Biosurfactant plays an important role in bioremediation of crude oil contamination and microbial enhanced oil recovery (MEOR). In the present study, a salt-tolerant, biosurfactant-producing bacterium, designated A-8, was isolated from wastewater contaminated with petroleum collected from the Changqing reservoir in China. A phylogenetic analysis based on the 16S rRNA sequence suggests that strain A-8 belongs to the genus Achromobacter. The optimal growth conditions for strain A-8 in mineral salt (MS) medium were 30°C, pH 7, and 10 g/L NaCl, while the optimal conditions for biosurfactant production in a fermentation medium were 40–45°C, pH 7, and more than 70 g/L NaCl. Better biosurfactant production was obtained from strain A-8 when edible oil and liquid paraffin were used as carbon sources and when (NH₄)₂SO₄ was used as an inorganic nitrogen source compared with other tested carbon and nitrogen sources. The biodegradation of petroleum in MS medium in different optimized conditions reached 56.23–73.87% for 20 days. The biodegradation of petroleum, together with the production of organic acid and biosurfactant, decreased the viscosity of petroleum by about 45%. The decrease in petroleum viscosity and the biodegradation of petroleum suggest the potential use of strain A-8 for MEOR and bioremediation of petroleum-contaminated environments.

Bioremediation of crude oil contaminated environments is an economical, low-maintenance, environmentally friendly technology and has attracted increasing attention in recent years. In the present study, two efficient crude oil degrading bacteria strains were isolated from soils contaminated with crude oil. Phylogenetic analysis suggested they belonged to genus Bacillus, and were designated as Bacillus cereus T-04 and Bacillus halotolerans 1-1. The crude oil depletion of each strain under different conditions was tested. The optimum conditions for both strains’ oil degradation was pH 7, 15–20 g/L NaCl concentration, and 5–15 g/L original oil concentration. The crude oil depletion rate could reach to 60–80% after 20 days of treatment. The crude oil bioremediation simulation tests revealed that the bioremediation promoted the depletion of crude oil to a large extent. The inoculum group with inorganic medium showed the highest crude oil depletion (97.5%) while the crude oil depletion of control group was only 26.6% after 180 days of treatment. High-throughput sequencing was used to monitor the changes of microbial community using different treatments. In all groups, Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes were the dominant phyla. After contaminated with crude oil, the relative abundance of phylum Actinobacteria was dramatically increased and occupied 81.8%. Meanwhile although strains of Bacillus were added in the bioaugmentation groups, the relative abundance of genus Bacillus was not the most abundant genus at the end of simulation tests. The crude oil contamination dramatically decreased the soil microbial diversity and bioremediation could not recover the microbial community in the short term.

Pennisetum sinese is a good forage grass with high biomass production and crude proteins. However, little is known about the endophytic fungi diversity of P. sinese, which might play an important role in the plant’s growth and biomass production. Here, we used high throughput sequencing of the Internal Transcribed Spacer (ITS) sequences based on primers ITS5-1737 and ITS2-2043R to investigate the endophytic fungi diversity of P. sinese roots at the maturity stage, as collected from four provinces (Shaanxi province, SX; Fujian province, FJ; the Xinjiang Uyghur autonomous prefecture, XJ and Inner Mongolia, including sand (NS) and saline-alkali land (NY), China). The ITS sequences were processed using QIIME and R software. A total of 374,875 effective tags were obtained, and 708 operational taxonomic units (OTUs) were yielded with 97% identity in the five samples. Ascomycota and Basidiomycota were the two dominant phyla in the five samples, and the genera Khuskia and Heydenia were the most abundant in the FJ and XJ samples, respectively, while the most abundant tags in the other three samples could not be annotated at the genus level. In addition, our study revealed that the FJ sample possessed the highest OTU numbers (242) and the NS sample had the lowest (86). Moreover, only 22 OTUs were present in all samples simultaneously. The beta diversity analysis suggested a division of two endophytic fungi groups: the FJ sample from the south of China and the other four samples from north or northwest China. Correlation analysis between the environmental factors and endophytic fungi at the class level revealed that Sordariomycetes and Pucciniomycetes had extremely significant positive correlations with the total carbon, annual average precipitation, and annual average temperature, while Leotiomycetes showed an extremely significant negative correlation with quick acting potassium. The results revealed significant differences in the root endophytic fungi diversity of P. sinese in different provinces and might be useful for growth promotion and biomass production in the future.

