4-Chlorobenzoate Uptake in Comamonas sp. Strain DJ-12 Is Mediated by a Tripartite ATP-Independent Periplasmic Transporter

Abstract

ABSTRACT The fcb gene cluster involved in the hydrolytic dehalogenation of 4-chlorobenzoate is organized in the order fcbB - fcbA - fcbT1 - fcbT2 - fcbT3 - fcbC in Comamonas sp. strain DJ-12. The genes are operonic and inducible with 4-chloro-, 4-iodo-, and 4-bromobenzoate. The fcbT1 , fcbT2 , and fcbT3 genes encode a transporter in the secondary TRAP (tripartite ATP-independent periplasmic) family. An fcbT1T2T3 knockout mutant shows a much slower growth rate on 4-chlorobenzoate compared to the wild type. 4-Chlorobenzoate is transported into the wild-type strain five times faster than into the fcbT1T2T3 knockout mutant. Transport of 4-chlorobenzoate shows significant inhibition by 4-bromo-, 4-iodo-, and 4-fluorobenzoate and mild inhibition by 3-chlorobenzoate, 2-chlorobenzoate, 4-hydroxybenzoate, 3-hydroxybenzoate, and benzoate. Uptake of 4-chlorobenzoate is significantly inhibited by ionophores which collapse the proton motive force.