PubMed · 16760359
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Marcelo Gama de Abreu. 2006-06-15. Negative studies deserve more attention.. https://doi.org/10.1164/ajrccm.173.12.1414a
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Perfluorooctane sulfonate (PFOS) is a prominent perfluorinated compound commonly found in the environment, known to pose various risks to human health. However, the removal of PFOS presents significant challenges, primarily due to the limited discovery of bacteria capable of effectively degrading PFOS. Moreover, single degradation bacteria often encounter obstacles in individual cultivation and the breakdown of complex pollutants. In contrast, microbial consortia have shown promise in pollutant degradation. This study employed a continuous enrichment method, combined with multiple co-metabolic substrates, to investigate a microbial consortium with the potential for PFOS degradation. By employing this methodology, we effectively identified a microbial consortium that demonstrated the capacity to reduce PFOS when exposed to an optimal concentration of methanol. The consortium predominantly comprised of Hyphomicrobium species (46.7%) along with unclassified microorganisms (53.0%). Over a duration of 20 days, the PFOS concentration exhibited a notable decrease of 56.7% in comparison to the initial level, while considering the exclusion of adsorption effects. Furthermore, by comparing the predicted metabolic pathways of the microbial consortium with the genome of a known chloromethane-degrading bacterium, Hyphomicrobium sp. MC1, using the KEGG database, we observed distinct variations in the metabolic pathways, suggesting the potential role of the unclassified microorganisms. These findings underscore the potential effectiveness of a "top-down" functional microbial screening approach in the degradation of stubborn pollutants.
A sensitive method has been developed for the trace analysis of the sulphur mustard metabolite thiodiglycol (TDG) in urine, and its oxidation product thiodiglycol sulphoxide (TDGO) after reduction to thiodiglycol. Thiodiglycol was extracted from urine by solid phase extraction onto a polymeric cartridge and, after isolation, converted to its bis-heptafluorobutyryl derivative with heptafluorobutyryl imidazole. An ion trap mass spectrometer in selected reaction monitoring mode detected spiked concentrations down to 0.2 ng/ml with a signal to noise ratio>3:1. Urine, from human volunteers with no known exposure to sulphur mustard, contained detectable but very low concentrations (<0.2 ng/ml) of thiodiglycol, consistent with previous observations using different methodologies. Combined concentrations of thiodiglycol and thiodiglycol sulphoxide were determined after reduction of the latter with titanium trichloride. In this case higher background levels (up to 3 ng/ml) were observed, consistent with the sulphoxide being the major excretion product of the two metabolites. The method was applied to urine samples, stored frozen for 13 years, from two casualties of accidental mustard poisoning. Levels of thiodiglycol were 1 and 3 ng/ml, which increased to 78 and 104 ng/ml after treatment of the urine with titanium trichloride.
Bis(trifluoroaceto) disulfide CF(3)C(O)OSSOC(O)CF(3) was prepared and studied by Raman, photoelectron spectroscopy (PES), and theoretical calculations. This molecule exhibits gauche conformation with both C=O groups cis to the S-S bond; the structure of the OSSO moiety is characterized by dihedral angle delta(OSSO) = -95.1 degrees due to the sulfur-sulfur lone pair interactions. The contracted S-S bond (1.979 Angstroms) and relatively high rotational barrier (19.29 kcal mol(-1) at the B3LYP/6-31G level) of the delta(OSSO) indicate the partial resonance-induced double bond character in this molecule. After ionization, the ground cationic-radical form of CF(3)C(O)OSSOC(O)CF(3)(*+) adopts a trans planar main-atom structure (delta(OSSO) = 180 degrees and delta(OCOS) = 0 degrees ) with C(2)(h) symmetry. The S-S bond elongates to 2.054 Angstroms, while the S-O bond shortens from 1.755 Angstroms in neutral form to 1.684 Angstroms in its corresponding cationic-radical form. The adiabatic ionization energy of 9.91 eV was obtained accordingly. The first two HOMOs correspond to the electrons mainly localized on the sulfur 3p lone pair MOs: 3ppi {36a (n(A)(S))](-1) and 3ppi [35b (n(B)(S), n(B)(O(C)(=)(O)))](-1), with an experimental energy separation of 0.16 eV. The first vertical ionization energy is determined to be 10.81 eV.