Oil pollution poses a persistent threat to soil ecosystems globally, and bioremediation using bacterial consortia has emerged as a cost-effective remediation strategy. However, the role of weak petroleum-degrading bacteria in enhancing the efficiency of specialized petroleum-degrading bacteria remains unclear. This study explores the synergy and remediation potential of a two-bacterial consortium: the petroleum-degrading bacterium Rhodococcus sp. OS62-1 and the weak petroleum-degrading bacterium Pseudomonas sp. P35. A 25-day microcosm experiment was conducted with petroleum-contaminated soil, and four treatments were set: (1) uninoculated control, (2) inoculation with Rhodococcus sp. OS62-1 alone, (3) inoculation with Pseudomonas sp. P35 alone, and (4) inoculation with the consortium. Soil samples were collected periodically to analyze petroleum degradation efficiency, soil enzyme activities (dehydrogenase, catalase, polyphenol oxidase, and lipase), and microbial community composition (16S rRNA gene sequencing). Inoculating the soils with this consortium produced a higher petroleum degradation rate, microbial activity, and soil enzyme activity than inoculation with strain OS62-1 or P35 alone. Inoculation with strain P35 also contributed to the maintenance of strain OS62-1 during bioremediation. The study of microbial community structure found that the relative abundance of phylum Acidobacteriota (57.6 ± 5.3% to 75.6 ± 8.1%) and the Nocardioides genus (36.4 ± 4.5% to 53.0 ± 9.2%) increased dramatically during the bioremediation process. Pearson’s correlation analysis revealed that inoculation with strain OS62-1 and/or strain P35 increases the soil enzyme activity, boosts native oil-degrading bacteria, and accelerates the degradation of petroleum contaminants. Molecular ecological networks analysis revealed that inoculation with strain OS62-1 and/or strain P35 increased the complexity and robustness of the microbial network. These findings confirm that weak petroleum-degrading bacteria can synergistically enhance the bioremediation efficiency of specialized petroleum-degrading bacteria, providing a practical strategy for optimizing the design of bacterial consortia in the bioremediation of oil-polluted soils.

To explore the effects of different fertilization regimes on physicochemical properties and microbial ecology of greenhouse soil, we set five treatments with original soil (BS) as the control: chemical fertilizer alone (GF), high/low-rate mushroom residue combined with chemical fertilizer (MH, ML), and high/low-rate organic fertilizer combined with chemical fertilizer (OH, OL). Metagenomic sequencing and bioinformatic analyses were adopted to characterize soil nutrients, microbial communities, and C-N-P-S metabolic functions. All treatments increased soil nutrients. MH had the highest organic matter, total nitrogen, nitrate nitrogen, and available phosphorus, while GF contained the most available potassium and ammonium nitrogen. Bacteria dominated the soil microbiota, with Pseudomonadota and Pseudomonas as keystone taxa. Mushroom residue amendments improved microbial richness and diversity. By improving soil physicochemical properties, the combined application of organic fertilizer with chemical fertilizer and mushroom residue with chemical fertilizer both enriched some beneficial microorganisms. Chemical fertilizer alone enhanced anaerobic metabolism, which was reversed by high-rate mushroom residue. Available phosphorus, available potassium, and ammonium nitrogen were key environmental factors driving the differentiation of microbial communities and their functions. Overall, mushroom residue combined with chemical fertilizer is effective for greenhouse soil improvement, with proper dosage and tillage recommended.