The first isolation of ustilaginomycetous anamorphic yeasts, Pseudozyma species, from patients' blood and a description of two new species: P. parantarctica and P. thailandica

Molecular Identification of Fungal Endophytes of Medicinal Plant Citrullus colocynthis (L.) Schrad as a Medicinal Plant: Role of Tissue Type and Sampling Location on the Diversity

Endophytic fungi are an important group of organisms in association with plants which are able to colonize all plant internal tissues and improve their fitness. The present research aims to isolate and identify endophytic fungi of Citrullus colocynthis plant and then investigate the effects of sampling location and tissue type on the fungal endophyte diversity of this plant. To do so, a sampling program was done in 11 geographically isolated C. colocynthis growing areas of Hormozgan province, Iran. For molecular identification of endophytic fungi of C. colocynthis, the internal transcribed spacer region (ITS1-5.8S-ITS4), as a universal DNA barcode marker for fungi, was amplified using primer sets. Totally, 12 taxa (Alternaria solani, Cladosporium halotolerans, Setosphaeria rostrata, Aspergillus niger, A. allahabadii, A. terreus, A. occultus, A. cristatus, Penicillium chrysogenum, Talaromyces purpureogenus, Fusarium sp., and Pseudozyma flocculosa) were isolated. Our findings also showed that the diversity of fungal endophytes isolated from C. colocynthis was affected by the tissue type and sampling site. Accordingly, the leaves and seeds were found to have the highest and lowest rates of endophyte colonization and richness in all sampling seasons, respectively. Simpson's diversity index of 0.8165 in root tissue indicated the high diversity of endophytes in this organ. In addition, Shannon's diversity index in the root (1.846) was higher than that in the other organs. The highest Shannon's and Simpson's indices were observed in Khoon Sorkh and Minab regions. Generally, at least two factors (region and type of tissue) played the most important roles in determining the composition of fungal endophytes in C. colocynthis.

A case of Moesziomyces antarcticus peritonitis in a patient undergoing peritoneal dialysis

Background

Fungal peritonitis is a common and serious complication associated with peritoneal dialysis (PD), and it is often refractory to treatment.

Case presentation

A 70-year-old patient undergoing peritoneal dialysis was admitted to our hospital with fever and cloudy PD fluid. A diagnosis of yeast-like fungal peritonitis was made by examining the PD fluid. After starting intravenous caspofungin acetate, the PD catheter was removed. A fungal pathogen was isolated from the peritoneal fluid and identified as Cryptococcus sp. Based on the results of antifungal susceptibility testing, the treatment was changed to oral voriconazole and continued for 6 weeks. However, because of the discrepancy between the morphological findings and culture results, we performed genetic analysis, which uncovered Moesziomyces antarcticus. This patient was diagnosed with PD-related peritonitis caused by M. antarcticus and was successfully treated with voriconazole and removal of the PD catheter.

Conclusions

Reports of human infection by M. antarcticus are rare, and only two cases have been recognized. This may be the first case of infection detected in PD fluid.

First Case of Subcutaneous Mycoses Caused by Dirkmeia churashimaensis and a Literature Review of Human Ustilaginales Infections

Objective

Dirkmeia churashimaensis, belonging to Ustilaginales fungi, has never been reported as clinical pathogenic until very recently. In this study, we report an unusual subcutaneous infection with Dirkmeia churashimaensis and reviewed all human Ustilaginales infections. The aim is to better understand their epidemiology, infection type, risk factors, and the sensitivity to antifungal agents.

Methods

An 80-year-old female farmer developed extensive plaques and nodules on her left arm within 2 years. Pathological and microbiological examinations identified a new pathological agent, Dirkmeia churashimaensis, as the cause of this infection. The patient was successfully cured by oral itraconazole. We reviewed a total of 31 cases of Ustilaginales cases, among of which only three were skin infections.

Results

Local barrier damage (i.e., surgery, trauma, and basic dermatosis) and systemic immunodeficiency (i.e., preterm and low birthweight, Crohn’s disease, malignant cancer, and chemotherapy) are risk factors for Ustilaginales infection. The D1/D2 and ITS regions are the frequently used loci for identifying the pathogens together with phenotype. Most patients could survive due to antifungal treatment, whereas seven patients died. Amphotericin B, posaconazole, itraconazole, and voriconazole showed good activity against these reported strains, whereas fluconazole, 5-flucytosine, and echinocandins usually showed low susceptibility. Itraconazole had good efficiency for subcutaneous infections.

Conclusions

The present case study and literature review reveal that Ustilaginales can be opportunistic pathogenic normally in immunocompromised and barrier damage people. A proper identification of fungi can be crucial for clinical treatment, and more data of antifungal are needed for choice of medication against this kind of infections.

