Toxic cyanobacteria: the evolving molecular toolbox

persist in both freshwater and marine systems. They range from organisms that form red and brown tides to cyanobacteria that turn lakes and ponds green (Figure 1) and red. The toxins (termed “cyanotoxins”) that these organisms produce are usually secondary metabolites, and are more numerically diverse than the organisms that produce them. Here we will focus on the use of molecular methods for detecting toxic cyanobacteria, as in-depth discussions of marine harmful algae, cyanobacterial ecology, cyanotoxin production, toxicology, and water management issues related to toxic cyanobacteria (Watanabe et al. 1996; Paerl and Millie 1996; Chorus and Bartram 1999; Whitton and Potts 2000; Carmichael 2001; Chorus 2001; Hoagland et al. 2002; Landsberg 2002) are beyond the scope of this review. The global distribution of toxic cyanobacteria attests to their ecological success, which at times causes problems for humans. Communities often use surface water and reservoirs for potable water. When these sources are subject to algal blooms, nontoxic taste and odor compounds that may be released by the cyanobacteria can compromise water quality. When the organism in question produces a toxin, the threat can be considerable. Although the health effects of exposure to low levels of cyanotoxins remain unknown, chronic exposure to toxic cyanobacteria in water sources over a long period of time could be harmful (Chorus and Bartram 1999; Carmichael 2001; Chorus 2001). The detection of toxic cyanobacteria and their cyanotoxins is therefore fundamental for sound water management. Traditionally, microscopic identification of cyanobacteria has been used alone or in combination with direct analysis for toxins. The morphological discrimination between toxic and nontoxic cyanobacteria can be difficult, as some genera contain both toxic and nontoxic members. Some cyanobacteria are known to be toxic, some may be genetically capable of producing toxins (toxigenic) but do not under all conditions, and some do not produce toxins at all. DNA-based detection methods have become popular because of their potential specificity (targeting genes involved in toxin biosynthesis), sensitivity, and speed. This review highlights some of these advances 359