title: The effect of triclosan on microbial community structure in three soils.
abstract: The application of sewage sludge to land can expose soils to a range of associated chemical toxicants. In this paper we explore the effects of the broad spectrum anti-microbial compound triclosan on the phenotypic composition of the microbial communities of three soils of contrasting texture (loamy sand, sandy loam and clay) using phospholipid fatty-acid (PLFA) analysis. Each soil type was dosed and subsequently re-dosed 6 weeks later with triclosan at five nominal concentrations in microcosms (10, 100, 500, 1000 mg kg(-1) and a zero-dose control). PLFA profiles were analysed using multivariate statistics focussing on changes in the soil phenotypic community structure. Additionally, ratios of fungal:bacterial PLFA indicators and cyclo:mono-unsaturated PLFAs (a common stress indicator) were calculated. It was hypothesised that triclosan addition would alter the community structure in each soil with a particular effect on the fungal:bacterial ratio, since bacteria are likely to be more susceptible to triclosan than fungi. It was also hypothesised that the PLFA response to re-dosing would be suppressed due to acclimation. Although the microbial community structure changed over the course of the experiment, the response was complex. Soil type and time emerged as the most important explanatory factors. Principal component analysis was used to detect phenotypic responses to different doses of triclosan in each soil. As expected, there was a significant increase in the fungal:bacterial ratio with triclosan dose especially in treatments with the highest nominal concentrations. Furthermore, the PLFA response to re-dosing was negligible in all soils confirming the acclimation hypothesis.
authors.affiliation: Department of Environmental Science and Technology, School of Applied Sciences, Cranfield University, College Road, Cranfield, Bedfordshire MK43 0AL, UK.
authors.forename: E
authors.initials: E
authors.lastname: Butler
authors.forename: M J
authors.initials: MJ
authors.lastname: Whelan
authors.forename: K
authors.initials: K
authors.lastname: Ritz
authors.forename: R
authors.initials: R
authors.lastname: Sakrabani
authors.forename: R
authors.initials: R
authors.lastname: van Egmond
mesh_terms: D000704:Analysis of Variance; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D005227:Fatty Acids / Q000032:analysis; D005658:Fungi / Q000187:drug effects* / Q000254:growth & development; D010743:Phospholipids / Q000737:chemistry; D025341:Principal Component Analysis; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000494:pharmacology*; D014260:Triclosan / Q000494:pharmacology*
chemical_list: D005227:Fatty Acids; D010743:Phospholipids; D012987:Soil; D012989:Soil Pollutants; D014260:Triclosan