Entomopathogenic Fungal Metabolites Useful in Agriculture and Healthcare

It has been documented that over 750 species of entomopathogenic fungus (EPF) from 85 genera infect over 1000 different kinds of insect pests. EPFs are effective biocontrol agents because of their normal means of action, which involves direct entry through the insect cuticle and grow in the host hemocoel. But in order to carry out this process, biochemical weapons such toxins, enzymes, and other metabolites that promote host invasion and infection must be produced. The first line of defense against EPF infection is the host cuticle, which is directly degraded by enzymes like lipase, proteinase, and chitinase. Secondary metabolites that speed up the EPF infection process include beauvericins of Beauveria, cordyols of Cordyceps, destruxins of Metarhizium, hirsutellides of Hirsutella, isarolides of Isaria, and vertihemipterins of Verticillium. These metabolites work both directly and indirectly to impair the defense mechanisms of insect hosts. These secondary metabolites’ chemical makeup varies from basic non-peptide pigments like oosporine to more intricate piperazine derivatives such as vertihemiptellides. In this chapter, we focus on a few key concerns regarding EPF’s use of metabolites for insect host invasion. The main emphasis is on the toxins, enzymes, and other metabolites that are produced by a few significant EPF species, as well as how they work to undermine the humoral and cellular defense systems of the host.