title: Effects of Ultraviolet Radiation on the Gram-positive marine bacterium Microbacterium maritypicum.
abstract: Although extensive information is available on the effect ultraviolet (UV) radiation has on Gram-negative marine bacteria, there is a scarcity of data concerning UV radiation and Gram-positive marine bacteria. The focus of this paper is on Microbacterium maritypicum, with the Gram-negative Vibrio natriegens being used as a standard of comparison. M. maritypicum exhibited growth over a NaCl range of 0-1000 mM: , with optimum growth occurring between 0 and 400 mM: NaCl. In contrast, V. natriegens grew over a NaCl span of 250-1000 mM: , with best growth being observed between 250 and 600 mM: NaCl. UV radiation experiments were done using the medium with 250 mM: NaCl. For solar (UV-A and B) radiation and log-phase cells, M. maritypicum was determined to be three times more resistant than V. natriegens. For germicidal (UV-C) radiation, the pattern of resistance of the log-phase cells to the lethal effects of the radiation was even more pronounced, with the Gram-positive bacterium being more than 12 to 13 times more resistant. Similar data to the solar and germicidal log-phase UV kill curves were obtained for stationary-phase cells of both organisms. Photoreactivation was observed for both types of cells exposed to UV-C but none for cells treated with UV-A and B. When log phase cells of M.maritypicum were grown at 0.0 and 0.6 M: NaCl and exposed to UV-C radiation, no difference in survivorship patterns was noted from that of 0.25 M: NaCl grown cells. Although this study has only focused on two marine bacteria, our results indicate that the Gram-positive M. maritypicum could have a built-in advantage for survival in some marine ecosystems.
authors.affiliation: School of Biological Sciences, E-157 Beadle Center, University of Nebraska-Lincoln, Lincoln, NE 68588-0666, USA.
authors.forename: Patrick D
authors.initials: PD
authors.lastname: Williams
authors.forename: Shaundra L
authors.initials: SL
authors.lastname: Eichstadt
authors.forename: Tyler A
authors.initials: TA
authors.lastname: Kokjohn
authors.forename: Eugene L
authors.initials: EL
authors.lastname: Martin
mesh_terms: D000192:Actinomycetales / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D018533:Biomass; D015169:Colony Count, Microbial; D050296:Microbial Viability / Q000528:radiation effects*; D012965:Sodium Chloride / Q000378:metabolism; D014466:Ultraviolet Rays; D014733:Vibrio / Q000528:radiation effects
chemical_list: D012965:Sodium Chloride