Comptes rendus de l'Académie des sciences, Série III, Sciences de la vie, 1997-04, Vol.320 (4), p.339-347
1997
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- Autor(en) / Beteiligte
- Titel
- Natural isotopic composition of heterotrophic bacteria to determine the origin of bioavailable dissolved organic carbon
- Ist Teil von
- Comptes rendus de l'Académie des sciences, Série III, Sciences de la vie, 1997-04, Vol.320 (4), p.339-347
- Erscheinungsjahr
- 1997
- Quelle
- Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
- Beschreibungen/Notizen
- Several studies of salt marsh systems have attempted to quantify the flow of organic matter between the land and coastal waters. However, the techniques used could not identify sources of dissolved organic carbon (DOC) rapidly assimilated by heterotrophic bacteria. Recently, the assay of carbon isotope ratios has allowed characterization of the different sources of organic matter in salt marshes. In this study, we wanted to find out if the natural isotopic composition assayed in heterotrophic bacteria distinguished the origin of bioavailable DOC. We determined the delta super(13)C values 1) three bacterial strains and their nucleic acids cultured on glucose and tryptose substrates, respectively, and 2) naturally occurring bacteria recovered from seawater in which salt marsh vegetation had been immersed. First, we showed that the isotopic fractionation was the same for the three bacterial strains cultured on the same synthetic substrate, but could vary depending on the nature of DOC. There was no significant difference between the delta super(13)C values of bacteria and their nucleic acids. Second, natural bacteria were grown in a medium enriched in DOC from halophytic plants. The delta super(13)C values of this community were close to those of dissolved organic carbon from plant leachates. The comparison between the isotopic ratios of natural bacteria in Vibrio alginolyticus showed that the heterogeneity of the bacterial community averaged the isotopic fractionation from the preferential assimilation of organic compounds in the medium by each bacterial strain. The delta super(13)C values recorded for the bacterial community in the field and their nucleic acids made it possible to identify the source of organic matter readily accessible to microorganisms in a coastal ecosystem.