Cyanobacterial Toxins as Allelochemicals with Potential Applications as Algaecides, Herbicides and Insecticides

Abstract

Cyanobacteria ("blue-green algae") from marine and freshwater habitats are known to produce a diverse array of toxic or otherwise bioactive metabolites. However, the functional role of the vast majority of these compounds, particularly in terms of the physiology and ecology of the cyanobacteria that produce them, remains largely unknown. A limited number of studies have suggested that some of the compounds may have ecological roles as allelochemicals, specifically including compounds that may inhibit competing sympatric macrophytes, algae and microbes. These allelochemicals may also play a role in defense against potential predators and grazers, particularly aquatic invertebrates and their larvae. This review will discuss the existing evidence for the allelochemical roles of cyanobacterial toxins, as well as the potential for development and application of these compounds as algaecides, herbicides and insecticides, and specifically present relevant results from investigations into toxins of cyanobacteria from the Florida Everglades and associated waterways.

Mosquito Larvicides from Cyanobacteria

“…The true nature of these toxic compounds is unknown but has been linked to allelopathic associations (Berry et al, 2008). Toxins produced by cyanobacteria are much more likely to be detoxified by microorganisms than synthetic insecticides because they already occur naturally in the environment in which they are to be employed (Lange and Lopez, 1996).…”

“…aegypti may have grown resistant to particular cyanobacteria toxins. A hypothesis being considered is that these secondary metabolites may be produced specifically to suppress the feeding of mosquito larvae and other invertebrate grazers (Berry et al, 2008). Mosquito larvae exposed to these secondary metabolites may subsequently develop resistance by the overexpression of genes involved in detoxification, cuticular mutations limiting toxin uptake, and target site mutations decreasing toxin efficiency.…”

“…Section 1.5, a review of Berry et al (2008), is a justification for the screening of cyanobacteria for arthrocidal compounds. Section 1.6 provides a justification for screening cyanobacteria for mosquito larvicidal compounds.…”

“…Many cyanobacteria derived metabolites have been evaluated using zebrafish assays (Berry et al, 2008 andWright et al, 2006). The assay has proven to be a useful tool in the purification of bioactive metabolites via bioassay guided fractionation (Berry et al, 2008).…”

Investigação de mecanismos bioquímicos e fisiológicos em organismos expostos a anatoxina-a(s)

“…O número de trabalhos referentes à possível aplicação comercial dos metabólitos secundários de cianobactérias como algicidas, herbicidas e inseticidas é limitado, porém mostra-se cada vez mais promissor. Sabe-se que as cianobactérias produzem uma grande diversidade de metabólitos biologicamente ativos, os quais podem ter potencial para aplicação no impedimento ou controle do crescimento de outros organismos (BERRY et al, 2008). Dentre as vantagens do uso das cianotoxinas para este fim, estaria o papel ecológico que eles possuem como agentes alelopáticos (alelopatia: processo que envolve metabólitos secundários produzidos por plantas, algas, bactérias e fungos, que influencia no crescimento e/ou desenvolvimento de outros organismos).…”