Comparative analysis of the strains over-expressing the genes <i>hoxEFUYH</i> (CE1) or <i>hoxEFUYHW</i> (CE4; CE4u) alone, or together with the <i>hypABCDEF</i> genes (CE5; CE5u).

<p>All experiments were performed at least three times. (<b>A</b>) Typical growth of the wild type (WT; squares), CE-<i>hoxEFUYH</i> (CE1; white triangles) and CE-<i>hoxEFUYHW</i> (CE4; black squares) cells incubated under standard conditions. (<b>B</b>) Histogram plot representation of transcript abundance (measured by Real-time quantitative PCR) of the <i>hoxEFUYHW</i> genes in strains WT (small light-grey bars), CE1 (grey rectangles) and CE4 (hatched bars) mutants. (<b>C</b>) Western blot analysis of the abundance of the HoxF and HoxH proteins in WT, CE1, CE4 and CE5 cells growing in MM* medium (MM + 17 μM Fe). (<b>D</b>) Histogram plot representation of the transcript abundance (RT-qPCR) of the <i>hypABC-F</i> genes in the strains WT (light-grey rectangles), CE1 (grey) and CE5 (arrow-filled bars). (<b>E</b>) Histograms representation of the hydrogenase activities of WT (light grey), CE1 (grey), CE2 (dark grey) CE4 (light grey-hatched bars), CE5 (white arrow-filled bars), CE4u (dark grey-hatched bars) and CE5u cells (grey arrow-filled bars) growing in standard medium (MM) or MM* (MM + 17 μM Fe) supplemented with 2.5 μM NiSO₄.</p

Influence of urea on the growth of <i>Synechocystis</i> WT and mutants overexpressing the <i>hoxEFUYHW</i> genes alone (CE4) or in combination with the <i>hypABCDEF</i> genes (CE5).

<p>(<b>A</b>) Typical growth of WT cells cultivated on medium containing Ni (1 μM) and urea (2.5–20 mM) as the sole nitrogen source. (<b>B</b>) Typical growth on urea (5 mM as the sole nitrogen source) and Ni (2.5 μM) of the WT strain, and the CE4 and CE5 strain without or with (CE4u and CE5u) a mutation in <i>ureG</i>. Influence of prolonged growth on urea (5 mM as the sole nitrogen source) and Ni (2.5 μM) on the cell appearance <b>C</b>) and urease activity (<b>D</b>) of the studied strains. All experiments were performed at least three times.</p

Schematic representation of the <i>Synechocystis</i> strains constructed in this study.

<p><i>Synechocystis</i> cells are represented by oval shapes showing their chromosome attached to the cell membrane. The pCE-<i>hypABCDEF</i> replicating plasmid is represented by circles. The <i>hoxEFUYHW</i> and <i>hypABCDEF</i> genes and the antibiotic resistance markers are shown by large arrows pointing towards the direction of their transcription. The triangle represents the strong lambda phage pR promoter (λ<i>p</i>_R); CE for strong <u>c</u>onstitutive <u>e</u>xpression.</p