PubMed · 14120107
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H D RILEY, A H START, E C BRACKEN, M WARREN, J E MAYS, R A BEARGIE. 1964. ENTEROPATHOGENIC E. COLI GASTROENTERITIS.. https://doi.org/10.1177/000992286400300208
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The extensive use of chloramphenicol (CAP) in livestock leads the accumulation of CAP in livestock manures, threatening environmental and human health. Therefore, eliminating or reducing CAP concentration in manures before its re-utilization and application through microbial remediation is necessary. Exiguobacterium sp. CAP4, isolated from the plastisphere in duck manures, was capable of degrading CAP with the biodegradation efficiency of 97.8 % at initial CAP concentration of 5 mg/L within 4 days. A total of twenty-four biotransformation products were determined, including two novel transformation products, TP166 and TP203, enriched the integrity of CAP biodegradation pathways. Furthermore, the biotransformation process was proposed as a detoxifying process through biotransformation products toxicity evaluation. Notably, Exiguobacterium sp. CAP4 successfully colonized in the cow manures after inoculation, and bioaugmented the biodegradation of CAP in virgin cow manures. This study significantly extended our understanding of the CAP biotransformation fate, and provided a promising bacterial strain for bioremediation of CAP containing wastewater in situ.
A method based on liquid chromatography-tandem mass spectrometry was developed and validated for the qualitative and quantitative detection of chloramphenicol (CAP) in seafood samples. The analysis of CAP residues in seafood is important because CAP can cause serious acute reactions in humans, including aplastic anemia and leukemia. The proposed methodology includes a cleanup solid-phase extraction procedure with high recovery efficiency (>90%). Chromatographic separation of CAP and the internal standard (IS) was carried out on a C(18) column, followed by mass spectrometric detection using electrospray ionization in the negative-ion mode. The precursor/product ion transitions 321-->257 (CAP) and 354-->290 (IS) were monitored. Statistical evaluation of this multiple reaction monitoring mass spectrometric procedure reveals good linearity, accuracy, and inter- and intraday precisions. The limit of detection was 0.1 ng/mL, and the limit of quantification for CAP in seafood samples is 0.02 microg/kg. Application in seafood samples allowed the detection of CAP in low parts per billion levels.
The genomic DNA of Escherichia coli is localized in one or a few compact nucleoids. Nucleoids in rapidly grown cells appear in complex shapes; the relationship of these shapes to underlying arrangements of the DNA is of structural interest and of potential importance in gene localization and nucleoid partition studies. To help assess this variation in shape, limited three-dimensional information on individual nucleoids was obtained by DNA fluorescence microscopy of cells as they reoriented in solution or by optical sectioning. These techniques were also applied to enlarged nucleoids within swollen cells or spheroplasts. The resulting images indicated that much of the apparent variation was due to imaging from different directions and at different focal planes of more regular underlying nucleoid shapes. Nucleoid images could be transformed into compact doublet shapes by exposure of cells to chloramphenicol or puromycin, consistent with a preexisting bipartite nucleoid structure. Isolated nucleoids and nucleoids in stationary-phase cells also assumed a doublet shape, supporting such a structure. The underlying structure is suggested to be two subunits joined by a linker. Both the subunits and the linker appear to deform to accommodate the space available within cells or spheroplasts ("flexible doublet" model).