With the increasing demand for diesel in various countries, the ecological pollution caused by the improper use, storage, and accidental leakage of diesel needs to be addressed urgently. As an environmentally friendly and cost-effective method, bioremediation generally uses various microorganisms to remove pollutants from the environment. Here, the strain KJ-1, obtained through an enrichment culture using n-dodecane from oil-contaminated soil near a gas station as the substrate, was identified as Acinetobacter vivianii according to its morphology, biochemistry, and molecular biology. The isolate KJ-1 was able to use diesel as a sole carbon source and more than 40% of diesel was degraded after 12 days of incubation with strain KJ-1 in mineral salts medium. The most suitable diesel concentration and nitrogen source concentrations were 4,140 mg/L and 350–700 mg/L, respectively, for diesel degradation and bacterial growth. The optimal initial pH and temperature for strain KJ-1 growth and diesel degradation were 6.5–8.0 and 20–37°C, respectively. To investigate the diesel-degrading mechanisms of this strain, the complete genome was sequenced and annotated. The complete genome consists of one chromosome with a total length of 3,927,757 base pairs and a G + C content of 41.5%. The genes related to the two-component regulatory system and alkane degradation were analyzed. In addition, two putative alkane monooxygenases were analyzed, and the protein sequences were characterized and compared with other AlkBs in Acinetobacter spp. using sequences downloaded from NCBI. The results demonstrated that A. vivianii KJ-1 may be particularly useful for future bioremediation of diesel-polluted soil.

Facile and sensitive methods for detecting neonicotinoids (NEOs) in aquatic environments are crucial because they are found in extremely low concentrations in complex matrices. Herein, nitrogen-based magnetic conjugated microporous polymers (Fe₃O₄@N-CMP) with quaternary ammonium groups were synthesized for efficient magnetic solid-phase extraction (MSPE) of NEOs from tap water, rainwater, and lake water. Fe₃O₄@N-CMP possessed a suitable specific surface area, extended π-conjugated system, and numerous cationic groups. These properties endow Fe₃O₄@N-CMP with superior extraction efficiency toward NEOs. The excellent adsorption capacity of Fe₃O₄@N-CMP toward NEOs was attributed to its π–π stacking, Lewis acid–base, and electrostatic interactions. The proposed MSPE-HPLC-DAD approach based on Fe₃O₄@N-CMP exhibited a wide linear range (0.1–200 µg/L), low detection limits (0.3–0.5 µg/L), satisfactory precision, and acceptable reproducibility under optimal conditions. In addition, the established method was effectively utilized for the analysis of NEOs in tap water, rainwater, and lake water. Excellent recoveries of NEOs at three spiked levels were in the range of 70.4 to 122.7%, with RSDs less than 10%. This study provides a reliable pretreatment method for monitoring NEOs in environmental water samples.

A hydrocarbon-degrading bacterium Providencia rettgeri L1 was isolated from petroleum in Shengli oil field, China. The petroleum-degradation characteristics were investigated. The degradation rate of petroleum by the strain was 45.9% in petroleum-mineral medium (5 g/L) in 14 d measured by ultraviolet-visible spectrophotometer. The intracellular crude enzymes of Providencia rettgeri L1 were prepared and supplemented with formate dehydrogenase to construct an enzyme cocktail. The petroleum degradation rate of the cocktail reached 49.5% in 8 h, which was much faster than the strain. The subfraction saturates and aromatics in petroleum were analyzed by gas chromatography and gas chromatography-mass spectrometry, respectively. After degradation for 8 h, the degradation rate of saturates C10-C40 was 50.4%, while the values for short, mid and long-chain saturates were 52.6%, 49.4% and 47.7%, respectively. Biodegradation assessment markers-pristane and phytane, were degraded by 49.3% and 44.9%, respectively. The degradation rate of aromatics was 29.5%. For 2, 3, 4 and 5-ring PAHs, the corresponding values were 47.8%, 24.2%, 29.5% and 19.8%, respectively. Source tracing experiment showed that Providencia rettgeri L1 was more dominant in enriched bacterial suspensions than in petroleum environment, indicating its advantage of rapid proliferation in culture media. This study can provide some insights into fast degradation of petroleum.

