Comparison of killing of gram-negative and gram-positive bacteria by pure singlet oxygen

Abstract

Gram-negative and gram-positive bacteria were found to display different sensitivities to pure singlet oxygen generated outside of cells. Killing curves for Salmonella typhimurium and Escherichia coli strains were indicative of multihit killing, whereas curves for Sarcina lutea, Staphylococcus aureus, Streptococcus lactis, and Streptococcus faecalis exhibited single-hit kinetics. The S. typhimurium deep rough strain TA1975, which lacks nearly all of the cell wall lipopolysaccharide coat and manifests concomitant enhancement of penetration by some exogenous substances, responded to singlet oxygen with initially faster inactivation than did the S. typhimurium wild-type strain, although the maximum rates of killing appeared to be quite similar. The structure of the cell wall thus plays an important role in susceptibility to singlet oxygen. The outer membrane-lipopolysaccharide portion of the gram-negative cell wall initially protects the bacteria from extracellular singlet oxygen, although it may also serve as a source for secondary reaction products which accentuate the rates of cell killing. S. typhimurium and E. coli strains lacking the cellular antioxidant, glutathione, showed no difference from strains containing glutathione in response to the toxic effects of singlet oxygen. Strains of Sarcina lutea and Staphylococcus aureus that contained carotenoids, however, were far more resistant to singlet oxygen lethality than were both carotenoidless mutants of the same species and other gram-positive species lacking high levels of protective carotenoids.

Escherichia coli γ-Glutamylcysteine Synthetase

“…Nevertheless, several studies comparing wild type bacteria to mutants that either lack or overexpress the enzymes of GSH biosynthesis suggest that GSH does have a role in bacterial defenses against many toxic insults including exposure to thiolreactive agents (7)(8)(9)(10)(11), methylglyoxal (7,8,12,13), certain oxidative (7,8,11) and nitrosative (14) stress molecules, x-rays (15,16), and some antibiotics (7). In contrast, other studies suggest bacterial GSH is not important in controlling toxicity from H 2 O 2 (17), tert-butyl hydroperoxide (18), redox-cycling agents such as paraquat (18), x-rays (7,17) or singlet O 2 (19). In several cases, the discrepancies among these reports remain unresolved in the literature (20).…”

Staphylococcus aureus Strain Newman Photoinactivation and Cellular Response to Sunlight Exposure

“…Alternatively, we hypothesize that the lack of membrane damage observed here may instead be due to the ROS-quenching ability of staphyloxanthin in the S. aureus cell membrane. Possibly, in the oxic system, ROS cause internal cellular damage rendering cells unculturable but are unable to significantly damage cellular membranes due to the presence of membrane-bound carotenoid pigments that quench any ROS generated near the cell membrane (42,47). In contrast, in the anoxic system, ROS production is reduced and sunlight energy may more significantly target the cell membrane (see Fig.…”

The hybrid methylene blue–zeolite system: a higher efficient photocatalyst for photoinactivation of pathogenic microorganisms

“…It is based on the presence of carotenoids, taking over the excitation from MB, thus lowering the concentration of 1 O 2 . This contributes to the inhibition effect of 1 O 2 on vital cells (Benabbou et al 2011;Dahl et al 1989). Higher resistance in C. albicans to killing by 1 O 2 is the result of presence of nuclear membrane, acting as additional barrier against penetration of 1 O 2 (Zeina et al 2001), or caused by cell size, these cells being 25-50 times larger than are cells of S. aureus and E. coli (Zeina et al 2001;Calzavara-Pinton et al 2005).…”