Abstract
Endophytic microbes isolated from plants growing in contaminated habitats possess specialized properties that help their host detoxify the contaminant/s. The possibility of using microbe-assisted phytoremediation for the clean-up of Arsenic (As) contaminated soils of the Ganga-Brahmaputra delta of India, was explored using As-tolerant endophytic microbes from an As-tolerant plant Lantana camara collected from the contaminated site and an intermediate As-accumulator plant Solanum nigrum. Endophytes from L. camara established within S. nigrum as a surrogate host. The microbes most effectively improved plant growth besides increasing bioaccumulation and root-to-shoot transport of As when applied as a consortium. Better phosphate nutrition, photosynthetic performance, and elevated glutathione levels were observed in consortium-treated plants particularly under As-stress. The consortium maintained heightened ROS levels in the plant without any deleterious effect and concomitantly boosted distinct antioxidant defense mechanisms in the shoot and root of As-treated plants. Increased consortium-mediated As(V) to As(III) conversion appeared to be a crucial step in As-detoxification/translocation. Four aquaporins were differentially regulated by the endophytes and/or As. The most interesting finding was the strong upregulation of an MRP transporter in the root by the As + endophytes, which suggested a major alteration of As-detoxification/accumulation pattern upon endophyte treatment that improved As-phytoremediation.
Highlights
Endophytic microbes isolated from plants growing in contaminated habitats possess specialized properties that help their host detoxify the contaminant/s
Another Enterobacter sp. from water hyacinth contained a plasmid responsible for conferring metal tolerance to the bacteria. Endophytes exert their plant growth promoting (PGP) properties on their hosts in a way analogous to the gut microflora of animals[9]. Host genotype impacts their properties to a certain degree, a number of studies have shown that this influence is limited indicating that the soil condition predominately drives their entry into a plant[10,11]
Our results revealed that S. nigrum had an innate ability to convert As(V) to As(III). 51% of As(V) was converted to As(III) in untreated plants
Summary
Endophytic microbes isolated from plants growing in contaminated habitats possess specialized properties that help their host detoxify the contaminant/s. While one of the selection forces determining the endophytic colonization is the nutritional status of the host[5], the necessity to detoxify a xenobiotic appears to be an additional driving force This is exemplified by the fact that the endophytic microbes isolated from plants surviving in contaminated habitats often contain properties useful for the detoxification of the related xenobiotic/s6. Endophytes isolated from plants growing in metal-contaminated habitats have been reported to harbor genome or plasmid coded strategies to detoxify metals[7] and contribute to the metal tolerance and accumulation property of the host plant. From water hyacinth contained a plasmid responsible for conferring metal tolerance to the bacteria Endophytes exert their plant growth promoting (PGP) properties on their hosts in a way analogous to the gut microflora of animals[9]. Nitrogen-fixing endophytes isolated from Typha angustifolia collected from a nutrient-deficient Uranium mine improved nitrogen metabolism in rice[16]
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