Dr. Julie Pfeiffer will discuss the unexpected alliances she discovered between gut bacteria and intestinal viruses at the fall installment of the President’s Lecture Series, which will be held as a virtual event.

The lecture, titled “With a Little Help From Their Friends: How Bacteria Promote Virus Infection,” is scheduled at 4 p.m. Thursday, Oct. 29. The lecture can be viewed live at utsouthwestern.edu/pls.

Dr. Pfeiffer will describe where viruses originate and how they interact with their hosts, with an emphasis on how RNA viruses evolve. As a postdoctoral fellow at Stanford University, she showed that RNA viruses such as polio, Ebola, Zika, and influenza benefit from a sloppy replication strategy that leads to mutations.

“They are mutation-prone and constantly evolving, which make them a threat for emergence,” said Dr. Pfeiffer, Professor of Microbiology at UT Southwestern. RNA viruses, consisting of strands of RNA wrapped in a protein shell, cannot replicate on their own. They must get inside a host cell and hijack the cellular machinery in order to reproduce, a strategy many RNA viruses are breathtakingly good at following.

Before COVID-19 arose as a global priority, Dr. Pfeiffer had been specializing in the study of polio, a nearly eradicated RNA virus found in the intestinal tract.

“No one ever thought how bacteria in the gut would influence a viral infection because virologists tend to study viruses and bacteriologists tend to study bacteria and there is not a lot of crosstalk between the two (disciplines),” she said of her definitive Science paper in 2011.

What Dr. Pfeiffer found was that the bacteria that line the gut – so-called commensals – not only aid in digestion but also increase the infectivity of polio, an intestinal virus.

Meanwhile, microbiologists around the world were confirming and building on her discovery that intestinal bacteria and viruses could form alliances. Several intestinal viruses, in addition to polio, have now been shown to create similar symbiotic survival relationships. “Bacteria stabilize enteric (intestinal) viruses and we have done a lot of work in that realm,” Dr. Pfeiffer said, adding, “It’s too soon to see if that’s relevant for SARS-CoV-2 transmission. It’s just too soon to tell.”