[Objective] To investigate the acclimation mechanisms of straw-decomposing microbiomes in response to historically different climate conditions as characterized by extreme temperature distinction, we collected two native forest soil samples from the tropical (annual mean temperature: 25 ℃) and cold-temperate (annual mean temperature: −2 ℃) zones at a distance of 3 860 km. [Methods] Microcosm incubation was conducted at a low temperature (10 ℃), a high temperature (35 ℃), and alternated high and low temperatures (10 ℃/35 ℃). The two native forest soil samples were inoculated for targeted cultivation of straw-decomposing microbiomes. After 12 consecutive weeks of passage, 16S rRNA gene sequencing was carried out to analyze the microbial community composition. [Results] At 10 ℃, higher straw decomposition rate was observed in the forest soil from Changbai Mountain in the cold-temperate zone (15.5%) than that from the tropical zone. At 35 ℃, the decomposition rate in the soil from Sanya in the tropical zone (33.1%) was higher than that from Changbai Mountain The results of linear discriminant analysis effect size (LEfSe) showed that the dominant straw-decomposing genera included Duganella, Pedobacter, Janthinobacterium, and Serratia after 12 weeks of enrichment at 10 ℃ with the forest soil from Changbai Mountain. The dominant genera were Paenibacillus and Rhodanobacter after enrichment at 35 ℃, and Stenotrophomonas, Burkholderia, and Achromobacter after enrichment at 10 ℃/35 ℃. As for the forest soil from the tropical zone, the enriched dominant genera were Pseudomonas, Acinetobacter, and Flavobacterium at 10 ℃, Cupriavidus at 35 ℃, and Enterobacter and Cohnella at 10 ℃/35 ℃. [Conclusion] This study revealed the indicator microbial species for straw decomposition at different temperatures in native forest soils from geographically highly distinct regions with a 3 860 km distance. The results suggest that temperature could have likely played a pivotal role in shaping the microbiomes for straw decomposition. The findings provide a scientific basis for mining the straw-decomposing microbial resources in the cold zone in northeast China and the tropical zone in south China.

[Objective] There are numerous non-rhizobia in addition to rhizobia in the root nodules of leguminous plants. Despite the extensive studies about the endophytic bacteria in other plant tissues, little attention has been paid to the species diversity of non-rhizobia in root nodules. Therefore, further research is needed to explore the significance and ecological roles of non-rhizobia. [Methods] The root nodules of wild Sophora davidii (Franch.) Skeels, a leguminous nitrogen-fixing shrub growing in the hilly-gully loess region of northern Shaanxi, were collected. The species diversity of rhizobia and non-rhizobia in the root nodules of S. davidii was systematically studied by the conventional culture method. The plant growth-promoting effects of the strains were evaluated and their growth-promoting effects on wheat seedlings were verified. [Results] A total of 320 strains of endophytic bacteria were isolated from the root nodules of S. davidii in six counties/districts in northern Shaanxi. The phylogenetic analysis based on the 16S rRNA gene sequences identified the strains into 55 genera, 35 families, 17 orders, 17 classes of 4 phyla. Pseudomonas (18.44%), Bacillus (17.81%), and Mesorhizobium (11.56%) were the dominant genera. The results of re-inoculation experiments showed that Mesorhizobium sp. and Ochrobactrum sp. HL-2 formed root nodules with the host plant. Furthermore, the plant growth-promoting characteristics of 192 strains isolated Baota District were studied. The results showed that 115, 20, 78, and 18 strains possessed the abilities of fixing nitrogen, solubilizing phosphorus, producing indole-3-acetic acid (IAA), and secreting siderophores, respectively. Four elite strains were selected and inoculated alone or in combination into the wheat seedlings in pots, and their growth-promoting effects on the agronomic traits of wheat seedlings were evaluated. The results indicated that the treatment HIJ increased the plant height and fresh weight of wheat seedlings by 49.65% and 140.00% respectively. The treatments HK and IK increased the root length and chlorophyll content by 45.84% and 25.48%, respectively. [Conclusion] There are diverse non-rhizobia in the root nodules of S. davidii. The results of this study have great scientific significance for exploring the role of such microbial resources in natural ecosystems and enriching the resource pool of endophytic bacteria. Additionally, the results provide a theoretical basis for the application of these strains in ecological restoration in the arid region of northern Shaanxi.

