Effect of EDTA on Salmonella enterica serovar Typhimurium involves a component not assignable to lipopolysaccharide release

1 VTT Biotechnology, PO Box 1500, FIN-02044 VTT, Espoo, Finland 2 Department of Applied Chemistry and Microbiology, Division of Microbiology, University of Helsinki, PO Box 56, FIN-00014 University of Helsinki, Finland Correspondence H.-L. Alakomi Hanna-Leena.Alakomi{at}vtt.fi The effect of EDTA on Salmonella enterica serovar Typhimurium was studied in different growth phases with cells grown with or without Ca 2+ and Mg 2+ supplementation. EDTA affected the outer membrane much more strongly in the early exponential phase than in the mid- or late exponential phase, as indicated by uptake of 1- N -phenylnaphthylamine (a nonpolar hydrophobic probe, M r 219), and detergent (SDS) susceptibility. This effect was, however, not paralleled by LPS release (determined by measuring LPS-specific fatty acids or 14 C-labelled LPS in cell-free supernatants, per a standardized cell density), which remained unchanged as a function of the growth curve. The conclusion from these results is that in the early exponential phase the effect of EDTA in S. enterica involves a component that is independent of LPS release. Abbreviations: KDO, 3-deoxy- D - manno -octulosonic acid; NPN, 1- N -phenylnaphthylamine; OM, outer membrane