Pseudozyma spp. human infections: A systematic review

Pseudozyma spp. are described as environmental yeasts but have also been identified as rare human pathogens found in immunocompromised patients. This systematic review details the clinical manifestations, diagnostic methodology, and empirical anti-fungal therapy for this rare yeast. PubMed, LILACS, Scielo, and Web of Science databases were searched for articles about Pseudozyma spp. infections from inception to June 2019. Inclusion criteria were any published studies that included patients with Pseudozyma spp. infection. Infections were identified using criteria set forth by the European Organization for Research and Treatment of Cancer, and were further classified according to clinical, laboratory, or radiologic findings, microbiologic confirmation, and response to therapy. Eleven articles were included with 15 patients. Oncological and/or hematological disorders were the most reported risk factors. Nontraditional microbiological methods correctly identified Pseudozyma spp., whereas traditional methods failed to identify fungal genus. Species were identified by sequencing, and most demonstrated a higher minimal inhibitory concentration (MIC) for fluconazole and echinocandins. MICs for itraconazole, voriconazole, and posaconazole varied by species. All isolates were susceptible to amphotericin B, which was the most used treatment. Pseudozyma spp. infections usually present with fever and are diagnosed by blood culture. Most species studied appeared to be resistant to fluconazole and echinocandin. Voriconazole, posaconazole, and amphotericin were effective in treating P. aphidis. However, more studies are needed to evaluate voriconazole and posaconazole in species other than P. aphidis.

Pseudozyma aphidis bloodstream infection in a patient with aggressive lymphoma and a history of intravenous drug use: Case report and review of the literature

Pseudozyma aphidis is an environmental fungus which causes opportunistic infections in immunocompromised patients. Here we report the case of a 54-year-old, intravenous drug user woman, newly diagnosed to have an aggressive lymphoma, who developed a bloodstream infection caused by P. aphidis treated successfully with amphotericin-B therapy. The precise identification was assessed by sequencing. We propose to consider intravenous drug use as a risk factor for invasive infections due to this environmental yeast.

Molecular Interactions Between Smut Fungi and Their Host Plants

Smut fungi are a large group of biotrophic plant pathogens that infect mostly monocot species, including economically relevant cereal crops. For years, Ustilago maydis has stood out as the model system to study the genetics and cell biology of smut fungi as well as the pathogenic development of biotrophic plant pathogens. The identification and functional characterization of secreted effectors and their role in virulence have particularly been driven forward using the U. maydis-maize pathosystem. Today, advancing tools for additional smut fungi such as Ustilago hordei and Sporisorium reilianum, as well as an increasing number of available genome sequences, provide excellent opportunities to investigate in parallel the effector function and evolution associated with different lifestyles and host specificities. In addition, genome analyses revealed similarities in the genomic signature between pathogenic smuts and epiphytic Pseudozyma species. This review elaborates on how knowledge about fungal lifestyles, genome biology, and functional effector biology has helped in understanding the biology of this important group of fungal pathogens. We highlight the contribution of the U. maydis model system but also discuss the differences from other smut fungi, which raises the importance of comparative genomic and genetic analyses in future research.

GC-MS based profiling of alkanes in the filamentous yeast Hyphozyma roseoniger (Moesziomyces antarcticus)

OBJECTIVES

Hyphozyma roseoniger, a filamentous yeast, is used as a biocatalyst in the bio-transformation of terpenoids; however, the microorganism's endogenous ability to synthesise and metabolise hydrophobic terpenes and alkanes has not been characterised.

RESULTS

When grown in potato dextrose broth the organism reached the stationary phase at 14 d. The non-polar fraction from cells, harvested every second day, were obtained with ethyl acetate extraction and analysed by gas chromatography with mass-spectrometric detection. Principal component-and hierarchical cluster analysis indicated growth-dependent clustering of the sample groups. A total of 26 alkanes were annotated across the different developmental stages.

CONCLUSIONS

The major hydrocarbons comprised linear and branched structures. The dominant alkanes were all odd- or even-carbon numbered long-chain n-alkanes, C15 > C18 > C24.

Diversity of Moesziomyces (Ustilaginales, Ustilaginomycotina) on Echinochloa and Leersia (Poaceae)

A combined ecological, morphological, and molecular approach was used to examine 26 herbarium specimens and eight strains of Moesziomyces. The phylogenetic analysis resolved eight well-supported clades, of which three contained type specimens of known species of Moesziomyces. One clade contained two specimens that produced a teleomorph in the flowers of Echinochloakimberleyensis in Australia. The name Moesziomyceskimberleyensis is proposed for this smut fungus. Another clade contained specimens that produced sori in the flowers of Leersiahexandra. The name Thecaphoraglobuligera (now Moesziomycesglobuligerus) is available for this species, which is lectotypified. The teleomorph of Moesziomycesantarcticus, previously known only from Japan, is found for the first time in China, on Echinochloacrus-galli.

