Transporters are a large class of membrane proteins, which mediate the exchange of chemicals and signals inside and outside the biofilm. Lipid bilayer forms a hydrophobic barrier around cells or organelles, isolating them from the surrounding environment. Although some small molecules can directly penetrate the membrane, most hydrophilic compounds, such as sugar, amino acids, ions and drugs, need special transporters to pass through the hydrophobic barrier. Therefore, transporters play an important role in a wide range of cellular activities such as nutrient uptake, metabolite release and signal transduction.