ABSTRACT
The present study evaluates the PCB-dehalorespiring capabilities and dynamics of indigenous Dehalococcoides mccartyi population in a PCB contaminated marine sediment. Specialized PCB-dechlorinase genes pcbA1, pcbA4 and pcbA5 previously characterized in pure cultures of D. mccartyi, were here found for the first time in environmental samples. Reductive dechlorination was stimulated by spiking Aroclor1254 to the sediment and by imposing strictly anaerobic conditions both with and without bioaugmentation with a Dehalococcoides mccartyi enrichment culture. In line with the contaminant dechlorination kinetics, Dehalococcoides population increased during the entire incubation period showing growth yields of 4.94E+07 Dehalococcoides per µmolCl-1 and 7.30E+05 Dehalococcoides per µmolCl-1 in the marine sediment with and without bioaugmentation respectively. The pcbA4 and pcbA5 dechlorinase genes, and to a lesser extent pcbA1 gene, were enriched during the anaerobic incubation suggesting their role in Aroclor1254 dechlorination under salinity conditions.
Subject(s)
Bacterial Proteins/genetics , Chloroflexi/genetics , Geologic Sediments/microbiology , Polychlorinated Biphenyls/metabolism , Bacterial Proteins/metabolism , Biodegradation, Environmental , Chloroflexi/metabolism , Halogenation , Microbial Consortia/genetics , Polychlorinated Biphenyls/chemistry , Water Pollutants, Chemical/chemistryABSTRACT
The interest in the measurement of the elastic properties of thin films is witnessed by a number of new techniques being proposed. However, the precision of results is seldom assessed in detail. Brillouin spectroscopy (BS) is an established optical, contactless, non-destructive technique, which provides a full elastic characterization of bulk materials and thin films. In the present work, the whole process of measurement of the elastic moduli by BS is critically analyzed: experimental setup, data recording, calibration, and calculation of the elastic moduli. It is shown that combining BS with ellipsometry a fully optical characterization can be obtained. The key factors affecting uncertainty of the results are identified and discussed. A procedure is proposed to discriminate factors affecting the precision from those affecting the accuracy. By the characterization of a model transparent material, silica in bulk and film form, it is demonstrated that both precision and accuracy of the elastic moduli measured by BS can reach 1% range, qualifying BS as a reference technique.
