Analysis of the Genome of the Heavy Metal Resistant and Hydrocarbon-Degrading Rhizospheric Pseudomonas qingdaonensis ZCR6 Strain and Assessment of Its Plant-Growth-Promoting Traits

Abstract

The Pseudomonas qingdaonensis ZCR6 strain, isolated from the rhizosphere of Zea mays growing in soil co-contaminated with hydrocarbons and heavy metals, was investigated for its plant growth promotion, hydrocarbon degradation, and heavy metal resistance. In vitro bioassays confirmed all of the abovementioned properties. ZCR6 was able to produce indole acetic acid (IAA), siderophores, and ammonia, solubilized Ca3(PO4)2, and showed surface active properties and activity of cellulase and very high activity of 1-aminocyclopropane-1-carboxylic acid deaminase (297 nmol α-ketobutyrate mg−1 h−1). The strain degraded petroleum hydrocarbons (76.52% of the initial hydrocarbon content was degraded) and was resistant to Cd, Zn, and Cu (minimal inhibitory concentrations reached 5, 15, and 10 mM metal, respectively). The genome of the ZCR6 strain consisted of 5,507,067 bp, and a total of 5055 genes were annotated, of which 4943 were protein-coding sequences. Annotation revealed the presence of genes associated with nitrogen fixation, phosphate solubilization, sulfur metabolism, siderophore biosynthesis and uptake, synthesis of IAA, ethylene modulation, heavy metal resistance, exopolysaccharide biosynthesis, and organic compound degradation. Complete characteristics of the ZCR6 strain showed its potential multiway properties for enhancing the phytoremediation of co-contaminated soils. To our knowledge, this is the first analysis of the biotechnological potential of the species P. qingdaonensis.

Effect of Novosphingobium sp. CuT1 inoculation on the rhizoremediation of heavy metal- and diesel-contaminated soil planted with tall fescue

“…These results suggest that the positive effects of CuT1 inoculation on the root growth of tall fescue are largely attributable to the IAA production activity of the strain. IAA can improve plant growth by stimulating root growth via nodule formation (Chlebek et al 2022).…”

“…Moreover, IAA can increase the amount of root exudates by slackening the cell walls (Chlebek et al 2022). Root exudates can prevent heavy metals from entering the plant by lowering their mobility (Chlebek et al 2022).…”

“…Fe is an essential micronutrient for plants and microorganisms. Fe is involved in various important biological processes, such as DNA synthesis, respiration, and photosynthesis (Chlebek et al, 2022). Siderophores not only stimulate plant growth but can also form stable complex compounds with other metals such as Al, Cd, Cu, and Pb.…”

“…Siderophores not only stimulate plant growth but can also form stable complex compounds with other metals such as Al, Cd, Cu, and Pb. In turn, these complexes can promote the absorption of heavy metals into plants (Chlebek et al 2022).…”

“…Some PGPR have plant growth-promoting traits such as indole-3-acetic acid (IAA) production, dehydrogenase (DH) production, and siderophore production in contaminated soil (Jung et al 2007; Kim et al 2010; Lee and Bae 2011; Chakraborty et al 2021). Additionally, some of them have been reported to possess tolerance against heavy metals, as well as plant growth-promoting traits (Chlebek et al 2022). Heavy metals in the rhizosphere adsorb to plant roots or are converted into insoluble species, which reduces their bioavailability (He et al 2021).…”