Unveiling the synergistic mechanism of autochthonous fungal bioaugmentation and ammonium nitrogen biostimulation for enhanced phenanthrene degradation in oil-contaminated soils.

Autochthonous bioaugmentation and nutrient biostimulation are promising bioremediation methods for polycyclic aromatic hydrocarbons (PAHs) in contaminated agricultural soils, but little is known about their combined working mechanism. In this study, a microcosm trial was conducted to explore the combined mechanism of autochthonous fungal bioaugmentation and ammonium nitrogen biostimulation, using DNA stable-isotope-probing (DNA-SIP) and microbial network analysis. Both treatments significantly improved phenanthrene (PHE) removal, with their combined application producing the best results. The microbial community composition was notably altered by all bioremediation treatments, particularly the PHE-degrading bacterial and fungal taxa. Fungal bioaugmentation removed PAHs through extracellular enzyme secretion but reduced soil microbial diversity and ecological stability, while nitrogen biostimulation promoted PAH dissipation by stimulating indigenous soil degrading microbes, including fungi and key bacteria in the soil co-occurrence networks, ensuring the ecological diversity of soil microorganisms. The combination of both approaches proved to be the most effective strategy, maintaining a high degradation efficiency and relatively stable soil biodiversity through the secretion of lignin hydrolytic enzymes by fungi, and stimulating the reproduction of soil native degrading microbes, especially the key degraders in the co-occurrence networks. Our findings provide a fresh perspective of the synergy between fungal bioaugmentation and nitrogen biostimulation, highlighting the potential of this combined bioremediation approach for in situ PAH-contaminated soils.

Four New Species of Aspergillus Subgenus Nidulantes from China.

Aspergillus subgenus Nidulantes includes species with emericella-like ascomata and asexual species. Subgenus Nidulantes is the second largest subgenus of Aspergillus and consists of nine sections. In this study, agricultural soils were sampled from 12 provinces and autonomous regions in China. Based on primary BLAST analyses, seven of 445 Aspergillus isolates showed low similarity with existing species. A polyphasic investigation, including phylogenetic analysis of partial ITS, ß-tubulin, calmodulin, and RNA polymerase II second largest subunit genes, provided evidence that these isolates were distributed among four new species (Aspergillus guangdongensis, A. guangxiensis, A. sichuanensis and A. tibetensis) in sections Aenei, Ochraceorosei, and Sparsi of subgenus Nidulantes. Illustrated morphological descriptions are provided for each new taxon.

Mechanism of salicylic acid in promoting the rhizosphere benzo[a]pyrene biodegradation as revealed by DNA-stable isotope probing.

Benzo[a]pyrene (BaP) is a typical high-molecular-weight PAH with carcinogenicity. Rhizoremediation is commonly applied to remove soil BaP, but its mechanism remains unclear. The role of inducers in root exudates in BaP rhizoremediation is rarely studied. Here, to address this problem, we firstly investigated the effect of the inducer salicylic acid on BaP rhizoremediation, rhizosphere BaP degraders, and PAH degradation-related genes by combining DNA-stable-isotope-probing, high-throughput sequencing, and gene function prediction. BaP removal in the rhizosphere was significantly increased by stimulation with salicylic acid, and the rhizosphere BaP-degrading microbial community structure was significantly changed. Fourteen microbes were responsible for the BaP metabolism, and most degraders, e.g. Aeromicrobium and Myceligenerans, were firstly linked with BaP biodegradation. The enrichment of the PAH-ring hydroxylating dioxygenase (PAH-RHD) gene in the heavy fractions of all 13C-treatments further indicated their involvement in the BaP biodegradation, which was also confirmed by the enrichment of dominant PAH degradation-related genes (e.g. PAH dioxygenase and protocatechuate 3,4-dioxygenase genes) based on gene function prediction. Overall, our study demonstrates that salicylic acid can enhance the rhizosphere BaP biodegradation by altering the community structure of rhizosphere BaP-degrading bacteria and the abundance of PAH degradation-related genes, which provides new insights into BaP rhizoremediation mechanisms in petroleum-contaminated sites.

The catabolic pathways of in situ rhizosphere PAH degraders and the main factors driving PAH rhizoremediation in oil-contaminated soil.

