DISTINCTION BETWEEN MULTIPLE ISOLATES OF CHLORELLA VULGARIS (CHLOROPHYTA, TREBOUXIOPHYCEAE) AND TESTING FOR CONSPECIFICITY USING AMPLIFIED FRAGMENT LENGTH POLYMORPHISM AND ITS RDNA SEQUENCES

Authors

  • Julia Müller,

    1. Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung Experimentelle Phykologie und Sammlung von Algenkulturen, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
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  • Thomas Friedl,

    1. Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung Experimentelle Phykologie und Sammlung von Algenkulturen, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
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  • Dominik Hepperle,

    1. Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung Experimentelle Phykologie und Sammlung von Algenkulturen, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
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  • Maike Lorenz,

    1. Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung Experimentelle Phykologie und Sammlung von Algenkulturen, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
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  • John G. Day

    1. Culture Collection of Algae and Protozoa (CCAP), Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Dunbeg, Argyll, PA37 1QA, UK
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  • 1Received 16 March 2005. Accepted 18 August 2005.

Abstract

Multiple strains of individual algal species are available from public culture collections, often with the same isolate being maintained in parallel at a number of collections under different culture regimes. To unravel genomic variation and to identify unique genotypes among such multiple strains, two approaches were used on a sample of 29 strains of Chlorella vulgaris Beijerinck, an alga of great value for applied research, from five culture collections. With the exception of two strains, internal transcribed spacer rDNA sequence data substantiated conspecificity of the studied strains and only minor sequence differences with the authentic “Beijerinck isolate” were observed. Amplified fragment length polymorphism (AFLP) detected considerable genomic variation when rDNA sequences were identical. Band detection and the construction of a binary matrix from AFLP patterns for phylogenetic analyses were fully automated, but comparison of similar patterns still required manual refinement. The AFLPs distinguished 11 unique genotypes and provided robust support for the presence of five cryptic species. This finding advocates the need to carefully record which strain has been used in any experiment or in applied research, because genomic variation may also correspond to differences in physiological/biochemical properties. No genomic differences could be detected between duplicate strains of the same isolate that were maintained by continuous subculturing over many decades or within those stored at ultralow temperatures.

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