Neighbor-joining phylogenetic trees showing taxonomic affiliation of LDPE-associated bacterial 16S rRNA gene sequences. Data are shown for the genera a) Arcobacter and b) Colwellia. Sequences (in bold) were obtained from LDPE fragments sampled after 14 days from sediment-LDPE microcosms from three sites (SP1, SP2 and WB, as indicated). Most-closely related GenBank database sequences are included in the trees. Tree branches are collapsed according to OTU designations using a 99% similarity cut-off threshold. Highlighted regions indicate predominant sediment-specific populations. Bootstrap values of ≥ 50% are shown adjacent to nodes. The scale bar represents 1% sequence divergence.