G. Valduga et al., EFFECT OF EXTRACELLULARLY GENERATED SINGLET OXYGEN ON GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA, Journal of photochemistry and photobiology.B, Biology, 21(1), 1993, pp. 81-86
In the separated surface-sensitizer system, a photosensitizer is physi
cally separated from the substrate by a thin air layer under such cond
itions that only singlet oxygen can reach and oxidize the substrate, p
reventing the competition by type I photosensitized processes. This me
thod has been used to study the reaction of singlet oxygen with Gram-p
ositive (Streptococcus faecium) and Gram-negative (Escherichia coli) b
acterial strains. Studies on cell samples exposed to singlet oxygen fo
r different periods of time show a drastic decrease in survival for S.
faecium, while E. coli becomes sensitive only when the integrity of t
he outer membrane is altered by treatment with CaCl2 or roxymethyl)ami
nomethane-ethylenediaminetetraacetic acid (Tris-EDTA). Biochemical and
ultrastructural analyses suggest that the cytoplasmic membrane and th
e genetic material are the main sites damaged by singlet oxygen.