[Objective] To study the physicochemical properties and active components of extracellular antibacterial substances from Bacillus subtilis subsp. spizizenii Bspi2104. [Methods] The Oxford cup method was employed to determine the antibacterial activities and physicochemical properties of B. subtilis subsp. spizizenii Bspi2104 with broad-spectrum antibacterial activity and B. subtilis subsp. spizizenii BspiL6 without antibacterial activity. Metabolomics was employed to detect the antibacterial components of the extracellular products of the strain Bspi2104. [Results] The treatment with trypsin, papain, protease K, pepsin, and lipase had no significant effect on the antibacterial activity of extracellular products. Extracellular products lost the antibacterial activity after treatment at 80 ℃ and 100 ℃ and presented decreased antibacterial activity at pH 9.0 and pH 11.0, especially at higher pH values. There was no significant difference in the antibacterial activity between the extracellular products treated with and without UV (P>0.05). The ammonium sulfate precipitates at 60%, 70%, and 80% saturation exerted antibacterial activities, which was the strongest at the saturation of 70%. The extracellular products of the two strains were extracted by hydrochloric acid precipitation, combined with methanol extraction, ethyl acetate extraction, and chloroform extraction, and all the extracts showed antibacterial activities. The ethyl acetate extract had the strongest antibacterial activity. LC-MS/MS was employed to analyze the composition of extracellular products of Bspi2104 and BspiL6 extracted with different methods. There were 35 common differential metabolites in the extracellular products of the two strains extracted with different methods. The differential metabolites belonged to 37 categories of compounds, including carboxylic acids and derivatives, fatty acids, organic oxygen-containing compounds, organic nitrogen-containing compounds, steroids and derivatives, pregnenolone lipids, phenols, alkaloids and derivatives, glycerol phosphates, isoflavonoids, and benzene and substituted derivatives. Some of these compounds, such as kurarinone, and surfactin B, had antibacterial activities. [Conclusion] The extracellular products of B. subtilis subsp. spizizenii Bspi2104 had good physicochemical stability and maintained high antibacterial activity after treatment with various proteases and lipases, and at −20 ℃ to 60 ℃, pH 1.0–11.0, and UV irradiation for 3 h. The ammonium sulfate precipitates and the extracts from hydrochloric acid precipitation combined with methanol extraction, ethyl acetate extraction, and chloroform extraction of the extracellular products of B. subtilis subsp. spizizenii Bspi2104 had antibacterial activities. Among them, the 70% ammonium sulfate precipitate and ethyl acetate extract had the best antibacterial effects. The extracellular products of the strain contained diverse categories of antibacterial compounds. The findings provide theoretical reference for the discovery and screening of antibacterial components of Bacillus, and the related metabolites have research prospects.

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 develop a rapid nucleic acid detection method for Marburg virus based on clustered regularly interspaced short palindromic repeats/associated protein 13a (CRISPR/Cas13a). [Methods] According to the conserved region of Marburg virus nucleoprotein (NP) gene, specific primers for reverse transcription recombinase-aided amplification (RT-RAA) and CRISPR RNA (crRNA) were designed and synthesized. RT-RAA was employed to amplify the target sequence. The amplification products were detected by the CRISPR-Cas13a system, and the results were interpreted by easy-readout and sensitive enhanced (ERASE) lateral flow test strips. Finally, the national reference panel was used to evaluate the sensitivity and specificity of the new method. [Results] A set of high-efficiency RT-RAA primers and crRNA targeting Marburg virus NP gene was screened, on the basis of which a CRISPR-ERASE method for the detection of Marburg virus was developed. The target nucleic acid with a concentration of 1 copy/μL could be detected within 1 h, and there was no cross-reaction with other several pathogens. [Conclusion] In this study, a rapid, simple, highly sensitive, and specific nucleic acid detection method for Marburg virus was developed based on CRISPR/Cas13a.

