Remediating petroleum hydrocarbons in highly saline-alkali soils using three native plant species

Remediation of phenanthrene contaminated soil by persulphate coupled with Pseudomonas aeruginosa GZ7 based on oxidation prediction model

Chemical oxidation coupled with microbial remediation has attracted widespread attention for the removal of polycyclic aromatic hydrocarbons (PAHs). Among them, the precise evaluation of the feasible oxidant concentration of PAH-contaminated soil is the key to achieving the goal of soil functional ecological remediation. In this study, phenanthrene (PHE) was used as the target pollutant, and Fe2+-activated persulphate (PS) was used to remediate four types of soils. Linear regression analysis identified the following important factors influencing remediation: PS dosage and soil PHE content for PHE degradation, Fe2+ dosage, hydrolysable nitrogen (HN), and available phosphorus for PS decomposition. A comprehensive model of "soil characteristics-oxidation conditions-remediation effect" with a high predictive accuracy was constructed. Based on model identification, Pseudomonas aeruginosa GZ7, which had high PAHs degrading ability after domestication, was further applied to coupling repair remediation. The results showed that the optimal PS dose was 0.75% (w/w). The response relationship between soil physical, chemical, and biological indicators at the intermediate interface and oxidation conditions was analysed. Coupled remediation effects were clarified using microbial diversity sequencing. The introduction of Pseudomonas aeruginosa GZ7 stimulated the relative abundance of Cohnella, Enterobacter, Paenibacillus, and Bacillus, which can promote material metabolism and energy transformation during remediation.

Nocardioides limicola sp. nov., an alkaliphilic alkane degrading bacterium isolated from oilfield alkali-saline soil

A Gram-stain-positive, rod-shaped, non-spore-forming, alkane degrading bacterium, designated DJM-14T, was isolated from oilfield alkali-saline soil in Heilongjiang, Northeast China. On the basis of 16 S rRNA gene sequencing, strain DJM-14T was shown to belong to the genus Nocardioides, and related most closely to Nocardioides terrigena KCTC 19,217T (95.53% 16 S rRNA gene sequence similarity). Strain DJM-14T was observed to grow at 25-35 °C, pH 7.0-11.0, in the presence of 0-6.0% (w/v) NaCl. The predominant respiratory quinone was MK-8 (H4) and LL-diaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan. The major fatty acids were identified as iso-C16:0 and C18:1 ω9c. It contained diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol as the polar lipids. The genome (3,722,608 bp), composed of 24 contigs, had a G + C content of 69.6 mol%. Out of the 3667 predicted genes, 3618 were protein-coding genes, and 49 were ncRNAs. Digital DNA-DNA hybridization (dDDH) estimation and average nucleotide identity (ANI) of strain DJM-14T against genomes of the type strains of related species in the same family ranged between 18.7% and 20.0%; 68.8% and 73.6%, respectively. According to phenotypic, genotypic and phylogenetic data, strain DJM-14T represents a novel species in the genus Nocardioides, for which the name Nocardioides limicola sp. nov. is proposed and the type strain is DJM-14T (= CGMCC 4.7593T, =JCM 33,692T). In addition, novel strains were able to grow with n-alkane (C24-C36) as the sole carbon source. Multiple copies of alkane 1-monooxygenase (alkB) gene, as well as alcohol dehydrogenase gene and aldehyde dehydrogenase gene involved in the alkane assimilation were annotated in the genome of type strain DJM-14T.