Mechanism of A. oleivorans S4 treating soluble phosphorus deficiency and hydrocarbon contamination simultaneously.

Both soluble phosphorus (P) deficiency and petroleum hydrocarbon contamination represent challenges in soil environments. While phosphate-solubilizing bacteria and hydrocarbon-degrading bacteria have been identified and employed in environmental bioremediation, the bacteria co-adapted to soluble P deficiency and hydrocarbon contamination has rarely been reported. This study explored the ability of Acinetobacter oleivorans S4 (A. oleivorans S4) to solubilize phosphate using n-hexadecane (H), glucose (G), and a mixed carbon source (HG) in tricalcium phosphate (TCP) medium. A. oleivorans S4 exhibited robust growth in H-TCP, releasing 31 mg L-1 of soluble P. Conversely, A. oleivorans S4 barely grew in G-TCP, releasing 654 mg L-1 of soluble P. In HG-TCP, biomass surpassed that in H-TCP, with phosphate release comparable to that in G-TCP. HPLC analysis revealed a small amount of TCA cycle acids in H-TCP and a large amount of gluconate in G-TCP and HG-TCP. Transcriptomic analysis showed elevated expression of genes associated with alkane degradation, P starvation, N utilization, and trehalose synthesis in H-TCP, revealing the molecular co-adaptation mechanism of A. oleivorans S4. Furthermore, the addition of glucose enhanced alkane degradation, P and N utilization, and reduced trehalose synthesis. It indicated that incomplete glucose metabolism may provide energy for other reactions, and the increase in soluble P mediated by gluconate may alleviate oxidative stress. Overall, A. oleivorans S4 proves promising for remediating soluble P-deficient and hydrocarbon-contaminated environments, and glucose stimulates its transformation into a super phosphate-solubilizing bacterium.

Doping engineering in S-scheme composite for Regulating the selectivity of photocatalytic CO2 reduction.

Regulating product selectivity in photocatalytic CO2 reduction to enhance the yield of valuable hydrocarbons remains a formidable challenge because of the diversity of reduction products and the competitive reduction of H2O. Herein, ultrathin Bi2O3/ Co-doped SrBi4Ti4O15 S-scheme photocatalysts (Co-BS) were synthesized using a hydrothermal method. The Bi2O3/Co-doped SrBi4Ti4O15 photocatalyst exhibited significantly higher selectivity for CH4 (62.3 µmolg-1) and CH3OH (54.1 µmolg-1) in CO2 reduction compared with pure SrBi4Ti4O15 (27.2 and 0.8 µmolg-1) and the Bi2O3/SrBi4Ti4O15 S-scheme without Co (30.2 and 0 µmolg-1). The experimental results demonstrated that the inclusion of Co into SrBi4Ti4O15 expanded the range of light absorption and generated an internal electric field between Co-doped SrBi4Ti4O15 and Bi2O3. Density functional theory calculations and other experimental findings confirmed the formation of a new doping energy level in the Bi2O3/SrBi4Ti4O15 S-scheme heterojunction after Co doping. The valence band electrons of Bi2O3/SrBi4Ti4O15 transitioned to the Co-doped level because of the interconversion between Co3+ and Co2+ under the action of the internal electric field. Furthermore, the corresponding characterizations revealed that the adsorption and electron transfer rates of the surface active sites were accelerated after Co doping, enhancing electron involvement in the photocatalytic reaction process. This study presented a metal-doped S-scheme heterojunction approach for CO2 reduction to produce high-value products, enhancing the conversion of solar energy into energy resources.

Characterization and genome analysis of Acinetobacter oleivorans S4 as an efficient hydrocarbon-degrading and plant-growth-promoting rhizobacterium.

Plant-growth-promoting rhizobacteria (PGPR) have received increasing attention for assisting phytoremediation. However, the effect of PGPR on total petroleum hydrocarbon (TPH) degradation and plant growth promotion and its underlying mechanism is not well understood. In this study, phenotypic analysis and whole genome sequencing were conducted to comprehensively characterize a newly isolated rhizobacterium strain S4, which was identified as Acinetobacter oleivorans, from a TPH-contaminated soil. The strain degraded 62.5% of initially spiked diesel (1%) in minimal media within six days and utilized n-alkanes with a wide range of chain length (i.e., C12 to C40). In addition, the strain showed phenotypic traits beneficial to plant growth, including siderophore production, indole-3-acetic acid synthesis and phosphate solubilization. Potential metabolic pathways and genes encoding proteins responsible for the phenotypic traits were identified. In a real TPH-contaminated soil, inoculation of Acinetobacter oleivorans S4 significantly enhanced the growth of tall fescue relative to the soil without inoculation. In contrast, inoculation of Bacillus sp. Z7, a hydrocarbon-degrading strain, showed a negligible effect on the growth of tall fescue. The removal efficiency of TPH with inoculation of Acinetobacter oleivorans S4 was significantly higher than those without inoculation or inoculation of Bacillus sp. Z7. These results suggested that traits of PGPR beneficial to plant growth are critical to assist phytoremediation. Furthermore, heavy metal resistance genes and benzoate and phenol degradation genes were found in the genome of Acinetobacter oleivorans S4, suggesting its application potential in broad scenarios.

Weak interaction-alleviated toxicity of aromatic compounds in EPS matrices: Quantifying the noncovalent bonding-to-EPS ecoservice chain.

Extracellular polymeric substances (EPSs) constitute a largely global carbon pool that could participate in geochemical process of organic chemicals. Besides the chemical hydrolysis and redox of chemicals exerted by the EPS, weakly noncovalent interactions with dispersive EPS control the toxicity of numerous organic compounds. Nevertheless, there has been a lack of in-depth research on this issue. This work quantified a chain of links from bonding to detoxification using natural biofilms to explore the control behavior of fragile noncovalent bonding to the ecotoxicity of aromatic compounds. Such bonding decreases cell absorbability of m-phenylenediamine, 2-naphthol, and phenanthrene by 5.3-53.6%, resultantly increasing the indices of microbial diversity by 122.2-279.5%. Herein, the 60 kDa chaperonin in EPS acts as the most important contributor (16.4% of the top 20 proteins) to noncovalent interactions. Hydrophilic carboxyl groups in EPS bind with hydroxyl and amino groups of m-phenylenediamine and 2-naphthol via H-bonds, respectively. Methylene and carboxyl groups combine with hydrophobic phenanthrene via CH···π and H-bonding, respectively. A quantified chain was consequently established that weak interaction linearly controls ecotoxicity of aromatic compounds via the above suppressive cell absorbability of aromatic compounds (R2 =0.82). Considering ubiquitous EPS and prevailing aromatic compounds, our findings revealed a previously unnoticed phenomenon in which seemingly fragile noncovalent bonding profoundly alleviates the ecotoxicity of aromatic compounds in Earth's surface system.