Introduction to the 18th IAC Symposium in České Budějovice 2010, Czech Republic - Some current problems of modern cyanobacterial taxonomy.

Cyanobacteria are remarkable organisms evolutionarily and they play an important ecological role in the world's ecosystems.Knowledge of their diversity, diversification and ecological significance are urgent questions for both terrestrial and aquatic ecology.They did not lose their vitality over their long existence from the early Precambrium and their ecological role increased with the increasing eutrophication of the whole biosphere of our planet.Taxonomic classification and knowledge of cyanobacterial diversity belong therefore to the important and basic problems of cyanobacterial research.Modern taxonomic classification is a method for recognizing and registering organismal diversity (both in nature and cultures), dependent on evolutionary (genetic) and ecological relations and phenotypic variation.It must be based on a molecular, genotypic characterization of the natural phylogenetic clades, combined with evaluation of biochemical, morphological, cytological and ecological markers, consistent with phylogenetic diversification.The method of modern classification of cyanobacterial diversity respecting all of these characters is commonly called as the "polyphasic approach", which should be the guide-line for the modern re-classification of cyanobacterial diversity.IAC-symposia, which are organized every 3 years already for over 50 years, are important meetings of cyanobacterial specialists, who discuss the problems, new methods and progress in cyanobacterial taxonomy.They were initiated in 1959 in the frame of the 14 th International Limnological Congress (SIL) in Austria by Edith Kann (Vienna) and Otto Jaag (Zürich).All of the symposia reports and proceedings were published, first in Schweizerische Zeitschrift für Hydrologie and later, since the 9 th symposium, in Algological Studies.The history of the first 9 symposia was presented by Kann & Golubić (1985).Prominent specialists in cyanobacterial taxonomy and ecology participated in IAC symposia during its history; it is necessary to remember, at least, the deceased K. Anagnostidis (Athens), P. Bourrelly (Paris), T.V. Desikachary (Madras), E.I. Friedmann (Tallahassee), O. Jaag (Zürich), E. Kann (Vienna), R.A.Lewin (San Diego), R.Y.Stanier (Paris), K. Starmach (Kraków).One of the most important was the 8 th symposium in 1979, the main theme of which was "Cyanophyta vs. Cyanobacteria, principles and problems in taxonomic treatment of natural populations vs. axenic cultures".In this meeting, Prof. Stanier stressed the bacterial character of cyanoprokaryotes and enhanced the molecular and experimental methods to solve taxonomic problems.This modernization was essential and supported distinctly the knowledge and understanding of cyanobacterial diversity.However, his proposal to transfer the nomenclature of cyanobacteria under the rules of the Code of Bacteriological Nomenclature (ICNB, later ICNP) was rather problematic (Stanier et al. 1978).This simple transfer was not possible, because all present knowledge of cyanobacterial diversity (results of about 150 years of investigation) was based on Botanical nomenclatoric principles.Moreover, the structure of cells and thallus, morphological and physiological characters, type of diversification and ecological role of cyanobacteria in nature are specific and different from other bacteria to such a degree that simple nomenclatoric changes (which must take these features in consideration) were not possible without many complications.Some of the main problems included the process of typification and the fact that the study of bacteria is based almost exclusively on cultures.