Poplar (Populus spp.) is a valuable tree species with multiple applications in afforestation. However, its growth in saline areas, including coastal regions, is limited. This study aimed to investigate the physiological mechanisms of arbuscular mycorrhizal fungi (AMF) symbiosis with 84K (P. alba × P. tremula var. glandulosa) poplar under salt stress. We conducted pot experiments using NaCl solutions of 0 mM (control), 100 mM (moderate stress), and 200 mM (severe stress) and evaluated the colonization of AMF and various physiological parameters of plants, including photosynthesis, biomass, antioxidant enzyme activity, nutrients, and ion concentration. Partial least squares path modeling (PLS-PM) was employed to elucidate how AMF can improve salt tolerance in poplar. The results demonstrated that AMF successfully colonized the roots of plants under salt stress, effectively alleviated water loss by increasing the transpiration rate, and significantly enhanced the biomass of poplar seedlings. Mycorrhiza reduced proline and malondialdehyde accumulation while enhancing the activity of antioxidant enzymes, thus improving plasma membrane stability. Additionally, AMF mitigated Na⁺ accumulation in plants, contributing to the maintenance of a favorable ion balance. These findings highlight the effectiveness of using suitable AMF to improve conditions for economically significant tree species in salt-affected areas, thereby promoting their utilization.

Plant endophytic bacteria play important roles in plants’ growth and resistance to stress. It is important to characterize endophytic bacteria to be able to understand their benefits. Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) has become a powerful technique for bacterial identification due to its high throughput and simple procedures. In this study, the endophytic bacteria separated from Populus (the leaves, roots and stems of Populus tomentosa Carrière; stems of Populus nigra Linn. var. nigra; and stems of Populus canadensis Moench) were identified and classified based on MALDI-TOF MS data and 16S rRNA gene sequencing. The sampling and preparation of bacteria were optimized to obtain meaningful protein mass fingerprints. The composite correlation index (CCI) values of the inter-genera and inter-species protein mass fingerprints demonstrated sufficient differences between the strains. In the CCI value matrix for ten species in the same genus, all the CCI values were less than 0.5. Among the species, 95.6% of all the CCI values were less than 0.5. After data processing, the classification capacity of the protein mass fingerprints was verified using inter-specific and inter-generic PCoA. To compare different methods’ potential for differentiation and phylogenetic analysis, a dendrogram of the MS profiles and a phylogenetic tree based on the 16S rRNA gene sequences were constructed using 61 endophytic bacteria found in Populus. The clustering and grouping results show that the phylogenetic analysis based on MALDI-TOF MS is similar to that based on 16S rRNA gene sequencing. This study provides a valuable reference for differentiating and identifying endophytic bacteria according to their protein mass fingerprints.

Petroleum-associated water harbors diverse microbial communities, including hydrocarbon-degrading bacteria, sulfate-reducing bacteria, and methanogenic archaea. The growth and metabolism of these organisms, as well as their community composition, can affect various aspects of oil field development and oil produced water treatment. In this study, Illumina-based 16S rRNA gene sequencing was used to analyze the microbial community structures of oilfield produced water processed at two treatment stations and subjected to different treatment protocols. Significant differences in microbial community α-diversity and richness resulted from the different treatment protocols. The treatment of oil produced water effectively reduced the oil content, accompanied by the a reduction in Desulfobacterota. Proteobacteria was the dominant phylum in oil produced water; its core presence, along with Patescibacteria and Desulfobacterota, was identified in a co-occurrence network analysis of the microbial community. Redundancy analysis showed significant positive correlations between microbial community diversity and the oil and suspended solids contents of the oil produced water, highlighting the role of treatment protocols in shaping both microbial composition and water characteristics. Thus, this study provides potential insights into the processes of souring in oil fields and contributes to the theoretical understanding of oil-produced water treatment, which may inform future optimization of treatment protocols.