title: Toxic effects of linear alkylbenzene sulfonate on metabolic activity, growth rate, and microcolony formation of Nitrosomonas and Nitrosospira strains.
abstract: Strong inhibitory effects of the anionic surfactant linear alkylbenzene sulfonate (LAS) on four strains of autotrophic ammonia-oxidizing bacteria (AOB) are reported. Two Nitrosospira strains were considerably more sensitive to LAS than two Nitrosomonas strains were. Interestingly, the two Nitrosospira strains showed a weak capacity to remove LAS from the medium. This could not be attributed to adsorption or any other known physical or chemical process, suggesting that biodegradation of LAS took place. In each strain, the metabolic activity (50% effective concentration [EC(50)], 6 to 38 mg liter(-1)) was affected much less by LAS than the growth rate and viability (EC(50), 3 to 14 mg liter(-1)) were. However, at LAS levels that inhibited growth, metabolic activity took place only for 1 to 5 days, after which metabolic activity also ceased. The potential for adaptation to LAS exposure was investigated with Nitrosomonas europaea grown at a sublethal LAS level (10 mg liter(-1)); compared to control cells, preexposed cells showed severely affected cell functions (cessation of growth, loss of viability, and reduced NH(4)(+) oxidation activity), demonstrating that long-term incubation at sublethal LAS levels was also detrimental. Our data strongly suggest that AOB are more sensitive to LAS than most heterotrophic bacteria are, and we hypothesize that thermodynamic constraints make AOB more susceptible to surfactant-induced stress than heterotrophic bacteria are. We further suggest that AOB may comprise a sensitive indicator group which can be used to determine the impact of LAS on microbial communities.
authors.affiliation: Section of Genetics and Microbiology, Department of Ecology, Royal Veterinary and Agricultural University, Frederiksberg, Denmark. kkb@kvl.dk
authors.forename: K K
authors.initials: KK
authors.lastname: Brandt
authors.forename: M
authors.initials: M
authors.lastname: Hesselsøe
authors.forename: P
authors.initials: P
authors.lastname: Roslev
authors.forename: K
authors.initials: K
authors.lastname: Henriksen
authors.forename: J
authors.initials: J
authors.lastname: Sørensen
mesh_terms: D017738:Alkanesulfonic Acids / Q000633:toxicity*; D020562:Betaproteobacteria / Q000187:drug effects*; D015169:Colony Count, Microbial; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants; D009606:Nitrosomonas / Q000187:drug effects*; D012722:Sewage; D013045:Species Specificity; D013501:Surface-Active Agents / Q000633:toxicity*
chemical_list: D017738:Alkanesulfonic Acids; D004785:Environmental Pollutants; D012722:Sewage; D013501:Surface-Active Agents; C030641:alkylbenzyl sulfonic acid