is the production of a broad spectrum of proteolytic enzymes and other key proteins involved in keratin biodegradation and utilization of its breakdown products. The initial stage of biodegradation of native keratin is considered to be sulfitolysis, in which the extensive disulfide bridges present in keratin are hydrolyzed, although some secreted subtilisins can degrade dye-impregnated keratin azure without prior reduction (Sub3 and Sub4). Sulfitolysis facilitates the extracellular biodegradation of keratin by the dermatophytes' extensive array of endo- and exoproteases. The importance of dermatophyte proteases in infection is widely recognized, and these enzymes have also been identified as important virulence determinants and allergens. Finally, the short peptide and amino acid breakdown products are taken up by the dermatophytes, using as yet poorly characterised transporters, and utilized for metabolism. In this review, we describe the process of keratin biodegradation by dermatophytes, with an especial focus on recent developments in cutting edge molecular biology and '-omic' studies that are helping to dissect the complex process of keratin breakdown and utilization.

Leveraging single-cell genomics to expand the fungal tree of life

Environmental DNA surveys reveal that most fungal diversity represents uncultured species. We sequenced the genomes of eight uncultured species across the fungal tree of life using a new single-cell genomics pipeline. We show that, despite a large variation in genome and gene space recovery from each single amplified genome (SAG), ≥90% can be recovered by combining multiple SAGs. SAGs provide robust placement for early-diverging lineages and infer a diploid ancestor of fungi. Early-diverging fungi share metabolic deficiencies and show unique gene expansions correlated with parasitism and unculturability. Single-cell genomics holds great promise in exploring fungal diversity, life cycles and metabolic potential.

The structure-function analysis of the Mpr1 metalloprotease determinants of activity during migration of fungal cells across the blood-brain barrier

Cryptococcal meningoencephalitis, the most common form of cryptococcosis, is caused by the opportunistic fungal pathogen, Cryptococcus neoformans. Molecular strategies used by C. neoformans to invade the central nervous system (CNS) have been the focus of several studies. Recently, the role of a novel secreted metalloprotease (Mpr1) in the pathogenicity of C. neoformans was confirmed by studies demonstrating that Mpr1 mediated the migration of fungal cells into the CNS. Given this central function, the aim here was to identify the molecular determinants of Mpr1 activity and resolve their role in the migration of cryptococci across the blood-brain barrier (BBB). The Mpr1 protein belongs to an understudied group of metalloproteases of the M36 class of fungalysins unique to fungi. They are generally synthesized as propeptides with fairly long prodomains and highly conserved regions within their catalytic core. Through structure-function analysis of Mpr1, our study identified the prodomain cleavage sites of Mpr1 and demonstrated that when mutated, the prodomain appears to remain attached to the catalytic C-terminus of Mpr1 rendering a nonfunctional Mpr1 protein and an inability for cryptococci to cross the BBB. We found that proteolytic activity of Mpr1 was dependent on the coordination of zinc with two histidine residues in the active site of Mpr1, since amino acid substitutions in the HExxH motif abolished Mpr1 proteolytic activity and prevented the migration of cryptococci across the BBB. A phylogenetic analysis of Mpr1 revealed a distinct pattern likely reflecting the neurotropic nature of C. neoformans and the specific function of Mpr1 in breaching the BBB. This study contributes to a deeper understanding of the molecular regulation of Mpr1 activity and may lead to the development of specific inhibitors that could be used to restrict fungal penetration of the CNS and thus prevent cryptococcal meningoencephalitis-related deaths.

Exoproteome Analysis of Human Pathogenic Dermatophyte Species and Identification of Immunoreactive Proteins

PURPOSE

Increasing incidence of onychomycosis and tinea pedis in humans of industrialized countries together with deep tissue infections are a therapeutic challenge in clinical mycology. For a better understanding of the pathology and immunology of infection, the authors analyze the exoproteomes of three reference strains of the most common clinical dermatophyte species (Trichophyton rubrum, Trichophyton interdigitale, Arthroderma benhamiae) and of Trichophyton strains isolated from affected patients.

EXPERIMENTAL DESIGN

Extracellular proteins of those in vitro grown strains are separated via 2D High Performance Electrophoresis and identified by mass spectrometry to find proteins with provoked host immune reactivity.

RESULTS

More than 80 secreted proteins including virulence factors such as peptidases and other hydrolases are identified. By Western blotting with respective patient sera, up to 31 proteins with significant antigen-antibody reactions are detected in comparison with control sera, for example, peptidases as well as several oxidoreductases. One protein, beta-glucosidase F2SZI9 seems to be a commonly processed antigen in all Trichophyton infections.

CONCLUSIONS AND CLINICAL RELEVANCE

These first global exoproteome data of three dermatophyte species can be a stepping stone on the way to further study the molecular mechanisms of Trichophyton pathogenicity-associated traits. Possible candidates for potential new diagnostic methods or vaccination have to be validated in further investigations.

