Open AccessA Na + :H + Antiporter and a Molybdate Transporter Are Essential for Arsenite Oxidation in Agrobacterium tumefaciens
Author(s) -
Des Raj Kashyap,
Lina M. Botero,
Corinne R. Lehr,
Daniel J. Hassett,
Timothy R. McDermott
Publication year - 2006
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.188.4.1577-1584.2006
Subject(s) - complementation , agrobacterium tumefaciens , biology , operon , transposable element , mutant , transposon mutagenesis , microbiology and biotechnology , arsenite , mutagenesis , symporter , antiporter , biochemistry , gene , transgene , chemistry , transporter , arsenic , organic chemistry , membrane
Transposon Tn5 -B22 mutagenesis was used to identify genetic determinants required for arsenite [As(III)] oxidation in anAgrobacterium tumefaciens soil isolate, strain 5A. In one mutant, the transposon interruptedmodB , which codes for the permease component of a high-affinity molybdate transporter. In a second mutant, the transposon insertion occurred inmrpB , which is part of a seven-gene operon encoding an Mrp-type Na+ :H+ antiporter complex. Complementation experiments withmod andmrp operons PCR cloned from the genome-sequencedA. tumefaciens strain C58 resulted in complementation back to an As(III)-oxidizing phenotype, confirming that these genes encode activities essential for As(III) oxidation in this strain ofA. tumefaciens . As expected, themrp mutant was extremely sensitive to NaCl and LiCl, indicating that the Mrp complex inA. tumefaciens is involved in Na+ circulation across the membrane. Gene expression studies (lacZ reporter and reverse transcriptase PCR experiments) failed to show evidence of transcriptional regulation of themrp operon in response to As(III) exposure, whereas expression of themod operon was found to be up-regulated by As(III) exposure. In each mutant, the loss of As(III)-oxidizing capacity resulted in conversion to an arsenate [As(V)]-reducing phenotype. Neither mutant was more sensitive to As(III) than the parental strain.