A bacterial strain designated TAPG2T was isolated from a freshwater creek in Taiwan and characterized using the polyphasic taxonomic approach. Cells of TAPG2T were Gram-stain negative, aerobic, motile, non-spore forming, short rods surrounded by a thick capsules and forming cream to dark-green colonies. Growth occurred at 15-37 �XC (optimum, 25-30 �XC), at pH 6.5-8 (optimum, pH 7) and with 0-1 % NaCl (optimum, 0.5 %). The major fatty acids (>10 %) of TAPG2T were summed feature 3 (C16 : 1�s7c and/or C16 : 1�s6c), C16 : 0 and C18 : 1�s7c. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, an uncharacterized aminophospholipid, an uncharacterized phospholipid, an uncharacterized aminolipid and an uncharacterized lipid. The polyamine profile was composed of the major compound putrescine and moderate amounts of spermidine. The only isoprenoid quinone was Q-8. The DNA G+C content was 53.6 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that TAPG2T represented a member of the genus Rheinheimera and was most closely related to Rheinheimera aquatica GR5T and Rheinheimera texasensis A62-14BT with 98.6 and 98.2 % 16S rRNA gene sequence identities, respectively. However, DNA-DNA hybridization values of TAPG2T with type strains of the species with validly published names were lower than 30 %. Differential phenotypic properties, together with the phylogenetic inference, demonstrate that TAPG2T should be classified as representing a novel species of the genus Rheinheimera, for which the name Rheinheimera coerulea sp. nov. is presented. The type strain is TAPG2T (=BCRC 81054T=LMG 30056T=KCTC 52815T).