Search

11 pages, 5 figures, 3 tables, The phylogenetic and functional diversity of the bacterioplankton assemblage associated with blooms of toxic Alexandrium spp. was studied in three harbours of the NW Mediterranean. Denaturing gradient gel electrophoresis and DNA sequence analysis revealed the presence of a bacterium within the Roseobacter clade related to the presence of Alexandrium cells. Phylogenetic diversity was affected by the presence of Alexandrium spp., geographic situation and seasonality. In contrast, functional diversity, assessed with Biolog plates, was clearly affected by seasonality, but not by the presence of Alexandrium, indicating that the presence of the bacterium associated with the blooms was not enough to modify the metabolic pattern of the bacterioplankton assemblage. © 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved, This work was supported by the projects BIOHAB (EVK3-CT99-00015), BASICS (EVK3-CT2002-00078) and PROCAVIR (CTM 2004-04404-C02-01/MAR) and by a post-doctoral contract from the Spanish Ministry of Science and Education to M.M.S.

14 pages, 6 figures, 3 tables, additional supporting information may be found in the online version of this article: http://onlinelibrary.wiley.com/doi/10.1111/j.1574-6941.2011.01247.x/suppinfo, The sensitivity of coastal marine bacterioplankton to natural photosynthetically active radiation (PAR, 400-700 nm) and ultraviolet radiation (UVR, 280-400 nm) was evaluated in five experiments over a seasonal cycle in the Blanes Bay, NW Mediterranean Sea. Exposure to natural solar radiation generally inhibited bulk bacterial activities or damaged membrane integrity when irradiances were high (i.e. spring and summer experiments) and, in general, UVB (280-320 nm) accounted for most of the inhibition. When assessing activity ( 3H-leucine uptake) at the single-cell level by microautoradiography and rRNA gene probing, seasonally varying responses and sensitivities were found among bacterial groups. While autumn and winter irradiances seemed too low to cause changes in activity, variable effects were found in spring and summer. SAR11 was consistently inhibited by UVR and PAR exposure, whereas Gammaproteobacteria and Bacteroidetes showed higher resistance. Roseobacter, Synechococcus and the NOR5 clade were occasionally photostimulated in their activity, mainly because of PAR. Our results indicate that a component of seasonality exists in the bacterial responses to solar radiation, which vary not only depending on the irradiance and the spectral characteristics, but also on the previous light history and the taxonomic composition of the community. © 2011 Federation of European Microbiological Societies, This work has been supported by the Spanish Ministry of Science and Innovation through projects ICARO (200830I120), MODIVUS (CTM2005-04795/MAR) and SUMMER (CTM2008-03309/MAR) and through a PhD scholarship to C. R.-G.