Flow-Cytometric Cell Sorting and Subsequent Molecular Analyses for Culture-Independent Identification of Bacterioplankton Involved in Dimethylsulfoniopropionate Transformations
Xiaozhen Mou,1 Mary Ann Moran,1* Ramunas Stepanauskas,2
Jose M. Gonzalez,3 and Robert E. Hodson1
Department of Marine Sciences, University of Georgia, Athens, Georgia1;
Savannah River Ecology Laboratory, University of Georgia, Aiken, South
Carolina2; and Departamento de Microbiologia y Biologia Celular,
Facultad de Farmacia, Universidad de La Laguna, La Laguna, Tenerife, Spain3
Received 2 August 2004/Accepted 3 October 2004
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 fLM 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, Proteobacteria);
Caulobacter (Proteobacteria); and Brachymonas
and Xenophilus (~-Proteobacteria) in the May-02 sample
and to Ketogulonicigenium (Roseobacter lineage, (Proteobacteria)
and novel y-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.
