[Objective] To explore the role of VraSR in regulating the biological functions of Staphylococcus epidermidisvia the CidA-LrgAB system. [Methods] The recombinant plasmid pKOR1-ΔlrgAB was constructed and then electroporated into SE1457 ∆vraSR to delete lrgAB from the genome of ∆vraSR by homologous recombination. The suspected mutant ∆vraSR-lrgAB was verified by PCR, RT-PCR, and sequencing. The growth, drug susceptibility, autolysis, and biofilm formation of ∆vraSR-lrgAB were determined. [Results] The S. epidermidis mutant ∆vraSR-lrgAB was successfully constructed. Compared with SE1457, ∆vraSR, and ∆lrgAB, ∆vraSR-lrgAB exhibited retarded growth, especially at 25 ℃ and 40 ℃ (P<0.001), increased drug susceptibility (P<0.01), enhanced autolysis (P<0.001), and reduced biofilm formation (P<0.01). [Conclusion] VraSR may regulate the growth, drug susceptibility, autolysis, and biofilm formation of S. epidermidis partly via the LrgAB system.

[Objective] Microorganisms are key executors of the migration and transformation of geochemical elements in intertidal zones. Fungi play an important role in the cycling of carbon, nitrogen, and phosphorus and the degradation of organic pollutants. [Methods] In this study, soil samples were collected from the rhizosphere and non-rhizosphere of Phragmites australis, Tamarix chinensis, and Suaeda salsa (intertidal zone and saline inland), which were the typical intertidal plants in the Yellow River Delta. The fungal community structures in different soil samples were investigated by high-throughput sequencing. [Results] In the rhizosphere, the soil sample of S. salsa in saline inland showed higher fungal abundance, richness, and evenness than other soil samples, with a distinct fungal community structure. In the non-rhizosphere, the fungal abundance, richness, and evenness were the highest in the soil samples of P. australis, S. salsa in saline inland, and T. chinensis, respectively, and the fungal community structure of P. australis was similar with that of S. salsa in saline inland. Ascomycota and Basidiomycota were the dominant fungal phyla in both the rhizosphere and non-rhizosphere. However, the functional fungi were different among plants. Saprophytic fungi such as Alternaria and Aspergillus were the dominant functional fungi in the rhizosphere and non-rhizosphere of P. australis, T. chinensis, and S. salsa in saline inland, with the relative abundance of 13.60%, 6.33%, and 20.16% in the rhizosphere and 11.98%, 24.25%, and 8.52% in the non-rhizosphere, respectively. Saprophytic fungi were essential for the production of humus by decomposition of organic matter and the improvement of soil aeration and physicochemical properties. Aureobasidium (1.51%) were identified in the non-rhizosphere of T. chinensis, and they were haloduric fungi and could work synergistically with plants to prevent soil salinization. The dominant functional fungi in the rhizosphere of S. salsa in intertidal zone were mainly Talaromyces (15.90%) and Stachybotrys (0.53%), which were involved in sugar degradation. They were able to break down cellulose into glucose, produce humus, and form a stable soil aggregate structure to improve soil aeration. Trichoderma (0.13%) were identified in the rhizosphere of S. salsa in saline inland, and they could promote soil nitrogen and phosphorus conversion and prevent the soil pollution caused by excessive inorganic phosphorus. The relative abundance of functional fungi was less than 0.10% in the non-rhizosphere. In addition, Phanerochaete (0.15%) capable of degrading persistent organic pollutants and Penicillium (1.16%) capable of degrading quinones were identified in the non-rhizosphere, providing microbial resources for the remediation of organic pollution in soil. However, they were not identified in the plant rhizosphere. The fungal diversity and evenness in the rhizosphere were positively correlated with soil factors such as electrical conductance (EC), calcium concentration, and salinity. In the non-rhizosphere, the fungal richness and diversity were positively correlated with total nitrogen, while the fungal evenness was positively correlated with pH, salinity, and ammonia nitrogen. [Conclusion] This study established a framework for understanding the structures and functions of fungal communities in the intertidal zone of the Yellow River Delta. Additionally, it provides a theoretical foundation for the future application of different functional fungi in soil structure improvement, biodiversity maintenance, organic pollution treatment, ecological protection, and saline-alkali land restoration.