[Objective] To use microorganisms to mobilize unavailable nutrients in soil for the utilization by leguminous crops and the sustainable and long-term utilization of soil resources. [Methods] Microbial culture and micro-plot experiments were carried out with Ceriporia lacerata HG2011, a new isolate of white-rot fungus, to investigate the fungal secretion, soil nitrogen (N) and phosphorus (P) mobilization, and influences on the nutrient uptake, growth, and yields of Vigna radiata and Vicia villosa. [Results] C. lacerata released cellulase, chitinase, β-l,3-glucanase, protease, phosphatase, and siderophore, and dissolved Ca₃(PO₄)₂ in pure culture. After being inoculated on the soil surface, this fungus formed colonies, with some mycelia extending into the soil, which decrease soil pH but increase the content of NH₄⁺-N, alkali-hydrolyzed N, water-soluble P and Olsen P, and the activities of protease and phosphatase. In general, C. lacerata inoculation improved soil N and P supplies, enhanced root activity, and promoted root growth, nodule formation and development, thus increasing the nutrient uptake, grain yield of V. radiata, and biomass of V. villosa. [Conclusion] C. lacerata dwelling in soil mobilized soil N and P to increase fertilizer use efficiency and promote crop growth. C. lacerata can be cultured with sawdust, straw, husk and other organic agricultural and forestry wastes, with low production costs. This study provides a new strategy for mobilizing soil nutrients, promoting the growth of leguminous crops such as V. radiata and V. villosa, and benefiting the conservation and sustainable use of cultivated lands.

[Objective] We compared the microbial communities in the rhizosphere of plants with different genotypes and explored the relationship between microbial community and soil-borne disease occurrence, aiming to reveal the underlying mechanisms by which rhizosphere microorganisms assist plants in defending against pathogen invasion. [Methods] A pot experiment was conducted with the soil experiencing severe continuous cropping obstacles to compare the microbial communities in the rhizosphere of a susceptible watermelon variety 'zaojia 8424' and a resistant variety 'xinong 8' to Fusarium wilt. Furthermore, the relationship between microbial community and the occurrence of Fusarium wilt was explored. [Results] The resistant watermelon variety exhibited significantly lower disease index and pathogen (Fusarium oxysporum f. sp. niveum, FON) abundance than the susceptible watermelon variety. Although no significant difference was observed in the bacterial and fungal alpha diversity in the rhizosphere between resistant and susceptible varieties, the microbial beta diversity showcased significant difference between the two varieties. Moreover, both bacterial and fungal community composition was significantly correlated with pathogen abundance. Linear discriminant analysis effect size (LEfSe) further revealed that the resistant watermelon variety enriched more potential antagonistic or plant growth-promoting taxa represented by Actinobacteria and Rhizobiaceae in the rhizosphere. Interestingly, Fusarium was also enriched in the rhizosphere of the resistant variety, mainly composed of unclassified Fusarium and F. solani. Notably, the co-occurrence network of microorganisms in the rhizosphere of the resistant variety exhibited higher complexity and stability than that of the susceptible variety, with an increase of 18.18% in average degree and the nodes and edges dominated by Actinobacteria. [Conclusion] The watermelon varieties resistant and susceptible to Fusarium wilt demonstrate different microbial community composition in the rhizosphere. The enrichment of beneficial microbial taxa and interconnected co-occurrence network of the resistant variety contribute to plant defense against the pathogen invasion. This study disentangles the relationship between rhizosphere microbial community and soil-borne disease occurrence, providing important information and a theoretical basis for preventing and managing soil-borne diseases.

