A bacterial strain designated CMJ-15(T) was isolated from a freshwater shrimp culture pond in Taiwan and characterized using a polyphasic taxonomic approach. Cells of strain CMJ-15(T) were facultatively anaerobic, Gram-stain-negative and motile by a single polar flagellum and formed light-yellow colonies. Growth occurred at 20-40 �XC (optimum, 25-30 �XC), with 0-0.7% NaCl (optimum, 0-0.2%) and at pH 5.0-9.0 (optimum, pH 6.0-7.0). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain CMJ-15(T) belonged to the genus Undibacterium and its closest neighbour was Undibacterium oligocarboniphilum EM 1(T), with sequence similarity of 96.3%. The predominant cellular fatty acids were summed feature 3 (C16:1�s7c and/or C16:1�s6c), C16:0 and C18:1�s7c. The major cellular hydroxy fatty acid was C10:0 3-OH. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The polyamine profile was composed of the major compound putrescine and moderate amounts of 2-hydroxyputrescine. The major respiratory quinone was Q-8 and the DNA G+C content was 52.2 mol%. On the basis of these phylogenetic and phenotypic data, strain CMJ-15(T) should be classified as representing a novel species, for which the name Undibacterium squillarum sp. nov. is proposed. The type strain is CMJ-15(T) (= BCRC 80404(T) = LMG 26892(T) = KCTC 23917(T)).