Affiliation:
1. Department of Biological and Ecological Engineering, Oregon State University, Corvallis, Oregon 97331
Abstract
ABSTRACT
Heavy metals have been shown to be strong inhibitors of nitrification in wastewater treatment plants. In this research, the effects of cadmium, copper, and mercury on
Nitrosomonas europaea
were studied in quasi-steady-state batch reactors. When cells were exposed to 1 μM CdCl
2
, 6 μM HgCl
2
, or 8 μM CuCl
2
, ammonia oxidation rates were decreased by about 90%. Whole-genome transcriptional and proteomic responses of
N. europaea
to cadmium were used to identify heavy metal stress response genes. When cells were exposed to 1 μM CdCl
2
for 1 h, 66 genes (of the total of 2,460 genes) were upregulated, and 50 genes were downregulated more than twofold. Of these, the mercury resistance genes (
merTPCADE
) averaged 277-fold upregulation under 1 μM CdCl
2
, with
merA
(mercuric reductase) showing 297-fold upregulation. In
N. europaea
cells exposed to 6 μM HgCl
2
or to 8 μM CuCl
2
,
merA
showed 250-fold and 1.7-fold upregulation, respectively. Cells showed the ability to recover quickly from Hg
2+
-related toxic effects, apparently associated with upregulation of the mercury resistance genes and
amoA
, but no such recovery was evident in Cd
2+
-exposed cells even though
merTPCADE
were highly upregulated. We suggest that the upregulation of
merA
in response to CdCl
2
and HgCl
2
exposure may provide a means to develop an early-warning indicator for inhibition of nitrification by these metals.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
55 articles.
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