A maximum-likelihood phylogenetic tree of the C-terminal region of Pcb/IsiA LH peptides (a). Pcb and IsiA proteins (sequence details see Table 1) from the sequenced representatives of Prochlorococcus and Synechococcus in the NCBI database are included as references of phylogenetic classification. The tree was rooted from the middle point. Shading indicates the environmental location of recovered sequences (coastal, dark blue; open ocean, light blue). Three phylogenetic groups are resolved, see text for details (I, gray; II, yellow; III, pink). The bar corresponds to the average substitutions per site. Bootstrapping support numbers are shown. The pie chart (b) represents the metagenomic profile of LH genes identified at open-ocean or coastal locations. Referred sequences (unshaded): PcbA_ss120, PcbA of Prochlorococcus sp. CCMP1375 (SS120) (NP_875175); PcbB ss120, NP_875561; PcbC_ss120, NP_875277; PcbD_ss120, NP_875559; PcbE_ss120, NP_875841; PcbF_ss120, NP_875679; PcbG_ss120, NP_875284; PcbH_ss120, NP_875566. PcbA_9211, PcbA of Prochlorococcus sp. MIT9211 (ZP_01005558); PcbB_9211, ZP_01005122; PcbC_9211, ZP_01005122; PcbD_9211, ZP_01005331; PcbE_9211, ZP_01004848; PcbF_9211, ZP_01004824; PcbH_9211, ZP_01005119. PcbA_MED4, PcbA of Prochlorococcus sp CCMP1986 (MED4) (NP_892745); PcbA_TAK, PabA of Prochlorococcus sp TAK9803 (AAK69281); Pcb_GB2, Pcb of Prochlorococcus sp. GP2 (AAK69280); Pcb_SB, Pcb of Prochlorococcus sp. SB (AAK69279); PcbC/IsiA_9301, PcbD of Prochlorococcus sp. MIT9301 (YP_001091596); PcbC/IsiA_9312, PcbD of Prochlorococcus sp. MIT9312 (ABB50330); PcbB_9313, PcbB of Prochlorococcus sp. MIT9313 (NP_894329). PcbC/IsiA_CC9605, PcbD of Synechococcus sp. CC9605 (YP_381894); PcbC/IsiA_CC9902, PcbD of Synechococcus sp. CC9902 (YP_377013); PcbC/IsiA_BL107, PcbD of Synechococcus sp. BL107 (ZP_01468016).