Sublethal streptomycin concentrations and lytic bacteriophage together promote resistance evolution

Area of Science:

• Microbial Ecology
• Evolutionary Biology
• Environmental Microbiology

Background:

• Sub-minimum inhibitory concentrations (sub-MICs) of antibiotics are prevalent in the environment due to human activities.
• These low antibiotic levels can drive bacterial adaptation, promoting antibiotic resistance and accelerating evolution.
• The impact of sub-MICs on crucial ecological interactions, like bacteria-phage dynamics, remains understudied.

Purpose of the Study:

• To investigate how sub-MICs of streptomycin affect bacteria-phage interactions.
• To determine if sub-MICs alter the rate of phage resistance evolution.
• To examine the combined effects of sub-MICs and phages on the evolution of antibiotic resistance.

Main Methods:

• Experimental evolution of bacterial populations exposed to sub-MIC streptomycin (Sm) and/or a specific phage.
• Quantification of phage resistance evolution rates.
• Assessment of phage population dynamics and bacterial Sm resistance evolution.

Main Results:

• Sub-MICs of streptomycin significantly increased the rate of phage resistance evolution.
• Exposure to sub-MIC streptomycin led to the extinction of the phage population.
• The combination of sub-MIC streptomycin and phage enhanced the evolution of streptomycin resistance in bacteria compared to streptomycin alone.

Conclusions:

• Sub-MIC antibiotics can profoundly alter key microbial ecological interactions, leading to unexpected evolutionary outcomes.
• These findings highlight the critical role of low-level antibiotic pollution in shaping microbial community evolution and the spread of antibiotic resistance.
• Understanding these ecological and evolutionary dynamics is essential for effective antibiotic resistance management strategies.