Development of enzyme immunoassays (ELISA and Western blot) for the serological diagnosis of dermatophytosis in symptomatic and asymptomatic cats

Dermatophytosis is the most common fungal infection in cats worldwide and plays an important role in both animal and human health due to their high zoonotic potential. Effective screening is a strong preventive measure and the fungal culture is quite useful but requires full laboratorial experience and it takes a long time to obtain the result. A rapid and accurate screening test for dermatophytosis in cats is crucial for the effective control of disease outbreaks. The aim of this study was to develop and evaluate the diagnostic efficacy of enzyme immunoassays (ELISA and Western blot [WB]) for the rapid and precise diagnosis of dermatophytosis in cats. Seventy cats of various ages were divided into three groups: S (symptomatic, n = 20), AS (asymptomatic, n = 30), and N (negative, n = 20). All animals were submitted to fungal culture and blood samples for carrying out the serological tests. A significant difference (P < 0.05) was found between IgG-specific levels of sera of Microsporum canis positive and negative animals. There was no statistic difference between groups symptomatic and asymptomatic. The ELISA test showed sensitivity of 94% and specificity of 75%. Receiver operating characteristic (ROC) analysis also showed higher diagnostic accuracy (AUC 0.925). The WB technique detected 13 bands, and the 50 kDa protein was considered the most immunogenic protein, observing reactivity in 83.3% in the symptomatic group and 66.6% in the asymptomatic group. The study concluded that ELISA and WB were useful tools to reliably detect cats that have been exposed to M. canis.

Anti-fungal potential of ozone against some dermatophytes

Dermatophytes are classified in three genera, Epidermophyton, Microsporum and Trichophyton. They have the capacity to invade keratinized tissue to produce a cutaneous infection known as dermatophytoses. This investigation was performed to study the effect of gaseous ozone and ozonized oil on three specific properties of six different dermatophytes. These properties included sporulation, mycelia leakage of sugar and nutrients and the activity of their hydrolytic enzymes. Generally, ozonized oil was found to be more efficacious than gaseous ozone. Microsporum gypseum and Microsporum canis were the most susceptible, while Trichophyton interdigitale and T. mentagrophytes were relatively resistant. The study revealed a steady decline in spore production of M. gypseum and M. canis on application of ozonated oil. An increase in leakage of electrolytes and sugar was noticed after treatment with ozonized oil in the case of M. gypseum, M. canis, T. interdigitale, T. mentagrophytes and T. rubrum. The results also revealed loss in urease, amylase, alkaline phosphatase, lipase and keratinase enzyme producing capacity of the investigated fungi.

Comparative Transcriptome Analysis of the Cosmopolitan Marine Fungus Corollospora maritima Under Two Physiological Conditions

Marine sandy beaches represent dynamic environments often subject to harsh conditions and climate fluctuations, where natural and anthropogenic inputs of freshwater from fluvial and pluvial sources alter salinity, which has been recognized as a key variable affecting the distribution of aquatic organisms and influencing critical physiological processes. The marine arenicolous fungus Corollospora maritima is a worldwide-distributed saprobe that has been reported to present tolerance to freshwater. Here, we present a transcriptome analysis that will provide the first insight of the genomic content for this fungus and a gene expression comparison between two different salinity conditions. We also identified genes that are candidates for being differentially expressed in response to environmental variations on salinity during the fungal growth. The de novo reconstruction of C. maritima transcriptome Illumina sequencing provided a total of 14,530 transcripts (16 megabases). The comparison between the two growth conditions rendered 103 genes specifically overexpressed in seawater, and 132 genes specifically up-regulated under freshwater. Using fungal isolates collected from different beaches, the specific environmental regulation of particular transcript differential expression was confirmed by RT-qPCR. To our knowledge, this is the first analysis that explores the marine fungus C. maritima molecular responses to overcome freshwater stress, and these data could shed light to understand the fungal adaptation and plasticity mechanisms to the marine habitat.

Metalloprotease genes of Trichophyton mentagrophytes are important for pathogenicity

Metalloproteases (Mep) of the M36 family are important virulence factors for the host invasion by the dermatophyte Trichophyton mentagrophytes. Dermatophytes secrete keratinase to degrade human and animal keratin and invade the skin. In previous studies, primers designed from the MEP gene sequences of Aspergillus fumigatus and A. oryzae were used to amplify the MEP genes from T. mentagrophytes, and the five MEP genes (MEP1-MEP5) were expressed. Differences in the expression of these five MEP genes in different dermatophytes were observed in an in vitro protein induction study, indicating their different functions and proteolytic abilities. However, specific pathogenic functions and mechanisms of each of the metalloproteases, as well as differences in their proteolytic activities, remain uncertain. In the current study, Agrobacterium tumefaciens-mediated transformation (ATMT) was used to successfully transform five MEP genes, resulting in five MEP mutant strains. MEP3 showed strongest proteolytic activity, hair biodegradation ability, and animal pathogenicity among the mutant strains. The MEP4 and MEP5 mutants were the least pathogenic through the above tests. Therefore, we hypothesize that the MEP4 and MEP5 genes are most likely to significantly affect the pathogenicity of T. mentagrophytes.

