Résumé
Three bacterial isolates identified as Alcanivorax borkumensis SK2, Rhodococcus erythropolis HS4 and Pseudomonas stutzeri SDM, based on 16S rRNA gene sequences, were isolated from crude oil enrichments of natural seawater. Single strains and four bacterial consortia designed by mixing the single bacterial cultures respectively in the following ratios: (Alcanivorax: Pseudomonas, 1:1), (Alcanivorax: Rhodococcus, 1:1), (Pseudomonas: Rhodococcus, 1:1), and (Alcanivorax: Pseudomonas: Rhodococcus, 1:1:1), were analyzed in order to evaluate their oil degrading capability. All experiments were carried out in microcosms systems containing seawater (with and without addition of inorganic nutrients) and crude oil (unique carbon source). Measures of total and live bacterial abundance, Card-FISH and quali-, quantitative analysis of hydrocarbons (GC-FID) were carried out in order to elucidate the co-operative action of mixed microbial populations in the process of biodegradation of crude oil. All data obtained confirmed the fundamental role of bacteria belonging to Alcanivorax genus in the degradation of linear hydrocarbons in oil polluted environments.
Sujets)
Alcanivoraceae/métabolisme , Pétrole/métabolisme , Pseudomonas stutzeri/métabolisme , Rhodococcus/métabolisme , Alcanivoraceae/classification , Alcanivoraceae/génétique , Alcanivoraceae/isolement et purification , Biotransformation , Analyse de regroupements , ADN bactérien/composition chimique , ADN bactérien/génétique , ADN ribosomique/composition chimique , ADN ribosomique/génétique , Consortiums microbiens , Données de séquences moléculaires , Phylogenèse , Pseudomonas stutzeri/classification , Pseudomonas stutzeri/génétique , Pseudomonas stutzeri/isolement et purification , /génétique , Rhodococcus/classification , Rhodococcus/génétique , Rhodococcus/isolement et purification , Analyse de séquence d'ADN , Eau de mer/microbiologieRésumé
Oil spill microcosms experiments were carried out to evaluate the effect of bioemulsificant exopolysaccharide (EPS2003) on quick stimulation of hydrocarbonoclastic bacteria. Early hours of oil spill, were stimulated using an experimental seawater microcosm, supplemented with crude oil and EPS2003 (SW+OIL+EPS2003); this system was monitored for 2 days and compared to control microcosm (only oil-polluted seawater, SW+OIL). Determination of bacterial abundance, heterotrophic cultivable and hydrocarbon-degrading bacteria were carried out. Community composition of marine bacterioplankton was determined by 16S rRNA gene clone libraries. Data obtained indicated that bioemulsificant addition stimulated an increase of total bacterial abundance and, in particular, selection of bacteria related to Alcanivorax genus; confirming that EPS2003 could be used for the dispersion of oil slicks and could stimulate the selection of marine hydrocarbon degraders thus increasing bioremediation process.