The bacterial strain C3(T) was isolated from permafrost soil in Beijicun, Mohe County, Heilongjiang province, China. Cells of strain C3(T) were Gram-stain-negative rods, 0.3-0.4 µm in diameter and 1.0-2.6 µm in length. Strain C3(T) was strictly aerobic. Growth occurred at 15-37 °C but not at 4 or 42 °C, at pH 5.0-9.0 (optimum pH 6.0-7.0) and in the presence of 0-8 g NaCl l(-1) (optimum 0-1 g l(-1)). The analysis of 16S rRNA gene sequences indicated that strain C3(T) was phylogenetically related to members of the genus Undibacterium, with similarities ranging from 94.7 to 96.5%. Strain C3(T) contained ubiquinone 8 as the major respiratory quinone. The major cellular fatty acids were summed feature 3 (C16:1ω7c/C16:1ω6c), C17:0 cyclo, straight-chain C16:0, C12:0 and C10:0, unsaturated C18:1ω7c and hydroxylated fatty acids C10:0 3-OH and C12:0 2-OH. The polar lipids were mainly phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The polyamines were putrescine and 2-hydroxyputrescine. The DNA G+C content was 57.4 mol% (determined from Tm). Based on these results, it is concluded that strain C3(T) represents a novel species of the genus Undibacterium, for which the name Undibacterium terreum sp. nov. is proposed, with C3(T) (=CGMCC 1.10998(T)=NBRC 108789(T)) representing the type strain.