## 4 Conclusions  
In this study, we confirmed that the _P. qingdaonensis_ ZCR6 strain isolated from the rhizosphere of maize exhibits potential for the bioremediation of sites co-contaminated with hydrocarbons and heavy metals using this plant. However, the potential contamination of plant biomass should be considered when conducting the phytoremediation experiments using crop plants, e.g., maize. On the other hand, in most cases, the seeds of plants are protected, and heavy metals are not accumulated in such structures; thus, their application is possible. Nevertheless, phytoremediation should be conducted under controlled conditions, and plant biomass cannot be used as food for animals and humans.  
The examined strain shows the potential to promote plant growth through a wide range of mechanisms, such as the production of IAA, ACC deaminase, siderophores, ammonia and solubilization of phosphate. It is worth noting that these mechanisms can also affect the effectiveness of the bioremediation process. Additionally, sequencing of the ZCR6 strain genome provided important information about features that may be crucial for bioremediation. Notably, genetic analyses were linked with the outcomes of previously performed assays, expanding the understanding of genome-phenotype interplays. We identified the genes involved in the metabolism and degradation of xenobiotics. Furthermore, genome sequencing of ZCR6 opened up a number of opportunities to study the mechanisms involved in the production of secondary metabolites via PGP, including biosurfactants and metal resistance. We believe that our research provided substantial interesting data about a new _P. qingdaonensis_ species. Complete characteristics of the ZCR6 strain are beneficial for fully understanding the mechanisms involved in the bioremediation of co-contaminated sites.  
**Author Contributions:** Conceptualization, M.P.-P.; Data curation, M.P.-P.; Formal analysis, D.C. and M.P.-P.; Funding acquisition, M.P.-P.; Investigation, D.C., S.G., A.K. and M.P.-P.; Methodology, D.C., T.P. and M.P.-P.; Project administration, M.P.-P.; Resources, D.C., K.H.-K. and M.P.-P.; Software, D.C., T.P. and M.P.-P.; Supervision, M.P.-P.; Validation, D.C. and M.P.-P.; Visualization, D.C., T.P. and M.P.-P.; Writing--original draft, D.C., T.P., K.H.-K. and M.P.-P.; Writing--review and editing, M.P.-P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The research was supported by grants No. 2018/31/D/NZ9/01610 (biochemical characteristics, cellular fatty acid analysis, minimal inhibitory concentration determination, whole genome sequencing and bioinformatic analysis) and No. 2016/23/D/NZ9/01400 (hydrocarbon degradation analysis, plant-growth-promoting activities and surface-active properties) financed by the National Science Centre (Poland).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Genome sequences were deposited in the GenBank database under BioProject accession number PRJNA681194 under accession number JADWSX00000000 ([[https://www.ncbi.nlm.nih.gov/nucore/JADWSX000000000](https[PERSON]www.ncbi.nlm.nih.gov/nucore/JADWSX000000000)]([https://www.ncbi.nlm.nih.gov/nucore/JADWSX000000000](https://www.ncbi.nlm.nih.gov/nucore/JADWSX000000000)), accessed on 1 December 2020). 165 rRNA gene sequence was deposited in the GenBank database under accession number OK597188.1 ([[https://www.ncbi.nlm.nih.gov/nucore/OK597188](https[PERSON]www.ncbi.nlm.nih.gov/nucore/OK597188)]([https://www.ncbi.nlm.nih.gov/nucore/OK597188](https://www.ncbi.nlm.nih.gov/nucore/OK597188)), accessed on 1 December 2020).  
**Conflicts of Interest:** The authors declare no conflict of interest.