A novel Gram-negative and rod-shaped bacterium, designated N8(T), was isolated from tidal flat sediment. Phylogenetic analysis based on 16S rRNA gene sequences showed that N8(T) strain is associated with the family Phyllobacteriaceae: two uncultured clones (98.4 and 99.8% 16S rRNA gene sequence similarity) and the genus Mesorhizobium (< or =97.0%). The novel strain formed a separate clade with uncultured clones in the phylogenetic tree based on 16S rRNA gene sequences. Cellular fatty acid profiles predominately comprised C(18:1) omega7c and C(19:0) cyclo omega8c. The major isoprenoid quinone is ubiquinone-10 and genomic DNA G+C content is 53.4 mol%. The polyphasic taxonomic study indicates that the novel strain N8(T) represents a novel species of the new genus in the family Phyllobacteriaceae, named Aliihoeflea aestuarii. The type strain is N8(T) (= KCTC 22052(T)= JCM 15118(T)= DSM 19536(T)).