초록
<P><B>Abstract</B></P> <P>The gene <I>cycA</I> encodes a periplasmic protein, cytochrome c<SUB>2</SUB> (cyt c<SUB>2</SUB>), which dominates electron transfer from the membrane-bound ubiquinol: cyt c<SUB>2</SUB> oxidoreductase (cyt bc<SUB>1</SUB>) to the photosynthetic reaction center, contributing to the production of transmembrane proton potential and then the synthesis of ATP. For photosynthetic bacteria, the total energy supply for light anaerobic growth and hydrogen production comes from photophosphorylation. As a result, the key protein encoding gene plays an important role in hydrogen production. To figure out the specific effect of <I>cycA</I> expression level on H<SUB>2</SUB> production ability of <I>Rhodobacter sphaeroides</I> HY01, <I>cycA</I>-expression plasmids derived from pRK415 and pBBR1MCS-2 were constructed and then crossed into the parent strain <I>R. sphaeroides</I> HY01 for H<SUB>2</SUB> production test. And further verification by RT-PCR suggested that there was about 20% enhancement of <I>cycA</I> expression level by pBBR1MCS-2 where the H<SUB>2</SUB> production performance of corresponding strain was improved by 6–8% compared with blank control. In contrast, <I>cycA</I> expression level was about 3.4 folds by vector pRK415 compared with control strain, but corresponding strains showed slightly depressed H<SUB>2</SUB> production performance. Besides, the mutant XJ01 with <I>cycA</I> gene overexpressing by 70% in the genome of HY01(<I>hupSL</I>:<I>cycA</I>) also showed positive effect on hydrogen production performance. The results demonstrated that slightly overexpression of <I>cycA</I> could enhance the hydrogen production rate, but too much higher level of <I>cycA</I>-expression could show negative effect on H<SUB>2</SUB> production performance of <I>R. sphaeroides</I> HY01.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>cycA</I> overexpression implemented using both plasmids and genomic insertion methods. </LI> <LI> <I>cycA</I> genes on pRK415 showed 3–4 folds enhancement on transcriptional level. </LI> <LI> Overexpression <I>cycA</I> by around 20%–70% could enhance the H<SUB>2</SUB> production performance. </LI> <LI> Overexpression <I>cycA</I> by pBBR1MCS-2 enhanced H<SUB>2</SUB> production performance under low light intensity. </LI> <LI> Overexpression <I>cycA</I> by pRK415 slightly decreased its H<SUB>2</SUB> production performance. </LI> </UL> </P>