Bacterial Dynamics in a Microphytobenthic Biofilm: a Tidal Mesocosm Approach

Type Article
Date 2014-09
Language English
Author(s) Agogue Helene1, Mallet Clarisse2, Orvain Francis3, de Crignis Margot1, 3, Mornet Francoise4, Dupuy Christine1
Affiliation(s) 1 : Univ La Rochelle, UMR CNRS Lab LIENSs 7266, F-17000 La Rochelle, France.
2 : Univ Clermont Ferrand, UMR CNRS 6023, Lab Microorganismes Genome & Environm, F-63177 Aubiere, France.
3 : Univ Caen Basse Normandie, BioMEA CNRS FRE3484, F-14032 Caen, France.
4 : IFREMER, Lab Ressources Halieut La Rochelle, Stn La Rochelle, F-17137 Lhoumeau, France.
Source Journal Of Sea Research (1385-1101) (Elsevier Science Bv), 2014-09 , Vol. 92 , P. 36-45
DOI 10.1016/j.seares.2014.03.003
WOS© Times Cited 18
Keyword(s) Muddy sediment, Microphytobenthos, Bacteria, Extracellular polymeric substances, Interactions, Mesocosm
Abstract In intertidal mudflats, during low tide exposure, microphytobenthos (MPB) migrate vertically through the surface sediment and form, with the heterotrophic bacteria, a transient biofilm. Inside this biofilm, multiple interactions exist between MPB and bacteria. These micro-organisms secrete a wide range of extracellular polymeric substances (EPS), which are major components of the biofilm matrix. In this study, we used a tidal mesocosm experiment in order to decipher the interactions of the MPB-EPS-bacteria complex within the biofilm. We tried to determine if the EPS could control bacterial activities and/or production and/or richness according to the age of the biofilm and to the immersion/emersion period. The dynamics of biomasses of MPB and prokaryotes, the bacterial production, the hydrolysis of predominating organic constituents in the dissolved organic carbon (DOC) pool (i.e., carbohydrates and polypeptides), and the bacterial structure were studied in relation to the different EPS fractions (carbohydrates and proteins: colloidal and bound) dynamics during 8 days. Our experiment had emphasized the influence of the environmental conditions (light, immersion/emersion) on the interactions within the biofilm and also on the effects on biofilm ageing. Bacterial production was always inhibited by the bound EPS-carbohydrate, especially during low tide. Our results suggest that the concentration and composition of EPS had a major role in the bacterial/MPB interactions: these interactions can be either positive or negative in order to regulate the productive phases of MPB and bacteria.
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