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Exploração de interações microbianas com vista ao aumento do antagonismo contra fungos potencialmente fitopatogénicos
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Orientador(es)
Resumo(s)
A utilização de fungicidas sintéticos afeta negativamente a saúde do solo, das plantas e de todos os
elementos da cadeia alimentar, acarretando riscos ambientais. O controlo biológico de doenças em
plantas por ação de microrganismos ou dos seus produtos surge como alternativa sustentável. Uma
estratégia inovadora e pouco explorada no desenvolvimento de soluções para controlo biológico é a
otimização de formulações enriquecidas em metabolitos extracelulares recorrendo a abordagens
envolvendo interações entre microrganismos.
No presente estudo, um conjunto de isolados de Pseudomonas e Bacillus com características de
plant growth promoting bacteria (PGPB) foi selecionado para avaliação do seu potencial antagonista
contra fungos potencialmente fitopatogénicos. Após um rastreio da atividade antagonista contra isolados
de Alternaria e Fusarium, foram exploradas interações microbianas com vista ao aumento da atividade
antagonista e analisadas a natureza e estabilidade dos metabolitos extracelulares presentes nas
formulações obtidas.
Os resultados obtidos expressam a necessidade de interação bactéria-fungo para o aumento ou
indução de atividade antagonista. A estirpe Bacillus sp. BS36 apresentou a maior atividade antagonista,
inibindo o crescimento de Alternaria sp. AF12 e Fusarium sp. AF68 em cerca de 74 e 65 %,
respetivamente, em ensaio de cultura dupla. O potencial antagonista da estirpe foi também estabelecido
contra isolados dos géneros Botrytis e Stemphylium.
O co-cultivo de Bacillus sp. BS36 com outras estirpes promoveu a intensificação da atividade
antimicrobiana registada em monocultura. O cultivo na presença de células de fungo inativadas pelo
calor revelou também efeitos positivos no aumento da atividade antagonista da estirpe. A análise dos
dados obtidos por espectrometria de massa FTICR revelou a produção de lipopéptidos pertencentes às
famílias fengicinas e surfactinas por parte de Bacillus sp. BS36. Estes parecem ser responsáveis pela
atividade antagonista dos filtrados da estirpe contra Alternaria sp. AF12 e Fusarium sp. AF68.
The use of chemical fungicides negatively affects the health of soil, plants and all elements of the food chain, leading to environmental risks. The biological control of plant diseases by the action of microorganisms or their products emerges as a sustainable alternative. An innovative and underexplored strategy in the development of solutions for biological control is the optimization of formulations enriched in extracellular metabolites using microbial interactions. In the present study, a set of isolates of Pseudomonas and Bacillus with characteristics of plant growth promoting bacteria (PGPB) was selected to evaluate their antagonistic activity against potentially phytopathogenic fungi. After screening for the antagonist activity against isolates of Alternaria and Fusarium, microbial interactions were explored prospecting an increasing antagonist activity. Further, the nature and stability of extracellular metabolites present in obtained formulations with potential for application in agriculture were analysed. The results express the need for bacterial-fungal interaction to increase or induce antagonistic activity. Bacillus sp. BS36 showed the greatest antagonistic potential, inhibiting the growth of Alternaria sp. AF12 and Fusarium sp. AF68 by about 74 and 65 %, respectively, in dual culture assay. The antifungal potential of the strains has also been established against isolates of Botrytis and Stemphylium. The co-cultivation of Bacillus sp. BS36 with other strains promoted the enhancement of antimicrobial activity recorded in monoculture. The growth in the presence of heat-inactivated fungal cells also revealed positive effects in increasing antagonist activity. An analysis of the data obtained by FTICR mass spectrometry revealed a production of lipopeptides of the families fengycins and surfactins by Bacillus sp. BS36. These seem to be responsible for the antagonistic activity of the Bacillus sp. BS36 filtrates against Alternaria sp. AF12 and Fusarium sp. AF68.
The use of chemical fungicides negatively affects the health of soil, plants and all elements of the food chain, leading to environmental risks. The biological control of plant diseases by the action of microorganisms or their products emerges as a sustainable alternative. An innovative and underexplored strategy in the development of solutions for biological control is the optimization of formulations enriched in extracellular metabolites using microbial interactions. In the present study, a set of isolates of Pseudomonas and Bacillus with characteristics of plant growth promoting bacteria (PGPB) was selected to evaluate their antagonistic activity against potentially phytopathogenic fungi. After screening for the antagonist activity against isolates of Alternaria and Fusarium, microbial interactions were explored prospecting an increasing antagonist activity. Further, the nature and stability of extracellular metabolites present in obtained formulations with potential for application in agriculture were analysed. The results express the need for bacterial-fungal interaction to increase or induce antagonistic activity. Bacillus sp. BS36 showed the greatest antagonistic potential, inhibiting the growth of Alternaria sp. AF12 and Fusarium sp. AF68 by about 74 and 65 %, respectively, in dual culture assay. The antifungal potential of the strains has also been established against isolates of Botrytis and Stemphylium. The co-cultivation of Bacillus sp. BS36 with other strains promoted the enhancement of antimicrobial activity recorded in monoculture. The growth in the presence of heat-inactivated fungal cells also revealed positive effects in increasing antagonist activity. An analysis of the data obtained by FTICR mass spectrometry revealed a production of lipopeptides of the families fengycins and surfactins by Bacillus sp. BS36. These seem to be responsible for the antagonistic activity of the Bacillus sp. BS36 filtrates against Alternaria sp. AF12 and Fusarium sp. AF68.
Descrição
Tese de mestrado, Microbiologia Aplicada , 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Pseudomonas Bacillus atividade antagonista interações microbianas lipopéptidos Teses de mestrado - 2023