title: Sensitivity of Haloquadratum and Salinibacter to antibiotics and other inhibitors: implications for the assessment of the contribution of Archaea and Bacteria to heterotrophic activities in hypersaline environments.
abstract: Antibiotics and bile salts have been used to differentiate between heterotrophic activity of halophilic Archaea and Bacteria in saltern ponds. In NaCl-saturated brines of crystallizer ponds, most activity was attributed to Archaea. Following the recent isolation of Haloquadratum, the dominant archaeon in the salterns (reported to be sensitive to chloramphenicol and erythromycin), and the discovery of Salinibacter, a representative of the Bacteria, in the same ecosystem, reevaluation of the earlier data is required. The authors measured amino acid incorporation by Haloquadratum and Salinibacter suspended in crystallizer brine to investigate the suitability of antibiotics and bile salts to distinguish between archaeal and bacterial activities. The amino acid uptake rate per cell in Salinibacter was two orders of magnitude lower than that of Haloquadratum under the same conditions. Salinibacter was inhibited by chloramphenicol, erythromycin, and deoxycholate, but not by taurocholate. Erythromycin did not inhibit incorporation by Haloquadratum, but moderate inhibition was found by chloramphenicol at 10-50 microg mL(-1). Deoxycholate was highly inhibitory, but only partial inhibition was obtained in the presence of 25 microg mL(-1) taurocholate. Inhibition by chloramphenicol and taurocholate increased with increasing salt concentration. Erythromycin and taurocholate proved most valuable to differentiate between archaeal and bacterial activities in saltern brines.
authors.affiliation: Department of Plant and Environmental Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Rahel
authors.initials: R
authors.lastname: Elevi Bardavid
authors.forename: Aharon
authors.initials: A
authors.lastname: Oren
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D041963:Bacteroidetes / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D001647:Bile Acids and Salts / Q000494:pharmacology*; D002701:Chloramphenicol / Q000494:pharmacology; D017753:Ecosystem; D004917:Erythromycin / Q000494:pharmacology; D005618:Fresh Water / Q000382:microbiology*; D006216:Halobacteriaceae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D012965:Sodium Chloride; D013656:Taurocholic Acid / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D000900:Anti-Bacterial Agents; D001647:Bile Acids and Salts; D012965:Sodium Chloride; D013656:Taurocholic Acid; D004917:Erythromycin; D002701:Chloramphenicol