Phylogenetic tree of bacterial 16S rRNA gene sequences from methanogenic alkanes-degrading enrichment culture (in red) and rooted with outgroup sequence from Methanocaldococcus jannaschii DSM 2661 (L77117). The OTUs are shown with clone names and accession numbers. Sequences from oil or hydrocarbon-impacted environments are in black bold. Values below 75% are not shown. The topology of the tree was obtained by the neighbor-joining method. Bootstrap values (n = 1,000 replicates).