[Objective] The protein SakA encoded by sakA is a member of the mitogen-activated protein kinase (MAPK) family in Aspergillus niger. However, little is known about the roles of SakA in A. niger. In this study, we constructed the A. niger strains with knockout of sakA to investigate the roles of this gene. [Methods] The Agrobacterium-mediated method was utilized to construct ΔsakA strains from A. niger RAF106 (the wild type, WT). The growth and spore production of ΔsakA and WT were observed on three different media. The sensitivity of ΔsakA and WT to different stress conditions was studied. The intracellular and extracellular levels of amylase, pectinase, and cellulase were compared between ΔsakA and WT. Real-time quantitative polymerase chain reaction (qRT-PCR) was employed to determine the relative transcript levels of the genes associated with spore production, amylase, pectinase, cellulase, and hyperosmotic regulation. [Results] Three ΔsakA strains were successfully obtained and verified by PCR and qRT-PCR. The ΔsakA strains had slow growth, delayed spore production, and delayed conidiophore differentiation compared with WT. The ΔsakA strains showcased slower colony growth than WT under the stress conditions of 0.6 mol/L KCl, 0.8 mol/L NaCl, and 1.2 mol/L NaCl. Compared with WT, the knockout of sakA increased the extracellular amylase production by 20.68%–21.43% and decreased the intracellular amylase production by 19.18%–20.26%, decreased the extracellular pectinase production by 36.71%–38.30% and increased the intracellular pectinase production by 35.68%–36.53%, decreased the extracellular cellulase production by 28.04%–33.82% and increased the intracellular cellulase production by 15.28%–18.19%. Compared with WT, the knockout of sakA down-regulated the transcript levels of spore production-related genes (fluG, sfgA, flbA, flbB, flbD, laeA, brlA, abaA, vosA, stuA, and velB) by 8.53%–90.87%. Furthermore, it down-regulated the transcript levels of amylase-related genes (amyC, amyD, amyE, amyF, amyG, and amyH) and the transcription factor (amyR) by 8.87%–87.50%, the pectinase-related genes (aglB, lacA, pexB, pecA, pecC, pecB, endA, endC, and poly) by 23.23%–84.01%, the cellulase-related genes (xlnR, chbA, chbB, and eglB) by 3.75%–81.02%, and the hyperosmotic regulation-related genes (ena1, ena2, sho1, nik1, ypdl, pkA, and hAD) by 5.27%–94.36%. [Conclusion] The sakA gene of A. niger positively regulates spore production and is essential for spore production. The knockout of sakA affects the spore production of A. niger. Furthermore, SakA plays a crucial role in the synthesis and secretion of amylase, pectinase, and cellulase as well as osmotic stress response.

[Objective] To study the morphological and physiological characteristics of hybrids compared with their parents and contribute to research on the mechanisms of speciation and evolution. [Methods] Sonneratia×hainanensis, a natural hybrid of the mangrove plants Sonneratia alba and S. ovata, usually presents hybrid weakness than its parents. In this study, Illumina high-throughput sequencing was employed to compare the rhizosphere microbiomes (including bacteria and fungi) between the hybrid and its parents, on the basis of which the reason for hybrid weakness was explored. [Results] The principal coordinate analysis (PCoA) revealed no significant difference in the rhizosphere bacterial or fungal community structure between the hybrid and its parents. However, the rhizosphere microbiome of the hybrid was different from that of the female parent S. alba with strong survival ability but similar to that of the male parent S. ovata. The rhizosphere bacteria belonged to 388 genera, 320 families of 76 phyla. The dominant phylum Pseudomonadota had the relative abundance above 41.00% in the rhizosphere of the three plant species, reaching 55.33% in the hybrid, which was higher than that in the parents. At the genus level, 18 common genera including Desulfococcus (3.23%) and Rhodoplanes (0.94%) in all the three mangrove plants showed the relative abundance of 15.77%. Among them, 8 salt-tolerant genera such as Mariprofundus showed decreased relative abundance in the hybrid, which may affect the salt tolerance. The rhizosphere fungi were dominated by Ascomycota and Basidiomycota with the relative abundance of 41.89% and 4.53%, respectively, which was significantly lower than that in the parents. Moreover, the predominant fungal genera were different in the three mangrove plants. Functional annotation of prokaryotic taxa (FAPROTAX) predicted that the mangrove prokaryotes were involved in sulfur metabolism and nitrogen metabolism. Although the hybrid had higher Shannon and Simpson indexes of rhizosphere bacteria than S. alba, some dominant taxa such as B-42 (unclassified Trueperaceae), Mariprofundus, and Sulfurimonas participating in the nitrogen cycle were not inherited by the hybrid. The soil total nitrogen (TN) and total phosphorus (TP) of the hybrid was significantly lower than that of S. alba. TN was significantly positively correlated with the relative abundance of Mariprofundus, B-42, Aspergillus, and Rhodotorula, which, however, demonstrated decreased relative abundance in the rhizosphere of the hybrid. [Conclusion] The results help to understand the mechanisms of hybrid weakness in Sonneratia×hainanensis.