[Objective] Microplastics (particle size < 5 mm) with hydrophobic surface, strong adsorption capacity, and difficult degradation can be retained in the environment for a long time and easily colonized by microorganisms, which poses a potential risk to the ecosystem. To study the distribution characteristics of microorganisms on the surface of microplastics in the wetland of Poyang Lake in wet and dry seasons. [Methods] Samples of water, sediments, and microplastics in sediments were collected from the wetland during the wet and dry seasons. The bacterial diversity and community structure in the samples were analyzed by high-throughput sequencing of the 16S rRNA gene. [Results] The richness and diversity of bacteria in the environment were higher than those on the microplastic surface in wet and dry seasons. During the wet season, the bacterial community structure was similar between the water and sediment samples and had large differences between the environment and the microplastic surface. During the dry season, the bacterial community structure was different among different samples. At the phylum level, the bacteria in the environment were dominated by Proteobacteria, Bacteroidetes, and Actinobacteria, while the bacteria on the microplastic surface during the wet season mainly included Proteobacteria, Bacteroidetes, and Firmicutes. The dominant bacterial phyla on the microplastic surface were similar to those in the environment during the dry season. The relative abundance of Pseudomonas on the microplastic surface was higher than that in the environment. Most of the keystone bacterial species in the wet and dry seasons belonged to Proteobacteria, including Sphingomonas. [Conclusion] This study reveals the differences in the bacterial community structure in the environment and on the microplastic surface in the Poyang Lake wetland in wet and dry seasons. The findings can enrich the knowledge about microplastics in lake wetlands in China and provide a theoretical basis for the management of lake environments including the Poyang Lake wetland.

The spread of antibiotic resistance has aroused global concern. The development of technologies for detecting antibiotic resistance genes (ARGs) is essential for curbing the migration and spread of ARGs from the environment to plants/animals and human populations. This paper describes the development timeline of existing nucleic acid detection technologies and their first applications to the detection of ARGs and summarizes their detection principles, advantages and disadvantages, and development potential. Furthermore, this paper prospects that isothermal amplification combined with CRISPR/Cas might be the core technology for the development of in-situ rapid detection methods. By reviewing the development history of each technology, this paper aims to give insights into the development and applications of technologies for detecting ARGs and provide technical support for the research and control of antibiotic resistance transmission.

Since the formation of a committee under the guidance of R. E. Buchanan in 1936, microbiologists have developed and refined a nomenclatural code for bacteriology, the International Code of Nomenclature of Prokaryotes (ICNP). This code has greatly facilitated recent advances in taxonomy and related fields of microbiology. Technical developments in omics have led to a surge in genome-based discoveries of novel uncultured species, many of which play important roles in environmental and medical microbiology. Nevertheless, the ICNP only recognizes cultures as nomenclatural types, thereby preventing the names of the uncultured microorganisms from being validly published. To compensate for the ineffectiveness of the ICNP in creating permanent and stable names of uncultured taxa, the Code of Nomenclature of Prokaryotes Described from Sequence Data (SeqCode) was published in 2022. The SeqCode was formed with the intention of complementing and someday merging with the ICNP. However, as the two nomenclatural codes currently work independently, the consequences of the concurrence of both codes on the scientific community are still not clear. Here, we introduce the histories and principles of the ICNP and SeqCode, summarize their advantages and limitations, and call for scholars to both respect and utilize the two nomenclatural codes of prokaryotes, aiming to facilitate the establishment of a more reasonable and beneficial naming system.

[Objective] To clarify the promotion effects of different organic compounds on the formation of magnetosomes inAcidithiobacillus ferrooxidans BYM, so as to provide a new idea for safely and effectively improving the magnetosome yield. [Methods] Single-factor experiments were conducted to measure the effects of ten organic compounds on the ferrous oxidation ofA.ferrooxidans BYM, and the organic compounds promoting the synthesis of magnetosomes were further screened by a 4 L fermentation system. The classical kinetic models (Logistic, Luedeking-Piret, and substrate consumption kinetic equations) were employed to build the kinetic models for the growth, magnetosome synthesis, and ferrous consumption ofA.ferrooxidans BYM by batch fermentation experiments. [Results] The maximum magnetosome yield (2.00×10⁻³ g/L) was achieved with the addition of 10 mmol/L gluconic acid, in the presence of which the bacterial cells were oval and had a smooth surface. With the addition of gluconic acid, the fermentation kinetics ofA.ferrooxidans BYM was in accordance with Logistic, Luedeking-Piret, and substrate consumption kinetic equations. [Conclusion] The addition of 10 mmol/L gluconic acid increases the magnetosome yield ofA.ferrooxidans BYM by eight times. Gluconic acid changes the cell morphology and surface ofA.ferrooxidans BYM. The kinetics models of cell growth, product formation, and substrate consumption can illustrate the batch fermentation ofA.ferrooxidans BYM in the presence of gluconic acid.