Rhizoremediation is a potential technique for polycyclic aromatic hydrocarbon (PAH) remediation; however, the catabolic pathways of in situ rhizosphere PAH degraders and the main factors driving PAH rhizoremediation remain unclear. To address these issues, stable-isotope-probing coupled with metagenomics and molecular ecological network analyses were first used to investigate the phenanthrene rhizoremediation by three different prairie grasses in this study. All rhizospheres exhibited a significant increase in phenanthrene removal and markedly modified the diversity of phenanthrene degraders by increasing their populations and interactions with other microbes. Of all the active phenanthrene degraders, Marinobacter and Enterobacteriaceae dominated in the bare and switchgrass rhizosphere respectively; Achromobacter was markedly enriched in ryegrass and tall fescue rhizospheres. Metagenomes of 13 C-DNA illustrated several complete pathways of phenanthrene degradation for each rhizosphere, which clearly explained their unique rhizoremediation mechanisms. Additionally, propanoate and inositol phosphate of carbohydrates were identified as the dominant factors that drove PAH rhizoremediation by strengthening the ecological networks of soil microbial communities. This was verified by the results of rhizospheric and non-rhizospheric treatments supplemented with these two substances, further confirming their key roles in PAH removal and in situ PAH rhizoremediation. Our study offers novel insights into the mechanisms of in situ rhizoremediation at PAH-contaminated sites.

Electron shuttles enhance anaerobic oxidation of methane coupled to iron(III) reduction.

Anaerobic oxidation of methane (AOM) has recently been coupled with the reduction of insoluble electron acceptors such as iron minerals. However, effects of electron shuttles (ESs) on this process and the underlying coupling mechanisms remain not well understood. Here, we evaluated AOM-coupled ferrihydrite reduction by a mixed culture in the absence and presence of ESs. The results showed that ESs (AQS, flavin, HA and AQDS) significantly enhanced the rate (up to 7.4 times) of AOM-dependent ferrihydrite reduction compared with the control. The enhancements were linearly related with the electron transfer capacity of ESs. Illumina high-throughput sequencing and DNA-based stable isotope probing revealed that the AOM-coupled iron reduction depended on the syntrophic interaction of Methanobacterium and the partner bacteria. Methanobacterium as the dominant microorganism, did not assimilate methane into its biomasses. However, it played a crucial role in the partial oxidation of methane into an intermediate (i.e. propionate), which was then assimilated by the partner bacteria (e.g. Cellulomonas, Desulfovibrio, Actinotalea, etc.) for ferrihydrite reduction. This work suggests that ESs in natural environments can mitigate the methane emissions by facilitating the AOM process and biogeochemical cycles of iron.

MiR-26a Mediates Ultraviolet B-Induced Apoptosis by Targeting Histone Methyltransferase EZH2 Depending on Myc Expression.

BACKGROUND/AIMS: Ultraviolet B (UVB) damage is the most essential etiological factor in skin carcinogenesis, and apoptosis leads to the efficient elimination of UVB-damaged cells. However, the mechanisms underlying resistance to UVB-induced apoptosis remain unclear. METHODS: HaCaT and A431 cells were used in the present study. Quantitative real-time PCR, single cell PCR, and western blotting were used to examine cancer-related gene expression at the mRNA and protein levels. RESULTS: We report that miR-26a, which is upregulated upon UVB irradiation, promotes UVB-induced apoptosis in HaCaT cells by targeting the histone methyltransferase EZH2. Moreover, the UVB/miR-26a/EZH2 regulatory axis largely depends on the MYC expression level. Interestingly, treatment with EZH2 inhibitors significantly enhanced UVB-induced apoptosis. CONCLUSION: miR-26a/EZH2 might be potential targets for skin cancer prevention and therapy.

Ornithinibacillus composti sp. nov., isolated from sludge compost and emended description of the genus Ornithinibacillus.

A Gram-stain positive, aerobic, motile, endospore-forming and rod-shaped bacterium, designated GSS05(T), was isolated from a sludge compost sample and was characterized by means of a polyphasic taxonomic approach. Growth was observed to occur with 0-3 % (w/v) NaCl (optimum 1 %), at pH 5.5-10 (optimum pH 7.5) and at 15-50 °C (optimum 37 °C). According to the results of a phylogenetic analysis, strain GSS05(T) was found to belong to the genus Ornithinibacillus and to be related most closely to the type strains of Ornithinibacillus halotolerans and Ornithinibacillus contaminans (96.5 and 95.1 % 16S rRNA gene sequence similarity, respectively). The peptidoglycan amino acid type was determined to be A4ß. The major respiratory quinone was identified as menaquinone-7 (MK-7). The polar lipid profile of strain GSS05(T) was found to contain a predominance of diphosphatidylglycerol, moderate amounts of phosphatidylglycerol and minor amounts of two unknown phospholipids and two unknown lipids. The G+C content of genomic DNA was determined to be 42.1 mol%. The dominant cellular fatty acids were identified as iso-C15:0 and anteiso-C15:0. The phenotypic, chemotaxonomic, phylogenetic and genotypic data indicated that strain GSS05(T) represents a novel species of the genus Ornithinibacillus, for which the name Ornithinibacillus composti sp. nov. is proposed. The type strain is GSS05(T) (=CCTCC AB 2013261(T) = KCTC 33192(T)).