Fungal zinc metabolism and its connections to virulence

Zinc is a ubiquitous metal in all life forms, as it is a structural component of the almost 10% of eukaryotic proteins, which are called zinc-binding proteins. In zinc-limiting conditions such as those found during infection, pathogenic fungi activate the expression of several systems to enhance the uptake of zinc. These systems include ZIP transporters (solute carrier 39 family) and secreted zincophores, which are proteins that are able to chelate zinc. The expression of some fungal zinc uptake systems are regulated by a master regulator (Zap1), first characterized in the yeast Saccharomyces cerevisiae. In this review, we highlight features of zinc uptake and metabolism in human fungal pathogens and aspects of the relationship between proper zinc metabolism and the expression of virulence factors and adaptation to the host habitat.

Genetic variability in Microsporum canis isolated from cats, dogs and humans in Brazil

Dermatophytosis caused by Microsporum canis is a heterogeneous disease with variable clinical manifestations. M. canis is a zoophilic dermatophyte and the most frequent fungi isolated from dogs, cats and children in Brazil. The aim of this study was to investigate the genetic variability of M. canis isolates from different animal species using two microsatellite markers, namely, McGT(13) and McGT(17), and to correlate the results with the clinical and epidemiological patient data in Brazil. The study included a global set of 102 M. canis strains, including 37 symptomatic cats, 35 asymptomatic cats, 19 human patients with tinea, 9 asymptomatic dogs and 2 symptomatic dogs. A total of 14 genotypes were identified, and 6 large populations were distinguished. There was no correlation between these multilocus genotypes and the clinical and epidemiological data, including the source, symptomatology, clinical picture, breed, age, sex, living conditions and geographic location. These results demonstrate that the use of microsatellite polymorphisms is a reliable method for the differentiation of M. canis strains. However, we were unable to demonstrate a shared clinical and epidemiological pattern among the same genotype samples.

Isolation of Microsporum gypseum in soil samples from different geographical regions of brazil, evaluation of the extracellular proteolytic enzymes activities (keratinase and elastase) and molecular sequencing of selected strains

A survey of Microsporum gypseum was conducted in soil samples in different geographical regions of Brazil. The isolation of dermatophyte from soil samples was performed by hair baiting technique and the species were identified by morphology studies. We analyzed 692 soil samples and the recuperating rate was 19.2%. The activities of keratinase and elastase were quantitatively performed in 138 samples. The sequencing of the ITS region of rDNA was performed in representatives samples. M. gypseum isolates showed significant quantitative differences in the expression of both keratinase and elastase, but no significant correlation was observed between these enzymes. The sequencing of the representative samples revealed the presence of two teleomorphic species of M. gypseum (Arthroderma gypseum and A. incurvatum). The enzymatic activities may play an important role in the pathogenicity and a probable adaptation of this fungus to the animal parasitism. Using the phenotypical and molecular analysis, the Microsporum identification and their teleomorphic states will provide a useful and reliable identification system.

Mechanisms of skin adherence and invasion by dermatophytes

Dermatophytes are keratinophilic fungi that can be pathogenic for humans and animals by infecting the stratum corneum, nails, claws or hair. The first infection step consists of adherence of arthroconidia to the stratum corneum. The mechanisms and the kinetics of adherence have been investigated using different in vitro and ex vivo experimental models, most notably showing the role of a secreted serine protease from Microsporum canis in fungal adherence to feline corneocytes. After germination of the arthroconidia, dermatophytes invade keratinised structures that have to be digested into short peptides and amino acids to be assimilated. Although many proteases, including keratinolytic ones, have been characterised, the understanding of dermatophyte invasion mechanisms remains speculative. To date, research on mechanisms of dermatophyte infection focused mainly on both secreted endoproteases and exoproteases, but their precise role in both fungal adherence and skin invasion should be further explored.

Biodegradation of keratin waste: Theory and practical aspects

Keratin-rich by-products, i.e. bristles, horns and hooves, chicken feathers and similar, are a source of nutrients for animals (amino acids) and plants (N, S). Contemporary developments in the management of keratin waste in feeds and fertilizers comply with human and animal health protection regulations and respect the principles of ecological development. Biotechnological methods employing keratinolytic bacteria and microscopic fungi play a key role in processing keratin waste. This study reviews the current knowledge on the ecology and physiology of keratinolytic microorganisms and presents the biodegradation mechanism of native keratin. The structure and chemical composition of keratin proteins are described, and methods of keratin waste biotransformation into products of practical industrial and natural value, especially composts, are discussed.

Biochemical and spectroscopic characterization of a novel metalloprotease, cotinifolin from an antiviral plant shrub: Euphorbia cotinifolia

