Extracellular Polymeric Substances Acting as a Permeable Barrier Hinder the Lateral Transfer of Antibiotic Resistance Genes

Abstract

Antibiotic resistance genes (ARGs) in bacteria are emerging contaminants as their proliferation in the environment poses significant threats to human health. It is well recognized that extracellular polymeric substances (EPS) can protect microorganisms against stress or damage from exogenous contaminants. However, it is not clear whether EPS could affect the lateral transfer of ARGs into bacteria, which is one of the major processes for the dissemination of ARGs. This study investigated the lateral transfer of ARGs carried by plasmids (pUC19, pHSG298, and pHSG396) into competent Escherichia coli cells with and without EPS. Transformant numbers and transformation efficiency for E. coli without EPS were up to 29 times of those with EPS at pH 7.0 in an aqueous system. The EPS removal further increased cell permeability in addition to the enhanced cell permeability by Ca 2+ , which could be responsible for the enhanced lateral transfer of ARGs. The fluorescence quenching experiments showed that EPS could strongly bind to plasmid DNA in the presence of Ca 2+ and the binding strength (Log K A = 10.65–15.80 L mol -1 ) between EPS and plasmids was positively correlated with the enhancement percentage of transformation efficiency resulting from the EPS removal. X-ray photoelectron spectroscopy (XPS) analyses and model computation further showed that Ca 2+ could electrostatically bind with EPS mainly through the carboxyl group, hydroxyl group, and RC-O-CR in glucoside, thus bridging the plasmid and EPS. As a result, the binding of plasmids with EPS hindered the lateral transfer of plasmid-borne ARGs. This study improved our understanding on the function of EPS in controlling the fate and transport of ARGs on the molecular and cellular scales.

Response of soil bacterial communities to sulfadiazine present in manure: Protection and adaptation mechanisms of extracellular polymeric substances

“…Owing to such a possible protective pathway, the bloom of ARGs did not occur, even when exposed to high concentrations of SDZ. On the other hand, a previous study showed that Ca 2+ could electrostatically bind with the function groups of EPS, consequently, the bridge between plasmids and EPS was established (Hu et al, 2019). This bond could impede the horizontal transfer of plasmid-borne ARGs into recipient cells (Hu et al, 2019).…”

Biofilms: Formation, drug resistance and alternatives to conventional approaches

“…Resistance and survival, even in adverse conditions, help microbes colonize in various implantable materials, such as dental implants and catheters [100] . Most organisms in a biofilm are protected by the EPS layers and are resistant to various antimicrobial drugs [79] , [117] , [118] . The glycocalyx can trap antibacterial drugs at their maximum capacity, reducing the effectiveness of the drugs against the organisms present in a biofilm as well as plays an antimicrobial role [30] , [118] .…”

The Antibiofilm Nanosystems for Improved Infection Inhibition of Microbes in Skin

“…The increased resistance to antimicrobial drugs or agents compared to planktonic cells is the emergent property of a biofilm. The biomass can be considered a fortress in which the antimicrobial tolerance and survival of desiccation form buttresses [58]. The EPS in a biofilm can quench the activity of antimicrobial agents that transfer into the biofilm in a form of suppression known as diffusion-reaction inhibition.…”