Acheta domesticus densovirus (AdDV) was first isolated from infected crickets in Switzerland, 1977 and caused several outbreaks in Europe and the United States. Cricket iridovirus (CrIV), first identified in the Netherlands in 1996, caused a high mortality rate, reduced the fertility, and shortened the life span of infected crickets. The house cricket (Acheta domesticus), was originated from south west Asia and introduced into China as food for reptile pets in recent decades. AdDV and CrIV are common pathogenic viruses that infect house crickets. Unveiling the virus epidemics of house crickets becomes increasingly important with the development of the house cricket industry. [Objective] To understand the epidemic status of AdDV and CrIV in China, so as to lay a theoretical basis for controlling AdDV and CrIV infections in the house cricket industry and developing effective prevention and control measures. [Methods] Virus-specific PCR was performed to detect pathogens of the crickets reared in farms spanning different regions of China. The pathogens of the infected crickets were further proved by Sanger sequencing. Transmission electron microscopy was employed to observe the virions in different tissue samples (e.g., gut and fat body) of the infected crickets. [Results] AdDV virions were icosahedral-shaped particles, nearly spherical, without envelope, with a diameter around 20 nm. It formed dense chromatin regions in the nucleus of the host cell, showing typical features of densovirus. CrIV virions were nonenveloped icosahedral-shaped particles with a diameter of 120-140 nm. A large number of CrIV virions formed a lattice-like arrangement in the cytoplasm, which is a typical feature of iridovirus. The virus-specific PCR detected AdDV in crickets collected from all the on-line shops distributed in different regions of China. CrIV was also detected in crickets collected from most (91%) of the on-line shops. The majority (91%) of detected crickets were infected with both AdDV and CrIV. [Conclusion] For the first time AdDV and CrIV were found to have been widely spread in China.

Plants require a large amount of phosphorus for metabolic processes. However, the available phosphorus in the soil is typically less than 0.1% of total phosphorus, which is difficult to meet the growth and development of plants. The symbiosis system of ectomycorrhizal fungi and mycorrhizal helper bacteria can significantly improve the availability of soil phosphorus and promote the efficient uptake of phosphorus by plants. In this review, we discussed the solubilization and mineralization of chelated inorganic phosphorus, soluble organic phosphorus, and chelated organic phosphorus by ectomycorrhizal fungi and mycorrhizal helper bacteria. Ectomycorrhizal fungi mainly promote the solubilization of chelated inorganic phosphorus by regulating the organic acid and proton metabolism of mycorrhizal helper bacteria. They accelerate the mineralization of soluble organic phosphorus by enhancing the activities of related phosphatases in themselves and in mycorrhizal helper bacteria. Ectomycorrhizal fungi may first stimulate the mycorrhizal helper bacteria to secrete organic acids for solubilizing chelated organic phosphorus into soluble phosphorus before mineralization. Moreover, we explored the molecular mechanisms of metabolite signal exchange and secretion in the symbiosis system and outlined the prospects for studying the interactions between ectomycorrhizal fungi and mycorrhizal helper bacteria in promoting plant phosphorus uptake.

