UV-A Oxidative Damage Modified by Environmental Conditions inEscherichia Coli

Abstract

The effect of sublethal fluences (50-200 kJ m-2) of UV-A radiation (320-400 nm) in bacterial cells is a transient growth inhibition related to photo-modified tRNA and is associated with changes in membrane structure and function. Higher UV-A fluences result in cell death due to the production of reactive oxygen species, so far undetected at sublethal doses. Oxidative mechanisms of toxicity induced by 120 kJ m-2 UV-A radiation can be recorded by ultra-weak chemiluminescence, useful in quantifying oxidative reactions. When Escherichia coli was exposed to UV-A stress at a fluence rate equivalent to that of the Sun in the biosphere (33 W m-2), chemiluminescence levels were proportional to the photodamage. Chemiluminescence and photo-damage are linearly proportional and dependent on environmental conditions of the cells. It is postulated that in addition to tRNA photo-modification, UV-A alters the membrane structure of E. coli by oxidative damage, since changes in the membrane structure under different environmental conditions play a key role in the cell's response to UV-A injury.

Impact of UVA radiation on algae and bacteria in Baltic Sea ice

“…comm.) is one-third of the UVA fluence rate used for studying sublethal oxidative damage to Escherichia coli (Pizarro 1995), and thus it can be assumed that the possible direct effects of UVA were mainly sublethal. The relatively stable TBN in the PAR+UVA treatment also points to the sublethal role of UVA.…”

Functionally undefined gene, yggE, alleviates oxidative stress generated by monoamine oxidase in recombinant Escherichia coli

“…Two-dimensional gel electrophoresis revealed that heat shock induced the enhanced expression of certain antioxidant proteins in E. coli cells (VanBogelen et al 1987). Furthermore, damage caused by near-UV were largely O 2 -dependent, suggesting that reactive oxygen species and relevant proteins may be involved in such kind of damages (Pizarro 1995;Shennan et al 1996). At a first step, in the present work, real-time PCR analysis was conducted to examine the inductive response of yggE gene to the reported stimulation.…”

Role of the Quorum Sensing Mechanism in the Response of Pseudomonas aeruginosa to Lethal and Sublethal UVA Irradiation

“…This assumption was confirmed by monitoring the generation of active oxygen species during irradiation by the chemiluminescence method. The procedure was employed in the study of photon emission related to oxidative stress in microorganisms (37) and a very close relationship was found between the increase of chemiluminescence levels and the UVA‐induced damage in E. cloacae , P. aeruginosa and E. coli (7,38). Ultraweak chemiluminescence in the visible region has been attributed to photon emission by excited carbonyl groups and singlet O 2 dimers arising from the decomposition of membrane lipid peroxides (37), which in turn are associated with an increase in reactive oxygen species generated by UVA radiation (2).…”

“…In addition to the stringent response, previous studies have reported that oxidative disturbance of bacterial membranes induced by UVA exposure contributes to increase the UVA‐dependent growth delay in E. coli (38,56). According to results reported here, the QS system acts against oxidative damage in irradiated bacteria, and it could be proposed that the difference found in the extent of growth delay between the wild type PAO1 strain and rhlI mutants (PDO100 and PAO‐JP2 strains) at 36 kJ m −2 (Fig.…”