A high molecular mass novel metalloprotease, cotinifolin is purified from the latex of Euphorbia cotinifolia by a combination of anion exchange and hydrophobic interaction chromatography. The nonglycosylated enzyme has a molecular mass of 79.76 kDa (ESI-MS) and the isoelectric point of the enzyme is pH 7.7. Cotinifolin hydrolyzes denatured natural substrates such as casein, azoalbumin, and hemoglobin with high specific activity. The K(m) value of the enzyme was found to be 20 μM with azocasein. The enzyme is not prone to autolysis even at very low concentrations. Polyclonal antibodies specific to enzyme was raised and immunodiffusion reveals that the enzyme has unique antigenic determinants. Maximum caseinolytic activity of cotinifolin is observed in the range of pH 7.0-8.0 and temperature of 50 °C. Using 0.2 mL of 1 mM solution of each metal ion, the purified protease was inhibited slightly by Ba²⁺ and Mn²⁺, moderately by Mg²⁺, Ca²⁺ and Cs²⁺ and significantly by Zn²⁺, Cu²⁺ and Co²⁺. On the other hand, substantial activation in caseinolytic activity was achieved by Ni²⁺. The enzyme activity was also inhibited by EDTA and o-phenanthroline but not by any other protease inhibitors. Perturbation studies by temperature, pH, and chaotrophs of the enzyme also reveal its high stability as seen by CD, fluorescence and proteolytic activity. Spectroscopic studies reveal that cotinifolin has secondary structural features with α/β type with approximately 9% of α-helicity. Easy availability and simple purification procedure makes the enzyme a good system for biophysical study, biotechnological and industrial applications.

Keratinolytic activity of purified alkaline keratinase produced by Scopulariopsis brevicaulis (Sacc.) and its amino acids profile

Sodium dodecyl sulfate-polyacrlyamide gel electrophoresis (SDS-PAGE) was used to assess the purity and molecular weight of the previously purified alkaline keratinase enzyme of Scopulariopsis brevicaulis. The enzyme was homogenous, as seen by a single band of protein, and had an apparent molecular weight of 28.5 kDa. Amino acid profile of the purified keratinase revealed that it was composed of 14 different amino acids with high proportions of glutamic acid (20.86%), alanine (14.52%), glycine (14.21%), leucine (8.59%) and serine (7.81%). The enzyme contained moderate amounts of valine (6.01%), threonine (5.58%) and phenyl alanine (5.22%). The purified enzyme of S. brevicaulis exerted a potent keratinolytic activity and was capable to hydrolyze different keratinaceous materials with highest activity on chicken feathers followed by human nails and human hair.

Fungal proteases and their pathophysiological effects

Proteolytic enzymes play an important role in fungal physiology and development. External digestion of protein substrates by secreted proteases is required for survival and growth of both saprophytic and pathogenic species. Extracellular serine, aspartic, and metalloproteases are considered virulence factors of many pathogenic species. New findings focus on novel membrane-associated proteases such as yapsins and ADAMs and their role in pathology. Proteases from fungi induce inflammatory responses by altering the permeability of epithelial barrier and by induction of proinflammatory cytokines through protease-activated receptors. Many fungal allergens possess proteolytic activity that appears to be essential in eliciting Th2 responses. Allergenic fungal proteases can act as adjuvants, potentiating responses to other allergens. Proteolytic enzymes from fungi contribute to inflammation through interactions with the kinin system as well as the coagulation and fibrinolytic cascades. Their effect on the host protease-antiprotease balance results from activation of endogenous proteases and degradation of protease inhibitors. Recent studies of the role of fungi in human health point to the growing importance of proteases not only as pathogenic agents in fungal infections but also in asthma, allergy, and damp building related illnesses. Proteolytic enzymes from fungi are widely used in biotechnology, mainly in food, leather, and detergent industries, in ecological bioremediation processes and to produce therapeutic peptides. The involvement of fungal proteases in diverse pathological mechanisms makes them potential targets of therapeutic intervention and candidates for biomarkers of disease and exposure.

Extracellular protease expression in Microsporum gypseum complex, its regulation and keratinolytic potential

Two soil isolates of Microsporum gypseum were studied for the production of extracellular proteases. Both the strains secreted protease on glucose-gelatin medium. The enzyme activity peaked on day 15 at 28 °C. Asparagine repressed protease yield. Sugars caused catabolite repression of protease formation. Protease activities of both the isolates were significantly affected by incubation period, culture media and carbohydrates used. Both the strains grew on the skin bait and caused a gravimetrically measurable loss of the substrate. Despite less pronounced differences in the keratinase levels, great variations occurred in the amount of keratin degraded by two isolates. Keratinase production as well as loss in substrate mass was better in glucose-lacking flasks than those containing the sugar. Although the rate of keratin degradation was independent of enzyme production, statistically positive correlations were recorded between loss in substrate mass: yielded dry mycelial weight and substrate degradation: keratinase levels.

Comparative analysis of secreted enzymes between the anthropophilic-zoophilic sister species Trichophyton tonsurans and Trichophyton equinum

Trichophyton tonsurans (TT) and Trichophyton equinum (TE) are two closely related dermatophytes with very different host preferences. This study was designed to examine the genetic and transcript level variations of secreted enzymes between TT and TE. Thirty-one genes representing 10 gene families were selected for comparison and complete genomic and cDNA sequences were elucidated. Sequence analyses of the selected genes identified 104 polymorphisms between the two dermatophytes, 37 of which are expected to encode changes in their polypeptide sequence. Quantitative RT-PCR was used to examine the differences in levels of transcript between TT and TE grown over 14d in aqueous keratin medium. Differences in transcript expression between TT and TE were gene specific and ranged from 1.1-fold to 33-fold. Intra-specific variability across all genes ranged from 41% to 250%. Despite their overall genetic similarity, TT and TE exhibit a moderate degree of variability in the genomic make-up of their secreted enzymes and the extent to which they are transcribed when grown in an aqueous keratin medium. Such differences may contribute to how these genetically similar organisms have adapted to infect divergent host organisms.

