12th International Conference on Harmful Algae

INTERNATIONAL SOCIETY FOR THE STUDY OF HARMFUL ALGAE12 th <strong>International</strong> <strong>Conference</strong> on Harmful Algae, Copenhagen, Denmark, 4-8 September 2006using reverse transcription andquantitative PCR. We have selectedtwo target genes coding for theRubisCO enzyme (performingcarbon fixation and reflecting cellmetabolic activity) and the PCNA(proliferating cell nuclear antigen)protein involved in cell division. Totest these assays, we will presentvariations of gene expressionanalyzed in various experimentalconditions.PO.06-22Effect of selenium on PseudonitzschiaseriataSession: PO.06 - Population dynamicsIC Guimarães Nogueira 1 , VMVasconcelos 1 , P Vale 21 Ciimar, PORTO, Portugal2 IPIMAR-Instituto de Investigação das Pes,LISBOA, PortugalThe laboratory culture of toxigenicpennate diatoms of the genusPseudo-nitzschia often gives lowergrowth rates. This is inadequate forecophysiological studies and forstudies involving acid domoicquantification or web-transfer. It issuggested in the literature thataddition of extra silicon andselenium is beneficial for growth ofdiatom cultures, such as Pseudonitzschiasp. In this work weevaluated the effect of selenium onPseudo-nitzschia seriata growthrates and also on f/2 mediumfeatures such as pH, salinity andconductivity, over 15 days at 10 ºC.Addition of selenium, atconcentration of 1.29 mg Na 2 SeO 3/L, caused a slight increase of thegrowth rate and pH. In contrast,significant differences were found inconductivity and salinity betweenculture mediums with and withoutselenium. No domoic acidproduction was detected by HPLC.PO.14-05Flow cytometry in conjunctionwith dual staining assessesviability of Microcystis cells afterexposure to bacteriaSession: PO.14 - MitigationJR Gumbo, TE CloeteUniversity of Pretoria, PRETORIA, SouthAfricaFlow cytometric (FCM) techniquewas used to assess viability ofMicrocystis cells after exposure toBacillus mycoides B16. The FCManalysis involved assessment oftwo cellular functions, esteraseactivity and membrane integrity,after dual staining with Fluoresceindiacetate (FDA) and Propidiumiodide (PI). The dual staining ofMicrocystis cells revealed differentcell populations: living, membranecompromised and dead cells. Theresults show that after 2 h ofincubation with B. mycoides B16 thepopulation of dead Microcystis cellswas 12%, membrane-compromisedcells was 80% and live cells was8%. The demography of Microcystiscells changed after 6 d ofincubation, with population of deadMicrocystis cells was 51%, thosewith membrane- compromised cellswas 34% and live cells was 15%. Inbacteria treated samples theMicrocystis biomass was reducedby over 95% whereas with thecontrol samples the biomassincreased by over 1000%. Thebiocontrol agent B mycoides B16appeared to cause Microcystis celllysis resulting in cells withcompromised membranes with aSEM micrographs signatureequivalent to samples that havebeen lysed with copper sulphate, aknown algicide. B. mycoides B16could therefore be considered as a182