Development of new procedures for the isolation of phytoplankton DNA from fixed samples

Phytoplankton samples collected for routine monitoring programmes have traditionally been preserved with fixatives before subsequent analytical procedures such as microscope-based identification, or simply to permit transport between laboratories. In recent years, to simplify identification and enumeration, the use of DNA or RNA probes coupled with the PCR assay has progressed and now represents a routine procedure for screening cultured and field samples. However, the phytoplankton cells have often still to be treated as fixed samples. The extraction of genomic DNA from fixed cultures of Alexandrium minutum cultures was compared using two new methods based on Magnetisable Solid Phase Support (MSPS) techniques with that using three commercial kits. Genomic DNA recovery and PCR amplification were observed and the results obtained from culture samples were validated using field samples. Among the DNA extraction techniques considered, the MSPS methods provided the best results.