Photogeneration of singlet oxygen by humic substances: comparison of humic substances of aquatic and terrestrial origin

Abstract

The singlet oxygen (1(O2)) luminescence of 27 isolated humic substances (HS), natural organic matter, ultrafiltrates, and the synthetic fulvic acid HS1500 has been investigated by time-resolved spectroscopy in buffered D(2)O. The samples include both reverse osmosis isolates from lakes in Scandinavia, Canada, and Germany, and IHSS fulvic and humic acids of aquatic and terrestrial origin. The quantum yields of 1(O2) formation (PhiDelta) obtained on laser excitation at 480 nm ranged between 0.06 (HS1500) and 2.7%(fulvic acid from soil, IHSS). In our study, a general trend towards higher PhiDelta in terrestrial HS was observed. The comparison of reverse osmosis isolates from surface waters collected during fall 1999 and spring 2000 from five Scandinavian sites yielded, in all cases, higher PhiDelta for the spring samples. For the aquatic sampling sites Hietajarvi and Birkenes, PhiDelta even exceeded values of 0.6%, which were found to be typical for terrestrial or soil water material. Investigation of the excitation wavelength dependence of PhiDelta in the spectral range 355-550 nm yielded different spectral shapes for aquatic HS and "non-aquatic" HS, respectively. On the basis of these excitation spectra, 1(O2) production rates were calculated for eight representative HS.

Deletion of the Regulatory Subunit of Protein Kinase A in Aspergillus fumigatus Alters Morphology, Sensitivity to Oxidative Damage, andVirulence

“…Therefore, we sought to compare the susceptibility to environmental stress, specifically oxidative damage, of a mutant that lacked the regulatory subunit of PKA with that of the wild type and a complemented mutant. Since reactive oxygen species are known to be responsible for killing A. fumigatus conidia in alveolar macrophages and to be produced in composts, we reasoned that oxidative damage would be a biologically relevant stress for this opportunistic pathogen (33,35). We have used four different agents to cause the oxidative damage, since no one oxidant is representative of oxidative stress.…”

“…The adaptive responses that make A. fumigatus successful in one ecological niche may also be utilized when the organism finds itself in a different environment, that of the mammalian lung. Temperature shifts, wide variations in pH, and oxidizing agents may be common stressors within both environments (13,24,33,37). We have been interested in how A. fumigatus responds to various stresses and whether these responses may be involved in its pathogenicity, since the prevalence of A. fumigatus as a pathogen exceeds it prevalence in the air (17).…”

“…In order to survive in this niche, A. fumigatus must compete with many other microbes in the compost environment, sensing various forms of stress and nutrient deprivation and mounting an effective response (24,33,37). The adaptive responses that make A. fumigatus successful in one ecological niche may also be utilized when the organism finds itself in a different environment, that of the mammalian lung.…”

“…In nature, the fungus plays a key role in the compost cycle by recycling carbon and nitrogen from plant material (24, 42). In this environment, A. fumigatus is likely to be exposed to broad fluctuations in pH, temperatures up to 50°C, and reactive oxygen species (24,33,45). These stressors are not unlike the kinds of factors an organism might encounter in vivo (13).…”

Processos de tratamento não convencionais para degradação do antibiótico sulfadiazina em meio aquoso.

“…Estes ácidos absorvem radiação UV-vis com comprimento de onda superior a 300 nm, dando origem a espécies reativas como oxigênio singlete e radicais hidroxila, responsáveis pela transformação de muitos poluentes orgânicos em meio aquoso (VAUGHAN e BLOUGH, 1998;PAUL et al, 2004).…”