title: Dynamic of bacterial communities attached to lightened phytodetritus.
abstract: The effects of singlet oxygen ((1)O2) transfer to bacteria attached on phytodetritus were investigated under laboratory-controlled conditions. For this purpose, a nonaxenic culture of Emiliania huxleyi in late stationary phase was studied for bacterial viability. Our results indicated that only 9 ± 3% of attached bacteria were alive compared to 46 ± 23% for free bacteria in the E. huxleyi culture. Apparently, under conditions of low irradiance (36 W m(-2)), during the culture, the cumulative dose received (22,000 kJ m(-2)) was sufficiently important to induce an efficient (1)O2 transfer to attached bacteria during the senescence of E. huxleyi cells. At this stage, attached bacteria appeared to be dominated by pigmented bacteria (Maribacter, Roseobacter, Roseovarius), which should resist to (1)O2 stress probably due to their high contents of carotenoids. After subsequent irradiation of the culture until fully photodegradation of chlorophyll, DGGE analyses showed that the diversity of bacteria attached to E. huxleyi cells is modified by light. Photooxidative alterations of bacteria were confirmed by the increasing amounts of cis-vaccenic photoproducts (bacterial marker) per bacteria observed during irradiation time. Interestingly, preliminary chemotaxis experiments showed that Shewanella oneidensis considered here as a model of motile bacteria was attracted by phytodetritus producing or not (1)O2. This lack of repulsive effects could explain the high mortality rate of bacteria measured on E. huxleyi cells.
authors: Aix-Marseille Université, Mediterranean Institute of Oceanography (MIO), Université du Sud Toulon-Var, 83957, CNRS-INSU/IRD UM 110, 13288, Marseille, Cedex 9, France.
authors: Morgan
authors: M
authors: Petit
authors: Patricia
authors: P
authors: Bonin
authors: Rémi
authors: R
authors: Amiraux
authors: Valérie
authors: V
authors: Michotey
authors: Sophie
authors: S
authors: Guasco
authors: Joshua
authors: J
authors: Armitano
authors: Cécile
authors: C
authors: Jourlin-Castelli
authors: Frédéric
authors: F
authors: Vaultier
authors: Vincent
authors: V
authors: Méjean
authors: Jean-François
authors: JF
authors: Rontani
mesh_terms: D001422:Bacterial Adhesion; D002633:Chemotaxis; D058087:Haptophyta / Q000382:microbiology*; D008027:Light; D050296:Microbial Viability; D010782:Photolysis; D011836:Radiation Tolerance; D020592:Shewanella / Q000502:physiology* / Q000528:radiation effects; D026082:Singlet Oxygen / Q000502:physiology
chemical_list: D026082:Singlet Oxygen