title: Specific ion effects on the growth rates of Staphylococcus aureus and Pseudomonas aeruginosa.
abstract: Motivated by recent advances in the physical and chemical basis of the Hofmeister effect, we measured the rate cell growth of S. aureus--a halophilic pathogenic bacterium--and of P. aeruginosa, an opportunistic pathogen, in the presence of different aqueous salt solutions at different concentrations (0.2, 0.6 and 0.9 M). Microorganism growth rates depend strongly on the kind of anion in the growth medium. In the case of S. aureus, chloride provides a favorable growth medium, while both kosmotropes (water structure makers) and chaotropes (water structure breakers) reduce the microorganism growth. In the case of P. aeruginosa, all ions affect adversely the bacterial survival. In both cases, the trends parallel the specific ion, or Hofmeister, sequences observed in a wide range of physico-chemical systems. The correspondence with specific ion effect obtained in other studies, on the activities of a DNA restriction enzyme, of horseradish peroxidase, and of Lipase A (Aspergillus niger) is particularly striking. This work provides compelling evidence for Hofmeister effects, physical chemistry in action, in these organisms.
authors.affiliation: Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3-50019 Sesto Fiorentino (Firenze), Italy. pln@csgi.unifi.it
authors.forename: Pierandrea
authors.initials: P
authors.lastname: Lo Nostro
authors.forename: Barry W
authors.initials: BW
authors.lastname: Ninham
authors.forename: Antonella
authors.initials: A
authors.lastname: Lo Nostro
authors.forename: Giovanna
authors.initials: G
authors.lastname: Pesavento
authors.forename: Laura
authors.initials: L
authors.lastname: Fratoni
authors.forename: Piero
authors.initials: P
authors.lastname: Baglioni
mesh_terms: D000327:Adsorption; D018407:Bacterial Physiological Phenomena; D001703:Biophysics / Q000379:methods*; D004247:DNA / Q000378:metabolism; D004262:DNA Restriction Enzymes / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial; D007477:Ions; D008954:Models, Biological; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000502:physiology*; D012492:Salts / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000502:physiology*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D007477:Ions; D012492:Salts; D014867:Water; D004247:DNA; D004262:DNA Restriction Enzymes