Rhytidhysteron Rufulum Research Articles

Cytology of Rhytidhysteron rufulum: An emerging cause of phaeohyphomycosis.

Fine-needle aspiration cytology (FNAC) is often the first-line investigation for detection of any fungal infection. Rhytidhysteron rufulum is an emerging dematiaceous fungus detected as a human pathogen. FNAC combined with molecular techniques helps in the detection of rare fungal species, especially in cases of non-sporulating fungi. We describe the cytomorphologic features of this species in a 62-year immunocompetent male who presented with a localised subcutaneous infection. Molecular studies helped in the final diagnosis.

P276 Molecular epidemiology of clinical filamentous fungi in Qatar beyond Aspergillus and Fusarium

Poster session 2, September 22, 2022, 12:30 PM - 1:30 PM ObjectivesDue to an increasing number of patients at risk, (ie, with a highly compromised immune system and/or receiving aggressive chemotherapy treatment), invasive fungal infections (IFI) are increasingly being reported. They are associated with significantly high mortality rates. Aspergillus spp., particularly A. fumigatus, is the major cause of mold-related IFI around the world followed by Fusarium spp., however, other molds are emerging as human pathogens. The aim of this study was to explore the epidemiology and prevalence of the non-Aspergillus and non-Fusarium molds in human clinical samples over 11 years period in Qatar based tertiary hospital using molecular techniques.MethodsA total of 91 clinical specimens positive for molds belonging to 90 patients were recorded in about 11 years (September 2003 to November 2014). The isolates were identified based on morphological characteristics and by sequencing the internal transcribed spacer (ITS) gene. To confirm the identifications, a phylogenetic tree based on ITS sequences was constructed.ResultsMost patients were males (72%), 6% were immunocompromised, 12% had IFI, and 7% died within 30 days of diagnosis. The fungal isolates were recovered from a variety of clinical samples, including nails, skin, hair, scalp, nasal cavity, wounds, respiratory samples, body fluids, eye, ear, tissue, abscess, and blood specimens. Dematiaceous fungi were overall the most isolated (33/91, 36%), followed by dermatophytes (25/91, 27%), Mucorales (16/91, 18%), and other hyaline molds (17/91, 19%) (Fig. 1). Curvularia was the most isolated genus (22/91, 24%) and Mucorales were the major cause of IF (5/11, 45.5%) (Table 1). Superficial mycoses were caused by dermatophytes (66%) and non-dermatophytes (34%). Furthermore, rare fungi that are not commonly known to cause human disease were recovered such as Rhytidhysteron rufulum, Subramaniula asteroids, Dothichiza pimprina, and Quambalaria cyanescens.ConclusionThe current study highlights the epidemiology and spectrum of mold genera, other than Aspergillus and Fusarium, recovered from human clinical samples in Qatar, which can aid in surveillance of uncommon and emerging mycoses other than aspergillosis and fusuriosis.

P393 Clinical spectrum and molecular characterization of Rhytidhysteron spp. (now Gloniopsis) from India

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PMObjective Rhytidhysteron spp. are emerging dematiaceous fungi implicated in subcutaneous infections in immunocompromised as well as immunocompetent individuals. Diagnosis of Rhytidhysteron spp is delayed owing to non-sporulation and misidentification. The present study was conducted to characterize Rhytidhysteron spp. isolated from India by molecular techniques.MethodWe retrieved a total of eight isolates of Rhytidhysteron spp from our National Culture Collection for Pathogenic Fungi (NCCPF) that were received from various centers across India. Colony morphology on Sabouraud's dextrose agar (SDA) and potato dextrose agar (PDA) was recorded. Molecular identification was performed by sequencing internal transcribed spacer (ITS) and 28 s region of rDNA. Phylogenetic tree was constructed using the Neighbor-Joining method along with sequences of standard strains retrieved from the NCBI database.Results Rhytidhysteron spp was confirmed by sequencing from cutaneous specimens of eight cases. Six patients were immunocompetent while two were post-renal transplant recipients. Phenotypic features on SDA and PDA revealed growth of greyish-black mycelia on the obverse with black pigmentation on reverse after 7 days of incubation. On microscopic examination of lactophenol cotton blue mount, only dematiaceous septate hyphae without any spores were noted. On phylogenetic analysis of 28 s region, four of our isolates were closely clustered with Gloniopsis calami (Fig.1b), whereas two isolates with G. pneumonia and one each with G. percutanea, and Gloniopsis spp. (Fig.1b). On ITS phylogeny, the same four isolates closely clustered with G. calami (Fig.1a) as in 28 s region, one each isolate clustered with G. pneumonia, and G. percutanea while two isolates formed a separate clade with Rhytidhysteron rufulum (Fig.1a).ConclusionThis fungus is often difficult to identify due to lack of sporulation making morphological identification challenging. Therefore, molecular sequencing is a must for its identification. However, identification using the sequence of ITS and 28 s rDNA does not clearly correlate. Hence to confirm the identity additional genes needs to be sequenced and analyzed.