Microalgae are rich in lipids, proteins, and exopolysaccharides, serving as potential producers of high-value by-products. Compared with monoculture, microalgal co-culture offers advantages such as fast growth rates and strong resistance, increasing the microalgal biomass and lipid production. Biomass production by microalgae co-culture is influenced by environmental conditions, nutrient composition, and external stress, and the produced biomass can be utilized for biofuel production and food processing. This article introduces the types of microalgal co-culture systems and reviews the related studies on the production of high-value by-products. It summarizes the factors influencing biomass production in microalgal co-culture systems and highlights the potential of microalgal co-culture for resource utilization. Furthermore, this article discusses the prospects and challenges of microalgal co-culture.

Bacillus paralicheniformis, a Gram-positive, facultative anaerobic, motile rod-shaped endospore-forming bacterium, can be used as a species of potential plant growth-promoting rhizobacteria (PGPR). In this study, B. paralicheniformis HMPM220325 was isolated from the fruit fermented milk. This strain can form biofilms at the gas-liquid interface during static cultivation. [Objective] To study the effects of different environmental factors on the biofilm biomass of B. paralicheniformis HMPM220325 and provide data support for the later development and application of HMPM220325 as a PGPR strain. [Methods] Effects of different environmental factors and nutrients on the biofilm formation of B. paralicheniformis HMPM220325 were quantitatively detected by crystal violet staining, and the optimal conditions for the biofilm formation of the strain were optimized by orthogonal experiments. [Results] The optimal environmental conditions for the biofilm formation of B. paralicheniformis HMPM220325 were incubation at 50 ℃ and pH 9.0 for 36 h. The optimal medium was composed of maltose 15.0 g/L, urea 10.0 g/L, magnesium sulphate 20.0 mmol/L, disodium hydrogen phosphate 2.5 g/L, and bovine heart infusion 17.5 g/L. The optimized culture conditions increased the biofilm biomass by 58.28% compared with the original culture conditions. [Conclusion] This study explored the biofilm formation of B. paralicheniformis in a variety of environments and optimized the culture conditions for biofilm formation of this strain, providing an experimental basis for further development of PGPR.

Electromagnetic radiation is a widespread physical phenomenon and exerts complex and profound effects on microorganisms. Understanding the state and function changes of microorganisms exposed to radiation is helpful to reveal the environmental response mechanisms of microorganisms and discover potential risk factors that threaten human health. By reviewing the relevant articles, we first discuss the damage of different types of electromagnetic radiation, including microwave, infrared, ultraviolet, X-rays, and γ-rays, to microorganisms. Furthermore, we elaborate on the molecular mechanisms by which electromagnetic radiation damages microorganisms from multi-omics. Finally, we reveal the potential relationship between the changes in the microbiome composition and the development of diseases in humans exposed to electromagnetic radiation.

[Objective] To explore the effects of cell walls of Saccharomyces cerevisiae on the intestinal microbiota in finishing bulls by 16S rDNA and ITS sequencing. [Methods] A total of 40 simmental crossbred finishing bulls weighing about 550 kg were randomized into 4 groups, with 10 bulls in each group. The control group was fed with a basic diet, and 5, 10, and 15 g cell walls of S. cerevisiae were added to the diet of each bull per day in trial 1, 2, and 3 groups, respectively. The preliminary trial and trial lasted for 10 days and 94 days, respectively. Intestinal feces were collected 7 days before the end of the trial. [Results] 16S rDNA: (1) The Chao and ACE indices in the trial 3 group were higher than those in other groups (P < 0.05); (2) Firmicutes and Bacteroidota were the dominant phyla, and Prevotella_9, Faecalibacterium, Succinivibrio, Bacteroides, and Bifidobacterium were the dominant genera; (3) The linear discriminant analysis effect size (LEfSe) revealed one differential species (LDA≥4.0, P < 0.05) playing an important role in the trial 2 group. ITS: (1) There was no significant difference in the alpha or beta diversity among groups (P > 0.05); (2) Ascomycota with the relative abundance above 50.00% was the dominant phylum. Penicillium, unidentified_Ascomycota_sp., Aspergillus, Orpinomyces, and Eurotium were the dominant genera; (3) LEfSe revealed 8 differential species (LDA≥3.0, P < 0.05), which included 3, 3, and 2 differential species playing an important role in the control, trial 2, and trial 3 groups, respectively. [Conclusion] Under conditions of this study, adding 10–15 g/d cell walls of S. cerevisiae in the basic diet increased the richness of intestinal microbiota and the relative abundance of beneficial bacteria Provetella_9, Tolypocladium, and Torulaspora, which were conducive to improve intestinal microecological environment of finishing bulls.