The literature data on medusomyces published since 1913 are discussed. Different versions of appearance and distribution of this microorganism are considered. The features of its structure, metabolism and growth conditions are analyzed. It is shown that the tea fungus is a symbiosis is of several sorts of yeast and acetic acid bacteria. Evidence is presented indicating that fermented tea fungus has a therapeutic effect and can be applied in medicine. It was proved, that the antimicrobial properties of tea fungus metabolic products are due to the presence of particular antibiotic substances. The regularities of the biosynthesis of these substances and the pathways of its stimulation were studied. The results obtained will lead to the large-scale use of tea fungus in biotechnology. The fungus has unique adaptation properties, as confirmed by experiments on cultivation of the organism on deuterium oxide (D2O) and in the conditions of "cold stress". It is suggested that medusomyces is a unique model for the investigation of the phenomenon of symbiosis.