Extracellular tellurite concentration in culture supernatants.

<p>Tellurite concentration was determined in supernatants of <i>E. coli</i> cultures that had been exposed to tellurite (20 µg ml⁻¹) in the absence (control) or presence of the indicated CTX concentrations. Values represent the average of 3 independent experiments. Statistical significance was determined using t-test. (**) p<0.01.</p

Hydroxyl radical generation in <i>E. coli</i> exposed to CTX or Te/CTX.

<p><i>E. coli</i> was exposed for 3 h to tellurite/CTX (A) and to different antibiotic concentrations (B). As positive control, cells were exposed for 3 h to ampicillin. Units are expressed in µg ml⁻¹. The data correspond to a representative result of 3 independent trials.</p

Tellurite/CTX damage in <i>E. coli</i>.

<p>Peptidoglycan integrity (stability) is affected by CTX (1), favoring tellurite entry (2). Tellurite/CTX administration generates global transcriptional changes on different stress response pathways, transport, [Fe-S] clusters assembly, protein folding and different oxidative stress regulators (3). Finally, CTX and tellurite generate hydroxyl radical and superoxide respectively, damaging DNA, proteins and most probably other macromolecules.</p

Cefotaxime and potassium tellurite acts synergistically in <i>E. coli</i>.

<p>Growth curves (left panels) and cell viability (right panels) were determined at the indicated time intervals for <i>E. coli</i> exposed to 0.065 (A, sublethal), 0.13 (B, MIC) and 0.5 µg/ml (C, lethal) CTX in the absence or presence of 200 nM tellurite. Controls contained no tellurite or cefotaxime. Data represent the mean of at least 3 independent trials. Refer to inset in panel A for symbol meaning.</p

Tellurite-mediated antibiotic-potentiating effect in clinical isolates.

<p>Antibiotic susceptibility, in the absence or presence of the indicated tellurite concentrations, was assessed by growth inhibition zones (cm²) as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035452#s4" target="_blank">Methods</a>. Parentheses indicate per cent of susceptibility increase regarding the respective control.</p

Minimal tellurite concentration causing a cefotaxime-potentiating effect in <i>E. coli</i>.

<p>Inhibition growth zones were determined as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035452#s4" target="_blank">Methods</a> using LB plates amended with the indicated sub lethal tellurite concentrations (nM).</p

Tellurite-mediated antibiotic-potentiating effect in different bacteria.

<p>Antibiotic-mediated inhibition growth zones were determined for <i>E. coli</i> (A), <i>P. aeruginosa</i> (B) and <i>S. aureus</i> (C) grown in the absence (white bars) or presence of the indicated tellurite (T) concentrations as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035452#s4" target="_blank">Methods</a>. Values represent the average of at least 4 independent trials and significance was determined using t-test analysis (p<0.05). Significance values are (*) p<0.05, (**) p<0.01 and (***) p<0.001.</p

Total RSH and GSH content in <i>E. coli</i> overexpressing GSH biosynthesis genes.

<p>Cellular RSH (after 4 h IPTG induction, A) and GSH levels (B) after 4 h (white) or 16 h (striped) IPTG induction were determined in <i>E. coli</i> AG1 (wt), AG1/pCA24N<i>gshA</i> (<i>gshA</i>) and AG1/pCA24NgshB (<i>gshB</i>) cells (n = 3). *p<0.05; **p<0.005.</p

Elemental analysis of purified nano-sized structures.

<p>Cd and Te content (ppm) in purified NPs from cells exposed only to CdCl₂ (Cd) or CdCl₂/K₂TeO₃ (CdTe) were determined as described in Methods; bd stands for below detection limit.</p

Effect of temperature, microaerophilic conditions and citrate on <i>E. coli</i> fluorescence.

<p>UV-exposed <i>E. coli</i> AG1/pCA24N<i>gshA</i> cells previously incubated under NP biosynthesis conditions with some modifications: 1, control (37°C); 2, increased incubation temperature (42°C); 3, reducing agent (citrate buffer pH 7.0); 4, microaerophilic conditions.</p