Novel hydrocarbonoclastic metal-tolerant Acinetobacter and Pseudomonas strains from Aconcagua river oil-polluted soil

Abstract

Bioremediation of sites polluted with petroleum hydrocarbons and heavy metals is a major challenge. The aim of this study was the isolation and characterization of hydrocarbon-degrading and heavy metal-tolerant bacteria. Sixteen hydrocarbonoclastic bacteria were isolated by enrichment from a crude oil-contaminated soil at Aconcagua river mouth, Central Chile. Most strains were cocci-shaped and exhibited circular cream-colored colonies with smooth texture. Isolates were resistant to bacitracin and penicillin, and two isolates were motile. Isolates were identified by 16S rRNA and rpoD and rpoB genes sequence analyses. Most isolates belonged to Gammaproteobacteria including Acinetobacter radioresistens (4 isolates), Acinetobacter calcoaceticus (1), Pseudomonas stutzeri (2) and Pseudomonas chloritidismutans (1). Seven isolates possessed 97% 16S rRNA gene similarity with A. calcoaceticus ATCC 23055T, suggesting that these probably represent a new Acinetobacter species. One isolate is an Actinobacteria of the Kocuria genus. All isolates were able to grow on crude oil, whereas eleven Acinetobacter and Pseudomonas strains grew on n-hexadecane. Pseudomonas isolates grew on fluorene (DM88 and DM95) and naphthalene (DD74). Acinetobacter isolates grew on fluorene (DD75, DD79 and DM81) and phenanthrene (DM82). Remarkably, most isolates (except DD79) exhibited copper or cadmium tolerance. These novel hydrocarbonoclastic and heavy metal-tolerant Pseudomonas and Acinetobacter strains are potential biocatalysts for bioremediation.