Performance and mechanism of tetracycline removal by the aerobic nitrate-reducing strain Pseudomonas sp. XS-18 with auto-aggregation

The coexistence of multiple pollutants has become a distinctive feature of water pollution. However, there are a few strains that can remove nitrate and tetracycline (TC). Here, the efficiency of strain XS-18 in removing nitrate and TC was analyzed, and the mechanism of tolerance and removal of TC was investigated by infrared spec-troscopy, three-dimensional fluorescence spectroscopy, and genome analysis. XS-18 could efficiently remove TC (0.40 mg.L-1.h(-1)) at pH 7.0-11.0 with auto-aggregation. TC was removed via extracellular polymeric substance (EPS) (55.90%) and cell surface (44.10%) adsorption. TC (10 mg/L) could stimulate XS-18 to secrete more polysaccharides and hydrophobic proteins to improve its auto-aggregation ability. The findings also confirmed that TC resistance genes were present. Furthermore, the bacterial flagellum, signal transduction of the chemo-tactic system and regulatory genes were shown to be related to the auto-aggregation of the strain. XS-18 has potential applications in the treatment of wastewater containing nitrate and TC.

Automated summary

The coexistence of multiple pollutants is a distinct feature of water pollution. This study analyzed the efficiency of strain XS-18 in removing nitrate and tetracycline (TC) and investigated the mechanism of TC tolerance and removal. The findings showed that XS-18 could efficiently remove TC through extracellular polymeric substance and cell surface adsorption, and its auto-aggregation ability could be improved by the secretion of polysaccharides and hydrophobic proteins stimulated by TC.