Characterization of a New Pseudomonas aeruginosa Strain Isolated from Petroleum-Polluted Soil

Because of the extensive utilization of petroleum and petroleum products, soil pollution with monoaromatic hydrocarbons which are highly toxic for most organisms is an important issue in many countries, including Romania. Consequently, the bioremediation of petroleum-polluted environments has attracted much attention in recent decades. The present study aimed to assess the ability of a new Pseudomonas aeruginosa strain to tolerate and degrade several toxic monoaromatic hydrocarbons. The bacterium was also evaluated for its biosurfactant production ability. Pseudomonas aeruginosa IBB_Po25 (GenBank OP542588.1) was isolated from a petroleum sludge-polluted soil sample based on its capability to grow on minimal salt medium in the presence of petroleum, as the sole carbon source. P. aeruginosa IBB_Po25 tolerates and degrades monoaromatic hydrocarbons, like xylene isomers, ethylbenzene, and toluene. A direct correlation was observed between bacterial growth in these monoaromatic hydrocarbons and their respective biodegradation rates. Molecular screening revealed the presence in the genome of P. aeruginosa IBB_Po25 cells of several catabolic genes, such as todC1, todM, xylM, alkM1, and rhamnosyltransferase genes rhlAB which are involved in hydrocarbon biodegradation and the synthesis of rhamnolipid biosurfactant, respectively. The production of rhamnolipid biosurfactant by P. aeruginosa IBB_Po25 grown in the presence of monoaromatic hydrocarbons was confirmed by several screening methods, such as CTAB agar plate, methylene blue, drop-collapse, emulsification index, and HPTLC. The RND transporter gene HAE1 and regulatory gene recA were also detected in the genome of this bacterium. Owing to its ability to tolerate and degrade monoaromatic hydrocarbons, as well as produce rhamnolipid biosurfactant, the isolated bacterium could be an ideal candidate for bioremediation of petroleum-polluted soils.