[Objective] Rummeliibacillus, a genus encompassing three known species, R. stabekisii, R. pycnus, and R. suwonensis, has a wide range of potential applications in biodegradation, probiotics, animal feed, and production of arginine, caproic acid, and other compounds. This study aims to explore the genetic diversity of this genus at the genomic level. [Methods] A comparative pangenome analysis of 12 strains isolated from different sources was conducted. In addition, the phylogenetic analysis, functional annotation, genomic metabolic pathway analysis, and prediction of mobile genetic elements were carried out. [Results] A total of 8 024 gene clusters were identified. The core genome, accessory genome, and strain-specific genes comprised 1 550, 3 941, and 2 533 gene clusters, respectively. In the core genome, the arginine cycle of six strains was complete. Seven strains had the ability to completely biosynthesize acetoin. However, only R. pycnus and R. suwonensis 3B-1 were able to completely biosynthesize caproic acid. The phylogenetic tree, DNA-DNA hybridization, and average nucleotide identity showed that Rummeliibacillus sp. G93 and Rummeliibacillus sp. TYF-LIM-RU47 were strains of R. stabekisii. Rummeliibacillus sp. POC4 and Rummeliibacillus sp. TYF005 may belong to a new species of this genus. In addition, genomic islands were identified in all the 12 strains, with the number ranging from four (R. stabekisii DSM 25578 and R. stabekisii NBRC 104870) to 14 (Rummeliibacillus sp. SL167 and Rummeliibacillus sp. TYF005), and prophage sequences were found in five of the 12 strains. [Conclusion] This study provides a genomic framework for Rummeliibacillus that could assist the further exploration of this genus.

Galacto-oligosaccharides (GOS) as prebiotics can regulate gut microbiota to improve brain development, whereas antibiotics can affect the nervous system by interfering with gut microbiota. The mechanisms of antibiotics and GOS in regulating brain neurotransmitters and animal behaviors remain unknown. [Objective] To investigate the effects of antibiotics and GOS on the behaviors and neurotransmitters in weaned Sprague-Dawley (SD) rats. [Methods] Forty 3-week-old male SD rats were selected and assigned into four groups: control (CON, sterilized water), antibiotics (ABX), GOS (5 g/L), and antibiotics+GOS (AG). The antibiotics used in the experiment were composed of ampicillin, vancomycin, ciprofloxacin hydrochloride, imipenem, and metronidazole. The experiment lasted for 16 days. [Results] The body weight of rats in the ABX group was lower than that in the GOS group (P<0.05), and the liver index in the ABX, GOS, and AG groups was lower than that in the CON group (P<0.05). Compared with the CON group, the ABX group showcased decreased phototaxis index (percentage of time in bright during bright-dark box test) and reduced times of self-grooming (P<0.05), and the GOS group had reduced times of self-grooming (P<0.05). The AG group had longer resting time in the open field than the other three groups (P<0.05) and shorter distance, shorter time, and slower movement than ABX and GOS groups (P<0.05). Compared with the CON group, the ABX group showcased elevated level of norepinephrine and lowered level of levodopa in the hippocampus (P<0.05). Compared with the CON group, the GOS and AG groups demonstrated elevated levels of norepinephrine and declined levels of levodopa and epinephrine (P<0.05). Compared with the CON group, the ABX and AG groups presented decreased microbial diversity (P<0.05), where Escherichia_Shigella became dominant. The Chao1 index in the GOS group was lower than that in the CON group (P<0.05). The dominant bacteria in the GOS group were Firmicutes and Bacteroidota. Compared with that in the ABX group, the relative abundance of Lactobacillus increased in the AG group (P<0.05). [Conclusion] ABX decreased anxiety-like behaviors compared with CON, while reducing levodopa and increasing norepinephrine in the hippocampus and enriching potentially pathogenic bacteria. GOS improved growth without influencing the behaviors of rats, and meanwhile it increased the relative abundance of Lactobacillus and decreased levodopamine and norepinephrine in the hippocampus. The combined use of ABX and GOS decreased the locomotor activity and increased the anxiety-like behaviors of rats.

