Treatment of Pseudomonas aeruginosa with metal ion chelators, especial
ly ethylenediaminetetraacetic acid (EDTA), causes both release of prot
ein-lipopolysaccharide complexes and cell death. We have examined the
effect of EDTA on P. aeruginosa and found that EDTA does not induce th
e rapid solubilization of the peptidoglycan sacculus and complete lysi
s as previously thought; the decrease in optical density of cultures i
ncubated with EDTA is primarily due to the loss of the outer membrane.
Of the other potential solubilizers examined, only ethylene-bis(oxyet
hylenenitrilo)tetraacetic acid (EGTA) resulted in some decrease in opt
ical density. The lytic effect of EDTA on 12 strains of P. aeruginosa
was examined and was found to vary greatly between strains; the sensit
ivity to EDTA varies from between 96% and 10% of the decrease in optic
al density resulting from incubation of cells with both EDTA and lysoz
yme. Sensitivity to EDTA is not constant during the growth of P. aerug
inosa; in the early exponential phase of growth, cells treated with ED
TA exhibit a 82% decrease in optical density after 30 min while in the
stationary phase the optical density decreases by only 40%. Nucleic a
cids were observed to leak from cells following treatment with EDTA an
d this was greatly facilitated by DNase and RNase. The release of gene
tic material was much reduced when cells were incubated at 4 degrees C
, supporting an enzymatic role in cell wall solubilization. We propose
that only small areas of the sacculus become hydrolysed via specific
peptidoglycan hydrolases, or autolysin(s), which are activated or de-r
egulated by EDTA.