Morphology and Molecular Analysis of Moesziomyces antarcticus Isolated From the Blood Samples of a Chinese Patient

Objective: To identify the pathogen causing fungemia in a Chinese patient and describe its morphological and molecular characterizes. Methods: Samples of central and peripheral venous blood were collected for blood culture. Morphology and drug sensitivities of the isolated yeast-like fungus were analyzed. rDNA sequencing and molecular phylogenetic analysis of the isolated strains were performed using DNAMAN and MEGA software. Results: A strain of yeast-like fungi was repeatedly isolated from blood samples of a Chinese patient. The isolates grew well on sabouraud medium broth plate. The colonies were smooth and round at 28°C, and were of rough surface and irregular shape at 35°C. Molecular phylogenetic trees constructed based on the internal transcribed spacer (ITS) and D1/D2 domains of 28S rDNA gene demonstrated the isolated yeast-like fungus was Moesziomyces antarcticus. Drug susceptibility test showed that this isolated M. antarcticus was resistant or had relatively low susceptibility to flucytosine, fluconazole, voriconazole, and itraconazole, and only sensitive to amphotericin. Conclusion: This study provided more information for the molecular and morphology characteristics of M. antarcticus and reviewed the species information of Moesziomyces associated with human infections, which will contribute to the identification and diagnosis of Moesziomyces infections.

Endophytic yeast diversity in leaf tissue of rice, corn and sugarcane cultivated in Thailand assessed by a culture-dependent approach

Endophytic yeasts are yeast that can colonize healthy plant tissues without causing any damage to the host plant. This work aimed to explore the diversity of endophytic yeasts in leaf tissue of main agricultural crops (rice, corn and sugarcane) in Thailand, by a culture-dependent approach. A total of 311 leaf samples, consisting of rice (n = 100), corn (n = 109) and sugarcane (n = 102). From the tissue of rice (n = 92), corn (n = 76) and sugarcane (n = 78) leaf samples, 117, 118 and 123 yeast strains were respectively isolated and identified based on the D1/D2 region of the large subunit (LSU) rRNA gene sequence analysis to be yeast species in both the phyla Basidiomycota and Ascomycota. Higher numbers of basidiomycetous yeast than ascomycetous yeast were detected in the leaf tissue of the three crops. Pseudozyma (Dirkmeia) churashimaensis (Ustilaginales) was the most prevalent yeast species in the rice and corn leaves with relative frequencies (RF) of 35.9 % and 17.8 %, respectively. Whereas the predominant species in the sugarcane leaves was Meyerozyma caribbica (Saccharomycetales) with an RF of 14.6 %. In addition, six new yeast species and one new yeast genus were proposed. Our findings suggest that these plant species are good sources from which new yeast species may be isolated.

Asexual and sexual morphs of Moesziomyces revisited

Yeasts of the now unused asexually typified genus Pseudozyma belong to the smut fungi (Ustilaginales) and are mostly believed to be apathogenic asexual yeasts derived from smut fungi that have lost pathogenicity on plants. However, phylogenetic studies have shown that most Pseudozyma species are phylogenetically close to smut fungi parasitic to plants, suggesting that some of the species might represent adventitious isolations of the yeast morph of otherwise plant pathogenic smut fungi. However, there are some species, such as Moesziomyces aphidis (syn. Pseudozyma aphidis) that are isolated throughout the world and sometimes are also found in clinical samples and do not have a known plant pathogenic sexual morph. In this study, it is revealed by phylogenetic investigations that isolates of the biocontrol agent Moesziomyces aphidis are interspersed with M. bullatus sexual lineages, suggesting conspecificity. This raises doubts regarding the apathogenic nature of asexual morphs previously placed in Pseudozyma, but suggests that there might also be pathogenic sexual morph counterparts for those species known only from asexual morphs. The finding that several additional species currently only known from their yeast morphs are embedded within the genus Moesziomyces, suggests that the yeast morph might play a more dominant role in this genus as compared to other genera of Ustilaginaceae. In addition, phylogenetic reconstructions demonstrated that Moesziomyces bullatus has a narrow host range and that some previously described but not widely used species names should be applied for Moesziomyces on other host genera than Echinochloa.