[Objective] To develop a rapid detector for biochemical oxygen demand (BOD) in the wastewater from ships entering ports in response to the stringent mandates of the International Maritime Organization (IMO). The objective is to facilitate swift detection of domestic wastewater produced by the multitude of vessels arriving at the port. [Methods] When testing the BOD standard solution, Clostridium butyricum and Bacillus subtilis were used to manufacture the biosensitive elements inducing electron transfer during the consumption of dissolved oxygen (DO), which led to a change in electrical conductivity (COND). By treating dissolved oxygen as a pivotal indicator and an intermediary in the monitoring process, this study explored the correlation between changes in electrical conductivity and sample concentration. Through the development of a quadratic polynomial fitting model that correlates electrical conductivity with dissolved oxygen levels, and by establishing a connection between dissolved oxygen and sample concentration, this research delves into the correlation between variations in electrical conductivity and the concentration of the sample. [Results] The changes in electrical conductivity exhibited by different solutions enabled the detector to rapidly distinguish between the wastewater with a BOD concentration higher than 25 mg/L (the slope of the COND variation value is less than -0.01) and that below 25 mg/L (the slope of the COND variation value is greater than -0.01). By establishing a highly correlated fitting curve between dissolved oxygen and electrical conductivity (coefficient of determination R²=0.977 83), this study achieved precise reading of samples within the ultra-low concentration range (BOD<25 mg/L). The accuracy rate of the measurements exceeded 85% in the in-suit tests conducted in Qinhuangdao, Hebei, China. [Conclusion] The measurement data read by the rapid detector for BOD is highly consistent with the results obtained by the dilution inoculation method. Moreover, the detector is capable of performing rapid quantitative analysis of BOD in domestic wastewater from ships entering ports within 30 min, demonstrating high detection efficiency.

The fermentation, morphological observation, and metabolite purification of mycelial pellets and the application of mycelial pellets in sewage treatment and energy recovery have gained widespread attention from researchers in the fields of environment and biology. To get a full picture of the research hotspots and trends of mycelial pellets. We screened 1 337 scientific articles related to the application of mycelial pellets that were published in the past 20 years from the Web of Science. The clustering and temporal trends of keywords and the co-occurrence of countries, authors or institutions were visually analyzed. The annual number of published articles was on the rise, involving a total of 97 topics, and interdisciplinary articles were abundant and tended to have higher cited frequency. China's achievements in this field kept a leading position and China maintained close cooperation with other countries. The hot keywords remained stable (growth, morphology, fermentation, removal, degradation, mycelial pellets, biological control, fungi, culture, optimization, biodegradation, and biosorption), and the uptrending and emerging keywords changed in recent years. The application of mycelial pellets in water treatment had been increasingly studied, with the related keywords (waste water, performance) becoming increasingly frequent. Emerging keywords related to wastewater treatment with mycelial pellets as carriers (biomass, bacteria), synthesis by mycelial pellets (biosynthesis), and water treatment with both mycelial pellets and algae (Chlorella vulgaris, microalgae) remained hot. This result indicates that research on the application of mycelial pellets in water treatment has gradually evolved into more systematic research directions, which will become future research hotspots and opportunities.