P216 Rare isolates from subcutaneous mycotic lesions; A study from tertiary care center in Chhattisgarh, India

Poster session 2, September 22, 2022, 12:30 PM - 1:30 PMAims and ObjectiveTo identify the causative agents of suspected subcutaneous mycosis patients attending to a tertiary care hospital, Chhattisgarh, India.IntroductionSubcutaneous mycoses are a group of fungal infections of dermis and subcutaneous tissue caused by both melanized and hyaline molds. It often affects patients with immunosuppressive conditions. It consists of Sporotrichosis, Chromoblastomycosis, Phaeohyphomycosis, Hyalohyphomycosis, Mycetoma, subcutaneous zygomycosis, Rhinosporidiosis, Lobomycosis, and disseminated Penicilliosis. There are proven pathogenic agents causing subcutaneous mycosis though are not regularly isolated and reported. Few of them are commonly come across in the laboratory. Herewith, emphasized on the unusual clinical isolates from the patients having subcutaneous mycotic lesions with their clinical details.MethodIt is a retrospective descriptive analysis of data of subcutaneous mycosis cases of duration January 2019 to March 2022.Total 52 clinical specimens from the suspected subcutaneous mycotic lesion were studied. Male dominance was observed amongst the patients. Amongst 52, 31% were detected positive for fungal elements by direct microscopy in 20% KOH mount, 55.7%, 25% positivity was observed in Culture and by both KOH wet mount and culture. Samples were processed and identified by using standard protocol.The significant unusual isolates identified were Conidiobolus coronatus from subcutaneous cyst from buttocks, Medicopsis romerai from fine needle aspiration from the nodule of left thumb, Rhytidhysteron rufulum from right lateral malleolus, Aquastroma magniostiolata species from subcutaneous cyst on lateral aspect of left lower leg above lateral malleolus, Aspergillus tamorii, Aspergillus glaucus, Chetomium species, Aspergillus montevidensis, Cladosporium sphaerospermum. Phenotypically unidentified isolates were sent to NCCPF PGI, Chandigarh for final identification.ConclusionThere is diversity in the etiological agents of subcutaneous mycoses. Every case is different and rare. With the help of molecular techniques, it became possible to identify unusual fungal isolates from subcutaneous infection. Awareness and extensive studies are required to evidence the pathogenicity and associated complication due to these fungal infections. It will also help to regulate the therapeutic management and to know the geographical distribution of unusual fungal agents.

Intrinsic and Extrinsic Programming of Product Chain Length and Release Mode in Fungal Collaborating Iterative Polyketide Synthases.

Combinatorial biosynthesis with fungal polyketide synthases (PKSs) promises to produce unprecedented bioactive "unnatural" natural products (uNPs) for drug discovery. Genome mining of the dothideomycete Rhytidhysteron rufulum uncovered a collaborating highly reducing PKS (hrPKS)-nonreducing PKS (nrPKS) pair. These enzymes produce trace amounts of rare S-type benzenediol macrolactone congeners with a phenylacetate core in a heterologous host. However, subunit shuffling and domain swaps with voucher enzymes demonstrated that all PKS domains are highly productive. This contradiction led us to reveal novel programming layers exerted by the starter unit acyltransferase (SAT) and the thioesterase (TE) domains on the PKS system. First, macrocyclic vs linear product formation is dictated by the intrinsic biosynthetic program of the TE domain. Next, the chain length of the hrPKS product is strongly influenced in trans by the off-loading preferences of the nrPKS SAT domain. Last, TE domains are size-selective filters that facilitate or obstruct product formation from certain priming units. Thus, the intrinsic programs of the SAT and TE domains are both part of the extrinsic program of the hrPKS subunit and modulate the observable metaprogram of the whole PKS system. Reconstruction of SAT and TE phylogenies suggests that these domains travel different evolutionary trajectories, with the resulting divergence creating potential conflicts in the PKS metaprogram. Such conflicts often emerge in chimeric PKSs created by combinatorial biosynthesis, reducing biosynthetic efficiency or even incapacitating the system. Understanding the points of failure for such engineered biocatalysts is pivotal to advance the biosynthetic production of uNPs.