Pseudozyma and other non-Candida opportunistic yeast bloodstream infections in a large stem cell transplant center

Non-Candida opportunistic yeasts are emerging causes of bloodstream infection (BSI) in immunocompromised hosts. However, their clinical presentation, management, and outcomes in stem cell transplant (SCT) recipients are not well described. We report the first case to our knowledge of Pseudozyma BSI in a SCT recipient. He had evidence of cutaneous involvement, which has not been previously described in the literature. He became infected while neutropenic and receiving empiric micafungin, which is notable because Pseudozyma is reported to be resistant to echinocandins. He was successfully treated with the sequential use of liposomal amphotericin B and voriconazole. A review of the literature revealed nine reported instances of Pseudozyma fungemia. We performed a retrospective review of 3557 SCT recipients at our institution from January 2000 to June 2015 and identified four additional cases of non-Candida yeast BSIs. These include two with Cryptococcus, one with Trichosporon, and one with Saccharomyces. Pseudozyma and other non-Candida yeasts are emerging pathogens that can cause severe and disseminated infections in SCT recipients and other immunocompromised hosts. Clinicians should have a high degree of suspicion for echinocandin-resistant yeasts, if patients develop breakthrough yeast BSIs while receiving echinocandin therapy.

First Two Cases of Fungal Infections Associated with Multi-drug Resistant Yeast, Fereydounia khargensis

The number of new fungal pathogens is increasing due to growing population of immunocompromised patients and advanced identification techniques. Fereydounia khargensis is a yeast and was first described in 2014 from environmental samples. As far as we know, this is the first report of human infections associated with F. khargensis. The yeasts were isolated from blood of a HIV-positive patient and pleural fluid of chronic renal failure patient. Amplification and sequencing of the internal transcribed spacer and the large subunit regions confirmed the identity of the isolates. Both isolates showed multi-drug resistance to antifungal agents tested.

Pseudozyma aphidis fungaemia with invasive fungal pneumonia in a patient with acute myeloid leukaemia: case report and literature review

Pseudozyma species rarely cause invasive diseases in humans, which are usually isolated from plants. There have been anecdotal reports regarding Pseudozyma species infections in patients with underlying diseases or in neonates. However, clinical data and the pathogenicity in humans are still insufficient. We experienced a case of Pseudozyma aphidis fungaemia with invasive fungal pneumonia that developed during reinduction chemotherapy in a 51‐year‐old male with acute myeloid leukaemia (AML). P. aphidis was suspected based on the morphology of the yeast isolated from the blood and was confirmed via rDNA gene sequencing analysis. The patient successfully underwent stem cell transplantation with continuing antifungal treatment and finally completely recovered from both the AML and infectious complications. Here, we report a case of P. aphidis infection that developed during neutropenia in an AML patient and review the global literature.

First Case of Fungemia Due to Pseudozyma aphidis in a Pediatric Patient with Osteosarcoma in Latin America

We report the first case of blood infection due to Pseudozyma aphidis in Latin America. We contribute evidence showing this organism to be a potential human pathogen, and we provide new data about its identification, drug susceptibility, and treatment outcome.

Assessment of epiphytic yeast diversity in rice (Oryza sativa) phyllosphere in Thailand by a culture-independent approach

The epiphytic yeast diversity in rice phyllosphere in Thailand was investigated by a culture-independent technique based on the RFLP pattern and the sequence of the D1/D2 domain of the large subunit rRNA gene. Forty-four samples of rice leaf were collected randomly from six provinces. The DNA was extracted from leaf washing samples and the D1/D2 domain was amplified using PCR technique. The PCR products were cloned and then screened by colony PCR. Of total 1121 clones, 451 clones (40.2 %) revealed the D1/D2 domain sequences closely related to sequences of yeasts in GenBank, and they were clustered into 45 operational taxonomic units (OTUs) at 99 % homology. Of total yeast related clones, 329 clones (72.9 %) were identified as nine known yeast species, which consisted of 314 clones (8 OTUs) in the phylum Basidiomycota including Bullera japonica, Pseudozyma antarctica, Pseudozyma aphidis, Sporobolomyces blumeae, Sporobolomyces carnicolor and Sporobolomyces oryzicola and 15 clones (6 OTUs) in the phylum Ascomycota including Metschnikowia koreensis, Meyerozyma guilliermondii and Wickerhamomyces anomalus. The D1/D2 sequences (122 clones) that could not be identified as known yeast species were closest to 3 and 14 species in Ascomycota and Basidiomycota, respectively, some of which may be new yeast species. The most predominant species detected was P. antarctica (42.6 %) followed by B. japonica (25.9 %) with 63.6 and 22.7 % frequency of occurrence, respectively. The results of OTU richness of each sampling location revealed that climate condition and sampling location could affect epiphytic yeast diversity in rice phyllosphere.

