Papers in the Biological Sciences
Date of this Version
2013
Citation
Microbiology (2013), 159, 1198–1208
Abstract
Crenarchaeota include extremely thermoacidophilic organisms that thrive in geothermal
environments dominated by sulfidic ores and heavy metals such as mercury. Mercuric ion, Hg(II),
inactivates transcription in the crenarchaeote Sulfolobus solfataricus and simultaneously
derepresses transcription of a resistance operon, merHAI, through interaction with the MerR
transcription factor. While mercuric reductase (MerA) is required for metal resistance, the role of
MerH, an adjacent small and predicted product of an ORF, has not been explored. Inactivation of
MerH either by nonsense mutation or by in-frame deletion diminished Hg(II) resistance of mutant
cells. Promoter mapping studies indicated that Hg(II) sensitivity of the merH nonsense mutant
arose through transcriptional polarity, and its metal resistance was restored partially by single
copy merH complementation. Since MerH was not required in vitro for MerA-catalysed Hg(II)
reduction, MerH may play an alternative role in metal resistance. Inductively coupled plasma-mass
spectrometry analysis of the MerH deletion strain following metal challenge indicated that there
was prolonged retention of intracellular Hg(II). Finally, a reduced rate of mer operon induction in
the merH deletion mutant suggested that the requirement for MerH could result from metal
trafficking to the MerR transcription factor.
Comments
Copyright 2013 SGM