Antibiotics promote aggregation within aquatic bacterial communities

Area of Science:

• Environmental microbiology
• Aquatic ecosystems
• Antibiotic resistance

Background:

• Antibiotic release into the environment threatens human health via resistant bacteria.
• Low-dose antibiotic use in healthcare and farming leads to significant environmental presence.
• Impacts of antibiotics on bacterial community composition, productivity, and resistance evolution are poorly understood.

Purpose of the Study:

• To investigate the response of a freshwater bacterial community to low and high doses of antibiotics.
• To explore microbial community adaptation mechanisms beyond individual resistance genes.
• To understand the phenotypic changes in bacterial communities under antibiotic stress.

Main Methods:

• A chemostat-based experiment was conducted using four coexisting bacterial strains.
• The experiment mimicked freshwater bacterial community responses to varying antibiotic concentrations.
• Bacterial abundance, community composition, and phenotypic adaptations like co-aggregation were analyzed.

Main Results:

• Bacterial abundance decreased by 75% in the presence of antibiotics, regardless of dose.
• Isolated strains showed no antibiotic resistance, but reassembled communities from stressed treatments performed better.
• Antibiotic presence significantly increased bacterial co-aggregation by 5-6 fold.

Conclusions:

• Co-aggregation emerged as a novel phenotypic strategy for antibiotic resistance in aquatic bacterial communities.
• This study highlights the importance of studying community-level responses to environmental stressors.
• Findings contribute to understanding the ecological effects of antibiotics in aquatic ecosystems.