In vivo control andin vitro antifungal activity of rhamnolipid B, a glycolipid antibiotic, againstPhytophthora capsici andColletotrichum orbiculare

Abstract

The glycolipid antibiotic rhamnolipid B isolated from Pseudomonas aeruginosa strain B5 was evaluated for in vitro antifungal activity and in vivo control against phytophthora blight and anthracnose under glasshouse conditions. Rhamnolipid B showed antifungal activity against Cercospora kikuchii, Cladosporium cucumerinum, Colletotrichum orbiculare, Cylindrocarpon destructans, Magnaporthe grisea and Phytophthora capsici. Microscopic observation revealed that the high level of antifungal activity (10 mg ml À1 ) against P capsici was mainly due to a lytic effect on zoospores. Zoospore lysis began in the presence of 10 mg ml À1 of rhamnolipid B and most of the zoospores were collapsed at 25 mg ml À1 . Rhamnolipid B showed inhibitory activity against the germination of zoospores and hyphal growth of P capsici at concentrations of 50 mg ml À1 . Spore germination of the anthracnose plant pathogen C orbiculare was also inhibited in the presence of 50 mg ml À1 of rhamnolipid B, although hyphal growth was not affected at this concentration. In the glasshouse, the ef®cacy of rhamnolipid B against phytophthora blight was similar to that of metalaxyl on pepper plants when treated just before inoculation with P capsici. Treatment with either at 500 mg ml À1 completely protected pepper plants from phytophthora blight. Rhamnolipid B also suppressed the development of C orbiculare infection on leaves of cucumber plants.

Phenolics and antifungal activities analysis in industrial crop Jerusalem artichoke (Helianthus tuberosus L.) leaves

“…The application in storage was evaluated by assessment of disease severity (Kim et al, 2000). Mature and healthy red tomato (Lycopersicon esculentum cv.…”

The emulsifying effect of biosurfactants produced by food spoilage organisms in Nigeria

“…This is supported by the work of Calvo et al (2004) where it was reported that biosurfactants produced by microbes during growth on water-immiscible substrates, permit their growth on such substrates by reducing the surface tension thereby making the hydrophobic substrate more readily available for uptake and metabolism. Kim, Lee, and Hwang (2000) also found that very often, the growth of microorganisms on hydrocarbons is accompanied by the emulsification of insoluble carbon sources in the culture medium and in most cases has been attributed to the production of emulsifying agents in the presence of these substrates. Several authors have reported diesel oil and crude oil as excellent substrates for microbial growth and also for biosurfactant production (Ilori et al, 2005;Adebusoye, Ilori, Amund, Teniola, & Olatope, 2007).…”

Respuesta de biosurfactantes producidos por Pseudomonas fluorescens para el control de la gota de la papa Phytophthora infestans (Mont) de Bary, bajo condiciones controlada.

“…La actividad lítica de los bPP producidos por las cepas de P. fluorescens 021V y 039t sobre las zoosporas de P. infestans, se debe a su composición química que permite una afinidad con la membrana de la zoospora. Por lo cual el biosurfactante se puede intercalar entre la membrana plasmática y generar un desequilibrio en su integridad y permeabilidad, provocando ruptura de la membrana y liberación del contenido citoplasmático (stanghellini y Miller, 1997; Kim et al, 2000;Martínez y osorio, 2007). sin embargo, aunque es posible que el efecto de los biosurfactantes sobre las zoosporas pueda reducirse por el enquistamiento natural que ocurre en las zoosporas después de 2 h para la formación de la pared celular, estos productos pueden continuar reduciendo la infección de P. infestans, ya que estudios de Kim et al (2000) en P. capsici, De Jonghe et al (2005 en P. cryptogea, y Martínez y osorio (2007) en P. infestans, han demostrado que los ramnolípidos también tienen efecto inhibitorio sobre otras estructuras con pared celular del patógeno.…”

“…Lo anterior orienta a que los biosurfactantes y/o las suspensiones bacterianas de P. fluorescens productoras de biosurfactantes deben estar presentes antes de la llegada del patógeno, para que ejerzan un mecanismo de acción preventivo mediante la reducción de la concentración de inóculo (Jonghe et al, 2005;Kim et al, 2000).…”

“…Esta condición le confiere a los biosurfactantes la capacidad de penetrar e intercalarse dentro de la membrana plasmática de las zoosporas, compuesta por glicolípidos (en lugar de fosfolípidos) y proteínas, y conseguir una afinidad química de la porción hidrofílica del biosurfactante para la entrada y el desequilibrio en la integridad y la permeabilidad de la membrana, conduciendo al rompimiento de la zoospora y la liberación del contenido citoplasmático (Kim et al, 2000;ePA, 2009). …”