Transcriptional profiling reveals the expression of novel genes in response to various stimuli in the human dermatophyte Trichophyton rubrum

Background

Cutaneous mycoses are common human infections among healthy and immunocompromised hosts, and the anthropophilic fungus Trichophyton rubrum is the most prevalent microorganism isolated from such clinical cases worldwide. The aim of this study was to determine the transcriptional profile of T. rubrum exposed to various stimuli in order to obtain insights into the responses of this pathogen to different environmental challenges. Therefore, we generated an expressed sequence tag (EST) collection by constructing one cDNA library and nine suppression subtractive hybridization libraries.

Results

The 1388 unigenes identified in this study were functionally classified based on the Munich Information Center for Protein Sequences (MIPS) categories. The identified proteins were involved in transcriptional regulation, cellular defense and stress, protein degradation, signaling, transport, and secretion, among other functions. Analysis of these unigenes revealed 575 T. rubrum sequences that had not been previously deposited in public databases.

Conclusion

In this study, we identified novel T. rubrum genes that will be useful for ORF prediction in genome sequencing and facilitating functional genome analysis. Annotation of these expressed genes revealed metabolic adaptations of T. rubrum to carbon sources, ambient pH shifts, and various antifungal drugs used in medical practice. Furthermore, challenging T. rubrum with cytotoxic drugs and ambient pH shifts extended our understanding of the molecular events possibly involved in the infectious process and resistance to antifungal drugs.

L-methioninase production by Aspergillus flavipes under solid-state fermentation

Solid-state fermentation was carried out for the production of extra-cellular L-methioninase by Aspergillus flavipes (Bain and Sart.) using nine agro-industrial residues, namely wheat bran, rice bran, wheat flour, coconut seeds, cotton seeds, ground nut cake, lentil hulls, soya beans and chicken feathers. Chicken feathers were selected as solid substrate for L-methioninase production by A. flavipes. The maximum L-methioninase productivity (71.0 U/mg protein) and growth (11 mg protein/ml) of A. flavipes was obtained using alkali pretreated chicken feathers of 50% initial moisture content as substrate supplemented with D-glucose (1.0% w/v) and L-methionine (0.2% w/v). External supplementation of the fermentation medium with various vitamin sources has no overinductive effect on L-methioninase biosynthesis. The partially purified A. flavipes L-methioninase preparation showed highest activity (181 U/ml) at pH 8.0 with stability over a pH range (pH 6-8) for 2 h. L-methioninase activity was increased by preincubation of the enzyme for 2 h with Co(2+), Mn(2+), Cu(2+) and Mg(2+) and strongly inhibited by the presence of EDTA, NaN(3), Li(2+), Cd(2+), DMSO and 2-mercaptoethanol. The enzyme preparation has a broad substrate spectrum showing a higher affinity to deaminate L-glycine, N -acetylglucosamine and glutamic acid, in addition to their proteolytic activity against bovine serum albumin, casein, gelatin and keratin. The partially purified enzyme was found to be glyco-metalloproteinic in nature as concluded from the analytical and spectroscopic profiles of the enzyme preparation. The demethiolating activity of the enzyme was also visualized chromogenially.

Development of transformation system for Trichophyton rubrum by electroporation of germinated conidia

Dermatophytes are the fungi that can cause infections of skin, hair, and nails due to their ability to utilize keratin. The genetic transformation systems of dermatophytes were successfully applied to Trichophyton mentagrophytes and Microsporum canis. Here we describe the procedure for genetic transformation of Trichophyton rubrum by electroporation of their germinated conidia. A linearized transformation vector (pCHSH75-Pch/GFP/TtrpC) containing bacterial hygromycin B phosphotransferase gene (hph) and green fluorescent protein gene (egfp) was introduced into the germinated conidia of T. rubrum by electroporation. PCR reaction analysis showed that egfp gene was integrated randomly and Southern blotting analysis demonstrated a single integration of hph gene into the chromosomal DNA of randomly selected transformant. In this work we report the efficient transformation and selection of the stable T. rubrum transformants.

Production, characterization and application of keratinase from Streptomyces gulbargensis

A Streptomyces gulbargensis newly isolated, thermotolerant feather-degrading bacterial strain was investigated for its ability to produce keratinase enzyme. Maximum keratinolytic activity was observed at 45 degrees C and pH 9.0 at 120 h of incubation. Activity was completely stable (100%) between 30 and 45 degrees C and pH 7.0-9.0, respectively. Addition of starch to the growth medium affects the activity by means of increase in keratinase secretion. After seven days of cultivation, 10-fold increase (14.3 U ml(-1)) in keratinase activity was observed in the presence of 3g starch (per liter) of the medium. The enzyme was monomeric and had a molecular mass of 46 kDa. The enzyme activity was significantly inhibited by CaCl(2) and partly inhibited by EDTA, whereas, Na(2)SO(3) enhance the enzyme activity by 2.9 times more. In addition, native chicken feather was completely degraded at 96 h of incubation. The results obtained showed that newly isolated strain S. gulbargensis could be a useful in biotechnology in terms of valorization of keratin-containing wastes or in the leather industry.

