Two enterococcal strains LMG 16607 T and LMG 16612 originating from sea water were analysed in a polyphasic taxonomic study. Both strains, assigned as Enterococcus sp. in the BCCM/LMG culture collection, possessed analogous protein profiles, but these were different from all other enterococcal species. 16S rRNA gene sequence analysis of one strain showed the highest similarity, 96?9-96?1 %, with its closest phylogenetic neighbours Enterococcus saccharolyticus, Enterococcus sulfureus, Enterococcus saccharominimus and Enterococcus italicus. Further genomic analysis by (GTG) 5 -PCR fingerprinting and sequence analysis of the housekeeping gene phenylalanyl-tRNA synthase (pheS) and distinct biochemical features confirmed that the two strains represent a novel enterococcal species for which the name Enterococcus aquimarinus sp. nov. is proposed. The type strain is LMG 16607 T (=CCM 7283 T ).Enterococci are Gram-positive cocci inhabiting various environments. They are generally considered to be commensal inhabitants of warm-blooded animals, including humans, but are also isolated from reptiles and insects. Moreover, they occur on different kinds of food and can be found on plants and in water (Devriese et al., 1992). It has become impossible to achieve a reliable identification using classical biochemical tests as the number of enterococcal species with validly published names has increased. For some of the more recently described Enterococcus species, characteristics traditionally considered to be typical for the genus, e.g. acetoin production, ribose acidification, resistance to 6?5 % NaCl and growth at 10 and 45 uC, are no longer applicable (Devriese et al., 1993;Devriese & Pot, 1995;Domig et al., 2003). Other methods, such as SDS-PAGE analysis of whole-cell proteins, have been used intensively as routine and validated identification systems for enterococci (Devriese et al., 2002;De Graef et al., 2003;Vancanneyt et al., 2004).The present study deals with two strains presumptively assigned as Enterococcus sp. in the large BCCM/LMG inhouse database containing SDS-PAGE whole-cell protein profiles of all described lactic acid bacteria. Both strains, LMG 16607 T (=CCM 7283 T ) and LMG 16612 (=CCM 7284), originate from sea water and were deposited in BCCM/LMG in 1995 via bioMérieux with strain numbers API 8407116 and API 8407104, respectively. BioMérieux collected the strains in 1984 from the Istituto Superiore di Sanita of Roma, Italy. Further inquiries to determine the origin of the strains were unsuccessful. The taxonomic position of both sea-water isolates was further elucidated in this work. The reference strains used for comparison in this study were obtained from the BCCM/LMG bacteria collection (http://www.belspo.be/bccm/).To determine the phylogenetic position of the sea-water isolates, 16S rRNA gene sequence analysis was performed on one strain, LMG 16607 T , as described by Vancanneyt et al. (2004). The sequence obtained (a continuous stretch of 1510 bp) was aligned with reference sequences obtained from GenBan...