Arsenic stress mitigation using a novel plant growth promoting bacterial
strain Bacillus mycoides NR5 in spinach plant (Spinacia oleracea L.)
Abstract
The present study aimed to identify arsenic (As)-resistant bacterial
strains that can be used to mitigate arsenic stress. A bacterium
Bacillus mycoides NR5 having As tolerance limit of 1100 mg L -1 was
isolated from Nag River, Maharashtra, India. It was also equipped with
plant growth-promoting (PGP) attributes like P solubilization,
siderophores, ammonia and nitrate reduction, with added antibiotic
tolerance. Further, Scanning Electron Microscopy (SEM) and Transmission
Electron Micrograph (TEM) suggested biosorption as possible mechanisms
of arsenic tolerance. A strong peak in FTIR spectra at 3379.0
corresponding to amine in As-treated NR5 also indicated metal
interaction with cell surface protein. Amplification of the arsenic
reductase gene in NR5 further suggested intracellular transformation of
As speciation. Moreover, the As tolerance capability of NR5 was shown in
spinach plants in which the bacterium effectively mitigated 25ppm As by
the production of defence-related proline molecules. Evidence from SEM,
TEM and FTIR, concluded biosorption is possibly the primary mechanism of
As tolerance in NR5 along with the transformation of arsenic. B.
mycoides NR5 with PGP attributes, high As tolerance and antibiotic
resistance mediated enhanced As tolerance in spinach plants advocated
that the strain can be a better choice for As bioremediation in
contaminated agricultural soil and water.