Biomedical subjects

S El Fantroussi

Publications and source records attributed to S El Fantroussi.

3 recordsLinked to original sources

PubMed2000

Effect of dissemination of 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids on 2,4-D degradation and on bacterial community structure in two different soil horizons.

Transfer of the 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids pEMT1 and pJP4 from an introduced donor strain, Pseudomonas putida UWC3, to the indigenous bacteria of two different horizons (A horizon, depth of 0 to 30 cm; B horizon, depth of 30 to 60 cm) of a 2,4-D-contaminated soil was investigated as a means of bioaugmentation. When the soil was amended with nutrients, plasmid transfer and enhanced degradation of 2,4-D were observed. These findings were most striking in the B horizon, where the indigenous bacteria were unable to degrade any of the 2,4-D (100 mg/kg of soil) during at least 22 days but where inoculation with either of the two plasmid donors resulted in complete 2,4-D degradation within 14 days. In contrast, in soils not amended with nutrients, inoculation of donors in the A horizon and subsequent formation of transconjugants (10(5) CFU/g of soil) could not increase the 2,4-D degradation rate compared to that of the noninoculated soil. However, donor inoculation in the nonamended B-horizon soil resulted in complete degradation of 2,4-D within 19 days, while no degradation at all was observed in noninoculated soil during 89 days. With plasmid pEMT1, this enhanced degradation seemed to be due only to transconjugants (10(5) CFU/g of soil), since the donor was already undetectable when degradation started. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes showed that inoculation of the donors was followed by a shift in the microbial community structure of the nonamended B-horizon soils. The new 16S rRNA gene fragments in the DGGE profile corresponded with the 16S rRNA genes of 2,4-D-degrading transconjugant colonies isolated on agar plates. This result indicates that the observed change in the community was due to proliferation of transconjugants formed in soil. Overall, this work clearly demonstrates that bioaugmentation can constitute an effective strategy for cleanup of soils which are poor in nutrients and microbial activity, such as those of the B horizon.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1998

Effect of specific inhibitors on the anaerobic reductive dechlorination of 2,4,6-trichlorophenol by a stable methanogenic consortium.

The transformation of 2,4,6-trichlorophenol (TCP) into 4-chlorophenol (4CP) was studied using a stable methanogenic enrichment culture derived from an anaerobic fixed bed reactor. Using acetate as a growth substrate, different inhibitors of methanogenesis exhibited distinct effects on TCP dechlorination. Whereas reductive dechlorination activity was not affected by 2% ethylene in the gas phase, 25 mM bromoethanesulfonic acid (BESA) had a direct inhibitory effect on this process. The choice of BESA as a specific inhibitor for identifying the subpopulations involved in reductive dechlorination of chloroaromatics is thus questionable. Inhibitors of sulfate reduction such as molybdate (20 mM) and selenate (20 mM) had a direct inhibitory effect on reductive dechlorination independently of the presence of sulfate in the medium supplemented with acetate as growth substrate. Consequently much more care must also be taken with these inhibitors to prove that reductive chlorination is coupled to sulfate reduction.

Journal Article↗

PubMedDate not supplied

Anaerobic dechlorinating bacteria.

Anaerobic dehalogenation is attracting great interest since it opens new research horizons based on the novel biochemical mechanisms identified in this field such as halorespiration, i.e. the utilization of halogenated compounds as electron acceptors. Moreover, anaerobic bacteria seem to be more efficient than their aerobic counterparts in removing halogen atoms from polyhalogenated compounds. Thus, anaerobic dehalogenation can be considered as a promising means for bioremediation treatments of persistently polluted environments. In this line, identification of pure strains capable of dehalogenation will give important information about the diversity of organisms implicated in this process and also fundamental explanations of the diverse biochemical mechanisms involved. In light of these considerations, we chose to focus this review on the physiological descriptions, dechlorination activities, phylogenetic diversity, and potential biotechnological applications of these pure anaerobic strains capable of dehalogenation.

Bacteria, Anaerobic↗