Journal
ENVIRONMENTAL POLLUTION
Volume 220, Issue -, Pages 112-123Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.envpol.2016.09.029
Keywords
Fluoroquinolone antibiotics; Biofilms; Alkali-earth metals; Bridging energy; Computational chemistry; Escherichia coli
Categories
Funding
- National Science Foundation of China [41401543, 41502170]
- National Science Foundation for Postdoctoral Scientists of China [2014M561662]
- Natural Science Foundation of Jiangsu Province of China [BK20140725]
- Fundamental Research Funds for the Central Universities [KJQN201518]
- Special Fund for Agro-Scientific Research in the Public Interest, China [201503107]
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Bacterially extracellular biofilms play a critical role in relieving toxicity of fluoroquinolone antibiotic (FQA) pollutants, yet it is unclear whether antibiotic attack may be defused by a bacterial one-two punch strategy associated with metal-reinforced detoxification efficiency. Our findings help to assign functions to specific structural features of biofilms, as they strongly imply a molecularly regulated mechanism by which freely accessed alkali-earth metals in natural waters affect the cellular uptake of FQAs at the water-biofilm interface. Specifically, formation of alkali-earth-metal (Ca2+ or Me2+) bridge between modeling ciprofloxacin and biofilms of Escherichia coli regulates the trans-biofilm transport rate of FQAs towards cells (135-nm-thick biofilm). As the addition of Ca2+ and Mg2+ (0-3.5 mmol/L, CIP: 1.25 mu mol/L), the transport rates were reduced to 52.4% and 63.0%, respectively. Computational chemistry analysis further demonstrated a deprotonated carboxyl in the tryptophan residues of biofilms acted as a major bridge site, of which one side is a metal and the other is a metal girder jointly connected to the carboxyl and carbonyl of a FQA. The bacterial growth rate depends on the bridging energy at anchoring site, which underlines the environmental importance of metal bridge formed in biofilm matrices in bacterially antibiotic resistance. (C) 2016 Elsevier Ltd. All rights reserved.
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