Secreted dipeptidyl peptidases as potential virulence factors for Microsporum canis

Dermatophytoses caused by Microsporum canis are frequently encountered in cats and dogs; they are highly contagious and readily transmissible to humans. In this study, two single genes, respectively coding for dipeptidyl peptidases IV and V (DppIV and DppV), were isolated and characterized. Both proteins share homology with serine proteases of the S9 family, some of which display properties compatible with implication in pathogenic processes. Both genes are expressed in vivo in experimentally infected guinea-pigs and in naturally infected cats, and when the fungus is grown on extracellular matrix proteins as the sole nitrogen and carbon source. DppIV and V were produced as active recombinant proteases in the yeast Pichia pastoris; the apparent molecular weight of rDppV is 83 kDa, whereas rDppIV appears as a doublet of 95 and 98 kDa. Like other members of its enzymatic subfamily, rDppIV has an unusual ability to cleave Pro-X bonds. This activity does not enhance the solubilization of keratin by fungal secreted endoproteases, and the protease probably acts solely on small soluble peptides. RDppV showed no ability to induce delayed-type hypersensitivity (DTH) skin reactions in guinea-pigs, despite the known immunogenic properties of homologous proteins.

Secreted proteases from dermatophytes

Dermatophytes are highly specialized pathogenic fungi that exclusively infect the stratum corneum, nails or hair, and it is evident that secreted proteolytic activity is important for their virulence. Endo- and exoproteases-secreted by dermatophytes are similar to those of species of the genus Aspergillus. However, in contrast to Aspergillus spp., dermatophyte-secreted endoproteases are multiple and are members of two large protein families, the subtilisins (serine proteases) and the fungalysins (metalloproteases). In addition, dermatophytes excrete sulphite as a reducing agent. In the presence of sulphite, disulphide bounds of the keratin substrate are directly cleaved to cysteine and S-sulphocysteine, and reduced proteins become accessible for further digestion by various endo- and exoproteases secreted by the fungi. Sulphitolysis is likely to be an essential step in the digestion of compact keratinized tissues which precedes the action of all proteases.

Complete genome sequence of the fish pathogen Flavobacterium psychrophilum

We report here the complete genome sequence of the virulent strain JIP02/86 (ATCC 49511) of Flavobacterium psychrophilum, a widely distributed pathogen of wild and cultured salmonid fish. The genome consists of a 2,861,988-base pair (bp) circular chromosome with 2,432 predicted protein-coding genes. Among these predicted proteins, stress response mediators, gliding motility proteins, adhesins and many putative secreted proteases are probably involved in colonization, invasion and destruction of the host tissues. The genome sequence provides the basis for explaining the relationships of the pathogen to the host and opens new perspectives for the development of more efficient disease control strategies. It also allows for a better understanding of the physiology and evolution of a significant representative of the family Flavobacteriaceae, whose members are associated with an interesting diversity of lifestyles and habitats.

Isolation of transcripts over-expressed in human pathogen Trichophyton rubrum during growth in keratin

Trichophyton rubrum is a cosmopolitan and anthropophilic fungus able to invade keratinized tissue, causing infection in human skin and nails. This work evaluated the changes in the extracellular pH during its growth in keratin (after 6, 12, 24, 48, 72h and 7 days) at initial pH 5.0. We observed a gradual increase of basal pH under keratin exposure when compared to glucose condition. Also, we identified 576T. rubrum transcripts differentially expressed by subtractive suppression hybridization (SSH) using conidia cultivated for 72h in keratin as tester, and cultivated in glucose as driver. The over-expression of 238 transcripts obtained under keratin condition was confirmed by macro-array dot-blot, revealing 28 unigenes. Putative proteins encoded by these genes showed similarity to fungi proteins involved in basic metabolism, growth and virulence, i.e., transporters ABC-MDR, MFS and ATPase of copper, NIMA interactive protein, Gag-Pol polyprotein, virulence factors serine-protease subtilisin and metalloprotease, cytochrome P450, GlcN-6-phosphate deaminase and Hsp30. The upregulation of T. rubrum genes encoding subtilisin, metalloprotease and Gag-Pol polyprotein was also validated by northern blot. The results of this study provide the first insight into genes differentially expressed during T. rubrum grown in keratin that may be involved in fungal pathogenesis.

Actividad proteolítica extracelular y análisis molecular de cepas de Microsporum canis aisladas de gatos con y sin sintomatología

Microsporum canis is the main zoophylic dermatophyte in dogs and cats, and it is also an important zoonotic agent. The literature showed that cats are asymptomatic carriers of M. canis. This is apparently due to host resistance and/or the presence of strains with lower virulence. This study was aimed to evaluate the keratinolytic, elastinolytic and collagenolytic activities of M. canis strains and their relationship with symptomatic and asymptomatic cats. In addition, these strains were analysed by RFLP. The strains isolated from cats with clinical dermatophytosis had higher keratinase and elastase activity than those isolated from asymptomatic animals (p minus than 0.05). There were not differences in RFLP patterns based on Hind III digestion.

