International Journal of Systematic Bacteriology (1999), 49, 859–865 Printed in Great Britain Desulfovibrio zosterae sp. nov., a new sulfate reducer isolated from surface-sterilized roots of the seagrass Zostera marina Jens T. Nielsen, 1 Werner Liesack 2 and Kai Finster 1 Author for correspondence : Kai Finster. Tel : 45 8942 3241. Fax:45 8612 7191. e-mail : kai.finsterbiology.aau.dk 1 Dept of Microbial Ecology, University of Aarhus, Building 540, Ny Munkegade, 8000 A  rhus C, Denmark 2 Max-Planck-Institute for Terrestrial Microbiology, Karl von Frisch Strasse, D- 35043, Marburg, Germany A sulfate-reducing bacterium, designated strain lac T , was isolated from surface-sterilized roots of the benthic macrophyte Zostera marina. Cells were motile by means of a single polar flagellum. Strain lac T utilized lactate, pyruvate, malate, ethanol, L-alanine, fumarate, choline and fructose with sulfate as electron acceptor. In addition, fumarate, pyruvate and fructose were also degraded without an external electron acceptor. Sulfate could be substituted with thiosulfate, sulfite and elemental sulfur. Optimal growth was observed between 325 and 345 C, at an NaCl concentration of 02 M and in a pH range between 68 and 73. The GMC content of the DNA was 427O02 mol%. Desulfoviridin and catalase were present. Strain lac T contained c-type cytochromes. Comparative 16S rRNA gene sequence analysis and the fatty acid pattern grouped this isolate into the genus Desulfovibrio. However, strain lac T differs from all other described Desulfovibrio species on the bases of its 16S rRNA gene sequence, the GMC content, its cellular lipid pattern and the utilization pattern of substrates. These characteristics establish strain lac T (DSM 11974 T ) as a novel species of the genus Desulfovibrio, for which the name Desulfovibrio zosterae sp. nov. is proposed. Keywords : root-associated bacteria, seagrass, Desulfovibrio zosterae sp. nov., fructose metabolism, sulfate reducer INTRODUCTION Sulfate-reducing bacteria have been isolated from a large number of different habitats, which has led to the conclusion that they are widespread in nature (Widdel & Bak, 1992). Typically, sulfate-reducers are found in anoxic, marine environments where sulfate is available in excess (Widdel, 1988 ; Jørgensen & Bak, 1991), but they have also been isolated from freshwater environ- ments such as lake sediment (Bak & Pfennig, 1991), from anaerobic digesters (Oude Elferink et al., 1995), the rumen of sheep (Howard & Hungate, 1976) and the intestines of humans and termites (Beerens & Romond, 1977 ; Gibson et al., 1988 ; Trinkerl et al., 1990). Recently, we demonstrated that high sulfate-reducing activity was associated with sediment-free roots and rhizomes of the marine macrophyte Zostera marina (Blaabjerg & Finster, 1998). We also showed that sulfate-reducing activity prevailed after surface steriliz- ................................................................................................................................................. The EMBL/GenBank/DDBJ accession number for the 16S rDNA sequence of strain lac T ( DSM 11974 T ) reported in this paper is Y18049. ation of roots and rhizomes with hypochlorite (105%, wv) for 30 s. This finding led us to carry out the enrichment and isolation of root-cortex-inhabiting sulfate reducers. In the present communication, we report on the enrichment, isolation and phenotypic and genotypic characterization of strain lac T , a mesophilic, marine, fructose-oxidizing sulfate reducer isolated from sur- face-sterilized root tissue of the marine angiosperm Zostera marina. METHODS Source of organisms. Strain lac T was isolated from a mixed culture obtained from surface-sterilized roots of the eelgrass Zostera marina. The plants were obtained from a dense eelgrass meadow, in Løgstør Broad, Denmark. Root-surface sterility was achieved by washing sediment-free roots in a saline, 105 % (wv) hypochlorite solution for 30 s (Blaabjerg & Finster, 1998). Strain lac T was isolated by repeated application of the agar- shake dilution method in an iron-rich APW medium, previously described by Coates et al. (1995). Agar (1%, 00970  1999 IUMS 859