CatABC genes encode proteins that are responsible for the first three steps of one branch of the beta-ketoadipate pathway involved in the degradation of various aromatic compound by bacteria. Aniline-assimilating Acinetobacter lwoffii K24 is known to have the two-catABC gene clusters (cat(1) and cat(2)) on the chromosome (Kim et al., J. Bacteriol., 179: 5226-5231, 1997). The order of the cati gene cluster is catB(2)A(2)C(2), which has not been found in other bacteria. In this report, we analyzed the transcriptional pattern of the cat(2) gene cluster and completely sequenced a 5.8 kbp fragment containing the compactly clustered catB(2)A(2)C(2) genes and four ORFs. Similar to the ORFR1 of the cat(1) gene cluster, an ORF highly homologous with the catR gene was found 102 bp upstream of the catB(2) gene and was designated as ORFR2,. Three ORFs, one putative reductase component (ORFX2) and two putative LysR family regulatory proteins (ORFY2, ORFZ2) were located next to the catC(2) gene in the opposite direction of the cat(2) gene cluster. Two ORFs, ORFX2 and ORFY2, were significantly homologous with tdnB and tdnR of the aniline oxygenase complex of Pseudomonas putida UCC22, RT-PCR analysis and Northern blotting revealed that the catB(2) gene is independently transcribed and that the catA(2)C(2) genes are cotranscribed. A primer extension assay revealed that transcription of the catA(2)C(2) gene starts in the C-terminal region of the catB(2) gene. These results suggest that the cat(2) gene cluster may be under a different gene adaptation from other cat gene clusters.