CO₂ promotes the conjugative transfer of multiresistance genes by facilitating cellular contact and plasmid transfer

Area of Science:

• Environmental microbiology
• Molecular biology
• Public health

Background:

• Antibiotic resistance genes (ARGs) spread through plasmid-mediated conjugation, posing a global health threat.
• Anthropogenic carbon dioxide (CO2) emissions are increasing, with implications for environmental processes.
• The impact of elevated CO2 on ARG dissemination remains largely unexplored.

Purpose of the Study:

• To investigate the effect of increased CO2 on the conjugative transfer of ARGs.
• To elucidate the underlying mechanisms by which CO2 influences plasmid transfer.
• To assess the potential risks of elevated CO2 on ARG propagation.

Main Methods:

• Conjugative transfer experiments using plasmid RP4 under varying CO2 concentrations.
• Analysis of bacterial cell surface properties (hydrophobicity, charge).
• Gene expression analysis of key regulatory and transfer genes.
• Measurement of intracellular calcium levels and transmembrane potential.

Main Results:

• CO2 enhanced ARG transfer by 2.4-9.0 fold within genera and 1.3-3.8 fold across genera.
• CO2 increased cell surface hydrophobicity and decreased surface charge, reducing repulsion.
• CO2 modulated the expression of genes involved in plasmid transfer and mating pair formation.
• CO2 induced Ca2+ release and increased recipient cell transmembrane potential, boosting proton motive force (PMF) for DNA uptake.

Conclusions:

• Elevated CO2 levels significantly facilitate the spread of antibiotic resistance genes through plasmid conjugation.
• CO2 influences bacterial cell properties and gene expression to promote plasmid transfer.
• This study reveals a novel environmental risk of anthropogenic CO2 emissions and storage concerning ARG propagation.