Response of Freshwater Biofilms to Antibiotic Florfenicol and Ofloxacin Stress: Role of Extracellular Polymeric Substances.

Chaoqian Wang,Liwen Zhang,Zhiyong Guo,Xiuyi Hua,Ziwei Song,Deming Dong

doi:10.3390/ijerph16050715

Chaoqian Wang, Liwen Zhang + Show 4 more

Open Access

https://doi.org/10.3390/ijerph16050715

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Abstract

Antibiotic residues have been detected in aquatic environments worldwide. Biofilms are one of the most successful life forms, and as a result are ubiquitous in natural waters. However, the response mechanism of freshwater biofilms to the stress of various antibiotic residues is still unclear. Here, the stress of veterinary antibiotic florfenicol (FF) and fluoroquinolone antibiotic ofloxacin (OFL) on freshwater biofilms were investigated by determining the changes in the key physicochemical and biological properties of the biofilms. The results showed that the chlorophyll a content in biofilms firstly decreased to 46–71% and then recovered to original content under the stress of FF and OFL with high, mid, and low concentrations. Meanwhile, the activities of antioxidant enzymes, including superoxide dismutase and catalase, increased between 1.3–6.7 times their initial values. FF was more toxic to the biofilms than OFL. The distribution coefficients of FF and OFL binding in extracellular polymeric substances (EPS)-free biofilms were 3.2 and 6.5 times higher than those in intact biofilms, respectively. It indicated that EPS could inhibit the FF and OFL accumulation in biofilm cells. The present study shows that the EPS matrix, as the house of freshwater biofilms, is the primary barrier that resists the stress from antibiotic residues.

Highlights

The ecological risk of antibiotics in the aquatic environment has attracted widespread concerns due to their wide production, use, and discharge
Results showed that chlorophyll a content in biofilms firstly decreased to 46–71%, and recovered to original content under the stress of FF and OFL
The extracellular polymeric substances (EPS) content increased between 1.1–1.9 times their initial values, and the activities of superoxide dismutase (SOD) and CAT increased between 1.3–6.7 times their initial values under the stress of FF and OFL

Summary

Introduction

The ecological risk of antibiotics in the aquatic environment has attracted widespread concerns due to their wide production, use, and discharge. Florfenicol (FF) and ofloxacin (OFL) are chloramphenicol and fluoroquinolone antibiotics, respectively. Their consumption were 10,000 tons and 5110 tons in China in. Due to their relatively high consumption, discharge, and persistence, FF and OFL have been widely detected in various aquatic compartments [5,6]. Previous studies have demonstrated that the accumulation of FF and OFL residues in waters could cause direct toxicity to algae [7,8]

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