title: Effect of solar UV-B radiation on a phyllosphere bacterial community.
abstract: The effect of solar UV-B radiation on the population dynamics and composition of the culturable bacterial community from peanut (Arachis hypogeae L.) was examined in field studies using plants grown under UV-B-transmitting (UV-B+) or UV-B-excluding (UV-B-) plastic filters. Our data demonstrate that solar UV-B selection alters phyllosphere bacterial community composition and that UV tolerance is a prevalent phenotype late in the season. The total bacterial population size was not affected by either UV-B treatment. However, isolates from the UV-B+ plots (n = 368) were significantly more UV tolerant than those from the UV-B- (n = 363) plots. UV sensitivity was determined as the minimal inhibitory dose of UV that resulted in an inhibition of growth compared to the growth of a nonirradiated control. The difference in minimal inhibitory doses among bacterial isolates from UV-B+ and UV-B- treatments was mainly partitioned among nonpigmented isolates, with pigmented isolates as a group being characterized as UV tolerant. A large increase in UV tolerance was observed within isolate groups collected late (89 and 96 days after planting) in the season. Identification of 200 late-season isolates indicated that the predominant UV-tolerant members of this group were Bacillus coagulans, Clavibacter michiganensis, and Curtobacterium flaccumfaciens. We selected C. michiganensis as a model UV-tolerant epiphyte to study if cell survival on UV-irradiated peanut leaves was increased relative to UV survival in vitro. The results showed an enhancement in the survival of C. michiganensis G7.1, especially following high UV-C doses (300 and 375 J m(-2)), that was evident between 24 and 96 h after inoculation. A dramatic increase in the in planta/in vitro survival ratio was observed over the entire 96-h experiment period for C. michiganensis T5.1.
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843-2132, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Jacobs
authors.forename: G W
authors.initials: GW
authors.lastname: Sundin
mesh_terms: D010367:Arachis / Q000254:growth & development / Q000382:microbiology* / Q000528:radiation effects; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification / Q000528:radiation effects*; D015169:Colony Count, Microbial; D017753:Ecosystem; D010860:Pigments, Biological; D018515:Plant Leaves / Q000254:growth & development / Q000382:microbiology* / Q000528:radiation effects; D011836:Radiation Tolerance; D012621:Seasons; D014466:Ultraviolet Rays
chemical_list: D010860:Pigments, Biological