Isolation and Identification of Arsenic Hyper-Tolerant Bacterium with Potential Plant Growth Promoting Properties from Soil

Abstract

The soil and groundwater of the Bhagobangola I block of Murshidabad district, West Bengal, India is severely arsenic-contaminated. A bacterium was isolated from the garden soil of the Mahishasthali village, which could tolerate 36.49 mM arsenic (III), 280.44 mM arsenic (V) and 63 mM chromium (III), which makes it arsenic (III and V) and chromium (III) hyper-tolerant bacterium. The growth pattern of this bacterium does not show much alteration in the presence of 10 mM arsenic (III) and chromium (III), emphasizing its resistance to these heavy metals. Scanning electron microscopic analysis depicted this bacterium to be rod-shaped with a size of ~1.45 µm. 16S rDNA sequencing, followed by subsequent phylogenetic analysis, established the identity of this bacterium as Microbacterium paraoxydans. This bacterium is capable of bioremediation of arsenic and showed 30.8% and 35.2% of bioremediation for 1mM and 22.6%, and 30.5% of bioremediation for 4mM arsenite, over a period of 24 and 48 h, respectively. Microbacterium paraoxydans also exhibits potential plant growth-promoting properties such as nitrogen fixation, phosphate solubilization, indole-3-acetic acid production and production of siderophores. Therefore, the heavy metal resistance, bioremediation potential and plant growth-promoting potential of the bacterium could be utilized not only for reduction in arsenic toxicity in soil and groundwater but also for plant growth promotion.

Genome sequencing, annotation and application of a strain of Microbacterium paraoxydans – a heavy metal hypertolerant and plant growth promoting bacterium

“…It was a free living bacterium that could ferment glucose, sucrose, fructose and mannitol. The isolated strain could grow profoundly in presence of 1000 ppm sodium arsenite (7.7 mM arsenic) (Table 1) (Mandal et al, 2022). The bacterium showed moderate tolerance to copper (5 mM), zinc (5 mM), iron (10 mM) and manganese (5 mM) and was sensitive to low concentration of cobalt (II) (3 mM), lead (II) (2 mM), cadmium (II) (1 mM), nickel (II) (1 mM), mercury (II) (0.5 mM) and chromium (VI) (1 mM).…”

“…The minimum inhibitory concentration (MIC) of arsenic (III) and arsenic (V) for the bacterium was 36.95 mM and 280.44 mM, respectively. Therefore, the bacterium was considered as a strain of arsenic hypertolerant Microbacterium paraoxydans (Mandal et al, 2022). The tolerance and sensitivity of a bacterium to various heavy metals is the result of multiple heavy metal tolerant genes and gene clusters present in its genome.…”

“…The bioremediation potential of the isolated strain of Microbacterium paraoxydans was tested in presence of two different concentration of arsenic (1 mM and 4 mM arsenic in the form of sodium arsenite) (Mandal et al, 2022). The bioremediation potential of the strain was further optimized in presence of four different parameters, pH, temperature, incubation time and initial concentration of arsenic.…”

“…The isolated strain of Microbacterium paraoxydans could produce 0.77 ug/ml of auxin and 21.16% siderophore. The bacterium could also solubilize insoluble phosphate in Pikovskaya medium (Mandal et al, 2022). All the three servers could recognize multiple genes for different types of trehalose biosynthetic pathways.…”

“…Also, the plant growth promoting properties exhibited by the bacterium were studied in In Vitro condition. Pot experiments and eld trials needs to be conducted to ensure the potential of Microbacterium paraoxydans gets translated into the growth and development of the plants for which this bacterium will be used as a biofertilzer (Mandal et al, 2022). These experiments will not only corroborate the annotation of different arsenic resistant and plant growth promoting genes, but also their expression and manifestation with respect to bioremediation and plant growth promotion, respectively.…”