There were 441 transport-related proteins (13.6% of all CDSs) in the L. hongkongensis genome, comprising an extensive variety of transporters, which may reflect its ability to adapt to the freshwater fish and human intestines, and freshwater environments. According to the Transporter Classification Database (TCDB) (http:// www.tcdb.org/), all seven major categories of transporters are present in L. hongkongensis. Primary active transporters (class 3 transporters) were the most abundant class of transporters, accounting for 43.3% (191 CDSs) of all annotated CDSs related to transport, among which 104 belong to the ATP-binding cassette (ABC) transporter superfamily and 41 were oxidoreduction-driven transporters. Electrochemical potential-driven transporters (class 2 transporters) were the second most abundant class of transporters, accounting for 27.9% (123 CDSs) of all annotated CDSs related to transport, most of which (117 CDSs) are various kinds of porters including major facilitator superfamily (MFS) (19 CDSs), resistance-nodulation-cell division (RND) superfamily (22 CDSs), amino acid-polyamine-organocation family (8 CDSs), dicarboxylate/amino acid:cation symporter (DAACS) family (5 CDSs) and monovalent cation:proton antiporter-2 family (3 CDSs), and various heavy metal transporters which may be involved in detoxification and resistance against environmental hazards. Three different types of class 2 transporters, belonging to the DAACS, tripartite ATP-independent periplasmic transporter and