DNA analyses of a private collection of microbial green algae contribute to a better understanding of microbial diversity

BACKGROUND: DNA comparison is becoming the leading approach to the analysis of microbial diversity. For eukaryotes, the internal transcribed spacer 2 (ITS2) has emerged as a conspicuous molecule that is useful for distinguishing between species. Because of the small number of usable ITS data in GenBank, ITS2 sequence comparisons have only been used for limited taxa. However, major institutions with planktonic algal culture collections have now released small subunit (SSU) to ITS rDNA sequence data for their collections. This development has uplifted the level of molecular systematics for these algae. RESULTS: Forty-three strains of green algae isolated from German inland waters were investigated by using SSU-ITS rDNA sequencing. The strains were isolated through the direct plating method. Many of the strains went extinct during the years of culture. Thus, it could be expected that the surviving strains would be common, vigorous species. Nevertheless, 12 strains did not match any known species for which rDNA sequences had been determined. Furthermore, the identity of one strain was uncertain even at the genus level. CONCLUSIONS: The aforementioned results show that long-forgotten and neglected collections may be of great significance in understanding microbial diversity, and that much work still needs to be done before the diversity of freshwater green algae can be fully described.