Isolation of dipicolinic acid as an insecticidal toxin from Paecilomyces fumosoroseus

Abstract

Several entomopathogenic fungi produce toxins that could be used as bioinsecticides in integrated pest management programs. Paecilomyces fumosoroseus is currently used for the biological control of the whiteflies Bemisia tabaci and B. argentifolii. Supernatants from submerged batch culture, where the fungus produced abundant dispersed mycelium, conidia and blastospores, were toxic to the whitefly nymphs. The most abundant metabolite was purified by HPLC and identified by mass spectrometry and NMR as dipicolinic acid. Both the dipicolinic acid produced by the fungus and the chemically synthesized compound had insecticidal activity against third-instar nymphs of the insect. Dipicolinic acid was toxic to the whitefly nymphs in bioassays involving topical applications. In submerged culture, the specific growth rate of P. fumosoroseus was 0.054 h-1, the specific glucose consumption rate was 0.1195 g g-1 h-1 and the specific dipicolinic acid production rate was 0.00012 g g-1 h-1. Dipicolinic acid was detected after 24 h when the fungus started growing; and dipicolinic acid production was directly correlated with fungal growth. Nevertheless, the yield was low and the maximal concentration was only 0.041 g l-1. The maximal concentrations of conidia and blastospores (per milliliter) were 1.4x10(8) and 7x10(7), respectively.

Efecto del Hongo Isaria fumosorosea Wize Sobre la Herbivoría por los Adultos del Escarabajo de Margen Amarillo, Microtheca ochroloma Stal (Coleoptera: Chrysomelidae)

“…Además, el consumo, por el falso gorgojo de cacahuate (Callosobruchus maculatus F (Coleptera: Chrysomelidae)), de hojas tratadas con B. bassiana CPD 3 fue significativamente menor en los 2 días consecutivos al tratamiento, y esta tendencia continuó hasta el día 7, cuando todos los escarabajos murieron (Ekesi 2001). Otra razón de una tasa baja de consumo de los adultos infectados en este estudio, podría estar relacionada con una sinergia entre la colonización del hongo y la producción de toxinas por I. fumosorosea (Assaf et al 2005). Una disminución en el consumo pudo ser mayor si los escarabajos evitaron alimentarse de las hojas cubiertas con esporas del hongo.…”

Isolation and characterization of an Isaria fumosorosea isolate infecting the Asian citrus psyllid in Florida

“…Ifr AsCP may be necrotrophic, killing D. citri with toxins and then utilizing the dead insect for development. The toxin dipicolinic acid was found in an Ifr isolate that killed immature whiteflies (Asaff et al, 2005), and another toxin was found in Isaria tenuipes (=Paecilomyces tenuipes) (Nam et al, 2001); however, this has not yet been demonstrated in Ifr AsCP. Further investigation is warranted to provide a detailed account of the infection mechanisms used by Ifr AsCP and H. citriformis in D. citri.…”

The Bacillus subtilis spore coat provides “eat resistance” during phagocytic predation by the protozoan Tetrahymena thermophila

“…This concentration might be high enough to affect the intraphagosomal pH, which is normally reduced to a value of pH of 4-5 during phagosome acidification (48,49). DPA has also been reported to be toxic, at least for insects (50). However, the phagosomes and T. thermophila appear capable of dealing with the large amount of DPA released upon cotE spore lysis.…”