Oceanobacter-related bacteria are important for the degradation of petroleum aliphatic hydrocarbons in the tropical marine environment

1 NITE Biotechnology Development Center (NBDC), National Institute of Technology and Evaluation (NITE), 2-5-8 Kazusakamatari, Kisarazu, Chiba 292-0818, Japan 2 Research Center for Oceanography, Indonesian Institute of Sciences (LIPI), Jakarta Utara 14430, Indonesia Petroleum-hydrocarbon-degrading bacteria were obtained after enrichment on crude oil (as a ‘chocolate mousse’) in a continuous supply of Indonesian seawater amended with nitrogen, phosphorus and iron nutrients. They were related to Alcanivorax and Marinobacter strains, which are ubiquitous petroleum-hydrocarbon-degrading bacteria in marine environments, and to Oceanobacter kriegii (96.4–96.5 % similarities in almost full-length 16S rRNA gene sequences). The Oceanobacter -related bacteria showed high n-alkane-degrading activity, comparable to that of Alcanivorax borkumensis strain SK2. On the other hand, Alcanivorax strains exhibited high activity for branched-alkane degradation and thus could be key bacteria for branched-alkane biodegradation in tropical seas. Oceanobacter -related bacteria became most dominant in microcosms that simulated a crude oil spill event with Indonesian seawater. The dominance was observed in microcosms that were unamended or amended with fertilizer, suggesting that the Oceanobacter -related strains could become dominant in the natural tropical marine environment after an accidental oil spill, and would continue to dominate in the environment after biostimulation. These results suggest that Oceanobacter -related bacteria could be major degraders of petroleum n-alkanes spilt in the tropical sea. Correspondence Maki Teramoto teramoto-maki{at}aist.go.jp Abbreviations: rep-PCR, repetitive extragenic palindromic sequence PCR; T-RF, terminal restriction fragment; T-RFLP, terminal restriction fragment length polymorphism The GenBank/EMBL/DDBJ accession numbers for the sequences determined in this work are listed in Table 1.