Abstract
Beneficial interactions between plants and some bacterial species have been long recognized, as they proved to exert various growth-promoting and health-protective activities on economically relevant crops. In this study, the growth promoting and antifungal activity of six bacterial strains, Paenarthrobacter ureafaciens, Beijerinckia fluminensis, Pseudomonas protegens, Arthrobacter sp., Arthrobacter defluii, and Arthrobacter nicotinovorans, were investigated. The tested strains resulted positive for some plant growth promoting (PGP) traits, such as indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate-deaminase (ACC-deaminase), siderophore production, and solubilization of phosphates. The effect of the selected bacteria on Arabidopsis thaliana seedlings growth was assessed using different morphological parameters. Bacterial activity against the phytopathogenic fungal species Aspergillus flavus, Fusarium proliferatum, and Fusarium verticillioides was also assessed, since these cause major yield losses in cereal crops and are well-known mycotoxin producers. Strains Pvr_9 (B. fluminensis) and PHA_1 (P. protegens) showed an important growth-promoting effect on A. thaliana coupled with a high antifungal activity on all the three fungal species. The analysis of bacterial broths through ultra performance liquid chromatography–mass spectrometry (UPLC–MS) and liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS/MS) confirmed the presence of potential PGP-compounds, among these are desferrioxamine B, aminochelin, asperchrome B, quinolobactin siderophores, and salicylic acid.
Highlights
IntroductionThe rhizosphere is a complex ecosystem in which many relationships are established between bacteria, fungi, and plant root apparatus, and represents the main source of nutrients for plant growth [1]
The chrome azurol S (CAS) assay revealed that all bacterial strains are able to produce, in both growth media, molecules involved in chelating ferric ions, as indicated by the elevated percent siderophore units (PSU) values observed (Table 1)
The bacterial strains analyzed in this study were chosen amongst a previously described panel, containing isolates recovered from the rhizosphere—or the surrounding soil—of plants grown in stressful environments; the mining of harsh ecosystems is considered promising for seeking plant-beneficial bacteria, having the microbiota from these areas subjected to evolutionary pressures that have, in turn, led to adaptive features related to a more effective stress response of their hosts than plants found in cultivated land [32]
Summary
The rhizosphere is a complex ecosystem in which many relationships are established between bacteria, fungi, and plant root apparatus, and represents the main source of nutrients for plant growth [1]. Many soil microbes have established good relationships with plants, supporting their growth and health, for example helping plants to manage both biotic and abiotic stress [2,3,4]. Plant growth promoting rhizobacteria (PGPR) are microorganisms, which form symbiotic interactions with plant roots, promoting plant health and productivity through different mechanisms such as production of plant hormones (auxins, cytokinin, and gibberellins); inhibition of plant senescence; N2 fixation; phosphate solubilization and mineralization of other nutrients; and siderophores production [5]. Being present in the rhizosphere, PGPR may be endophytic (PGPE) (for example, by colonizing the plant’s tissues), symbiotic (for example, by colonizing the interior of the roots of specific plants by forming nodules), or phyllospheric (i.e., they can be found on the surfaces of plant leaves and stems) [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
