title: A comparative cytotoxicity study of isomeric alkylphthalates to metabolically variant bacteria.
abstract: This work investigated the toxicity of two isomeric alkylphthalates, i.e., di-n-octyl phthalate (DOP) and di-2-ethylhexyl phthalate (DEHP) to two model bacteria, Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), which have been previously used to study the toxicity of environmental pollutants. Microcalorimetry was used as the key analytical tool alongside scanning electron microscopy (SEM) and traditional microbiology techniques. The thermokinetic parameters from microcalorimetry showed that the phthalates had a biphasic effect on the metabolic activities of the bacteria; serving as energy sources for the bacteria thereby stimulating their growth at low dosages (< or = 150 microg/mL), but displaying inhibitory effects at higher dosages (> or = 300 microg/mL), indicated by a sharp decrease in growth rate constants at 450 microg/mL. The SEM revealed that the bacterial cells were morphological deformed, with shrunk cells and elongated strands at 600 microg/mL of both phthalates. The elongated strands inferred that the phthalates inhibited the reproductive processes of the bacteria by possibly impeding some stages of cell division. The half inhibitory concentrations of the phthalates showed that DEHP was more toxic than DOP. Additionally, E. coli, a facultative anaerobe, was more susceptible to the toxic effects of phthalates than B. subtilis, an obligate aerobe capable of forming endospores crucial for tolerating extreme environmental conditions.
authors.affiliation: Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Sandy
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.forename: Shixue
authors.initials: S
authors.lastname: Zheng
authors.forename: Alhaji B
authors.initials: AB
authors.lastname: Gogra
authors.forename: Huilun
authors.initials: H
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Zheng
authors.forename: Thomas B R
authors.initials: TB
authors.lastname: Yormah
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Gyula
authors.initials: G
authors.lastname: Zaray
authors.forename: Brunello
authors.initials: B
authors.lastname: Ceccanti
authors.forename: Martin M F
authors.initials: MM
authors.lastname: Choi
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism*; D002151:Calorimetry / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism*; D007536:Isomerism; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D010795:Phthalic Acids / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*
chemical_list: D010795:Phthalic Acids