Abstract
BackgroundBiocontrol agents are sustainable eco-friendly alternatives for chemical pesticides that cause adverse effects in the environment and toxicity in animals including humans. An improved understanding of the phyllosphere microbiology is of vital importance for biocontrol development. Most studies have been directed towards beneficial plant-microbe interactions and ignore the pathogens that might affect humans when consuming vegetables. In this study we extended this perspective and investigated potential biocontrol strains isolated from tomato and lettuce phyllosphere that can promote plant growth and potentially antagonize human pathogens as well as plant pathogens. Subsequently, we mined into their genomes for discovery of antimicrobial biosynthetic gene clusters (BGCs), that will be further characterized.ResultsThe antimicrobial activity of 69 newly isolated strains from a healthy tomato and lettuce phyllosphere against several plant and human pathogens was screened. Three strains with the highest antimicrobial activity were selected and characterized (Bacillus subtilis STRP31, Bacillus velezensis SPL51, and Paenibacillus sp. PL91). All three strains showed a plant growth promotion effect on tomato and lettuce. In addition, genome mining of the selected isolates showed the presence of a large variety of biosynthetic gene clusters. A total of 35 BGCs were identified, of which several are already known, but also some putative novel ones were identified. Further analysis revealed that among the novel BGCs, one previously unidentified NRPS and two bacteriocins are encoded, the gene clusters of which were analyzed in more depth.ConclusionsThree recently isolated strains of the Bacillus genus were identified that have high antagonistic activity against lettuce and tomato plant pathogens. Known and unknown antimicrobial BGCs were identified in these antagonistic bacterial isolates, indicating their potential to be used as biocontrol agents. Our study serves as a strong incentive for subsequent purification and characterization of novel antimicrobial compounds that are important for biocontrol.
Highlights
Biocontrol agents are sustainable eco-friendly alternatives for chemical pesticides that cause adverse effects in the environment and toxicity in animals including humans
Three bacteria with the highest antimicrobial activity were selected: Bacillus subtilis STRP31 isolated from tomato, and Bacillus velezensis SPL51, and Paenibacillus sp
Various biosynthetic gene clusters (BGCs) identified in Bacillus velezensis SPL51 and Bacillus subtilis STRP31 were already known, and both strains represent two well studied species with high potential as biocontrol agents to be applied in agriculture, the ones we isolated could have additional advantages
Summary
Biocontrol agents are sustainable eco-friendly alternatives for chemical pesticides that cause adverse effects in the environment and toxicity in animals including humans. Most studies have been directed towards beneficial plant-microbe interactions and ignore the pathogens that might affect humans when consuming vegetables. In this study we extended this perspective and investigated potential biocontrol strains isolated from tomato and lettuce phyllosphere that can promote plant growth and potentially antagonize human pathogens as well as plant pathogens. Solanum lycopersicum better known as tomato is one of the most important vegetable plants in the world [1]. Tomato is a healthy food that supplies a wide range of vitamins needed for the organism, since it contains high levels of zinc, potassium, anthocyanins and lycopene, which provide a high antioxidant power. Lactuca sativa better known as lettuce is another important crop with a growing interest from people due to its healthy and beneficial properties and richness in antioxidants (e.g., vitamins C, E and carotenoids) [3]
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