Hundred and twenty eighty halophilic bacterial isolated from the soil and water of Karnataka mangrove regions were examined for multi-metal tolerance. Bacillus pumilus (accession no.MF472596) was found to be tolerant against four toxic heavy metal ions (Cd²⁺, Cu²⁺, Fe^3+, and Ba²⁺) up to 1000 ppm each. Chemical analysis was carried out by ICP-AES for Ba²⁺ and AAS for rest of the metal ions. The bioremediation efficiency against metals are as follows Fe>Cu>Ba>Cd (90%, 71%, 52% and 19% respectively) at pH 7. Altering the pH in a range of 6 to10 the bioremediation rate increased to 96%, 88%, 54% and 52% for Fe, Cu, Ba, and Cd respectively. The metal absorption efficiency increases on altering pH i.e. from 136 ppm, 52 ppm and 35 ppm to 196 ppm, 82 ppm and 60 ppm in Fe³⁺, Ba²⁺, Cd²⁺ respectively, whereas reduction in Cu²⁺ absorption was noted i.e. from 114 ppm to 41 ppm. This investigation justifies that specific pH exposure can play a key role in enhancing bioremediation activity of bacterial isolate towards metal ion.

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