A fungus-type β-galactofuranan in the cultivated Trebouxia photobiont of the lichen Ramalina gracilis

• Published in: FEMS microbiology letters Vol. 244; no. 1; pp. 193 - 198
• Main Authors: Cordeiro, Lucimara M.C., Carbonero, Elaine R., Sassaki, Guilherme L., Reis, Rodrigo A., Stocker-Wörgötter, Elfriede, Gorin, Philip A.J., Iacomini, Marcello
• Format: Journal Article
• Language: English
• Published: Oxford, UK Elsevier B.V 01.03.2005; Blackwell Publishing Ltd; Blackwell; Oxford University Press
• Subjects: Amylose; beta-galactofuranan; Biological and medical sciences; Cell walls; Chlorophyta - chemistry; Chlorophyta - isolation & purification; Freeze-thawing; Fundamental and applied biological sciences. Psychology; Fungi; Glucans; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; Lichen; Lichens; Lichens - microbiology; Magnetic Resonance Spectroscopy; Microbiology; Molecular Structure; Molecular Weight; Mycology; Photobiont; photobionts; Polysaccharides; Polysaccharides - chemistry; Polysaccharides - isolation & purification; Purification; Ramalina; Ramalina gracilis; Saccharides; Structural analysis; symbionts; Symbiosis; Thallus; Thawing; Trebouxia; Water purification; β-Galactofuranan; Ramalina gracilis; Trebouxia; β-Galactofuranan; Photobiont; Amylose; Lichen; Molecular weight determination; Lichenes; Methylation; Polysaccharide; Thallophyta
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/j.femsle.2005.01.040

A structural characterization of polysaccharides extracted from the aposymbiotically cultured photobiont of the lichen Ramalina gracilis was carried out in order to compare them with those previously found in the symbiotic thallus. The photobiont was isolated from thallus fragments, following the method of Yamamoto, and cultivated in a liquid nutrient medium. Freeze-dried cells were defatted, and the polysaccharides extracted successively with water and aq. 10% KOH, each at 100 °C. After purification, the soluble fractions provided a polysaccharide containing a (1 → 5)-linked β-galactofuranosyl backbone, substituted in a small proportion at O-6 by β-Gal f units. Amylose was also found, as insoluble material obtained on freeze-thawing of the alkaline extract. These polysaccharides have not been found in the symbiotic thallus of Ramalina gracilis, which contained only water-soluble (isolichenan) and insoluble glucans (nigeran and laminaran), and galactomannan. Surprisingly, the galactofuranan has similarities with those found in some fungal cell walls.