RESUMEN
This study examines how the dynamics of fungus-insect interactions can be modulated by temperature. The wax moth, Galleria mellonella, is a well-studied and important model insect whose larvae in the wild develop optimally at around 34 °C in beehives. However, surprisingly little research on wax moths has been conducted at relevant temperatures. In this study, the entomopathogenic fungus Metarhizium robertsii inflicted rapid and substantial mortality on wax moth larvae maintained at a constant temperature of 24 °C, but at 34 °C a 10 fold higher dose was required to achieve an equivalent mortality. The cooler temperature favored fungal pathogenicity, with condial adhesion to the cuticle, germination and hemocoel invasion all significantly enhanced at 24 °C, compared with 34 °C. The wax moth larvae immune responses altered with the temperature, and with the infective dose of the fungus. Enzyme-based immune defenses (lysozyme and phenoloxidase) exhibited enhanced activity at the warmer temperature. A dramatic upregulation in the basal expression of galiomicin and gallerimycin was triggered by cooling, and this was augmented in the presence of the fungus. Profiling of the predominant insect epicuticular fatty acids revealed a 4-7 fold increase in palmetic, oleic and linoleic acids in larvae maintained at 24 °C compared with those at 34 °C, but these failed to exert fungistatic effects on topically applied fungus. This study demonstrates the importance of choosing environmental conditions relevant to the habitat of the insect host when determining the dynamics and outcome of insect/fungus interactions, and has particular significance for the application of entomopathogens as biocontrol agents.
Asunto(s)
Interacciones Huésped-Patógeno , Metarhizium/fisiología , Mariposas Nocturnas/microbiología , Control Biológico de Vectores , Animales , Defensinas/metabolismo , Ácidos Grasos/fisiología , Monofenol Monooxigenasa/metabolismo , Muramidasa/metabolismo , Esporas Fúngicas/fisiologíaRESUMEN
Candida oral flora from 52 Brazilian HIV-infected children was characterized while they received antiviral monotherapy therapy and subsequently, HAART with the use of protease inhibitor. There was a significant increase in non-C. albicans Candida isolates from 9.6-28.8% (P=0.005) after the children were placed on protease inhibitor therapy. Although Candida albicans still remained the most commonly isolated species, relative presence of C. tropicalis (n=9) followed by C. parapsilosis (n=8) markedly increased in association with protease inhibitor therapy. Furthermore, rare Candida species including C. dubliniensis, C. norvegensis, C. humicula and C. rugosa also appeared after the onset of protease inhibitor therapy. Subsequent investigation of the antifungal sensitivity of these diverse isolates, derived during protease inhibitor therapy, demonstrated some variation in antifungal sensitivity. With notable exceptions, the majority were sensitive to amphotericin B while most C. albicans and non-C. albicans Candida isolates were also susceptible to fluconazole, itraconazole and ketoconazole. Amongst exceptions was a single C. tropicalis isolates which was resistant to fluconazole (MIC>64 microl/ml) and one C. albicans-B isolate which showed cross-resistance to all azoles and amphotericin.