Escherichia
coli
bacteria -- those at the root of hard-to-treat urinary tract infections (UTIs)
-- hijack trace amounts of copper in the body and use it as a nutrient to fuel
growth. This finding suggests blocking this system may starve E. coli infections, opening the door to
treating UTIs using drugs that work differently from traditional antibiotics.
Copper is an essential mineral -- found in
shellfish, whole grains, nuts, beans and other foods. It can kill pathogens in
high concentrations. But it was unclear how E. coli handles copper ions present
in urine, an extremely complex medium containing many trace metals and other
compounds.
In past work studying strains of E. coli known to cause
difficult-to-treat UTIs, the researchers showed that a molecule called yersiniabactin
that is secreted by the bacteria sequesters copper, preventing it from
accumulating to antibacterial levels. But what it does with this bound copper
has been unknown.
While bacteria are known to bring iron -- another
essential mineral -- into the cell, the researchers noted that E. coli have long been thought to lack a
method to import copper. Indeed, scientists have assumed that yersiniabactin
only imports iron.
In the new study, the researchers showed that
yersiniabactin imports copper ions into the cell, where these charged particles
help trigger the many biochemical reactions that bacteria require to grow and
reproduce. The scientists further showed that once relieved of its mineral
cargo, yersiniabactin goes back outside the cell to mop up more copper. The
researchers dubbed this strategy "nutritional passivation." In
metallurgy, passivation refers to treating or coating metal to make it less
reactive.
The researchers also have shown that yersiniabactin
can bind to a variety of metals beyond copper and iron, including nickel,
cobalt and chromium.
See:
Posted by Dr. Tim Sandle
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