Friday, 10 November 2017

Aggressive UTI bacteria hijack copper


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:

Eun-Ik Koh, Anne E Robinson, Nilantha Bandara, Buck E Rogers, Jeffrey P Henderson. Copper import in Escherichia coli by the yersiniabactin metallophore systemNature Chemical Biology, 2017; DOI: 10.1038/nchembio.2441

Posted by Dr. Tim Sandle