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Human parasite adapts in surprising ways

by CIFAR Jan 31 / 13

Infectious microorganisms find different, and sometimes surprising, ways to adapt to their environment. Understanding the root cause of their adaption can help scientists find better drug treatments to fight the changing nature of infectious diseases.

A light micrograph of the human intestinal parasite, Blastocystis. Image credit: Andrew Roger

A team of researchers, including Fellow Andrew Roger (Dalhousie University) and Associate Julius Lukeš (Czech Academy of Sciences), was amazed to find that one human intestinal parasite called Blastocystis picked up genes from bacteria, improving the parasite’s ability to survive in the human gut. The parasite acquired the genes through horizontal gene transfer, a process in which genetic material is transferred between distantly-related species.

The newly acquired genes create proteins that are beneficial to the parasite, but luckily, do not exist in human cells, and therefore, are potential candidates for drug therapies that could be developed to selectively target Blastocystis.

“Our findings were a direct result of an idea conceived at a CIFAR program meeting,” explains Dr. Roger. “I was sharing our preliminary results with the group and Julius suggested a unique way of performing genetic tests, initiating not only a fruitful collaboration, but also surprising results.”

The team’s initial findings were reported in the Proceedings of the National Academy of Sciences. In the study, the team used genetic testing to reveal that Blastocystis had a new version of a protein that makes iron-sulfur clusters, which are inserted into many essential proteins needed for cellular activities such as metabolism and DNA repair. They found that the gene that produced this protein was acquired from a group of single-celled microbes called Archaea. This finding led the team to further explore the nature of the parasite’s genome.

From these genome studies, Roger’s group identified a number of other genes in the parasite Blastocystis that were acquired from bacteria through horizontal gene transfer, possibly helping it to survive in the human gut. For instance, one particular gene they identified produces an enzyme that metabolizes toxic compounds called aldehydes that are produced during an immune reaction.

Another gene they discovered produces a protein that is believed to help Blastocystis regulate its intracellular pH to protect it from the acidic environment of the human gut, and another which makes a particular protein thought to be involved in drug resistance.