Thrush fungus may mate when the going gets tough - Microbiology Today: November 2004 issue

26 October 2004

Fungi that infect man do not easily learn to become resistant to antifungal drugs. However, antifungal resistance sometimes arises and, according to an article in the November 2004 issue of Microbiology Today, the quarterly magazine of the Society for General Microbiology, new studies suggest that when one important fungal pathogen does so, it can rearrange its genetic makeup to favour mating and other changes that could accelerate its evolution.

A few strains of Candida albicans, the agent that causes thrush and sometimes more serious disease in the immunocompromised, have developed resistance to antifungal treatments. However, with fungi the problem of resistance is much less serious - at least so far - than with the well known 'superbug' bacteria.

"The main difference is that fungi can't spread the genes for antifungal resistance between strains in the same way that bacteria can," explains Professor Frank Odds from the University of Aberdeen. "This means that when a fungus becomes resistant to a drug it normally does so within just one patient and the resistant strain doesn't get passed on to others."

However, new research has shed light on the phenomenon of resistance in Candida that rapidly reached high levels when HIV infection was itself untreatable, but has since fallen back. "We are entering a fascinating phase of research in which data are emerging to suggest that Candida albicans - an organism that normally doesn't indulge in sex - may start trying to mate or otherwise reassort its genes in response to the pressure of antifungal drugs," says Professor Odds. "The clinical problem of antifungal resistance may not yet be great, but what we have learned about the mechanisms for resistance development in Candida albicans show us we cannot afford to be complacent and assume nothing will ever change."

Microbiologists confront evolution in action on a daily basis in their work. Microbes resistant to antimicrobial agents have emerged through mutation or by acquiring protective genes from other microbes. Gene swapping or genetic reassortment allows viruses to stay one step ahead of the immune system. Natural selection lets individuals within a microbial community adapt and survive in a new environment or experiment.

Other features in the November 2004 issue of Microbiology Today include:
· Microbial evolution in action (page 158)
· Bacterial populations adapt - genetically, by natural selection - even in the lab! (page 160)
· RNA viruses - evolution in action (page 163)
· Catabolic plasmids: fast-track bacterial evolution to combat pollution (page 168)
· Serial endosymbiotic theory (SET) and composite individuality (page 172)

These are just some of the articles that appear, together with all the regular features and reports of Society activities.

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