Adaptability in diversification processes of cyanobacteria; the example of Synechococcus bigranulatus

In world collections strains are often cultured which are designated by the same name and which should be taxonomically identical (sometimes originated from the same clonal culture). However, substantial phenotypic and/or physiological differences are sometimes detected if such strains are compared. Our comparison of two subcultures of Synechococcus bigranulatus proves, that cultivation under distinctly different conditions can change their characters relatively quickly and substantially. Two substrains of the clonal thermophilic strain of the cyanoprokaryotic morphospecies Synechococcus higranulatu isolated in 1972 from hot springs in Kunashir, Kuril Islands, were cultured in two distinctly different temperatures from 1983: in 56°C (originally found as optimal for growth of this strain), and 20-24°C (near the original lowest temperature limit). Other culture conditions were also different: The strain from 56°C was cultured in medium after KRAT7JMYERS (1955) under strong illumination of about 150 W.m -2 , the strain from 20-24 °C in medium Z after ZEHNDER in STAUB (1961) under weak illumination about 5-10 W. m -2 . After 18 years, important characters (ecophysiological temperature limits, cytomorphology, content of fatty acids, 16S rRNA sequencing) were repeatedly analysed. Both subcultures were distinctly different and constant in studied markers. The results are summarised in Figs 1-3 and they were supported with experimetns of NICKOVA & STYS (2002), who analysed both subcultures after cultivation under the same conditions. The methods and results in detail are described in a special article (KOMAREK et al. in prep.).