Intraspecific chemical variation within the crustose lichen genus Haematomma : anthraquinone production in selected cultured mycobionts as a response to stress and nutrient supply

The mycobionts isolated from selected species of Haematomma (Haematomma africanum, Haematomma fenzlianum, Haematomma flourescens, Haematomma persoonii, Haematomma stevensiae) have been successfully cultured. The chemical profile of the mycobionts could be effectively influenced and modulated by varying the composition of the nutrient medium using alternative carbohydrates (glucose, sucrose, and polyols). Under artifical laboratory conditions and simulated environmental stress (exposure to UV light, desiccation, and lower temperatures) the mycobionts began producing typical secondary lichen metabolites after an incubation time of 5-6 months. Modified Lilly and Barnett medium (LBM) and Murashige Skoog Medium favoured the production of depsides such as sphaerophorin and isosphaeric acid. Surprisingly, the mycobiont from H. stevensiae in modified MS medium produced two anthraquinones in the mycelia, haematommone at the base and russulone in the upper parts of the mycelium. By contrast, the natural lichen only produced these anthraquinones in the reddish orange apothecia. The mycobiont from H. flourescens only produced the expected lichexanthone in LBM, enriched with the polyols, sorbitol and mannitol. Once the media requirements and environmental stress factors that trigger polyketide production in lichen mycobionts have been determined, it is possible to obtain a particular lichen product by a completely defined procedure. Using such knowledge, we should be able to study polyketide expression in mycobionts under optimized culture conditions for various genetic applications

Ascospore discharge, germination and culture of fungal partners of tropical lichens, including the use of a novel culture technique

A total of 292 lichen samples, representing over 200 species and at least 65 genera and 26 families, were collected, mainly in Thailand; 170 of the specimens discharged ascospores in the laboratory. Generally, crustose lichens exhibited the highest discharge rates and percentage germination. In contrast, foliose lichen samples, although having a high discharge rate, had a lower percentage germination than crustose species tested. A correlation with season was indicated for a number of species. Continued development of germinated ascospores into recognizable colonies in pure culture was followed for a selection of species. The most successful medium tried was 2 % Malt-Yeast extract agar (MYA), and under static conditions using a liquid culture medium, a sponge proved to be the best of several physical carriers tested; this novel method has considerable potential for experimental work with lichen mycobionts

Secondary chemistry of cultured mycobionts: formation of a complete chemosyndrome by the lichen fungus of Lobaria spathulata

The study aimed to optimize culture conditions and nutrient requirements for the production of secondary metabolites by the cultured mycobiont Lobaria spathulata. This species proved to be an excellent model system for such studies, as the complete chemosyndrome found in the natural lichen thallus was repeatedly formed in the cultured mycobiont with differentiated, aerial mycelia. Nutrient media containing the disaccharide, sucrose, were found to favour both rapid growth and the production of typical lichen substances. Higher proportions of the secondary compounds were detected in the developing mycobiont than in mature lichen thalli

Morphogenetic strategies and induction of secondary and induction of secondary metabolite biosynthesis in cultured lichen-forming Ascomycota, as exemplified by Cladia retipora (Labill.) Nyl. and Dactylina arctica (Richards) Nyl

Over the last ten years a considerable number of lichen fungi (200 voucher specimens and their corresponding mycobionts) have been cultured and screened for the formation of secondary compounds (lichen substances). The production of lichen polyketides was found to be strongly affected by the composition of the nutrient media, dominant environmental parameters in the micro-habitat, and also by morphogenesis and cell differentiation of the mycelia. The present investigation deals with two lichens exhibiting very complex and unusual growth forms. The Australasian lichen Cladia retipora is one of the more fascinating fruticose lichens given its capacity to form very complex net-like structures (fenestrations). The North American and Asian lichen Dactylina arctica forms finger-like stalks which are well adapted to the harsh climatic conditions of arctic habitats. Cultures of both lichens and their corresponding mycobionts were found to exhibit exceptional morphogenetic strategies and capacities during their development and a well determined pattern (physiological and chronological) for producing typical secondary chemistry. In a re-synthesis and re-lichenization experiment (after culturing for 2 years) complete thalli containing the typical lichen substances were formed in vitro

Secondary Chemistry of Lichen-forming Fungi: Chemosyndromic Variation and DNA-analyses of Cultures and Chemotypes in the Ramalina farinacea Complex

The Ramalina farinacea (L.) Ach. complex has a world-wide distribution. The thalli are highly variable both morphologically and chemically, with various β-orcinol depsidones being produced as secondary medullary compounds. In the present study a new, ra

Protousnea Fibrillatae Sp. Nov. (Parmeliaceae, Lichenized Ascomycota) from Argentina, Southern South America

Protousnea fibrillatae from south-western Argentinean Nothofagus forests, is described as new to science. While the apothecia are typical of Protousnea, this new species is characterized by the presence of fibrils, a character previously unknown in the genus. The meta-depsides, subsekikaic and 4′-O-demethylsekikaic acids are reported the first time for Protousnea

Protousnea (Parmeliaceae), a Genus Endemic to Southern South America

A comprehensive revision of the genus Protousnea is presented based on morphological, chemical, anatomical, and extensive field studies in the Patagonian Andes and Tierra del Fuego, as well as by comparisons with herbarium material. A complete chemical profile is detailed for each species and sekikaic acid has been shown to be the major medullary metabolite. The new despide, 4′-O-demethylsubsekikaic acid, is described for the first time. The circumscription of species and intraspecific variability is discussed with reference to key morphological, anatomical, and chemical characters, as well as ecological preferences. Conidia are described for the first time. Protousnea malacea and P. scrobiculata have been synonymized with P. poeppigii. A key to the species is given. All the species are illustrated and new data are presented on their distribution, substrate preferences, and ecology