Biosensing 2,4-dichlorophenol toxicity during biodegradation by Burkholderia sp. RASC c2 in soil

<p>Biodegradation of the model pollutant, 2,4-dichlorophenol (2,4-DCP) by Burkholderia sp. RASC c2, in contaminated soil was assessed by combining chemical analysis with a toxicity test using Escherichia coli HB101 pUCD607. E. coli HB101 pUCD607 was previously marked with luxCDABE genes, encoding bacterial bioluminescence and was used as an alternative to Microtox. Mineralization of ¹⁴C-2,4-DCP (196.2 μg g^-1 dry wt) in soil occurred rapidly after a 24 h lag. Correspondingly, 2,4-DCP concentrations in soil and soil water extracts decreased with time and concentrations in the latter were at background levels (&lt;0.12 μg mL^-1) after day 2. Toxicity of soil water extracts to the lux-based biosensor also decreased with time. Mean light output of E. coli was stimulated by ~1.5 X control values in soil water extracts when concentrations of 2,4-DCP were approaching the limit of detection by HPLC but returned to values equivalent to those of controls when soil water 2,4-DCP concentrations were below the detection limit. No mineralization or microbial growth was detected in noninoculated microcosms. 2,4-DCP concentration in sterile controls decreased significantly with time as did toxicity to E. coli Lux-based E. coli was a sensitive biosensor of 2,4-DCP toxicity during biodegradation and results complemented chemical analysis.</p>

Total Synthesis of the Potent HIF-1 Inhibitory Antitumor Natural Product, (8<i>R</i>)-Mycothiazole, via Baldwin–Lee CsF/CuI sp³â€“sp²-Stille Cross-Coupling. Confirmation of the Crews Reassignment

A convenient asymmetric total synthesis of the potent HIF-1 inhibitory antitumor natural product, (−)- or (+)-(8<i>R</i>)-mycothiazole (<b>1</b>), is described. Not only does our synthesis confirm the 2006 structural reassignment made by Crews (Crews, P., et al. <i>J. Nat. Prod</i>. <b>2006</b>, <i>69</i>, 145), it revises the [α]_D data previously reported for this molecule in MeOH from −13.7° to +42.3°. The newly developed route to (8<i>R</i>)-<b>1</b> sets the C(8)–OH stereocenter via Sharpless AE/2,3-epoxy alcohol reductive ring opening and utilizes two Baldwin–Lee CsF/cat. CuI Stille cross-coupling reactions with vinylstannanes <b>8</b> and <b>3</b> to efficiently elaborate the C(1)–C(4) and C(14)–C(18) sectors.