Transition Metals and Organic Ligands Influence Biodegradation of 1,4-Dioxane
Peerapong Pornwongthong ∙ Anjali Mulchandani ∙ Phillip B. Gedalanga ∙ Shaily Mahendra
Department of Civil and Environmental Engineering, University of California Los Angeles
120
% Biodegradation Rate
100
80
60
40
20
0
Cd(II)
Cu(II)
Low
Medium
Ni(II)
Zn(II)
High
Figure S1. Effects of four different transition metals at three different concentrations on the rate
of 1,4-dioxane biodegradation by Pseudonocardia dioxanivorans CB1190. % Biodegradation
rate plotted on y-axis is biodegradation rate measured in the presence of metals normalized with
that established for metal-free positive controls. White columns, 1 mg/L transition metal; light
grey columns, 10 mg/L transition metal; dark grey column, 20 mg/L transition metal. Addition
of Cd(II) to 10 and 20 mg/L, Cu(II) at all tested concentrations, and Ni(II) at 10 and 20 mg/L
significantly affected 1,4-dioxane biodegradation rates. The error bars correspond to the range
of duplicate samples.
40
0
% 1,4-dioxane remaining
0
4
6
Time (day)
8
80
40
0
2
4
6
Time (day)
8
10
BSA
80
40
0
10
L-Cysteine
120
0
% 1,4-dioxane remaining
2
% 1,4-dioxane remaining
80
120
0
% 1,4-dioxane remaining
% 1,4-dioxane remaining
Alginic acid
120
2
4
6
Time (day)
8
10
SRNOM
120
80
40
0
0
2
4
6
Time (day)
8
10
Tannic acid
120
80
40
0
0
2
4
6
Time (day)
8
10
Figure S2. 1,4-Dioxane biodegradation by Pseudonocardia dioxanivorans CB1190 exposed to
2 mg/L Cu(II) concurrently with each of the five organic ligands. Low, medium and high
concentrations of the ligands are represented by circles, dash signs and X signs, respectively.
Diamonds represent abiotic control as negative control, squares represent cultures with addition
of 2 mg/L Cu(II) alone, and triangles represent metal-free control as positive control. Alginic
acid, L-cysteine and tannic acid were added at 0.005, 0.05 and 0.5 mM, whereas BSA and
SRNOM were added at 0.01, 0.1 and 1 mg/L. Only low concentrations of tannic acid, and
medium and high concentrations of L-cysteine were able to partially mitigate the inhibitory
effects of 2 mg/L Cu(II) on biodegradation activity. The error bars correspond to the range of
duplicate samples.
a
7.4
DXMO gene abundance
log10(copies/mL)
7.1
6.8
Metal Free
DXMO Gene Abundance
log10(copies/mL)
b
Cd(II)
Cu(II)
Ni(II)
Zn(II)
8
7
6
5
4
MLF
Alginic acid
Cu(II)
Cu(II)+Ligand
Tannic acid
Ligand
L-cysteine
Figure S3. Dioxane monooxygenase (DXMO) gene abundance in Pseudonocardia
dioxanivorans CB1190 cultures. (a) In the presence of 20 mg/L transition metals after 4 days
incubation, DXMO copy numbers followed the same order as 1,4-dioxane biodegradation rates,
i.e., Cu(II) < Cd(II) < Ni(II) < Zn(II). (b) Like 16S rRNA, DXMO copy numbers were lowest
for Cu(II)-exposed cells but generally increased when 0.005 mM tannic acid, 0.5 mM alginic
acid, and 0.5 mM L-cysteine were added together with 2mg/L Cu(II). This implies that organic
ligands decreased bioavailability and toxicity of Cu(II) resulting in enhanced bacterial growth.
MLF stands for metal/ligand-free controls.