Department of Civil & Environmental
Engineering & Earth Science
November 12, 2015
136 DeBartolo Hall, 4:00 p.m-5:00 p.m.
Jean-Francois Gaillard, Ph.D.
Dept. of Civil & Environmental Engineering
Northwestern University
Title:
Metal Biouptake: The Complicated Case of Mercury
Abstract:
Life, since its inception, has evolved various transport mechanisms to acquire a
selected group of metals from the aquatic environment. These metals are
required to activate various enzymes and proteins. They cross biological
membranes either using specific transporter systems or by simple diffusion
when they are present as neutral species. As a result, the chemical speciation of
metals controls their biouptake. Other metals, with no known biological
functions, also utilize the same intake routes. The intake of toxic metals ends
up disrupting cell metabolism since they compete with metals that promote
biological processes.
These toxic metals are responsible for many environmental issues. Mercury,
however, occupies a very specific place within this group. Some
microorganisms, living in the anoxic or suboxic zones of aquatic systems, are
capable of methylating Hg2+to form one of the most potent neurotoxin known
to humans: mono-methyl mercury (CH3Hg+). This chemical species bioaccumulates significantly through aquatic trophic webs, leading to the highest
number of fish advisories in the US amongst all contaminants. For these
reasons, we are studying how the chemical speciation of Hg2+ controls its
biouptake. Our results show that previous paradigms used to predict the
bioavailability of metals, such as the free ion activity model, are not valid in the
case of Hg. In addition, we will present spectroscopic results that probe changes
in Hg coordination as a result of biouptake.