Efficiency of arsenic remediation from growth medium through Bacillus licheniformis modulated by phosphate (PO4)3- and nitrate (NO3)- enrichment.

Bacillus licheniformis DAS-1 and DAS-2 were found as potent tool for removal/uptake of arsenic [As(V) and As(III)] and reduction [(As(V) to As(III)] of arsenic from the liquid growth medium in our previous studies. Present work gives light on modulation of arsenic remediation (in terms of uptake and reduction) by two selected essential soil nutrients, phosphate (PO4)3- and nitrate (NO3)-. PO43- has structural analogy with arsenate [AsO43-/As(V)] that compete with cell uptake of As(V). It was found that enrichment of 0.75 mM of PO43- had significantly moderated the As(V) toxicity in liquid broth culture by retarding As(V) uptake. Lowering level of PO43- can lead to increase in As(V) removal from medium and vice versa. NO3- has strong oxidant properties which controls As(III) oxidation into As(V) in medium that resulted less toxicity favouring growth of bacteria and also more uptake via phosphate transporters. Hence, accelerated As(III) uptake has shown on enrichment of 0.5 mM of NO3- in medium. All the results of work give evidence that appropriate enrichment of PO43- and NO3- into liquid growth medium, can significantly contribute in alteration of efficiency for arsenic removal/uptake and reduction by bacteria from the medium.