.

1. 0
10
20
30
40
50
60
70
80
0 10 20 30 40 50 60 70 80
ng/LMeHg
Minutes
Cysteine
No Cysteine
-Cys
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 10 20 30 40 50 60 70 80
%ofTotalHgascellularHg
Minutes
Cys
No Cys
Effects of Cysteine on Mercury Methylation by Ethanoligenes harbinense
Ewelina Gwiszcz1, Sarah Janssen2 & Jeffra Schaefer2
1 Bloustein School of Public Health 2 Department of Environmental Sciences, Rutgers University
Mercury (Hg) is a toxic metal that is abundant in
the environment as several forms and several
microorganisms have the ability to methylate
inorganic mercury transforming it into
methylmercury (MeHg). The MeHg produced is
a potent neurotoxin, and more dangerous to
humans and ecosystems than inorganic mercury,
because of its ability to bioaccumulate up the
food chain (Fig. 1.).
INTRODUCTION
METHODS
All experiments and culturing of Ethanoligenes were performed under anaerobic
conditions . Washed cell assays were performed with and without the presence of
cysteine (10 mM), in addition inorganic mercury (10-50nM was added to the
cultures to observe methylation. All analyses for MeHg were performed via
distillation and analysis using a Tekran 2700 (Fig 2). Filtration experiments were
also performed to examine the extent of inorganic Hg attached to the cell . All
analyses for total Hg were performed using a tin reduction step and a Brooks
Rand MERX-T detector (Fig 3).
RESULTS
CONCLUSION
REFERENCES
Figure 5: Methylmercury measured in ng/L
produced by E. harbinense over a time course in
washed cell conditions.
 0.14% of Hg added methylated in 30 minutes.
After 30 minutes, no further methylation.
Figure 6: Effects of Cysteine on Methylation
Cystiene increases methylation in Ethanoligenes
when compared to the absence of a thiol.
2.0%- 3.5% of Hg was methylated in the presence of
cysteine at 5x lower mercury concentrations (Fig. 5).
 Methylation rates were near complete in the first
five minutes of methylation in the presence of cysteine.
Figure 7: Mercury Associated with Cells
Calculated from filtered and unfiltered samples
 More than 99.5% of the total Hg is not associated
with the cells, but remains in the dissolved phase.
 The percentage of cellular Hg in the presence of
cysteine begins at a low concentration and increases,
while the cellular Hg without cysteine stays fairly
constant.
 Data suggests that at a higher concentration of
Hg may inhibit methylation by Ethanoligenes
harbinense
Very little Hg is bioavailable to Ethanoligenes
harbinense , whether bound to cysteine or
chlorides
Very little Hg was associated with
Ethanoligenes harbinense , unlike Gram negative
Proteobacteria, which can bind 30% to 90% of
the Hg, depending on strain and conditions.
Figure 1:
Bioaccumulation of
Mercury
Figure 4: Tekran 2700 Figure 5: Brooks Rand MERX-T
Methylation of inorganic Hg is prominently
caused by sulfate, iron reducing, and
methanogenic bacteria, which are found in
anaerobic sediment, soil, and water
columns. Although a majority of testing for
methylation has been done in the group
Delta-Proteobacteria, MeHg production has
also been recently confirmed in Firmicutes
(Fig 2-Gilmour et al. 2013.)
Figure 2: MeHg Production in Different Species
Figure 3:Ethanoligenes harbinense
One of the discovered
species was E. harbinense
(Fig 3). This organisms is a
low pH anaerobic
fermenter. This firmicute
was shown to produce
MeHg under growth
conditions.
RESULTS
0
2
4
6
8
10
12
14
16
0 0.5 1 1.5 2 2.5 3
ng/LMeHg
Hours
Chen, C.Y., C.T. Driscoll, K.F. Lambert, R.P. Mason, L.R. Rardin, C.V. Schmitt, N.S. Serrell, and E.M.
Sunderland. 2012. Sources to Seafood: Mercury Pollution in the Marine Environment. Hanover, NH: Toxic
Metals Superfund Research Program, Dartmouth College.
Gilmour, Cynthia C., Mircea Podar, Allyson L. Bullock, Andrew M. Graham, Steven D. Brown, Anil C.
Somenahally, Alex Johs, Richard A. Hurt, Jr., Kathryn L. Bailey, and Dwayne A. Elias. "Mercury Methylation by
Novel Microorganisms from New Environments." Environmental Science and Technology 47 (2013): 11810-
1820. Web.
Schaefer, Jeffra K., and François M. M. Morel. "High Methylation Rates of Mercury Bound to Cysteine by
Geobacter Sulfurreducens." Nature Geoscience 2.2 (2009): 123-26. Web.
Xing, D. "Ethanoligenens Harbinense Gen. Nov., Sp. Nov., Isolated from Molasses Wastewater." International
Journal Of Systematic And Evolutionary Microbiology 56.4 (2006): 755-60. Web.
+Cys +Cys
+C
+Cys
-Cys
10,000 ng/L Hg
2000 ng/L Hg
2000 ng/L Hg