Abstract
The evolutionary origin of the broadly distributed mer system, which plays an important role in mercury detoxification and biogeochemistry, is presently unknown. The phylum Deinococcus/Thermus was found to be one of the deepest-branching bacterial lineage to have a homolog of merA, which specifies reduction of ionic to elemental mercury, and the mercuric reductase (MerA) of Thermus thermophilus HB27 was found to be basal to all bacterial MerA when this protein's phylogeny was constructed. A merA mutant of HB27 was fourfolds more sensitive to mercury toxicity than the wild type (wt), and lost detectable MerA-specific activities. The merA gene in HB27 was transcribed on a polycistronic message downstream from ORF encoding for homologs of O-acetyl-l-homoserine/O-acetyl-serine (OAH/OAS) sulfhydrylase and MerR, the mer operon transcription regulator, from a promoter located 69 nucleotides upstream of the sulfhydrylase translation start codon. The transcription of the putative mer operon in HB27 was induced 66.8±15.8-fold by exposure to 1 μM HgCl2. The optimal temperature for MerA-specific activity corresponded to this strain's optimal growth temperature, 70 °C. Thus, T. thermophilus is the earliest mercury-resistant bacterium identified to date, a finding consistent with the hypothesis that the mer system originated among thermophilic microorganisms from geothermal environments.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 118-129 |
| Number of pages | 12 |
| Journal | FEMS microbiology ecology |
| Volume | 67 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 1 2009 |
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All Science Journal Classification (ASJC) codes
- Microbiology
- Ecology
- Applied Microbiology and Biotechnology
Keywords
- Induction
- Mercuric reductase
- Mercury resistance
- Thermus thermophilus
- Transcription
Cite this
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An initial characterization of the mercury resistance (mer) system of the thermophilic bacterium Thermus thermophilus HB27. / Wang, Yanping; Freedman, Zachary; Lu-Irving, Patricia; Kaletsky, Rachel; Barkay, Tamar.
In: FEMS microbiology ecology, Vol. 67, No. 1, 01.01.2009, p. 118-129.Research output: Contribution to journal › Article
TY - JOUR
T1 - An initial characterization of the mercury resistance (mer) system of the thermophilic bacterium Thermus thermophilus HB27
AU - Wang, Yanping
AU - Freedman, Zachary
AU - Lu-Irving, Patricia
AU - Kaletsky, Rachel
AU - Barkay, Tamar
PY - 2009/1/1
Y1 - 2009/1/1
N2 - The evolutionary origin of the broadly distributed mer system, which plays an important role in mercury detoxification and biogeochemistry, is presently unknown. The phylum Deinococcus/Thermus was found to be one of the deepest-branching bacterial lineage to have a homolog of merA, which specifies reduction of ionic to elemental mercury, and the mercuric reductase (MerA) of Thermus thermophilus HB27 was found to be basal to all bacterial MerA when this protein's phylogeny was constructed. A merA mutant of HB27 was fourfolds more sensitive to mercury toxicity than the wild type (wt), and lost detectable MerA-specific activities. The merA gene in HB27 was transcribed on a polycistronic message downstream from ORF encoding for homologs of O-acetyl-l-homoserine/O-acetyl-serine (OAH/OAS) sulfhydrylase and MerR, the mer operon transcription regulator, from a promoter located 69 nucleotides upstream of the sulfhydrylase translation start codon. The transcription of the putative mer operon in HB27 was induced 66.8±15.8-fold by exposure to 1 μM HgCl2. The optimal temperature for MerA-specific activity corresponded to this strain's optimal growth temperature, 70 °C. Thus, T. thermophilus is the earliest mercury-resistant bacterium identified to date, a finding consistent with the hypothesis that the mer system originated among thermophilic microorganisms from geothermal environments.
AB - The evolutionary origin of the broadly distributed mer system, which plays an important role in mercury detoxification and biogeochemistry, is presently unknown. The phylum Deinococcus/Thermus was found to be one of the deepest-branching bacterial lineage to have a homolog of merA, which specifies reduction of ionic to elemental mercury, and the mercuric reductase (MerA) of Thermus thermophilus HB27 was found to be basal to all bacterial MerA when this protein's phylogeny was constructed. A merA mutant of HB27 was fourfolds more sensitive to mercury toxicity than the wild type (wt), and lost detectable MerA-specific activities. The merA gene in HB27 was transcribed on a polycistronic message downstream from ORF encoding for homologs of O-acetyl-l-homoserine/O-acetyl-serine (OAH/OAS) sulfhydrylase and MerR, the mer operon transcription regulator, from a promoter located 69 nucleotides upstream of the sulfhydrylase translation start codon. The transcription of the putative mer operon in HB27 was induced 66.8±15.8-fold by exposure to 1 μM HgCl2. The optimal temperature for MerA-specific activity corresponded to this strain's optimal growth temperature, 70 °C. Thus, T. thermophilus is the earliest mercury-resistant bacterium identified to date, a finding consistent with the hypothesis that the mer system originated among thermophilic microorganisms from geothermal environments.
KW - Induction
KW - Mercuric reductase
KW - Mercury resistance
KW - Thermus thermophilus
KW - Transcription
UR - http://www.scopus.com/inward/record.url?scp=57449098649&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=57449098649&partnerID=8YFLogxK
U2 - 10.1111/j.1574-6941.2008.00603.x
DO - 10.1111/j.1574-6941.2008.00603.x
M3 - Article
C2 - 19120462
AN - SCOPUS:57449098649
VL - 67
SP - 118
EP - 129
JO - FEMS Microbiology Ecology
JF - FEMS Microbiology Ecology
SN - 0168-6496
IS - 1
ER -