Halomonas Rhizobacteria of Avicennia marina of Indian Sundarbans Promote Rice Growth Under Saline and Heavy Metal Stresses Through Exopolysaccharide Production.

Pritam Mukherjee,Madhumita Roy,Abhijit Mitra

doi:10.3389/fmicb.2019.01207

Pritam Mukherjee, Madhumita Roy + Show 1 more

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https://doi.org/10.3389/fmicb.2019.01207

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Abstract

The Halomonas species isolated from the rhizosphere of the true mangrove Avicennia marina of Indian Sundarbans showed enhanced rice growth promotion under combined stress of salt and arsenic in pot assay. Interestingly, under abiotic stress conditions, Halomonas sp. Exo1 was observed as an efficient producer of exopolysaccharide. The study revealed that salt triggered exopolysaccharide production, which in turn, increased osmotic tolerance of the strain. Again, like salt, presence of arsenic also caused increased exopolysaccharide production that in turn sequestered arsenic showing a positive feedback mechanism. To understand the role of exopolysaccharide in salt and arsenic biosorption, purified exopolysaccharide mediated salt and arsenic sequestration were studied both under in vivo and in vitro conditions and the substrate binding properties were characterized through FT-IR and SEM-EDX analyses. Finally, observation of enhanced plant growth in pot assay in the presence of the strain and pure exopolysaccharide separately, confirmed direct role of exopolysaccharide in plant growth promotion.

Highlights

Soil salinity is one of the major abiotic stresses that limit plant productivity throughout the globe
The purpose of this paper is to understand the role of EPS produced by halophilic plant growth-promoting rhizomicrobes (PGPR) belonging to the genus Halomonas, isolated from the rhizosphere of the Avicennia marina of Indian Sundarbans, in abiotic stress alleviation during rice growth promotion under combined stress of salt and arsenic (As)
The root associated soil of Avicennia marina seedling growing in the intertidal mud flat of Bonnie Camp (21◦49′45.3′′ N; 88◦37′13.6′′ E) situated in the central region of Indian Sundarbans was collected during monsoon season in the month of September, 2014

Summary

Introduction

Soil salinity is one of the major abiotic stresses that limit plant productivity throughout the globe. Previous research on Indian saline ecosystem identified the potential of eco-friendly halo-tolerant plant growth-promoting rhizomicrobes (PGPR) for application in sustenance of agronomy under diverse saline ecologies (Shrivastava and Kumar, 2015) Application of these native PGPR to alleviate salt stress can be regarded as a better alternative toward sustainable agriculture than developing salt and other stress tolerant transgenic varieties due to high production cost and other environmental hazards (Shrivastava and Kumar, 2015). Bacterial determinants of IST and their activation pathways in plants have been significantly evaluated during the past decade but the response of the PGPR toward the abiotic stresses has been revealed very recently (Timmusk and Wagner, 1999; Zhang et al, 2008) Use of these PGPR for minimizing agricultural chemical load, HM load (Nadeem et al, 2014; Yu et al, 2014) and soil salinity (Siddikee et al, 2010) is earning considerable appreciation in boosting environmental quality. With a growing interest in extremophiles, a large number of halophiles, species belonging to the Halomonas genera have been found to be the possessors of EPS (Béjar et al, 1998; Arias et al, 2003; Martínez-Cánovas et al, 2004; Llamas et al, 2006; Poli et al, 2013)

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