## 4 Discussion
Additionally, in the current experiment, it was observed that plants did not show obvious signs of toxicity stress--i.e., necrosis--suggesting that this species can be grown in crude oil-contaminated soils and as a result is a feasible option for the phytoremediation of petroleum hydrocarbons. Various legumes and cereals species can be effectively used for the phytoremediation of petroleum hydrocarbons [1; 30]. The phytoremediation of petroleum hydrocarbons is significantly regulated by various factors such as environmental conditions, agronomic practices, plant species, and soil characteristics, affecting the petroleum hydrocarbon uptake in the rhizosphere [14; 31]. The screening of these four strains showed that the all the strains were found to be _Enterobacter cloace_ subsp. The results showed that S\({}_{4}\) (PMEL-79) was recognized to be from the genus _Enterobacter cloace_ subsp. dissolvens with a similarity of >97%. Meanwhile, the other strains S\({}_{1}\) (PMEL-63), S\({}_{2}\) (PMEL-67) and S\({}_{3}\) (PMEL-80) were also from the genus _Enterobacter cloace_ subsp. Dissolvens; the similarity percentage was 100% for S\({}_{1}\) (PMEL-63), but for S\({}_{2}\) (PMEL-67) and S\({}_{3}\) (PMEL-80), this value was 99.72%. These strains are all from the same genus _Enterobacter_ sp. [PERSON] et al. [30] conducted an experiment to evaluate the bioremediation potential of _Bacillus subtilis_, _Pseudomonas aeruginosa_ and _Acinetobacter luoffi_ individually and in combination to degrade crude oil. Hydrocarbon-contaminated soil and water was used for the inoculation of these bacteria. In addition, greater degradation by the combination of these bacterial strains was observed as compared to individual bacteria; however, at rates of 77.8% and 76.7%, respectively, crude oil degradation was detected in the experimental units receiving a sole inoculation of _Pseudomonas aeruginosa_ and _Bacillus subtilis_, respectively [30]. The proposed mechanism for the degradation of crude oil by _Enterobacter cloace_ subsp. may be cell uptake, which is comprised of two parts. The first phase is the immediate exposure of _Enterobacter cloace_ subsp. to massive hydrocarbon particles for absorption. In the second phase, the bacteria interact with small pseudo-soluble, quasi-soluble, or encapsulated hydrocarbons particles for absorption. Finally, the crude oil is degraded down into CO2 and H2O, which are basic hydrocarbons [51; 52; 53]. Moreover, soil contaminated with petroleum hydrocarbons should be kept properly aerated and moist to optimize the remediation of crude oil by microbes [10; 31]. [PERSON] et al. [54; 55; 56; 57] also reported the effectiveness of _Bacillus_ strains in the remediation of petroleum hydrocarbons. They used different species from dissimilar genera such as _Pseudomonas_, _Microoccus_, and _Bacillus_ and concluded an important role of species from the genus _Bacillus_ sp as they observed a greater degradation of petroleum hydrocarbons (57%) by a combination dominated by _Bacillus_ sp. as compared to a combination comprised of _Pseudomonas_ and _Microoccus_ species. Furthermore, appropriate agronomic practices--i.e., optimum nutrient management in contaminated soil--significantly improve the microbial biomass and density, further enhancing the biodegradation potential of microbes in petroleum-contaminated soils [29; 33; 56; 58; 59]. Findings from the present research expand our awareness of the plant-microorganism interaction in petroleum-contaminated soils and provide new insights on the use of beneficial microorganisms to enhance the remediation of petroleum hydrocarbons and crop productivity under petroleum hydrocarbon stress; furthermore, the results open new areas for researching the significance of biological interactions in petroleum hydrocarbon-contaminated ecosystems.