Halotolerant Endophytic Bacterium Serratia rubidaea ED1 Enhances Phosphate Solubilization and Promotes Seed Germination

Abstract

Quinoa is renowned for its nutritional value and ability to withstand harsh environmental conditions such as salinity. In the present work, we isolated 34 phosphate solubilizing endophytic bacteria associated with the roots of quinoa plants. Based on phosphate solubilization efficiency and biochemical characterization, we selected one isolate named ED1. Ribotyping using partial 16S RNA gene analysis revealed that the selected isolate shares 99.7% identity with Serratia rubidaea. Plant growth promoting (PGP) studies showed that the ED1 strain solubilized complexed forms of phosphate (Ca3(PO4)2). Zinc release from ZnO, Zn3(PO4)2, or ZnCO3 revealed the efficient ZnO solubilization by the ED1 strain. Except for proteases, the strain ED1 produced siderophores, cellulase, ammonia and exhibited oligonitrophilic features. Indole acetic acid (IAA) production was detected with and without the L-tryptophan precursor. Next, we demonstrated that the ED1 strain tolerated 1.5 M NaCl final concentration and exhibited intrinsic resistance to seven antibiotics frequently prescribed for medical use. Moreover, we found that ED1 strain withstood 2 mg/L of Cadmium and 1 mg/L of either Nickel or Copper. Furthermore, we observed that S. rubidaea ED1 stimulated quinoa seeds germination and seedlings growth under salt stress conditions. Lastly, we discuss the advantages versus disadvantages of applying the S. rubidaea ED1 strain as a beneficial agent for salty and/or heavy metals contaminated soils.

Stress-Tolerant Endophytic Isolate Priestia aryabhattai BPR-9 Modulates Physio-Biochemical Mechanisms in Wheat (Triticum aestivum L.) for Enhanced Salt Tolerance

“…The current investigation reveals a wide range of endophytic microbes capable of solubilizing mineral nutrients containing phosphate, potassium, and zinc. NaCl-tolerant endophytic PGPR strain Serratia rubidaea solubilized phosphate and zinc forms, thus increasing the salinity tolerance of plants by improving seed germination [ 57 ]. Similarly, endophytic strains such as Pseudomonas sp., Bacillus pumilus , and Enterobacter colacae recovered from sugarcane showed the anti-fungal potential for solubilizing the insoluble forms of P, K, and Zn minerals [ 58 ].…”

Variation of the seed endophytic bacteria among plant populations and their plant growth‐promoting activities in a wild mustard plant species, Capsella bursa‐pastoris

“…A limitation of this method is that it cannot measure the ability to dissolve metal phosphate, another common form of insoluble phosphate in soil (Bashan et al, 2013 ). Despite this limitation, the tricalcium phosphate method has been widely adopted in many studies as a useful screening method to identify candidate bacterial strains facilitating plant use of insoluble phosphates (Mahdi et al, 2021 ; Varga et al, 2020 ).…”

Effective Biocontrol of Rice Blast through Dipping Transplants and Foliar Applications

“…This may thus suggest that this specific isolate may have general beneficial effects in improving plant development in addition to its biocontrol ability, agreeing with previous studies of Serratia spp. on other plant hosts and pathogens [15,16,25]. The relative performance of individual biopesticides is likely to be context dependent.…”

“…Serratia is a group of enterobacteria with a notable secondary metabolism that is able to produce a wide range of natural bioactive products, including the β-lactam antibiotic carbapenem or the antifungal compound oocydin A [15]. A specific S. rubidaea Bizio 1823 isolate stimulated quinoa seeds germination and seedlings growth under salt stress conditions and survived salty and/or heavy-metal conditions [16].…”