Genomic and metabolic analysis of fluoranthene degradation pathway in Celeribacter indicus P73 ^T

Abstract

Celeribacter indicus P73 ^T, isolated from deep-sea sediment from the Indian Ocean, is capable of degrading a wide range of polycyclic aromatic hydrocarbons (PAHs) and is the first fluoranthene-degrading bacterium within the family Rhodobacteraceae. Here, the complete genome sequence of strain P73 ^T is presented and analyzed. Besides a 4.5-Mb circular chromosome, strain P73 ^T carries five plasmids, and encodes 4827 predicted protein-coding sequences. One hundred and thirty-eight genes, including 14 dioxygenase genes, were predicted to be involved in the degradation of aromatic compounds, and most of these genes are clustered in four regions. P73_0346 is the first fluoranthene 7,8-dioxygenase to be discovered and the first fluoranthene dioxygenase within the toluene/biphenyl family. The degradative genes in regions B and D in P73 ^T are absent in Celeribacter baekdonensis B30, which cannot degrade PAHs. Four intermediate metabolites [acenaphthylene-1( 2H)-one, acenaphthenequinone, 1,2-dihydroxyacenaphthylene, and 1,8-naphthalic anhydride] of fluoranthene degradation by strain P73 ^T were detected as the main intermediates, indicating that the degradation of fluoranthene in P73 ^T was initiated by dioxygenation at the C-7,8 positions. Based on the genomic and metabolitic results, we propose a C-7,8 dioxygenation pathway in which fluoranthene is mineralized to TCA cycle intermediates.