Abstract
Antibiotic resistance in bacteria is a significant public health concern. Some bacteria degrade penicillinderived antibiotics by expressing the enzyme beta-lactamase. This provides protection for the entire colony, creating an incentive for other bacteria to “cheat” by benefiting from the enzyme without incurring the resource costs associated with producing it. It may seem that this free-rider problem would prevent cooperation from arising within an evolutionary framework, but many instances have been described in nature. Previous research has shown that the expected outcome is a coexistence between cooperators and cheaters, with the group becoming increasingly susceptible to eradication as the fraction of cheaters increases. We are simulating this system using an Intraspecific Competitive Lotka-Volterra model and predicting the growth of normal and resistant bacteria under various initial populations and antibiotic concentrations. This reveals the critical points associated with colony collapse. The strongly non-linear nature of the equations leads to a pronounced Allee effect, in which the final population is very sensitive to the initial conditions. Thinking in terms of group selection at the colony level, “prosocial” behavior may be found to be evolutionarily adaptive, despite the fact that, at the individual level, invasion by cheaters is possible. Experimentally, we have genetically engineered bacteria to either express beta-lactamase internally (“cooperators”), or not (“cheaters”). The final ratio of cooperators to cheaters after being incubated for 12 hours depends on the initial ratio and the amount of antibiotic present. The results of this study may inform efforts to design antibiotic treatment regimens that minimize the risk of resistance.
Faculty Sponsors
Dr. Christopher A. Blanar, Dr. Robert Smith, Dr. Louis Nemzer
Project Type
Event
Location
Alvin Sherman Library
Start Date
4-8-2016 1:00 PM
End Date
4-8-2016 5:30 PM
Fighting Antibiotic Resistance by Encouraging Bacteria to Cheat
Alvin Sherman Library
Antibiotic resistance in bacteria is a significant public health concern. Some bacteria degrade penicillinderived antibiotics by expressing the enzyme beta-lactamase. This provides protection for the entire colony, creating an incentive for other bacteria to “cheat” by benefiting from the enzyme without incurring the resource costs associated with producing it. It may seem that this free-rider problem would prevent cooperation from arising within an evolutionary framework, but many instances have been described in nature. Previous research has shown that the expected outcome is a coexistence between cooperators and cheaters, with the group becoming increasingly susceptible to eradication as the fraction of cheaters increases. We are simulating this system using an Intraspecific Competitive Lotka-Volterra model and predicting the growth of normal and resistant bacteria under various initial populations and antibiotic concentrations. This reveals the critical points associated with colony collapse. The strongly non-linear nature of the equations leads to a pronounced Allee effect, in which the final population is very sensitive to the initial conditions. Thinking in terms of group selection at the colony level, “prosocial” behavior may be found to be evolutionarily adaptive, despite the fact that, at the individual level, invasion by cheaters is possible. Experimentally, we have genetically engineered bacteria to either express beta-lactamase internally (“cooperators”), or not (“cheaters”). The final ratio of cooperators to cheaters after being incubated for 12 hours depends on the initial ratio and the amount of antibiotic present. The results of this study may inform efforts to design antibiotic treatment regimens that minimize the risk of resistance.
