Curious Clinicians - Extremophiles (2025-2026)

Curious Clinicians - Extremophiles (2025-2026) is organized by VCU Health Continuing Education.

Thursday, November 20, 2025, 2:00 PM - Thursday, December 31, 2026, 11:59 PM

Description:
How does a bacterial species called Deinococcus radiodurans withstand extreme levels of radiation?

What comes to mind when we say tiny but mighty? Well, if Deinococcus radiodurans didn’t cross your mind, maybe it will earn your respect after this segment, so much so that it may come to mind the next time someone asks you that question. In our previous episode, “Wherefore Iodine?”, we learned about why iodine administration was a key public health intervention in Eastern Europe following the Chernobyl disaster. Then, in a follow-up episode, “The Mold that Eats Radiation for Breakfast”, we covered how various species of black radiation-eating fungi are not only surviving, but thriving within and around Chernobyl. In that episode, we discussed the concept of radioresistance, which refers to the degree to which an organism can withstand various levels of radiation exposure. And that brings us to this segment: how does the most radioresistant organism on the planet, a tiny bacterium called D. radiodurans, withstand extreme levels of radiation?

D. radiodurans is an extremophile, a term used to describe an organism that can live and even thrive in the most extreme environments. And as mentioned in a previous episode, bacteria are the most tolerant of environmental extremes among any form of life. The term “extremophile” was coined in 1974 by R.D. MacElroy, a scientist at NASA, when he described the microbes that exist in harsh environments that most forms of life cannot tolerate, such as extremes of temperature, pH, pressure, or radiation exposure. Fascinatingly, Koki Horikoshi and Alan Bull, in their book Extremophiles Handbook, note “definitions of extreme and extremophile are of course anthropocentric; from the point of view of the organism per se, its environment is that to which it is adapted and thence is completely normal.” In other words, what we humans view as extreme is entirely normal to an extremophile bacterium like D. radiodurans.

Objectives:

Upon completion of this activity, you will be able to:

1. Identify Deinococcus radiodurans as an example of an extremophile and explain characteristics that make it one of the most resilient known organisms.
2. Describe the mechanisms underlying the radioresilience of Deinococcus radiodurans by summarizing how genome organization, DNA-repair processes, and protection against radiation-induced protein oxidation contribute to its survival.
3. Explain how melanin contributes to fungal virulence by describing its role in protecting fungi from immune-mediated destruction.