1 research outputs found
New Copper Resistance Determinants in the Extremophile <i>Acidithiobacillus ferrooxidans</i>: A Quantitative Proteomic Analysis
<i>Acidithiobacillus ferrooxidans</i> is an extremophilic
bacterium used in biomining processes to recover metals. The presence
in <i>A. ferrooxidans</i> ATCC 23270 of canonical copper
resistance determinants does not entirely explain the extremely high
copper concentrations this microorganism is able to stand, suggesting
the existence of other efficient copper resistance mechanisms. New
possible copper resistance determinants were searched by using 2D-PAGE,
real time PCR (qRT-PCR) and quantitative proteomics with isotope-coded
protein labeling (ICPL). A total of 594 proteins were identified of
which 120 had altered levels in cells grown in the presence of copper.
Of this group of proteins, 76 were up-regulated and 44 down-regulated.
The up-regulation of RND-type Cus systems and different RND-type efflux
pumps was observed in response to copper, suggesting that these proteins
may be involved in copper resistance. An overexpression of most of
the genes involved in histidine synthesis and several of those annotated
as encoding for cysteine production was observed in the presence of
copper, suggesting a possible direct role for these metal-binding
amino acids in detoxification. Furthermore, the up-regulation of putative
periplasmic disulfide isomerases was also seen in the presence of
copper, suggesting that they restore copper-damaged disulfide bonds
to allow cell survival. Finally, the down-regulation of the major
outer membrane porin and some ionic transporters was seen in <i>A</i>. <i>ferrooxidans</i> grown in the presence of
copper, indicating a general decrease in the influx of the metal and
other cations into the cell. Thus, <i>A</i>. <i>ferrooxidans</i> most likely uses additional copper resistance strategies in which
cell envelope proteins are key components. This knowledge will not
only help to understand the mechanism of copper resistance in this
extreme acidophile but may help also to select the best fit members
of the biomining community to attain more efficient industrial metal
leaching processes