Analysis of the dermatophyte Trichophyton rubrum expressed sequence tags

Background

Dermatophytes are the primary causative agent of dermatophytoses, a disease that affects billions of individuals worldwide. Trichophyton rubrum is the most common of the superficial fungi. Although T. rubrum is a recognized pathogen for humans, little is known about how its transcriptional pattern is related to development of the fungus and establishment of disease. It is therefore necessary to identify genes whose expression is relevant to growth, metabolism and virulence of T. rubrum.

Results

We generated 10 cDNA libraries covering nearly the entire growth phase and used them to isolate 11,085 unique expressed sequence tags (ESTs), including 3,816 contigs and 7,269 singletons. Comparisons with the GenBank non-redundant (NR) protein database revealed putative functions or matched homologs from other organisms for 7,764 (70%) of the ESTs. The remaining 3,321 (30%) of ESTs were only weakly similar or not similar to known sequences, suggesting that these ESTs represent novel genes.

Conclusion

The present data provide a comprehensive view of fungal physiological processes including metabolism, sexual and asexual growth cycles, signal transduction and pathogenic mechanisms.

Isolation, characterization, and disruption of dnr1, the areA/nit-2-like nitrogen regulatory gene of the zoophilic dermatophyte, Microsporum canis

A homolog of the major nitrogen regulatory genes areA from Aspergillus nidulans and nit-2 from Neurospora crassa was isolated from the zoophilic dermatophyte, Microsporum canis. This gene, dnr1, encodes a polypeptide of 761 amino acid residues containing a single zinc-finger DNA-binding domain, which is almost identical in amino acid sequence to the zinc-finger domains of AREA and NIT-2. The functional equivalence of dnr1 to areA was demonstrated by complementation of an areA loss-of-function mutant of A. nidulans with dnr1 cDNA. To further characterize this gene, dnr1 was disrupted by gene replacement based on homologous recombination. Of 100 transformants analyzed, two showed the results expected for replacement of dnr1. The growth properties of the two dnr1(-) mutant strains on various nitrogen sources were examined. Unlike the A. nidulansareA(-) mutant, these dnr1(-) mutants showed significantly reduced growth on ammonia, a preferred nitrogen source for fungi. These mutant strains were also able to utilize various amino acids for growth. In comparison with wild-type M. canis, the two dnr1(-) mutants showed reduced growth on medium containing keratin as the sole nitrogen source. This is the first report describing successful production of targeted gene-disrupted mutants by homologous recombination and their phenotypic analysis in dermatophytes.

Partial purification and characterization of a 37 kDa extracellular proteinase from Trichophyton vanbreuseghemii

An exocellular proteinase synthesized by the geophilic dermatophyte Trichophyton vanbreuseghemii has been purified and characterized. The fungus obtained from soil in Iran was cultivated in modified Czapek-Dox liquid medium containing 0.1% bacteriological peptone and 1% glucose as the nitrogen and carbon sources. Partial purification of the proteinase was accomplished by (NH(4))(2)SO(4) precipitation, followed by ion exchange chromatography. Analysis of the enzyme by SDS-PAGE revealed a single polypeptide chain with an apparent molecular mass of 37 kDa. Proteinase activity was optimum at pH 8, but remained high in the range of pH 7-11. Moreover, the partially purified enzyme presented a keratinolytic activity as evidenced by the keratin azure test. The inhibition profile and the good activity of the enzyme towards the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide suggested that it belonged to the chymotrypsin/subtilisin group of serine proteinases. The keratinolytic properties of T. vanbreuseghemii suggest that this fungus may be an alternative for the recycling of industrial keratinic wastes.

Pseudallescheria boydii releases metallopeptidases capable of cleaving several proteinaceous compounds

Pseudallescheria boydii is an opportunistic filamentous fungus that causes serious infections in humans. Virulence attributes expressed by P. boydii are unknown. Conversely, peptidases are incriminated as virulence factors in several pathogenic fungi. Here we investigated the extracellular peptidase profile in P. boydii. After growth on Sabouraud for 7 days, mycelia of P. boydii were incubated for 20 h in PBS-glucose. The cell-free PBS-glucose supernatant was submitted to SDS-PAGE and 12 secretory polypeptides were observed. Two of these polypeptides (28 and 35 kD) presented proteolytic activity when BSA was used as a copolymerized substrate. The extracellular peptidases were most active in acidic pH (5.5) and fully inhibited by 1,10-phenanthroline, a zinc-metallopeptidase inhibitor. Other metallo-, cysteine, serine and aspartic proteolytic inhibitors did not significantly alter these activities. To confirm that these enzymes belong to the metallo-type peptidases, the apoenzymes were obtained by dialysis against chelating agents, and supplementation with different cations, especially Cu(2+) and Zn(2+), restored their activities. Except for gelatin, both metallopeptidases hydrolyzed various co-polymerized substrates, including human serum albumin, casein, hemoglobin and IgG. Additionally, the metallopeptidases were able to cleave different soluble proteinaceous substrates such as extracellular matrix components and sialylated proteins. All these hydrolyses were inhibited by 1,10-phenanthroline. Interestingly, Scedosporium apiospermum (the anamorph of P. boydii) produced a distinct extracellular peptidase profile. Collectively, our results demonstrated for the first time the expression of acidic extracellular metallopeptidases in P. boydii capable of degrading several proteinaceous compounds that could help the fungus to escape from natural human barriers and defenses.

