Most of the photosynthetic bacterial strains exhibit optimum hydrogen production at neutral initial pH, and lower initial pH resulted in a sharp decrease in hydrogen yield. Thus, screening of acid-tolerant hydrogen-producing photosynthetic bacteria is very important. To obtain acid tolerant mutants, a Tn7-based transposon was randomly inserted into the genomic DNA of Rhodovulum sulfidophilum P5. An acid tolerant mutant strain TH-102 exhibited increased hydrogen production in acidic environment (pH 4.5-6.5) and at higher temperatures (35 and 37 degrees C) than the wild-type strain. At pH 5.5 and 35 degrees C, the mutant strain TH-102 continuously produced hydrogen. The hydrogen yield and average rate were 2.16 +/- 0.10 mol/mol acetate and 10.06 +/- 0.47 mL/L h, which was about 17.32 and 15.37-fold higher than that of the wild-type strain, respectively. This acid-and temperature-tolerant mutant strain TH-102 could be used in a cost-effective hydrogen production process employing both dark fermentative and photosynthetic bacteria. (C) 2014 Elsevier Ltd. All rights reserved.