The present study aimed to comprehensively dissect the petroleum hydrocarbon degradation mechanism of Acinetobacter vivianii KJ-1. The isolated and identified strain was able to proliferate using diesel as the sole carbonaceous substrate. Via comparative genomics, an in-depth analysis was performed to elucidate the genome similarities and disparities between this strain and related strains, thereby uncovering a core genome as well as genes with uncharacterized functions. Transcriptome analysis, carried out under different substrate conditions (C16, diesel, sodium acetate) manifested distinct gene expression modalities. A multitude of genes associated with alkane metabolism were differentially expressed, among which alkB1_1 and alkB1_2 was conspicuously upregulated. Prokaryotic expression of alkB1_1 was implemented, and the enzyme activity of the recombinant protein peaked at a pH level of approximately 7.0 and within a temperature range of 30 to 40 °C. The recombinant strain was shown to possess the ability to degrade n-hexadecane. Collectively, this research not only augments the understanding of the degradation mechanism of A. vivianii KJ-1 but also provides a fundamental basis for developing bioremediation strategies targeting petroleum hydrocarbon-contaminated environments.

Bioremediation is a low-cost, eco-friendly technique to reduce and/or eliminate pollutants from environment. Moreover, effective biological degrader for contaminants removal is important during bioremediation process. Here, the strain RHZ01, isolated from petroleum-contaminated soil in Shengli Oilfield, was identified as Rhodococcus qingshengii by the morphology, physiology, biochemistry and molecular biology. Strain RHZ01 was able to use diesel as the sole carbon source. The optimal initial pH and temperature for strain RHZ01 growth and diesel degradation were 6-8.5 and 20-30ºC, respectively. Nutrients (NaNO3, NH4Cl, KNO3 and Urea) could replace NH4NO3. And Mg2+ was required for strain RHZ01 growth and diesel degradation. To investigate the diesel degrading mechanisms of this strain, the complete genome was sequenced and annotated. The complete genome consists of one chromosome with a total length 6,506,318 bp and a G+C content of 62.48%. Five putative alkane monooxygenases (AlkB) encoding genes were further analyzed, and their protein sequences were characterized and compared with other published AlkBs in Rhodococcus spp.. The physicochemical features of the five AlkBs were analyzed, and these monooxygenase proteins are alkaline, unstable and thermostable. AlkB1, AlkB2 and AlkB3 are hydrophilic protein while the other proteins were hydrophobic. All of these alkane monooxygenases share several conserved regions, such as HYG-motif and three Hist boxes. From the results, it is demonstrated that bacterial strain isolated from petroleum-contaminated could be the potential bioremediation agent for diesel removal.

Petroleum-contaminated terrestrial ecosystems require effective bioremediation strategies. In this study, genomic analysis revealed key biodegradation genes on the Acinetobacter calcoaceticus 21# chromosome: alkane hydroxylases (alkB, almA, LadA) and aromatic ortho-cleavage pathway genes (catABC). Phylogenetic and multiple sequence alignment analyses of the almA gene in strain 21# revealed the presence of signature motifs characteristic of Baeyer–Villiger monooxygenase. Functional annotation analysis demonstrated stronger phylogenetic affinity of this protein to previously characterized BVMOs than to hydroxylases. Therefore, it is suggested that the AlmA protein in 21# exhibits BVMO activity and participates in the subterminal oxidation pathway of alkane degradation. Wild-type 21# degraded both n-Octacosane (24.47%) and pyrene (34.03%). Engineered 21#-A3 showed significantly enhanced n-Octacosane degradation (28.68%). To validate AlmA function and assess impacts of exogenous gene integration, we expressed the almA gene from A. vivianii KJ-1 via pET-28a(+)-av-almA-BH vector. Enzymatic assays demonstrated no activity toward long-chain alkanes but high activity for 2-decanone (0.39 U/mg) and 2-dodecanone (0.37 U/mg). Metabolite analysis confirmed recombinant AlmA functions through subterminal oxidation. This study establishes a foundational framework for advancing the optimization of petroleum-degrading bacteria. To engineer more efficient hydrocarbon-degrading strains, future research should integrate meta-cleavage pathways to expand their substrate utilization range for polycyclic aromatic hydrocarbons.