A bacterial strain, designated MIB-4T, was isolated from a freshwater spring in Taiwan and characterized using a polyphasic taxonomy approach. Cells of strain MIB-4T were Gram-staining-negative, aerobic, non-motile rods that formed pale pink colonies. Growth occurred at 15-30 �XC (optimum, 25 �XC), at pH 7-8 (optimum, pH 7) and with 0-0.5 % NaCl (optimum, 0 %). Phylogenetic analyses based on 16S rRNA gene sequences showed that strain MIB-4T belonged to the genus Flectobacillus and was most closely related to Flectobacillus lacus CL-GP79T with sequence similarity of 98.7 %. Strain MIB-4T contained C16 : 1�s5c, iso-C15 : 0 and summed feature 3 (C16 : 1�s7c and/or C16 : 1�s6c) as the predominant fatty acids. The major isoprenoid quinone was MK-7. The polar lipid profile consisted of phosphatidylethanolamine, six unidentified aminophospholipids, one unidentified glycolipid, one unidentified phospholipid and three unidentified lipids. The DNA G+C content of the genomic DNA was 37.6 mol%. The DNA-DNA hybridization value for strain MIB-4T with F. lacus CL-GP79T was less than 32 %. On the basis of the phylogenetic inference and phenotypic data, strain MIB-4T should be classified as a representative of a novel species, for which the name Flectobacillus fontis sp. nov. is proposed. The type strain is MIB-4T (=BCRC 80926T=LMG 29292T=KCTC 33763T).