[Objective] Selenium (Se) is an essential trace element playing a critical role in maintaining the physiological metabolism of humans. Among its various forms, selenium nanoparticles (SeNPs) possess higher bioavailability and lower toxicity. The study aims to screen a probiotic strain that can efficiently synthesize SeNPs from selenite. [Methods] Lacticaseibacillus paracasei SCFF20 capable of converting sodium selenite to SeNPs was screened out from 14 strains of probiotics. The SeNPs produced byL.paracasei SCFF20 were purified, freeze-dried, and systematically characterized by scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDX), dynamic light scattering (DLS), X-ray diffractometer (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). [Results] SEM-EDX results revealed that Se was the primary constituent of SeNPs. The synthesized SeNPs were spherical and polydisperse, with an average particle size of 500.62 nm. XRD and Raman spectroscopy confirmed that the SeNPs were amorphous. Additionally, FTIR demonstrated the presence of proteins, exopolysaccharides, and lipids coating the surface of the SeNPs. Moreover, the reduction rate of SeNPs was determined to be 91.42% by inductively coupled plasma-optical emission spectroscopy (ICP-OES). [Conclusion] The findings of this study highlight the potential ofL.paracasei SCFF20 as a probiotic strain capable of producing SeNPs. The strain can be used as a cell factory for the safe production of biogenic SeNPs as nutritional supplements and functional food.

[Objective] High-temperature stacking fermentation is a key process in the production of Jiang-flavor Baijiu.Kroppenstedtia is a predominant bacterial genus in the stacked fermented grains, and investigating its growth and metabolic characteristics contributes to comprehensively understanding the crucial role of stacking fermentation. [Methods] The tryptic soy broth was used to screenKroppenstedtia strains from the stacked fermented grains, and the taxonomic status of each strain was determined by morphological observation and 16S rRNA gene sequencing. Furthermore, the growth characteristics and volatile compound metabolism of each strain were investigated by solid-state fermentation experiments on sorghum at different temperatures (45 ℃ and 50 ℃) in combination with pure culture. [Results] Three strains ofKroppenstedtia were isolated from the fermented grains of Jiang-flavor Baijiu and identified asK.eburnea. The liquid culture of strainK.eburnea 1613 significantly enhanced the production of pyrazines, which was 2.66 folds of that in the control group. The volatile compounds of sorghum in solid-state fermentation predominantly consisted of alcohols and acids, the total content of which increased over the fermentation time. The fermentation at 50 ℃ promoted the accumulation of alcohols, acids, and pyrazines, and that at 45 ℃ facilitated the accumulation of esters. The primary metabolites produced by the three strains during solid-state fermentation with sorghum as the substrate were phenethyl alcohol and isovaleric acid. The fermentation withK.eburnea 1615 at 50 ℃ for 15 days produced the highest levels of phenethyl alcohol and isovaleric acid, which reached (31.17±0.14) µg/g and (16.75±0.76) µg/g, respectively. The fermentation withK.eburnea 6E22 andK.eburnea 1613 at 50 ℃ yielded the highest levels of 2, 5-dimethyl pyrazine [(1.67±0.14) µg/g] and hexanoic acid [(3.74±0.19) µg/g], respectively, after 15 days. The accumulation of aldehydes and ketones was significant in sorghum fermented at 50 ℃. The partial least squares-discriminant analysis (PLS-DA) revealed significant influences of temperature and time on the volatile compound composition of sorghum fermented by the three strains. [Conclusion] K.eburnea contributes to the production of flavor compounds in fermented grains, particularly the characteristic flavor compounds such as alcohols, acids, and pyrazines of Jiang-flavor Baijiu.