title: The influence of pH and external K+ concentration on caesium toxicity and accumulation in Escherichia coli and Bacillus subtilis.
abstract: Toxicity screening of Escherichia coli NCIB 9484 and Bacillus subtilis 007, NCIB 168 and NCIB 1650 has shown Cs+ to be the most toxic Group 1 metal cation. However, toxicity and accumulation of Cs+ by the bacteria was affected by two main external factors; pH and the presence of other monovalent cations, particularly K+. Over the pH range 6-9 both E. coli and B. subtilis showed increasing sensitivity towards caesium as the pH was raised. The presence of K+ and Na+ in the laboratory media used lowered caesium toxicity and lowered accumulation of the metal. In order to assess accurately Cs+ toxicity towards the bacterial strains it was therefore necessary to define the K+:Cs+ ratio in the external medium. The minimum inhibitory K+:Cs+ concentration ratio for the Bacillus strains tested was in the range 1:2-1:3 while E. coli had a minimum inhibitory K+:Cs+ concentration ratio of 1:6.
authors.affiliation: Department of Biological Sciences, University of Dundee, UK.
authors.forename: J
authors.initials: J
authors.lastname: Perkins
authors.forename: G M
authors.initials: GM
authors.lastname: Gadd
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D002254:Carbonates / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002586:Cesium / Q000378:metabolism* / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D012413:Rubidium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013431:Sulfates / Q000494:pharmacology
chemical_list: D002254:Carbonates; D013431:Sulfates; D002586:Cesium; D008094:Lithium; D012964:Sodium; D012413:Rubidium; D011188:Potassium