| Summary: | Halophilic microorganisms and the metabolites involved in their adaptive strategies offer a wide variety of potential biotechnological applications and like other extreme environments, hypersaline habitats represent reservoirs of new bioactive compounds. The main objective of this work was to assess the biotechnological potential of halophilic bacteria from traditional salt pans of Ria de Aveiro in terms of biosurfactant production, plant growth promoting traits, quorum-quenching effect and extracellular enzymatic activity. Water from an active salt pan of Ria de Aveiro was collected in early autumn when the concentration of salt was at the saturation level. Using a culture-dependent approach, 14 bacterial strains were isolated and identified by sequencing of 16S rRNA gene fragments as species of Bacillus, Halobacillus, Idiomarina and Marinobacter. In order to assess the biotechnological potential of these halophiles, they were tested for biosurfactant production, plant growth promoting traits (motility, biocontrol effect and siderophore production), quorum-quenching effect and, activity of extracellular enzymes (phosphatase and esterase). None of the isolates demonstrated significant tensioactive or emulsification effects that could be interpreted as indicative of biosurfactant production. However, all isolates were motile even in presence of 10% NaCl and produced siderophores. All Idiomarina and Marinobacter strains caused growth inhibition of the phytopathogenic fungus Alternaria. Quorum sensing inhibition was also detected in isolates of the 4 genera although with differences between species and, in some cases, depending on the salinity of the culture medium. Esterase and phosphatase activity was detected in all isolates and maximum hydrolysis rates of the model substrates were the highest in Halobacillus species. Although biosurfactant production could not be demonstrated, the halophilic isolates displayed an interesting set of features in terms of plant-growth promoting traits with potential application on the emerging field of saline agriculture.
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