Morphology and development of the reticuloperidial ascomata of Auxarthron conjugatum

Anti-Cryptococcus Phenalenones and Cyclic Tetrapeptides from Auxarthron pseudauxarthron

Auxarthrones A-E (1-5), five new phenalenones, and two new naturally occurring cyclic tetrapeptides, auxarthrides A (7) and B (8), were obtained from three different solvent extracts of cultures of the coprophilous fungus Auxarthron pseudauxarthron. Auxarthrones C (3) and E (5) possess an unusual 7a,8-dihydrocyclopenta[a]phenalene-7,9-dione ring system that has not been previously observed in natural products. Formation of 1-5 was found to be dependent on the solvent used for culture extraction. The structures of these new compounds were elucidated primarily by analysis of NMR and MS data. Auxarthrone A (1) was obtained as a mixture of chromatographically inseparable racemic diastereomers (1a and 1b) that cocrystallized, enabling confirmation of their structures by X-ray crystallography. The absolute configurations of 7 and 8 were assigned by analysis of their acid hydrolysates using Marfey's method. Compound 1 displayed moderate antifungal activity against Cryptococcus neoformans and Candida albicans, but did not affect human cancer cell lines.

Gelatinomyces siamensis gen. sp. nov. (Ascomycota, Leotiomycetes, incertae sedis) on bamboo in Thailand

Gelatinomyces siamensis gen. sp. nov., incertae sedis within Leotiomycetes, the Siamese jelly-ball, is described. The fungus was collected from bamboo culms and branches in Nam Nao National Park, Phetchabun, Thailand. It presents as a ping-pong ball-sized and golf ball-like gelatinous ascostroma. The asci have numerous ascospores, are thick-walled, and arise on discoid apothecia which are aggregated and clustered to form the spherical gelatinous structures. An hyphomycete asexual morph is morphologically somewhat phialophora-like, and produces red pigments. On the basis of phylogenetic analysis based on rRNA, SSU, and LSU gene sequences, the lineage is closest to Collophora rubra. However, ITS sequences place the fungus on a well-separated branch from that fungus, and the morphological and ecological differences exclude it from Collophora.

Evidence of apothecial ancestry in the cleistothecial ascomata of Pleuroascus nicholsonii

Ascomata of Pleuroascus nicholsonii, a rarely reported cleistothecial ascomycete, show little overt evidence of a putative affiliation with the Leotiomycetes. However, close examination of the plectomycetous centrum reveals a distorted hymenium arising from a system of branched ascogenous hyphae, and twisted or coiled uniseriate ascospores enclosed within what appears to be the remains of the spore investing membrane of a clavate ascus precursor. Abundant sterile elements arising from the inner wall layer of the peridium and interspersed throughout the centrum are interpreted as representing vestiges of apically branched paraphyses. Whole ascomata show limited signs of polarity, although the characteristic, tightly coiled appendages generally arise along or below the equatorial region and there is a marked thinning of subicular hyphae over the crown of the cleistothecium. The mature peridium, which consists of a thin, melanized outer layer of squamulose cells, splits irregularly along intercellular grooves when disturbed. The adaptive significance of these characteristics is unknown, but the persistent paraphyses, the easily fractured and darkly pigmented membranous peridium, an ascospore mass that is dry at maturity, and the tendency for ascomata to cling together in clumps can be rationalized in the context of a coprophilous life-style. Collection data for P. nicholsonii provide further support for this supposition because five of the six reported specimens are from rodent dung.