Rhodobacter capsulatus (R. capsulatus), which is a typical purple nonsulfur photosynthetic bacterium, is able to produce hydrogen under photosynthetic condition. A mutant of R. capsulatus named MC122 was obtained by Tn5 transposon mutagenesis. The transposon mutant had improved photoheterotrophic hydrogen production performance using acetic acid as substrate and its mutation site was located by sequencing the rescued plasmid containing the transposon insertion from the genome of the mutant. It was found for the first time that disruption of the multidrug resistance protein (mdtB) gene resulted in improved hydrogen production. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.