Bespuiting van tomaten met Plantfood (19-22-16), 1953

<p><b>Copyright information:</b></p><p>Taken from "Cadmium triggers an integrated reprogramming of the metabolism of PCC6803, under the control of the Slr1738 regulator"</p><p>http://www.biomedcentral.com/1471-2164/8/350</p><p>BMC Genomics 2007;8():350-350.</p><p>Published online 2 Oct 2007</p><p>PMCID:PMC2190772.</p><p></p> indicated durations on solid BG11 medium with or without HO(3 mM), CdSO(50 μM), Co(NO)(350 μM), (NH)FeHCHO(350 μM) or ZnSO(350 μM or 776 μM). The spectra (normalized to light scattering at 800 nm) are displayed in panels A to F. These experiments were repeated three to five times

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

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

The abundance of total EPS influences the zeta potential of <i>Synechocystis</i>.

<p>(<b>A</b>) Zeta values for the WT and mutant cells harbouring either a single or a double deletion of the genes <i>sll0923</i>, <i>sll5052</i>, <i>slr1875</i> and <i>sll1581</i>, as indicated. (<b>B</b>) Histogram plots of the total amounts of EPS (CPS+RPS) of each strain. All results are expressed as means ± standard deviation of the data obtained after three biological repetitions of every assay.</p

The Challenge of Studying TiO₂ Nanoparticle Bioaccumulation at Environmental Concentrations: Crucial Use of a Stable Isotope Tracer

The ecotoxicity of nanoparticles (NPs) is a growing area of research with many challenges ahead. To be relevant, laboratory experiments must be performed with well-controlled and environmentally realistic (i.e., low) exposure doses. Moreover, when focusing on the intensively manufactured titanium dioxide (TiO₂) NPs, sample preparations and chemical analysis are critical steps to meaningfully assay NP’s bioaccumulation. To deal with these imperatives, we synthesized for the first time TiO₂ NPs labeled with the stable isotope ⁴⁷Ti. Thanks to the ⁴⁷Ti labeling, we could detect the bioaccumulation of NPs in zebra mussels (D<i>reissena polymorpha</i>) exposed for 1 h at environmental concentrations via water (7–120 μg/L of ⁴⁷TiO₂ NPs) and via their food (4–830 μg/L of ⁴⁷TiO₂ NPs mixed with 1 × 10⁶ cells/mL of cyanobacteria) despite the high natural Ti background, which varied in individual mussels. The assimilation efficiency (AE) of TiO₂ NPs by mussels from their diet was very low (AE = 3.0 ± 2.7%) suggesting that NPs are mainly captured in mussel gut, with little penetration in their internal organs. Thus, our methodology is particularly relevant in predicting NP’s bioaccumulation and investigating the factors influencing their toxicokinetics in conditions mimicking real environments

Multidisciplinary Evidences that <em>Synechocystis</em> PCC6803 Exopolysaccharides Operate in Cell Sedimentation and Protection against Salt and Metal Stresses

<div><p>Little is known about the production of exopolysaccharides (EPS) in cyanobacteria, and there are no genetic and physiological evidences that EPS are involved in cell protection against the frequently encountered environmental stresses caused by salt and metals. We studied four presumptive EPS production genes, <em>sll0923, sll1581, slr1875</em> and <em>sll5052</em>, in the model cyanobacterium <em>Synechocystis</em> PCC6803, which produces copious amounts of EPS attached to cells (CPS) and released in the culture medium (RPS) as shown here. We show that <em>sll0923, sll1581, slr1875</em> and <em>sll5052</em> are all dispensable to the growth of all corresponding single and double deletion mutants in absence of stress. Furthermore, we report that <em>sll0923</em>, <em>sll1581</em> and <em>slr1875</em> unambiguously operate in the production of both CPS and RPS. Both <em>sll1581</em> and <em>slr1875</em> are more important than <em>sll0923</em> for CPS production, whereas the contrary is true for RPS production. We show that the most EPS-depleted mutant, doubly deleted for <em>sll1581</em> and <em>slr1875</em>, lacks the EPS mantle that surrounds WT cells and sorbs iron in their vicinity. Using this mutant, we demonstrate for the first time that cyanobacterial EPS directly operate in cell protection against NaCl, CoCl₂, CdSO₄ and Fe-starvation. We believe that our EPS-depleted mutants will be useful tools to investigate the role of EPS in cell-to-cell aggregation, biofilm formation, biomineralization and tolerance to environmental stresses. We also suggest using the fast sedimenting mutants as biotechnological cell factories to facilitate the otherwise expensive harvest of the producer cell biomass and/or its separation from products excreted in the growth media.</p> </div

Characteristics of the plasmids used in this study.

<p>CS: coding sequence.</p

Influence of the <i>sll0923</i>, <i>sll1581</i>, <i>sll5052</i> and <i>slr1875</i> genes on exopolysaccharides abundance in <i>Synechocystis</i>.

<p>EPS amount of the WT and mutant cells harbouring either a single or a double deletion of the genes <i>sll0923</i>, <i>sll1581</i>, <i>sll5052</i> and <i>slr1875</i>, as indicated. (<b>A</b>) Histogram plots of the amounts of capsular exopolysaccharides (CPS) attached to the cells in each strain. (<b>B</b>) Histogram plots of the amounts of exopolysaccharides released (RPS) by each strain in culture medium. All results are expressed as means ± standard deviation of the data obtained after 3 biological repetitions of every assay.</p

Influence of the <i>sll0923</i>, <i>sll1581</i>, <i>sll5052</i> and <i>slr1875</i> genes on the spontaneous cell sedimentation of <i>Synechocystis</i>.

<p>Typical photographs of cultures of wild-type and mutant strains harbouring either a single or a double deletion of the genes <i>sll0923</i>, <i>sll1581</i>, <i>sll5052</i> and <i>slr1875</i>, as indicated. The suspensions were kept static on the bench for 18 days prior to imaging. These experiments were performed at least three times.</p