Metabolic potential of microorganisms associated with the halophyte Aster tripolium L. in saline soils

Abstract

Increased soil salinization may be caused by a natural (e.g. climate change) and anthropogenic (e.g. improper fertilization and irrigation of agricultural land) factors. The submitted work assumes that microorganisms associated with plant halophytes have a unique metabolic properties that can stimulate plant growth under salt stress. The aim of the study was to determine the abundance and metabolic biodiversity of endophytic and rhizosphere microorganisms co-existing with Aster tripolium L. and compare them with the properties of soil microorganisms not affected by plant roots at a salty meadows in the vicinity of a soda factory (central Poland). In order to select halotolerant and halophilic microorganisms culture medium was enriched with various concentrations of NaCl (0, 100, 200, 400, 600 mM NaCl). Total metabolic activity of endophytic, rhizosphere and soil populations was measured to compare the community-level physiological profiles. Results of our study revealed that bacterial and fungal density increased in the following order: endophytes < soil < rhizosphere. Only the highest concentration (600 mM) of NaCl decreased the number of microorganisms. The highest total microbial metabolic activity was observed for the rhizosphere, while the activity of endophytes was higher compare to soil populations. To carbon sources which significantly differentiated zones belonged: D-lactose, 4-hydroxybenzoic acid and L-asparagine. The results are preliminary studies leading to the development of inoculum based on selected microbial halotolerant and halophilic strains which can be used in agriculture and/or recultivation of saline soils.