[Objective] In view of the difficulty in the culture of chemoautotrophic bacteria, this study analyzed the reasons for the difficulty based on the theory of electron distribution and explored the feasibility of using the electron distribution strategy for increasing the biomass of chemoautotrophic bacteria based on pure culture. [Methods] From the perspective of maintaining intracellular pH balance and optimal energy metabolism, we calculated the optimal distribution ratios of electrons produced by the sulfur-oxidizing bacterial strain Halothiobacillus sp. DCM-3, nitrite-oxidizing bacterial strain Nitrobacter sp. N1, and ammonia-oxidizing bacterial strain Nitrosomonas sp. SCUT-1 to O₂ and CO₂ by oxidizing corresponding substrates. Furthermore, different molar ratios of O₂ to HCO₃^- (CO₂) were set respectively to form different electron distribution ratios for pure culture verification of the strains. Substrate and product concentrations were measured by ion chromatography and ultraviolet spectrophotometry, and cell density was measured by the dilution coating method. [Results] The optimal electron distribution ratios of strains DCM-3, N1, and SCUT-1 were 0.733:0.267, 0.867:0.133, and 0.6:0.4, respectively. Based on the optimal electron distribution ratios, strains DCM-3, N1, and SCUT-1 could synthesize 3.967 ATP/S₂O₃^2-, 0.433 ATP/NO₂^-, and 1.35 ATP/NH₃, respectively. According to the calculation results, the main reasons for the difficulty in culture were the small amount of ATP synthesized with the energy provided by per unit substrate and the need to control a low oxygen concentration and supplement an appropriate amount of inorganic carbon. The results of pure culture verification showed that the biomass of DCM-3 under the optimal ratio was 6.5×10⁷ CFU/mL, which was 2.2 times that of the control group. The biomass of N1 under the optimal ratio was 7×10⁶ CFU/mL, which was not significantly different from that of the control group. However, the HCO₃^- concentration (0.4 mmol/L) of the optimal ratio of strain N1 was significantly lower than that (2.5 mmol/L) of the control group, which meant that the strain showed a growth characteristic of tending to higher oxygen concentration but lower CO₂ demand, which was consistent with the calculated optimal ratio. The biomass accumulation per unit NH₄⁺ concentration of SCUT-1 strain in the group with controlled O₂ and CO₂ was more than 1.3×10⁶ CFU/(mL·(mmol/L)), which was 25%-40% higher than that obtained under sufficient O₂ and CO₂. [Conclusion] The culture strategy of chemoautotrophic bacteria based on electron distribution restricts the culture conditions of electron distribution by limiting the molar amounts and forming a certain ratio of O₂ and CO₂, which helps to improve the biomass accumulation under the same substrate condition and provides certain strategic reference for the culture of chemoautotrophic bacteria.

[Objective] This study isolated the dominant indole-3-acetic acid (IAA)-producing bacteria from the rhizosphere soil of Prunus sachalinensis, determined their plant growth-promoting properties, and clarified the growth-promoting effect by inoculation to the seedlings of the common rootstock Gisela 6, aiming to provide theoretical reference and practical approaches for exploring the biological potential of cherry, establish a benign root-microbial interaction relationship, and solve weak root development. [Methods] We used the beef extract peptone medium to isolate bacteria from the rhizosphere soil and selected various specific media to screen the bacteria and determine the IAA-producing, nitrogen-fixing, phosphorus-solubilizing, potassium-solubilizing, and chemotactic abilities of the bacteria. Then, we constructed a phylogenetic tree based on 16S rRNA gene sequences to identify the bacteria. Finally, potted cherry plants were used to explore the plant growth-promoting effects of the strains. [Results] Five IAA-producing strains were screened from the rhizosphere soil of P. sachalinensis, among which strain D46 had the highest IAA yield (53.10 mg/L). D5 was identified as Priestia sp. D27 and D46 were identified as Enterobacter sp. D43 and D79 were identified as Bacillus sp. All the five strains had the ability to fix nitrogen. D27, D46, and D79 had the ability to solubilize phosphorus, and D5 and D43 had the ability to solubilize potassium. Strains D27, D46, and D79 showed strong integrative chemotaxis to sugars, organic acids, and amino acids. Pot experiments showed that the inoculation of strains D27, D43, D46, and D79 significantly increased the root activity. After the inoculation of strain D27, the total root respiration rate increased by 51.40% compared with that in the control group (CK), and the root respiration rates of glycolysis (EMP), tricarboxylic acid cycle (TCA), and pentose phosphate pathway (PPP) also significantly increased. Strain D27 significantly improved the root architecture of cherry seedlings. After inoculation of strain D5, the net photosynthetic rate of leaves significantly increased by 58.82% compared with that in CK, and the inoculation of strain D27 demonstrated the best performance in improving the water use efficiency of leaves. Strains D27, D46, and D79 significantly increased the plant biomass. [Conclusion] There were IAA-producing bacteria in the rhizosphere of cherry, and the five IAA-producing strains isolated had other plant growth-promoting properties. Strains D27, D46, and D79 demonstrated comprehensive plant growth-promoting effects on cherry seedlings. In the future, we can explore the spectra of plants with growth promoted by the strains and the environmental tolerance of the strains, providing a theoretical basis for mining and enriching the strain resources of plant growth-promoting rhizobacteria.