title: Effect of chemical speciation on toxicity of mercury to Escherichia coli biofilms and planktonic cells.
abstract: While it is known that microbial uptake of mercury (Hg) by planktonic cultures is influenced by the extracellular speciation of mercury in aquatic systems, Hg uptake in biofilm cultures is understudied. We compared the importance of Hg(II) speciation in toxicity to both planktonic and biofilm cultures of the Gram-negative bacterium Escherichia coli 055. Variable chloride chemistry experiments were carried out to modify mercury speciation. Biofilms were observed to be more resistant to Hg than planktonic cells. In both planktonic and biofilm cultures, the toxicity of Hg increased and then decreased along the chloride gradient. The percent reduction in cell viability was linearly related to the concentration of HgCl2(0) when Hg-chloro complexes dominated the speciation, consistent with a passive diffusion model. However, toxicity to both planktonic cells and biofilms at low salinities could not be explained by passive diffusion alone, which suggests that microbial uptake of Hg in both planktonic cells and biofilms may occur by both passive diffusion of neutral species and facilitated uptake. The relationship between toxicity and chloride concentration was similar in the presence and absence of a biofilm, indicating that the presence of the biofilm does not drastically change the relative availability of the dominant mercury species.
authors.affiliation: Civil and Environmental Engineering Department, University of California-Los Angeles, 5732 H Boelter Hall, Los Angeles, California 90095-1593, USA.
authors.forename: Isaac
authors.initials: I
authors.lastname: Najera
authors.forename: Chu-Ching
authors.initials: CC
authors.lastname: Lin
authors.forename: Golenaz Adeli
authors.initials: GA
authors.lastname: Kohbodi
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Jay
mesh_terms: D018441:Biofilms; D004926:Escherichia coli / Q000254:growth & development; D008628:Mercury / Q000737:chemistry* / Q000493:pharmacokinetics / Q000633:toxicity*; D010933:Plankton; D012965:Sodium Chloride; D014867:Water / Q000737:chemistry; D014873:Water Pollutants / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D014873:Water Pollutants; D014867:Water; D012965:Sodium Chloride; D008628:Mercury