Plasma, the fourth state of matter, is created by introducing a gas - in this case, helium - to an electric field. This field ionizes the helium atoms, which in turn ionize other molecules, creating a wide variety of highly reactive species. Previous work at Edmonds Community College demonstrated the efficacy of an atmospheric pressure plasma jet (APPJ) in killing endospores of Bacillus atrophaeus for the purpose of spacecraft sterilization for NASA (Bernard et al., 2017). With increasing rates of antibiotic resistance, there is interest in using an APPJ in healthcare settings to eliminate harmful pathogens and therefore promote wound healing. However, given its destruction of endospores, it is unclear if the APPJ would damage living tissue. The purpose of this research was to analyze the effect of an APPJ on multicellular eukaryotic organisms. The impact of different exposure times of the APPJ upon both germinated and ungerminated Zinnia elegans seeds, and the effects on plant growth, was studied. The optimal exposure time for germinated seeds was between one and two minutes, while treatments greater than 2 minutes may increase germination rate.

The purpose of this study was to explore the interrelationship between two major DNA repair systems--photoreactivation, with blue light as an energy source, and excision repair, which uses ATP as an energy source--of Chlamydomonas reinhardtii, a single-celled algae, by studying the in vivo efficiency of photoreactivation when the excision repair system was suppressed. Working with a mutant which was completely lacking in excision repair, we found that this strain was also deficient in photoreactivation, as compared to wild-type, at low levels of post-UV visible light treatment, measured by killing on plates. We hypothesized that the level of light intensity might have an impact on the efficiency of the photoreactivating enzyme. Using alkaline agarose gel electrophoresis analysis, we quantitatively evaluated the extent of repair of DNA damage over 24 hours under two different light intensities. We found less damage removal in the mutant under low light intensity, suggesting that a positive correlation does indeed exist between the flux of visible light used in our experiments and the amount of photoreactivation for the mutant. This correlation was not observed in the wildtype. Our work is interesting in the context of human-caused changes to Earth’s atmosphere; both photoreactivation and excision repair of DNA damage are present in virtually all organisms studied, including bacteria, fungi, plants and most animals (although not in placental mammals). With the weakening of the stratospheric ozone layer, there is the possibility of increasing solar UV flux to the surface of Earth, with possible negative downstream effects on biological systems. Understanding the functional relationship between these two DNA repair systems could provide information of fundamental importance to ecological and agricultural problems arising from increased solar UV flux to Earth.