title: The effects of ultraviolet radiation on the moderate halophile Halomonas elongata and the extreme halophile Halobacterium salinarum.
abstract: Both the moderately halophilic bacterium, Halomonas elongata, and the extremely halophilic archaea, Halobacterium salinarum, can be found in hypersaline environments (e.g., salterns). On complex media, H. elongata grows over a salt range of 0.05-5.2 M, whereas, H. salinarum multiplies over a salt range of 2.5-5.2 M. The purpose of this study was to illustrate the effect that solar (UV-A and UV-B) and germicidal radiation (UV-C) had on the growth patterns of these bacteria at varied salt concentrations. Halomonas elongata grown on a complex medium at 0.05, 1.37, and 4.3 M NaCl was found to be more sensitive to UV-A and UV-B radiation, as the salt concentration of the medium increased. Halobacterium salinarum grown on a complex medium at 3.0 and 4.3 M NaCl did not show a significant drop in viability after 39.3 kJ.m-2 of UV-A and UV-B exposure. When exposed to UV-C, H. elongata exhibited substantially more sensitivity than H. salinarum. In H. elongata, differential sensitivity to UV-C was observed. At 0.05 M NaCl, H. elongata was less sensitive to UV-C than at 1.37 and 4.3 M NaCl. Both bacteria showed some photoreactivation when incubated under visible light following both UV-A, UV-B, and UV-C exposure. Mutagenesis following UV-C exposure was demonstrated by both organisms.
authors.affiliation: School of Biological Sciences, University of Nebraska, Lincoln 68588, USA. emartin1@unl.edu
authors.forename: E L
authors.initials: EL
authors.lastname: Martin
authors.forename: R L
authors.initials: RL
authors.lastname: Reinhardt
authors.forename: L L
authors.initials: LL
authors.lastname: Baum
authors.forename: M R
authors.initials: MR
authors.lastname: Becker
authors.forename: J J
authors.initials: JJ
authors.lastname: Shaffer
authors.forename: T A
authors.initials: TA
authors.lastname: Kokjohn
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004260:DNA Repair; D004352:Drug Resistance, Microbial; D019617:Halobacterium salinarum / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D020632:Halomonas / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects*; D016296:Mutagenesis; D009675:Novobiocin / Q000494:pharmacology; D012293:Rifampin / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents; D009675:Novobiocin; D012965:Sodium Chloride; D012293:Rifampin