Roles of metal ions in regulating the formation of a drinking water odorant (2,3,6-trichloroanisole) by Sphingomonas ursincola in drinking water

Abstract Haloanisoles (HAs) produced by bacteria have become a nonnegligible taste and odor issue in drinking water. However, the effects of conventional water quality parameters, particularly for metal ions on bacterial HA formation, have rarely been studied. In this study, the effects of six metal ions (Ca2+, Mg2+, Fe3+, Cu2+, Zn2+ and Mn2+) on the formation of 2,3,6-trichloroanisole (2,3,6-TCA) by Shingomons ursincola Z001 (Z001), a typical HA-producing bacterial strain, were explored. The intracellular 2,3,6-TCA produced by Z001 accounted for 87%–96% of the total 2,3,6-TCA. It was found that 1.0–10 mM Ca2+, 1.0–10 mM Mg2+, 0.010 mM Fe3+ and 0.010 mM Zn2+ could promote Z001 to produce more 2,3,6-TCA, while 0.010–0.10 mM Mn2+, 0.010–1.0 mM Cu2+, 0.10 mM Fe3+ and 0.010–1.0 mM Zn2+ reduced 2,3,6-TCA production. The chlorophenol O-methyltransferase (CPOMT) is mainly located in the cytoplasm of Z001 cells. Cell extract experiments demonstrated that Ca2+ and Mg2+ were activators of CPOMT, while Fe3+, Zn2+, Cu2+ and Mn2+ were its inhibitors. Flow cytometry proved that Cu2+ could significantly damage the integrity of cell membrane, leading to the release of 2,3,6-TCA. In addition to CPOMT activity, Mg2+ and Zn2+ may also influence the processes of S-adenosylmethionine cycle. The Z001 cell wall may precipitate Zn2+ and Cu2+ to reduce their toxicities toward CPOMT. According to the obtained findings, strict controls of Ca2+, Mg2+, Fe3+ and Zn2+ during drinking water treatment were proposed to reduce HA contamination.