Emergence of Highly Mercury Tolerant Plant Growth promoting Bacteria in Tea Plantation Soil of Darjeeling Hills

This study characterizes three strains of Gram-negative bacteria MTD10B, MTD10C and MTD10D isolated from soil collected from tea plantations of Darjeeling hills, exhibiting extreme tolerance towards mercury. The minimum inhibitory concentration of mercury against these strains sits at a high level of 0.2 mg/mL of HgCl2. The isolates also display an expansive pattern of resistance to known clinically relevant synthetic antibiotics and a host of other potent heavy metals such as lead, cadmium, arsenic, chromium, silver, nickel etc. Biochemical and molecular characterization via 16S rRNA sequencing identified MTD10B and MTD10C as strains of Brevundimonas diminuta and MTD10D as Alcaligenes faecalis respectively. This study also explores the plant growth promoting abilities of these strains and their respective growth trends under normal conditions in comparison to when they are under mercury stress. This work attempts to cultivate an understanding of their potential for use as candidates for the bioremediation of mercury contamination in diverse environments.