Pseudozyma aphidis fungemia after abdominal surgery: First adult case

Pseudozyma aphidis is an environmental Basidiomycete yeast, and has been involved in the ten past years in rare cases of invasive infection. Pseudozyma species are naturally resistant to caspofungin and often present decreased susceptibility or resistance to fluconazole. This fungus may be difficult to recognize and misidentifications are reported with conventional phenotypical methods. We report a case of P. aphidis invasive infection in an adult with a metastatic ampulloma who had gone through digestive surgery.

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Pseudozyma aphidis invasive infection after abdominal surgery.

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Identification of Pseudozyma aphidis: mass spectrometry could be promising if databanks include more spectra, whereas conventional phenotypical methods fail.

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Resistance to echinocandins and flucytosine and decreased susceptibility to fluconazole.

Pseudozyma spp catheter-associated blood stream infection, an emerging pathogen and brief literature review

Pseudozyma spp are amorphic yeasts. They are commonly plant pathogens, but rarely cause invasive fungal disease in humans. Only three cases of central venous catheter (CVC)-associated blood stream infections due to this organism have been reported in the literature. Main underlying risk factors for Pseudozyma spp infection are bowel surgery, CVC and total parenteral nutrition. We present a rare case of Pseudozyma spp catheter-associated blood stream infection that was successfully treated with antifungal therapy and removal of CVC. It is important to recognise and differentiate this species from other yeasts as it may require the use of amphotericin B or voriconazole instead of fluconazole, to which the organism is variably resistant.

Pseudozyma brasiliensis sp. nov., a xylanolytic, ustilaginomycetous yeast species isolated from an insect pest of sugarcane roots

A novel ustilaginomycetous yeast isolated from the intestinal tract of an insect pest of sugarcane roots in Ribeirão Preto, São Paulo State, Brazil, represents a novel species of the genus Pseudozyma based on molecular analyses of the D1/D2 rDNA large subunit and the internal transcribed spacer (ITS1+ITS2) regions. The name Pseudozyma brasiliensis sp. nov. is proposed for this species, with GHG001(T) ( = CBS 13268(T) = UFMG-CM-Y307(T)) as the type strain. P. brasiliensis sp. nov. is a sister species of Pseudozyma vetiver, originally isolated from leaves of vetiver grass and sugarcane in Thailand. P. brasiliensis sp. nov. is able to grow well with xylan as the sole carbon source and produces high levels of an endo-1,4-xylanase that has a higher specific activity in comparison with other eukaryotic xylanases. This enzyme has a variety of industrial applications, indicating the great biotechnological potential of P. brasiliensis.

Candida pseudohaemuloniiSp. Nov., an Amphotericin B- and Azole-Resistant Yeast Species, Isolated from the Blood of a Patient from Thailand

Candida haemulonii(types I and II) is rarely isolated from clinical specimens. We isolated a strain that is phylogenetically close to C. haemulonii from the blood of a Thai patient, and named it C. pseudohaemulonii sp. nov. (CBS 10099T = JCM 12453T = DMST 17134T). The new species and C. haemulonii types I and II were resistant to amphotericin B and azole agents but were susceptible to a 1,3-beta-D-glucan synthetase inhibitor, micafungin, and 5-flucytosine. The species were easily distinguished using an ID32 yeast identification kit. The taxonomic description of C. pseudohaemulonii sp. nov. is presented.

Pseudozyma vetiver sp. nov., a novel anamorphic ustilaginomycetous yeast species isolated from the phylloplane in Thailand

Three strains representing one novel yeast species were isolated from the phylloplanes of the vetiver grasses (DMKU-LV90 and DMKU-LV99(T)) and sugarcane (DMKU-SP260) collected in Thailand by leaf washing followed by a plating technique. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics and the sequence analysis of the D1/D2 region of the large subunit (LSU) rRNA gene and the internal transcribed spacer region (ITS), the three strains were found to represent a single novel anamorphic ustilaginomycetous yeast species in the genus Pseudozyma. The name Pseudozyma vetiver sp. nov. is proposed for this novel species. The type strain is DMKU-LV99(T) (BCC 61021 = CBS 12824). The novel species showed phylogenetic relationships to the other members of the genus Pseudozyma and to teleomorphic fungal genera, namely Ustilago, Sporisorium and Anomalomyces in Ustilaginaceae, Ustilaginales. The three strains showed identical sequences both in the D1/D2 and ITS regions. The Pseudozyma species closest to the novel species in terms of pairwise sequence similarity in the D1/D2 region was Pseudozyma pruni but with 2.3 % nucleotide substitutions (14 nucleotide substitutions and no gaps out of 606 nt). The novel species and P. pruni differed by 10.9 % nucleotide substitutions (75 nucleotide substitutions and 31 gaps out of 691 nt) in the ITS region. The phylogenetic analysis based on the combined sequences of the ITS region and the D1/D2 region of the LSU rRNA gene showed that the novel species was found to be most closely related to Pseudozyma fusiformata but with 2.9 % nucleotide substitutions in the D1/D2 region and 7.4 % nucleotide substitutions in the ITS region.

