Deadly sex of mushrooms

Research at Tel Aviv University: sexual reproduction helps a dangerous fungus develop drug resistance

Candida albicans (Candida albicans) is a fungus that causes diseases, and is known to most of us from infections of the vagina, or of the oral cavity. However, in wounded and sick people whose immune systems are weakened, the fungus causes fatal infections - it is estimated that they cause the death of hundreds of thousands of people worldwide every year. If that's not enough, the fungus is also showing increasing resistance to drug treatments. A discovery by Israeli researchers may pave the way for a more effective fight against the fungus, thanks to a better understanding of its sex life. Until now, researchers knew that Candida reproduces only through simple cell division, where each cell is almost identical to the previous one. In each such cell, there are two copies of the genetic material, just like in human cells, which is why the cells are called diploid. Such reproduction is typical of relatively simple life forms, such as bacteria for example.

Single copy

In the new study, researchers from the Department of Molecular Microbiology and Biotechnology at Tel Aviv University discovered that under certain conditions the Candida fungus undergoes sexual reproduction. In this way of reproduction, instead of the diploid cells, cells containing only a single copy of the genetic material, called haploids, are formed. Biologically, they are similar to our sperm and egg cells, each of which has only one copy of the chromosomes (23 in humans, eight in the fungus) - and their union into one cell creates a new diploid cell. "We did not know about the existence of these cells in the fungus, and the discovery allows us to better understand how a variety of changes occur in the cells of the fungus, especially when it develops drug resistance," says Prof. Judit Berman, head of the research team. "In addition, discovering cells that have only one copy of the genetic material, allows researchers to work with the cells more easily, and to more efficiently develop drugs against the fungus."

Sexuality in times of distress

Researchers still do not know exactly what causes the fungus to switch from normal reproduction to sexual reproduction. In an article in the journal Nature, Berman and her colleagues from several research institutions in the US, Singapore and Taiwan present findings that one of the factors may be the fungus' distress, for example due to exposure to drugs. This strengthens the suspicion that this mechanism helps to increase drug resistance, and in the next step, the researchers intend to search the haploid cells for the genes responsible for the fungus's ability to deal with drugs, in an attempt to find substances that the fungus has difficulty dealing with, and which could serve as a basis for new drugs. "Unlike antibiotics, which act on bacteria, the fungal cell is relatively similar to human cells, and it is much more difficult to find substances that will only harm the fungus, without endangering healthy tissues," Berman explains.

The tumors of Berman and her colleagues may pave the way for a better understanding of the reproduction methods of other fungi that cause diseases. This issue is becoming more and more central in medicine with the proliferation of patients with weakened immune systems, such as cancer and AIDS patients, or organ transplant recipients.

Related links:
The research article in the journal Nature