A study of microbial populations under a prolonged period of starvation by Indiana University Professor Jay T. Lennon and his laboratory could help researchers answer questions pertaining to chronic infections, the functioning of bacteria in the environment and the persistence of life itself.
In a paper published online Aug. 12 by the Proceedings of the National Academy of Sciences of the United States of America, Lennon and his colleagues explain their study of about 100 populations of different bacteria in closed systems, which had no access to external food for 1,000 days. The team tracked how long they survived, and almost all of them persisted.
"The larger question of how bacteria survive long periods of energy limitation is relevant to understanding chronic infections in humans and other hosts, and is related to how some pathogens tolerate drugs like antibiotics," said Lennon, a professor in the Department of Biology in the College of Arts and Sciences at IU Bloomington.
Many bacterial infections are difficult to treat, in part, because drugs are often designed to target the cellular machinery of metabolically active cells. Energy-limited bacteria often enter a quiescent, or dormant, state that makes them less sensitive to drug treatments, Lennon said. Not only can the pathogens persist under such conditions, the populations can also evolve antibiotic resistance, making the problem worse.
Microbes also play an important role in the environment. The bacteria in the study came from agricultural soils. In those habitats, Lennon said, microbes form symbiotic relationships with plants, and they carry out processes that are essential for the functioning of ecosystems, such as carbon sequestration, nutrient cycling and greenhouse gas emissions.
A major and unresolved question is how billions of microbial cells and thousands of microbial taxa coexist in a single gram of soil, often under harsh environmental conditions. One explanation supported by the research is that microbes seem to be well-adapted to feast-or-famine conditions, where resources can be in short supply for extended periods. This may help explain how complex microbial communities are maintained over time.