Rhodococcus sp. TMP2 is an alkane-degrading strain that can grow with a branched alkane as a sole carbon source. TMP2 degrades considerable amounts of pristane at 20 degrees C but not at 30 degrees C. In order to gain insights into microbial alkane degradation, we characterized one of the key enzymes for alkane degradation. TMP2 contains at least five genes for membrane-bound, non-heme iron, alkane hydroxylase, known as AlkB (alkB1-5). Phylogenetical analysis using bacterial alkB genes indicates that TMP2 is a close relative of the alkane-degrading bacteria, such as Rhodococcus erythropolis NRRL B-16531 and Q15. RT-PCR analysis showed that expressions of the genes for AlkB1 and AlkB2 were apparently induced by the addition of pristane at a low temperature. The results suggest that TMP2 recruits certain alkane hydroxylase systems to utilize a branched alkane under low temperature conditions.