Isolation of Pseudozyma churashimaensis sp. nov., a novel ustilaginomycetous yeast species as a producer of glycolipid biosurfactants, mannosylerythritol lipids

An ustilaginomycetous anamorphic yeast species isolated from the leaves of Saccharum officinarum (sugarcane) in Okinawa, Japan, was identified as a novel Pseudozyma species based on morphological and physiological aspects and molecular taxonomic analysis using the D1/D2 domains of the large subunit (26S) rRNA gene and the internal transcribed spacer 1 (ITS1)-5.8S-ITS2 regions. The name Pseudozyma churashimaensis sp. nov. was proposed for the novel species, with JCM 16988(T) as the type strain. Interestingly, P. churashimaensis was found to produce glycolipid biosurfactants, a mixture of mannosylerythritol lipids (MELs), including a novel tri-acetylated derivative (MEL-A2), from glucose. The observed critical micelle concentration (CMC) and the surface tension at CMC of MEL-A2 were 1.7 × 10⁻⁶ M and 29.2 mN/m, respectively. Moreover, on a water-penetration scan, MEL-A2 efficiently formed different lyotropic liquid crystalline phases, including the lamella phase at a wide range of concentrations, indicating its excellent surface-active and self-assembling properties. The novel strain of the genus Pseudozyma should thus facilitate the application of glycolipid biosurfactants in combination with other MEL producers.

Pseudozyma pruni sp. nov., a novel ustilaginomycetous anamorphic fungus from flowers in Taiwan

Two ustilaginomycetous anamorphic strains were isolated from flowers in Taiwan. Phylogenetic analysis based on the combined rRNA gene sequence of internal transcribed spacer 1 (ITS1)-5.8S-ITS2 and large-subunit D1/D2 domains indicated that the closest recognized species was Pseudozyma fusiformata. The results of DNA-DNA hybridization and physiological characteristics showed that the two strains represent a novel species within the genus Pseudozyma. The name Pseudozyma pruni sp. nov. is proposed, with FIRDI 005(T) (=BCRC 34227(T) =CBS 10937(T)) as the type strain.

Candida kanchanaburiensis sp. nov., a new ascomycetous yeast species related to Pichia nakazawae isolated in Thailand

Three yeast strains, ST-633, ST-634 and ST-635, isolated from the fruit body of a mushroom, Coprinus sp., and rotted fruit of guava collected in the western region of Thailand, were found to represent a hitherto undescribed species. This yeast is related to Pichia nakazawae var. akitaensis, P. nakazawae var. nakazawae and Pichia philogaea in the D1/D2 domain of 26S rDNA but 12 (2.3%), 13 (2.5%) and 15 (2.8%) nucleotides are different from these taxa, respectively, suggesting the distinctness of the Thai strains at species level. Since ascospore formation was not detected, it is described as a new species of Candida, Candida kanchanaburiensis. This species is distinguished from P. nakazawae by the ability to assimilate 2-ketogluconic acid and L-lysine, and inability to assimilate soluble starch.

Central venous catheter infection associated with Pseudozyma aphidis in a child with short gut syndrome

Pseudozyma aphidis is a heterobasidiomycetous yeast related to the smut fungi in the genus Ustilago. Pseudozyma species are usually isolated from plants and rarely from clinical specimens. We report what is believed to be the first paediatric case of central venous catheter (CVC)-related fungaemia associated with P. aphidis. Prompt removal of the CVC in conjunction with anti-fungal therapy resulted in a successful outcome.

