Diversity at the Bacterial Scale
Gastrointestinal surgeon John Alverdy sees the benefits of diversity every day—in the laboratory, in the disease presentations of his patients, and in the department of surgery.
Alverdy is investigating the ways that bacterial diversity in the intestine improves the body’s natural defenses. “You harbor a diverse microbial community,” he says. “The more heterogeneous those germs are, the more resilient the community is as a whole.” In other words, a patient whose gut is home to a wide variety of bacteria is more likely to have an immune system that will ward off invasion by toxic bacteria that cause severe infection.
“Bacteria even behave in social groups similar to humans,” Alverdy explains. “They sense changes in their environments and synchronize their behavior by spreading signals through communication pathways and sensory receptors.” Maintaining diversity in our intestinal microbial communities ensures that they will always behave to protect the good of the whole group and the host upon which their survival depends. When diversity is lost and highly opportunistic bacteria prevail, such as during extreme medical interventions and multiple antibiotic use, pathogens (harmful bacteria) can gain foothold and cause infection and sepsis. Studies now show that the single most important predictor of recovery from severe infection, trauma, and burn injury is maintaining this gut microbial diversity.
About 250,000 Americans die of severe sepsis every year, Alverdy says, and the crisis is getting worse as resistance to antibiotics grows stronger. Rather than prevent such serious infections by adding powerful antibiotic prophylactically, Alverdy has discovered another way to maintain microbial détente: create a resource-rich environment so that microbial diversity is maintained and opportunists cannot thrive. The approach has enormous potential to decrease the mortality rate of hospitalized patients who develop secondary infections. Work by the Alverdy lab, funded through the NIH, focuses on a novel polymer-based compound that delivers such goods to microbes, allowing for this response to bloom and thrive.
Alverdy believes diversity has a similar positive effect in other contexts—including the University of Chicago Medicine. “One might argue that the more diverse a department is, the more likely it is to be strong and productive,” he says. Alverdy frequently works on complex surgeries in which every member of the team votes on the most appropriate course of treatment. “There’s a strong biological basis to this,” he explains, “which is that each member both constrains and strengthens the thinking of the group.” The decision-making process is far more valuable when the people in the room represent different perspectives and approaches. “Diversity helps the group self-regulate to do the best thing for the patient, and this in turn strengthens the group as a whole.”
