Plant growth promotion potential of novel bacterium Ensifer adhaerens OV14 Wojciech Nowak1,3, David Ryan1, Guiomar Garcia-Cabellos1, Ewen Mullins2 and Anne-Marie Enright1 1EnviroCore,
Department of Science and Health, Dargan Centre, Institute of Technology Carlow, Kilkenny Road, Carlow, Co. Carlow, Ireland 2Crops
Research Oak Park, Teagasc, Oak Park, Carlow, Co. Carlow, Ireland
3Corresponding Author
Email Address:
[email protected]
Background: Current agricultural practice relies heavily on the use of chemical fertilizers, which can be environmentally damaging. One alternative is the development of a robust biological fertilizer, a microbial inoculum which can enhance plant growth. Such symbiotic relationships between bacteria and plants have been previously described (Saharan & Nehra, 2011). These plant growth promoting (PGP) bacteria have developed traits such as facilitation of nutrient uptake (N, P or Fe), modulation of phyto-hormones or phytopathogen antagonism. Researchers at Teagasc, Oak Park, Carlow have recently discovered a novel bacterium Ensifer adhaerens OV14, which displays PGP characteristics (Dr. Ewen Mullins, Teagasc, per. comm. 2015). Other strains of E. adhaerens which possess PGP traits have also been reported (Yutani et al., 2011; Zhou et al. 2012; Tak et al., 2016; Wang et al., 2016). The current research aims to assess the PGP effect of E. adhaerens OV14 using bioinformatic and in-vitro approaches.
Methods:
Key findings:
• Bioinformatic screening for bacterial PGP associated genes: • A model gene apparatus for a PGP trait was BLAST-ed against (Sayers et al., 2011) OV14 genome, • OV14 metabolic pathways were examined using the Kyoto Encyclopedia of Genes and Genomes (KEGG) (Kanehisa & Goto, 2000), • Resulting sequences were then analysed for false positives. • Preliminary in-vitro trails for PGP traits: • Nitrogen fixation (by NFb medium) (Bashan et al., 1993), • Phosphate solubilisation (by NBRIP medium) (Nautiyal, 1999), • Siderophore production (by SGA medium), • Production of indole-3-acetic acid (by Kovac and Salkowski reagents), • Fungal inhibition (by co-inoculation of OV14 with fungal isolates on PDA).
PGP traits involved in nutrient acquisition, phyto-hormone production and production of induced systemic resistance (ISR) triggering molecules have been detected. These findings were summarised in Figure 2 in relation to their presence (Green) or absence (Red).
Results:
Nutrient acquisition: Nitrogen fixation Phosphate solubilisation Siderophore production Phyto-hormone production: ACC deaminase Indole-3-acetic acid Abscisic acid Nitric oxide Cytokinins Salicylic acid ISR triggering molecules: Acetoin and 2-3 butanediol Figure 1. The bioinformatic screening of OV14 genome, 39 potential PGP genes detected. Figure 2. Representation of PGP traits possessed by OV14. Table 1. The results of preliminary in-vitro testing for PGP phenotypes Testing for Nitrogen fixation
Positive Control +
OV14 +
Negative Control Comment OV14 grew well on NFb* plates OV14- No zone of clearing present on NBRIP* however, abundant Phosphate solubilization + growth present. No growth observed on negative control plates (Escherichia coli S17.1) OV14- No growth detected on Siderophore production + SGA* OV14 did not grow in media ACC deaminase activity required for the test + No indole detected IAA production + No indole detected Fungal inhibition + Fungal inhibition not detected *NFb= Nitrogen fixating, NBRIP= National Botanical Research Institute's phosphate, SGA= Sucrose-Glutamic acid Agar, SOP= Standard operating procedure.
Future work: • • • •
Further analysis of in-vitro PGP traits. Greenhouse trails. Analysis of OV14 gene expression during plant trials. Development of OV14 based bio-fertilizer inoculum.
Acknowledgements: This work is funded by Government of Ireland Postgraduate Scholarship from the Irish Research Council.
Take home message: The overuse of chemical fertilization is an expensive and wasteful practice which has many negative impacts on the environment. Formulation of an innovative robust biofertilizer has the potential to accelerate the next green revolution in a sustainable manner.
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