The isolation and characterization of Pseudozyma sp. JCC 207, a novel producer of squalene

In examining the production of valuable compounds by marine microorganisms, we isolated a novel yeast strain that produces a large amount of squalene and several polyunsaturated fatty acids. Molecular and phylogenetic analyses of the ribosomal DNA suggest that the isolate belongs to the genus Pseudozyma, which comprises ustilaginomycetous anamorphic yeasts. The nucleotide sequence of an internally transcribed spacer region from isolate Pseudozyma sp. JCC207 showed 98% similarity with those of Pseudozyma rugulosa and Pseudozyma aphidis, which are close relatives of the isolate. In considering use of Pseudozyma sp. JCC207 for squalene production, the efficiency of squalene production was investigated under different conditions. Glucose was the best carbon source for the production of squalene. In the presence of yeast extract, squalene production was activated and an optimum ratio of glucose to yeast extract was 4.5. For the optimal squalene production, the concentration of glucose was 40 g l(-1) and the best nitrogen source was sodium nitrogen. Pseudozyma sp. JCC207 was shown to produce up to 5.20 g/L of biomass and 340.52 mg/L of squalene. In an optimal condition, the content and yield of squalene produced by Pseudozyma sp. JCC207 were much greater than those obtained from microorganisms previously reported as squalene producers. We identified, classified, and characterized Pseudozyma sp. JCC207 as a novel squalene producer. The squalene production rate of Pseudozyma sp. JCC207 makes it an ideal candidate for the commercialization of microbial squalene.

DOMESTICATION OF MAIZE, SORGHUM, AND SUGARCANE DID NOT DRIVE THE DIVERGENCE OF THEIR SMUT PATHOGENS

We investigated two alternative hypotheses for the origin of crop pathogen species: that human-mediated agricultural practices drove the divergence of many crop plant pathogen species or that coevolutionary processes in natural populations of the crops' ancestors drove divergence of pathogen species. We distinguished between these two hypotheses by constructing a robust multigene phylogeny and estimating the dates of divergence among four, monophyletic species of smut fungi (Ustilago maydis, U. scitaminea, Sporisorium reilianum, S. sorghi) known to specifically infect maize, sorghum, sugarcane, and their wild ancestors. Without a fossil record for smut fungi, we calibrated the pathogen species' divergence times to their plant host divergence times. Specifically, a calibration date of 10,000 years was employed to test the hypothesis that the fungal species originated at the time of domestication of their current hosts and a calibration date of 50 million years was employed to test the hypothesis that the fungal species originated on wild ancestors of their domesticated hosts. Substitution rates at five protein coding genes were calculated and rates obtained for the 10,000 year calibration date were orders of magnitude faster than those commonly reported for eukaryotes, thus rejecting the hypothesis that these smut pathogen species diverged at the time of domestication. In contrast, substitution rates obtained for the 50 million year calibration were comparable to eukaryotic substitution rates. We used the 50 million year calibration to estimate divergence times of taxa in two datasets, one comprised solely the focal species and one comprised the focal species and additional related taxa. Both datasets indicate that all taxa diverged millions of years ago, strongly supporting the hypothesis that smut species diverged before the time of domestication and modern agriculture. Thus, smut species diverged in the ecological context of natural host plant and fungal populations.

Production of different types of mannosylerythritol lipids as biosurfactants by the newly isolated yeast strains belonging to the genus Pseudozyma

Mannosylerythritol lipids (MEL), which are abundantly secreted by yeasts, are one of the most promising biosurfactants known. To obtain various types of MEL and to attain a broad range of applications for them, screening of novel producers was undertaken. Thirteen strains of yeasts were successfully isolated as potential MEL producers; they showed high production yields of MEL of around 20 g l(-1) from 40 g l(-1) of soybean oil. Based on the taxonomical study, all the strains were classified to be the genus Pseudozyma. It is interesting to note that they were categorized into three groups according to their production patterns of MEL. The first group, which included 11 strains taxonomically closely related to high-level MEL producers such as Pseudozyma antarctica and Pseudozyma aphidis, mainly produced 4-O-[(4',6'-di-O-acetyl-2',3'-di-O-alkanoyl)-beta-D-mannopyranosyl]-meso-erythritol (MEL-A) together with 4-O-[(6'-mono-O-acetyl-2',3'-di-O-alkanoyl)-beta-D-mannopyranosyl]-meso-erythritol (MEL-B) and 4-O-[(4'-mono-O-acetyl-2',3'-di-O-alkanoyl)-beta-D-mannopyranosyl]-meso-erythritol (MEL-C) as the minor components. The second group of one strain, which was related to Pseudozyma tsukubaensis, predominantly produced MEL-B. The third group of one strain, which was closely related to Pseudozyma hubeiensis, mainly produced MEL-C; this is the first observation of the efficient production of MEL-C from soybean oil. Moreover, the major fatty acids of the obtained MEL-C were C(6), C(12), and C(16) acids, and were considerably different from those of the other MEL hitherto reported. The biosynthetic manner for MEL is thus likely to significantly vary among the Pseudozyma strains; the newly isolated strains would enable us to attain a large-scale production of MEL and to obtain various types of MEL with different hydrophobic structures.

