How TB bacteria use iron to survive

Introduction

The tuberculosis (TB) bacteria kill two people every three minutes. The bacteria uses iron from the human body to survive. But the mechanism by which they source the iron was not known. Researchers from the University of Hyderabad have recently cracked the mechanism. Their research paves the way for new medicines to treat the disease better.

The tb pathogen sources its iron through molecules called siderophores, which have high affinity for iron. First, the pathogens release these molecules, which extracts iron from human cells, leaving them iron-scarce. The molecules are then transported back to the pathogen, which synthesizes the iron to sustain and grow at the cost of the host. These actions are dependent on two proteins that help complete the transportation cycle of siderophores. Blocking this transportation through medicines can be a breakthrough to cure tb.

First, it will stop the iron uptake and secretion. Since there will be no export pathway for siderophores, it will extract iron from the microbe itself.

"A proper pool of iron needs to be maintained because low or even high concentration of iron is harmful to the cell," says Aisha Farhana, the lead author of the study published in the May 7 issue of PLoS One. The other concern, she says, is that anaemia is often an offshoot of tb. This is because iron is a major component of blood.

According to K K Chopra of the New Delhi Tuberculosis Centre, "Till now, the anti- tb drugs that we have been using target protein uptake, not iron uptake. If developed and compared with a placebo, the drug might be more effective than the currently available drugs." Treatment at present involves a combination of drugs introduced in India in 1997, according to who recommendations. Also, who surveys in 1997 and 2007 found that multi-drug resistance tb strains were present in 63 of the 72 countries surveyed.

Source

Down to Earth, 30 June 2008