Organomercury Captured by Lyase Overexpressed Escherichia coli and Its Evaluation by In-Cell Radiometry*

Organomercury lyase (MerB) overexpressed in Escherichia coli captured and decomposed organomercury compounds, and it has been detected by radioactive analysis with neutron irradiation. Genetically modified E. coli captures a lot of mercury from a cultivation solution with about 80% recovery, when the bacteria are growing during 24 to 72 hours. Since the modified E. coli has no additive gene for mercury metabolism, the bacteria could hold mercury tightly by the MerB enzyme in their cell and do not release them into medium. In the later, 72 hours after, bacteria have less recovery ratio; it may be affected by undecompsed mercury compounds in bacteria growth. The recovery ability of the bacteria would not be changed by addition of the MerB producing reagent (IPTG). A quantitative value of mercury atom is estimated by an emission of γ-ray by reactor neutron from a dried cell or solution on a filter paper, which is available for nondestructive testing of bacteria holding mercury atoms. In this method an efficient recovery system of toxic mercury from a polluted solution has been archived without destruction of samples, so called in-cell analysis.