Reproducible genetic transformation system for two dermatophytes, Microsporum canis and Trichophyton mentagrophytes

A reproducible genetic transformation system was developed for two major dermatophytes, Microsporum canis and Trichophyton mentagrophytes. Two circular transformation vectors carrying either the bacterial hygromycin B phosphotransferase gene (hph) or both the hph and green fluorescent protein (eGFP) genes under the control of a promoter sequence from Cochlibolus heterostrophus were introduced independently into the protoplasts by a polyethylene glycol (PEG)-mediated method. Polymerase chain reaction (PCR) showed that the hph gene was integrated randomly into the chromosomal DNA of the transformants through non-homologous recombination. Southern blotting analysis also demonstrated a single or multiple integration of the hph gene into the chromosomal DNA. Fluorescence due to eGFP gene expression was observed in the T. mentagrophytes transformants, and the transformants retained mitotic stability through subculture. This reproducible transformation system provides a method for the genetic manipulation of these pathogens, which will facilitate detailed molecular analysis of dermatophytosis.

Aminopeptidases and dipeptidyl-peptidases secreted by the dermatophyte Trichophyton rubrum

The nature of secreted aminopeptidases in Trichophyton rubrum was investigated by using a reverse genetic approach. T. rubrum genomic and cDNA libraries were screened with Aspergillus spp. and Saccharomyces cerevisiae aminopeptidase genes as the probes. Two leucine aminopeptidases, ruLap1 and ruLap2, and two dipeptidyl-peptidases, ruDppIV and ruDppV, were characterized and compared to orthologues secreted by Aspergillus fumigatus using a recombinant protein from Pichia pastoris. RuLap1 is a 33 kDa nonglycosylated protein, while ruLap2 is a 58-65 kDa glycoprotein. The hydrolytic activity of ruLap1, ruLap2 and A. fumigatus orthologues showed various preferences for different aminoacyl-7-amido-4-methylcoumarin substrates, and various sensitivities to inhibitors and cations. ruDppIV and ruDppV showed similar activities to A. fumigatus orthologues. In addition to endopeptidases, the four aminopeptidases ruLap1, ruLap2, ruDppIV and ruDppV were produced by T. rubrum in a medium containing keratin as the sole nitrogen source. Synergism between endo- and exopeptidases is likely to be essential for dermatophyte virulence, since these fungi grow only in keratinized tissues.

Multiplication of an ancestral gene encoding secreted fungalysin preceded species differentiation in the dermatophytes Trichophyton and Microsporum

Dermatophytes are human and animal pathogenic fungi which cause cutaneous infections and grow exclusively in the stratum corneum, nails and hair. In a culture medium containing soy proteins as sole nitrogen source a substantial proteolytic activity was secreted by Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum canis. This proteolytic activity was 55-75 % inhibited by o-phenanthroline, attesting that metalloproteases were secreted by all three species. Using a consensus probe constructed on previously characterized genes encoding metalloproteases (MEP) of the M36 fungalysin family in Aspergillus fumigatus, Aspergillus oryzae and M. canis, a five-member MEP family was isolated from genomic libraries of T. rubrum, T. mentagrophytes and M. canis. A phylogenetic analysis of genomic and protein sequences revealed a robust tree consisting of five main clades, each of them including a MEP sequence type from each dermatophyte species. Each MEP type was remarkably conserved across species (72-97 % amino acid sequence identity). The tree topology clearly indicated that the multiplication of MEP genes in dermatophytes occurred prior to species divergence. In culture medium containing soy proteins as a sole nitrogen source secreted Meps accounted for 19-36 % of total secreted protein extracts; characterization of protein bands by proteolysis and mass spectrometry revealed that the three dermatophyte species secreted two Meps (Mep3 and Mep4) encoded by orthologous genes.

Evaluation of immunogenicity and protective efficacy of a Microsporum canis metalloprotease subunit vaccine in guinea pigs

In order to identify protective immunogens against Microsporum canis infection, a purified recombinant keratinolytic metalloprotease (r-MEP3) was tested as a subunit vaccine in experimentally infected guinea pigs. Both humoral and cellular specific immune responses developing towards r-MEP3 were evaluated, by enzyme-linked immunosorbent assay and by in vitro lymphocyte transformation tests respectively. Vaccination induced a strong antibody response, and a significant but transient lymphoproliferative response against the protein. However, the protocol failed to prevent fungal invasion or development of dermatophytic lesions. These results show that under the present experimental conditions, r-MEP3 specific antibodies are not protective against a challenge exposure. They also suggest that in the same model, the induction of cell-mediated immunity towards r-MEP3 is not sufficient, indicating the need for further research in the field of specific immune mechanisms involved in M. canis dermatophytosis.