SREL Reprint #2814




Flow-Cytometric Cell Sorting and Subsequent Molecular Analyses for Culture-Independent Identification of Bacterioplankton Involved in Dimethylsulfoniopropionate Transformations

Xiaozhen Mou,1 Mary Ann Moran1, Ramunas Stepanauskas2, Jose M. Gonzalez3, and Robert E. Hodson1

1Department of Marine Sciences, University of Georgia, Athens, Georgia
2Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina
3Departamento de Microbiologia y Biologia Celular, Facultad de Farmacia, Universidad de La Laguna,
La Laguna, Tenerife, Spain

Abstract: Marine bacterioplankton transform dimethylsulfoniopropionate (DMSP) into the biogeochemically important and climatically active gas dimethyl sulfide. In order to identify specific bacterial taxa mediating DMSP processing in a natural marine ecosystem, we amended water samples from a southeastern U.S. salt marsh with 20 µM DMSP and tracked community shifts with flow cytometry (FCM) coupled to 16S rRNA gene analyses. In two out of four seasons studied, DMSP amendments induced the formation of distinct bacterioplankton populations with elevated nucleic acid (NA) content within 24 h, indicative of cells actively utilizing DMSP. The 16S rRNA genes of the cells with and without elevated NA content were analyzed following cell sorting and PCR amplification with sequencing and terminal restriction fragment length polymorphism approaches. Compared to cells in the control FCM populations, bacteria with elevated NA content in the presence of DMSP were relatively enriched in taxa related to Loktanella, Oceanicola, and Sulfitobacter (Roseobacter lineage, α-Proteobacteria); Caulobacter (Proteobacteria); and Brachymonas and Xenophilus (β-Proteobacteria) in the May-02 sample and to Ketogulonicigenium (Roseobacter lineage, α-Proteobacteria) and novel γ-Proteobacteria in the Sept-02 sample. Our study suggests that diverse bacterioplankton participate in the metabolism of DMSP in coastal marine systems and that their relative importance varies temporally.

SREL Reprint #2814

Mou, X., M. A. Moran, R. Stepanauskas, J. M. Gonzalez, and R. E. Hodson. 2005. Flow-cytometric cell sorting and subsequent molecular analyses for culture-independent identification of bacterioplankton involved in dimethylsufoniopropionate transformations. Applied and Environmental Microbiology 71:1405-1416.

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