El género Rhytidhysteron (Dothideomycetes, Ascomycota) en México

Antecedentes y Objetivos: Actualmente, se reconocen 21 especies adscritas al género Rhytidhysteron. En México sólo se ha reportado Rhytidhysteron rufulum. El género se caracteriza por sus histerotecios naviculares a apoteciales, el borde es estriado o liso; los colores del epitecio varían de anaranjado-rojizo, amarillo, verde a negros y las ascosporas presentan tres septos longitudinales. El objetivo del presente estudio es realizar una revisión taxonómica del género Rhytidhysteron en México, basada en caracteres macro y micromorfológicos. Métodos: Se realizaron diez exploraciones entre 2017 y 2019 en diversas regiones de México. Además, se revisaron los especímenes depositados en la colección de hongos del herbario ENCB. Los ejemplares fueron estudiados, descritos y determinados de acuerdo con las técnicas tradicionales en micología. Resultados clave: Se revisaron 381 especímenes pertenecientes al género Rhytidhysteron, de los cuales se determinaron cuatro especies: Rhytidhysteron neohysterinum, una nueva especie para la ciencia, R. neorufulum y R. thailandicum que son nuevos registros para el país, y R. rufulum previamente citado. Conclusiones: El género Rhytidhysteron tiene una alta diversidad de especies en México. La mayoría de los especímenes se han encontrado sobre ramas en descomposición, principalmente en géneros de la familia Fabaceae en bosque tropical caducifolio, lo que podría sugerir que este grupo de plantas representa el microhábitat al que las especies de Rhytidhysteron se han adaptado.

Biomimetic Synthesis of Rhytidenone A and Mode of Action of Cytotoxic Rhytidenone F

AbstractThe rhytidenone family comprises spirobisnaphthalene natural products isolated from the mangrove endophytic fungus Rhytidhysteron rufulum AS21B. The biomimetic synthesis of rhytidenone A was achieved by a Michael reaction/aldol/lactonization cascade in a single step from the proposed biosynthetic precursor rhytidenone F. Moreover, the mode of action of the highly cytotoxic rhytidenone F was investigated. The pulldown assay coupled with mass spectrometry analysis revealed the target protein PA28γ is covalently attached to rhytidenone F at the Cys92 residue. The interactions of rhytidenone F with PA28γ lead to the accumulation of p53, which is an essential tumor suppressor in humans. Consequently, the Fas‐dependent signaling pathway is activated to initiate cellular apoptosis. These studies have identified the first small‐molecule inhibitor targeting PA28γ, suggesting rhytidenone F may serve as a promising natural product lead for future anticancer drug development.

Biomimetic Synthesis of Rhytidenone A and Mode of Action of Cytotoxic Rhytidenone F

The rhytidenone family comprises spirobisnaphthalene natural products isolated from the mangrove endophytic fungus Rhytidhysteron rufulum AS21B. The biomimetic synthesis of rhytidenone A was achieved by a Michael reaction/aldol/lactonization cascade in a single step from the proposed biosynthetic precursor rhytidenone F. Moreover, the mode of action of the highly cytotoxic rhytidenone F was investigated. The pulldown assay coupled with mass spectrometry analysis revealed the target protein PA28γ is covalently attached to rhytidenone F at the Cys92 residue. The interactions of rhytidenone F with PA28γ lead to the accumulation of p53, which is an essential tumor suppressor in humans. Consequently, the Fas-dependent signaling pathway is activated to initiate cellular apoptosis. These studies have identified the first small-molecule inhibitor targeting PA28γ, suggesting rhytidenone F may serve as a promising natural product lead for future anticancer drug development.

