Seventy isolates were obtained from a marine electroactive biofilm that was generated on a cathodically polarized stainless steel electrode (Genoa, Italy). The genetic diversity was investigated by means of BOX-PCR fingerprinting and two clusters of isolates with similar BOX-PCR profiles were delineated. Whole-cell fatty acid methyl ester analysis and 16S rRNA gene sequence analysis showed that the isolates belonged to the Roseobacter lineage of the class Alphaproteobacteria. DNA-DNA hybridization experiments and a biochemical analysis demonstrated that four isolates belonged to the species Ruegeria mobilis. However, 66 isolates from the second BOX-PCR cluster constituted a novel species within the genus Ruegeria, for which the name Ruegeria scottomollicae sp. nov. is proposed. The DNA G+C content was 61.0±0.4 %. The type strain is LMG 24367 T (5CCUG 55858 T ).The genus Ruegeria was created by Uchino et al. (1998) to accommodate the generically misclassified species Agrobacterium atlanticum, Agrobacterium gelatinovorum and Roseobacter algicola, with Ruegeria atlantica as the type species. This genus comprises marine, aerobic, Gram-negative, catalasepositive, oxidase-positive rods. Subsequently, Arahal et al. (2005) reclassified Ruegeria gelatinovorans as Thalassobius gelatinovorus and Martens et al. (2006) restricted the genus Ruegeria to its type species by transferring Ruegeria algicola to the genus Marinovum. More recently, Yi et al. (2007) transferred the two species of the genus Silicibacter [Silicibacter lacuscaerulensis (Petursdottir & Kristjansson, 1997) and Silicibacter pomeroyi (González et al., 2003)] to the genus Ruegeria; Ruegeria mobilis and Ruegeria pelagia were also described (Lee et al., 2007;Muramatsu et al., 2007). At the time of writing, the genus Ruegeria comprised five recognized species, i.e. Ruegeria atlantica, Ruegeria pomeroyi, Ruegeria lacuscaerulensis, Ruegeria pelagia and Ruegeria mobilis, although the assignation of Ruegeria pomeroyi and Ruegeria lacuscaerulensis is controversial (Muramatsu et al., 2007).The present taxonomic study was performed in the context of the analysis of the microbial population present in a marine, electroactive biofilm [EA BIOFILMS-508866 (NEST)], generated on a stainless steel cathode that was exposed to natural seawater at the ISMAR-CNR that is located in the port of Genoa, Italy (Faimali et al., 2008;Vandecandelaere et al., 2008). The biofilm was removed from the stainless steel cathode by sonication (Branson 3200 sonicator) for 90 s in a sterile plastic tube containing 30 ml 0.85 % NaCl solution. Diluted cell suspensions (10 21 to 10 26 ) were spread onto marine agar 2216 (MA; Difco) for aerobic incubation at 20 u C for several days. Pure cultures were obtained and the isolates were stored at 220 or 280 u C using Microbank vials.DNA was extracted from the 70 isolates as described by Pitcher et al. (1989) and the genetic diversity was investigated by means of repetitive DNA-PCR fingerprinting using the BOX-A1R primer (59-CTACGGCAAGGCGACGCTGACG-39) (Rad...
