Résumé:
From an agricultural soil sample from the region of Ain M'Lila and a sample of activated sludge
from the Ibn Ziad-Constantine wastewater treatment plant, we isolated respectively 80 and 18
phenotypically different actinobacteria. The samples in question were the subject of a physic-chemical
analysis. Firstly, we conducted a functional study by testing these isolates on a minimum solid
medium supplemented with 500 mg/L of different pesticides most commonly used in Algeria, namely
the Ortiva and Rodazime fungicides. Insecticides like Karate, Phoenix, Dursban and Cypermethrin.
Herbicides in several commercial forms such as Mamba, Zoom, Glyphosate, Herbasate, Roundup,
Traxos and Axial to characterize their abilities to use these pesticides as the sole source of carbon and
energy. The results showed that the majority of isolates had the ability to degrade these synthetic
compounds. Thus, in this thesis work, we have been interested in testing the ability of these isolates to
degrade BTEX, which is an important family of volatile organic compounds. They contaminate
various ecosystems such as air, surface water, groundwater and soil. These compounds have very toxic
effects on humans and animals. Several microorganisms have been tested for their ability to degrade
BTEX. Others have unfortunately been neglected despite their interesting metabolic and physiological
aptitudes. In the present study, we tested the degradation of these compounds by isolated
actinomycetes taken individually or in consortia. The results of growth and degradation kinetics
showed that 20 actinobacteria and 2 reconstituted consortia were able to use at least one BTEX
compound as the sole source of carbon and energy. Of these, four from activated sludge and one from
agricultural soils degraded all these volatile organic compounds in vitro under aerobic conditions at
concentrations ranging from 1400 to 1500 mg/L in 72 to 96 h of incubation. The second part of this
work aimed to identify active isolates. The physiological study informed us about the remarkable
metabolic diversity of the isolates tested. In addition, a taxonomic study was conducted by sequencing
16S rRNA of 25 strains. This identification showed that twenty-one of these isolates belonged to the
genus Streptomyces and three to the genus Nocardia. This result is very encouraging and shows that
actinomycetes that come from sewage treatment plants and agricultural soils have the ability to
biodegrade these organic volatil compounds and pesticides. The isolated strains are excellent
candidates for bioremedion of terrestrial and aquatic sites polluted by these xenobiotics.