Identification of spirobisnaphthalene derivatives with anti-tumor activities from the endophytic fungus Rhytidhysteron rufulum AS21B

The cultivation of the mangrove-derived fungus Rhytidhysteron rufulum AS21B in acidic condition changed its secondary metabolite profile. Investigation of the culture broth extract led to the isolation and identification of two new spirobisnaphthalenes (1 and 2) together with eleven known compounds (3–13) from the crude extract of the fungus grown under an acidic condition as well as six known compounds (4, 10, 14–17) were isolated from the crude extract of the fungus grown under a neutral condition. Their structures were elucidated on the basis of extensive spectroscopic data. The isolated compounds were evaluated for their cytotoxicity against two human cancer cell lines, Ramos lymphoma and drug resistant NSCLC H1975. Compounds 2 and 10 displayed the most promising anti-tumor activity against both cancer cell lines.

Hongos histerioides (Dothideomycetes, Ascomycota) del bosque tropical caducifolio en el Parque Nacional Lagunas de Chacahua, Oaxaca, México

Se describen e ilustran cuatro especies de hongos histerioides pertenecientes a la clase Dothideomycetes del phylum Ascomycota, que se encontraron en el bosque tropical caducifolio del Parque Nacional Lagunas de Chacahua, estado de Oaxaca. De éstas, Anteaglonium abbreviatum y Rhytidhysteron rufulum son nuevos registros para la entidad, Psiloglonium simulans se cita por primera vez para México y Gloniella tropicalis se describe como especie nueva para la ciencia.

Highly oxygenated chromones from mangrove-derived endophytic fungus Rhytidhysteron rufulum

Five highly oxygenated chromones, rhytidchromones A–E, were isolated from the culture broth of a mangrove-derived endophytic fungus, Rhytidhysteron rufulum, isolated from Thai Bruguiera gymnorrhiza. Their structures were determined by analysis of 1D and 2D NMR spectroscopic data. The structure of rhytidchromone A was further confirmed by single-crystal X-ray diffraction analysis. These compounds were evaluated for cytotoxicity against four cancer cell lines (MCF-7, Hep-G2, Kato-3 and CaSki). All compounds, except for rhytidchromone D, displayed cytotoxicity against Kato-3 cell lines with IC50 values ranging from 16.0 to 23.3μM, while rhytidchromones A and C were active against MCF-7 cells with IC50 values of 19.3 and 17.7μM, respectively.

New records of <I>Loculoascomycetes</I> from natural protected areas in Sonora, Mexico

Thirty collections of Loculoascomycetes from the Ajos-Bavispe National Forest Reserve and Wildlife Refuge, the Pinacate and Great Altar Desert Biosphere Reserve, and the Sierra of Alamos-Rio Cuchujaqui Biosphere Reserve, in Sonora, Mexico were studied. Ten new records for the Mexican mycobiota are presented: Capronia montana, Chaetoplea crossata, Didymosphaeria futilis, Glonium abbreviatum, Hysterographium mori, Montagnula infernalis, Patellaria atrata, Rhytidhysteron rufulum, Thyridaria macrostomoides, and Valsaria rubricosa. Photographs of macro- and microscopic characters are given for some species.

Molecular data indicate that Rhytidhysteron rufulum (ascomycetes , Patellariales) in Costa Rica consists of four distinct lineages corroborated by morphological and chemical characters

Rhytidhysteron rufulum is a poorly known, common, pantropical species, capable of utilizing different substrata and occupying diverse habitats, and is the only species of its genus in Costa Rica. We have employed molecular, morphological, and chemical data to assess the variability and differentiation of R. rufulum in Costa Rica, including sites from the Pacific and Atlantic coast. Phylogenetic analyses of nuclear ITS rDNA sequences revealed the presence of four distinct lineages in the R. rufulum complex. Re-examination of the morphology and anatomy showed differences between these lineages in ascomatal, ascal, and ascospore size that have previously been regarded as intraspecific variations. In addition, there was a correlation between molecular phylogenies and chemical components as determined by hplc and nuclear magnetic resonance (NMR). Two lineages (clades I and II) produced the palmarumycins MK-3018, CJ-12372, and CR 1, whereas clade III produced dehydrocurvularin, and clade IV unidentified compounds. Our results based on a polyphasic approach contradict previous taxonomic interpretations of one morphologically variable species.