physical science
Using Bacterial Molecules to Kill Bacteria
Image by Sage Ross [CC-BY-SA 3.0]
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By Henry Bryant
he discovery of the first antibiotic — Penicillin — in 1928 was one of the greatest accidents to have happened in the medical field. Being able to treat bacterial infections has saved millions of lives. Now nearly 100 years after the discovery, medicine is faced with a new problem: antibiotic resistance. In the U.S. alone, over 2.8 million people get antibiotic-resistant infections, out of which 35,000 die every year.1 As antibiotics are used more frequently, the chance that antibiotic resistance develops increases. While reducing the overuse of antibiotics can significantly combat resistance, the resistance still has a low potential of occurring during each use. Antibiotic resistance occurs when all bacteria susceptible to an antibiotic are killed, leaving only naturally resistant bacteria. The resistant bacteria no longer have to compete for space and resources and therefore grow and multiply rapidly. The potential for antibiotic resistance does not mean that antibiotic use should be stopped to prevent resistance, but rather creates a perpetual need for new antibiotic discoveries. Dr. Bo Li, an associate professor in the chemistry department at UNC-Chapel Hill, investigates three aspects related to antibiotic discovery: natural products, antibiotic modes of action, and virulence factors (Figure 1). Natural products are bioactive molecules that are made by a living organism. Specifically, Dr.
Li researches potential antibiotics that are produced naturally by bacteria. His research seeks to understand why bacteria themselves would make antibiotics.Although seemingly counterintuitive, antibiotics are quite effective in helping bacteria Dr. Bo Li, PhD. both survive and thrive in complex environments. Bacteria make antibiotics naturally to compete with other types of bacteria for the limited resources, and the bacteria have developed protections against the antibiotics they produce so that they are unharmed. Within the study of natural product antibiotics, the Li Lab has two main objectives: to find out which natural products could potentially be used as antibiotics, then discover how the bacteria make these natural product molecules. The most common way to test a molecule for antibiotic properties is by testing its potential to prevent bacterial growth and then, measuring the minimum concentration of the molecule needed to prevent growth. Once a molecule has been identified as an antibiotic, the Li Lab uses a va-
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