(511u) Low-Cost Specific Arsenic Accumulation And Removal By Engineered Bacteria Expressing Fucus Vesiculosus Metallothionein

Arsenic (As) which exists as As(V) & As(III), is an extremely toxic metalloid pollutant affecting health of millions of people worldwide; its exposure has been associated with increased risk of hypertension, skin, lung and bladder cancer. Current methods for As removal are either too costly, ineffective over a large scale, lack specificity, require alteration of water chemistry or are unable to remove trace quantities of the metalloid. Furthermore most methods are ineffective for the more toxic As(III) which is uncharged at natural pH. An arsenic-chelating metallothionein (MT) from the arsenic tolerant marine alga Fucus vesiculosus was functionally expressed as a fusion protein with the maltose binding protein (MBP) in Escherichia coli. E. coli cells expressing MT accumulated 36- & 26-fold higher As(V) and As(III), respectively than the control cells. This As-specific MT also offered high selectivity towards As as mimimal effect on As binding was observed in the presence of Zn or Pb except for Cd. To further improve the specific accumulation, an As(III) transporter GlpF was co-expressed, resulting in 2-fold higher As(III) accumulation than the MT-expressing cells. The GlpF and MT co-expression also improved the specificity of As accumulation even in the presence of Cd. Resting E. coli cells over-expressing MT and GlpF were able to completely remove trace amounts (50 ppb) of As(III) within 20 min, providing a promising technology to comply with the newly US-EPA recommended As limit of 10 ppb. These results pave the path for the use of GlpF & MT overexpressing bacterial cells as biosorbents for environmental friendly and cost effective specific removal of arsenic from contaminated drinking and ground water.