Marinomonas alcarazii sp. nov., M. rhizomae sp. nov., M. foliarum sp. nov., M. posidonica sp. nov. and M. aquiplantarum sp. nov., isolated from the microbiota of the seagrass Posidonia oceanica Patricia Lucas-Elı ´o, 1 Ester Marco-Noales, 2 Elena Espinosa, 1 Mo ´ nica Ordax, 2 Marı ´a M. Lo ´ pez, 2 Neus Garcı ´as-Bonet, 3 Nuria Marba `, 3 Carlos M. Duarte 3 and Antonio Sanchez-Amat 1 Correspondence Antonio Sanchez-Amat antonio@um.es 1 Department of Genetics and Microbiology, University of Murcia, Murcia 30100, Spain 2 Centro de Proteccio ´ n Vegetal y Biotecnologı ´a, IVIA, 46113 Moncada (Valencia), Spain 3 Department of Global Change Research, Instituto Mediterra ´ neo de Estudios Avanzados (CSIC-UIB), 07190 Esporles, Mallorca, Spain Five novel Gram-reaction-negative aerobic marine bacterial strains with DNA G+C contents ,50 mol% were isolated from the seagrass Posidonia oceanica. 16S rRNA sequence analysis indicated that they belonged to the genus Marinomonas. Major fatty acid compositions, comprising C 10 : 0 3-OH, C 16 : 0 ,C 16 : 1 v7c and C 18 : 1 v7c, supported the affiliation of these strains to the genus Marinomonas. Strains IVIA-Po-14b T , IVIA-Po-145 T and IVIA-Po-155 T were closely related to Marinomonas pontica 46-16 T , according to phylogenetic analysis. However, DNA–DNA hybridization values ,35 % among these strains revealed that they represented different species. Further differences in the phenotypes and minor fatty acid compositions were also found among the strains. Another two strains, designated IVIA-Po-181 T and IVIA-Po-159 T , were found to be closely related to M. dokdonensis DSW10-10 T but DNA–DNA relatedness levels ,40 % in pairwise comparisons, as well as some additional differences in phenotypes and fatty acid compositions supported the creation of two novel species. Accordingly, strains IVIA-Po- 14b T (5CECT 7730 T 5NCIMB 14671 T ), IVIA-Po-145 T (5CECT 7377 T 5NCIMB 14431 T ), IVIA-Po-155 T (5CECT 7731 T 5NCIMB 14672 T ), IVIA-Po-181 T (5CECT 7376 T 5NCIMB 14433 T ) and IVIA-Po-159 T (5CECT 7732 T 5NCIMB 14673 T ) represent novel species, for which the names Marinomonas alcarazii sp. nov., Marinomonas rhizomae sp. nov., Marinomonas foliarum sp. nov., Marinomonas posidonica sp. nov. and Marinomonas aquiplantarum sp. nov. are proposed, respectively. The genus Marinomonas is composed of Gram-negative bacterial strains that have been found distributed across many different marine environments (Sanchez-Amat & Solano, 2005). The number of species in this genus has increased during recent years, after the initial description of the genus by Van Landschoot & De Ley (1983). At the time of writing, the list of species with validly published names in the genus Marinomonas included M. communis and M. vaga (formerly Alteromonas communis and A. vaga; Van Landschoot & De Ley, 1983; Baumann et al., 1972), M. mediterranea (Solano & Sanchez-Amat, 1999), M. primoryensis (Romanenko et al., 2003), M. pontica (Ivanova et al., 2005), M. dokdonensis (Yoon et al., 2005), M. aquimarina (Macia ´n et al., 2005), M. ushuaiensis (Prabagaran et al., 2005), M. polaris (Gupta et al., 2006), M. ostreistagni (Lau et al., 2006), M. arctica (Zhang et al., 2008), M. basaltis (Chang et al., 2008), M. arenicola (Romanenko et al., 2009), M. balearica and M. pollencensis (Espinosa et al., 2010). M. brasilensis has since been added to the genus and M. communis and M. basaltis have been recognized as heterotypic synonyms (Chimetto et al., 2011). It has been reported that the microbiota of the marine seagrass Posidonia oceanica contains a diverse range of species of the genus Marinomonas, namely, M. balearica, M. pollencensis and M. mediterranea (Espinosa et al., 2010). Here, we report the characterization of five novel strains of the genus Marinomonas isolated from Posidonia oceanica. The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains IVIA-Po-181 T , IVIA-Po-159 T , IVIA-Po-14b T , IVIA- Po-145 T and IVIA-Po-155 T are EU188445, EU188447, EU188442, EU188443 and EU188444, respectively. International Journal of Systematic and Evolutionary Microbiology (2011), 61, 2191–2196 DOI 10.1099/ijs.0.027227-0 027227 G 2011 IUMS Printed in Great Britain 2191