DGGE images of PCR products, amplified for prokaryotic 16S rDNA by using eubacterial primers (31). DNA template was isolated from size-fractionated media from SFBs [0.2- to 5-μm fraction (Upper) and >5-μm fraction (Lower)]. Lanes 1–6, toxic P. shumwayae (two cultures evaluated, n = 3: CAAE1024C in lanes 1–3, CCMP2089 in lanes 4–6); lane 7, cryptoperidiniopsoid CAAE543A-AC1; lane 8, P. piscicida CAAE1332T-AC2 (CCMP2361); lanes 9–14, negative controls (media from fish cultures minus dinoflagellates). The presence of band 10 (arrow) in lanes 4–6 (toxic P. shumwayae CCMP2089) and lanes 9–14 (negative controls) suggests that this bacterium does not play a role in Pfiesteria toxicity.