초록
<P><B>Abstract</B></P> <P>In order to mitigate the ammonia-repression effect of nitrogenase in photosynthetic bacteria, we screened a library of transposon insertion mutants that showed better hydrogen production performance under ammonia-repressed conditions, revealing a relevant regulatory gene. The transposon plasmid pRL27 was engaged for transposon mutagenesis in a <I>cbbR</I> nullmutant of photosynthetic bacteria that has poor growth in the presence of ammonia, and mutants with better growth characteristics were successfully isolated. The hydrogen production yield and rate of one mutant (WRR04) were improved by 14.16% and 31.38%, respectively. BLAST analysis revealed that the interrupted DNA sequence encodes <I>trmB</I>, a transcriptional regulator. Additionally, the mutants WTF05 (<I>trmB</I> <SUP> <I>-</I> </SUP>) and WTR06 (<I>trmB</I> <SUP> <I>-</I> </SUP>, <I>cbbR</I> <SUP> <I>-</I> </SUP>) were constructed, and their H<SUB>2</SUB> production rates were increased remarkably by 54.72% and 41.44% comparing with the wild strain, respectively. The enhancement of nitrogenase activity demonstrates that the rupture of <I>trmB</I> could partly de-repress the activity of nitrogenase inhibited by ammonium for <I>Rhodobacter sphaeroides</I>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The transposon was employed for NH<SUB>4</SUB> <SUP>+</SUP> resistant controlgene from CBB deletion firstly. </LI> <LI> Disruption of <I>trmB</I> could partially derepress the ammonium inhibition of nitrogenase. </LI> <LI> The H<SUB>2</SUB> production rate and nitrogenase activity of mutant (<I>trmB</I> <SUP>−</SUP>) were enhanced. </LI> </UL> </P>