RESUMEN

AIMS: Assessment of antimicrobial activity of the mycoparasite Coniothyrium minitans and its macrolide antibiotic macrosphelide A. METHODS AND RESULTS: Thirteen isolates of C. minitans were tested for ability to inhibit a number of filamentous fungi, yeasts, oomycetes and bacteria in agar based tests. Activity was found against some ascomycetes, basidiomycetes, oomycetes and Gram-positive bacteria, but not against zygomycetes, yeasts or Gram-negative bacteria tested. Six C. minitans isolates (Conio, Contans, IVT1, CM/AP/3118, B279/1, A1/327/1) were found to produce macrosphelide A in liquid culture and no other antibiotics were detected. On agar, macrosphelide A inhibited growth of some ascomycetes, basidiomycetes, oomycetes and all four Gram-positive bacteria tested, including the medically important Staphylococcus aureus with a minimum inhibitory concentration of < or =500 microg ml(-1). There was no inhibition observed against the yeasts and Gram-negative bacteria when macrosphelide A was tested at 700 microg ml(-1). CONCLUSIONS: The spectrum and level of activity of macrosphelide A produced by C. minitans against micro-organisms are extended markedly compared to previous reports. SIGNIFICANCE AND IMPACT OF THE STUDY: Macrosphelide A was effective against Staph. aureus. Further study on the control of this bacterium is merited in view of the development of antibiotic resistance.

Asunto(s)

Antiinfecciosos/farmacología , Antibiosis , Ascomicetos/metabolismo , Bacterias/efectos de los fármacos , Oomicetos/efectos de los fármacos , Levaduras/efectos de los fármacos , Antiinfecciosos/aislamiento & purificación , Ascomicetos/aislamiento & purificación , Cromatografía en Capa Delgada , Compuestos Heterocíclicos/aislamiento & purificación , Compuestos Heterocíclicos/farmacología , Macrólidos/aislamiento & purificación , Macrólidos/farmacología , Pruebas de Sensibilidad Microbiana , Enfermedades de las Plantas/microbiología

RESUMEN

Manure-straw mixtures were composted and water extracts, made by incubating compost in water for 3 to 18 days, were assessed for antagonistic activity against Botrytis cinerea, using a range of tests. Extracts of all ages inhibited conidial germination on glass slides and reduced mycelial growth on agar. Mixing extracts of all ages with droplets of suspensions of B. cinerea conidia on detached Phaseolus bean leaves suppressed lesion development, but only 3- to 8-day-old extracts had an effect when sprayed onto leaves 2 days before inoculation. Extracts contained a large and varied microbial population of actinomycetes (0.3 to 2.4×10(5) c.f.u.ml(-1)), bacteria (1.5 to 5.6×10(10) c.f.u.ml(-1)), filamentous fungi (25.0 to 45.5 c.f.u. ml(-1)) and yeasts (26.1 to 62.6 c.f.u.ml(-1)). Eight- and 18-day-old extracts lost activity completely on filter sterilization or autoclaving. Weekly sprays of 8-day-old extracts onto lettuce in the glasshouse had no effect on the incidence of grey mould, but significantly reduced its severity and increased marketable yield. The use of compost extracts in biocontrol of plant diseases and their possible mode of action is discussed.