Mycocin production in Pseudozyma tsukubaensis

Killer activity expressed at pH values ranging from 3.5 to 6.0 was found in the ustilaginaceous yeast-like species, Pseudozyma tsukubaensis. Its killer phenotype was incurable, and extrachromosomal genetic elements were not detected. The toxin excreted with a molecular mass above 15 kDa is fungicidal, resistant to proteolytic cleavage, thermolabile and active only against fungi within the Ustilaginomycetes (the orders Microstromatales and Ustilaginales).

Discovery of Pseudozyma rugulosa NBRC 10877 as a novel producer of the glycolipid biosurfactants, mannosylerythritol lipids, based on rDNA sequence

The search for a novel producer of glycolipid biosurfactants, mannosylerythritol lipids (MEL) was undertaken based on the analysis of ribosomal DNA sequences on the yeast strains of the genus Pseudozyma. Pseudozyma rugulosa NBRC 10877 was found to produce a large amount of glycolipids from soybean oil. Fluorescence microscopic observation also demonstrated that the strain significantly accumulates polar lipids in the cells. The structure of the glycolipids produced by the strain was analyzed by (1)H and (13)C nuclear magnetic resonance and gas chromatography-mass spectrometry methods, and was determined to be the same as MEL produced by Pseudozyma antarctica, a well-known MEL producer. The major fatty acids of the present MEL consisted of C8 and C10 acids. Based on high performance liquid chromatography, the composition of the produced MEL was as follows: MEL-A (68%), MEL-B (12%), and MEL-C (20%). To enhance the production of MEL by the novel strain, factors affecting the production, such as carbon and nitrogen sources, were further examined. Soybean oil and sodium nitrate were the best carbon and nitrogen sources, respectively. The supplementation of a MEL precursor, such as erythritol, drastically enhanced the production yield from soybean oil at a rate of 70 to 90%. Under the optimal conditions in a shake culture, a maximum yield, productivity, and yield coefficient (on a weight basis to soybean oil supplied) of 142 g l(-1), 5.0 g l(-1) day(-1), and 0.5 g g(-1) were achieved by intermittent feeding of soybean oil and erythritol using the yeast.

Extracellular production of a glycolipid biosurfactant, mannosylerythritol lipid, by Candida sp. SY16 using fed-batch fermentation

Candida sp. strain SY16 produces a glycolipid-type biosurfactant, mannosylerythritol lipid (MEL-SY16), which can reduce the surface tension of a culture broth from 72 to 30 dyne cm(-1) and highly emulsify hydrocarbons when cultured in soybean-oil-containing media. As such, laboratory-scale fermentation for MEL-SY16 production was performed using optimized conditions. In batch fermentation, MEL-SY16 was mainly produced during the stationary phase of growth, and the concentration of MEL-SY16 reached 37 g l(-1) after 200 h. The effect of pH control on the production of MEL-SY16 was also examined in batch fermentation. The highest production yield of MEL-SY16 was when the pH was controlled at 4.0, and the production was significantly improved compared to batch fermentation without pH control. In fed-batch fermentation, glucose and soybean oil (1:1, w/w) were used in combination as the initial carbon sources for cell growth, and soybean oil was used as the feeding carbon source during the MEL production phase. The feeding of soybean oil resulted in the disappearance of any foam and a sharp increase in the MEL production until 200 h, at which point the concentration of MEL-SY16 was 95 g l(-1). Among the investigated culture systems, the highest MEL-SY16 production and volumetric production rate were achieved with fed-batch fermentation.

Candida easanensis sp. nov., Candida pattaniensis sp. nov. and Candida nakhonratchasimensis sp. nov., three new species of yeasts isolated from insect frass in Thailand

Six strains of anamorphic yeasts isolated from insect frass collected in several regions of Thailand were assigned to the genus Candida based on the conventional taxonomic criteria used for yeast classification. These strains have Q-7 as the major ubiquinone and are suggested to have close relationships to the genus Pichia. Three strains, ST-225, ST-228 and ST-229, have identical nucleotide sequences in the D1/D2 domain of 26S rDNA and are closely related to Pichia japonica, but differ by six nucleotides (1.1% ) from this species. These three strains are considered to represent a single new species, which is described as Candida easanensis sp. nov. Two strains, ST-311 and ST-320, have identical sequences in the D1/D2 domain and resemble Pichia veronae and Pichia fabianii but differ from them by nine nucleotides (1.6%) in D1/D2 sequences. The two strains are described as Candida pattaniensis sp. nov. The remaining strain, ST-37, is related to Pichia americana and Pichia bimundalis but differs by six(1.1%) and seven (1.2%) nucleotides from these species, respectively. This strain is described as Candida nakhonratchasimensis sp. nov.