Agar is one of the important components in the cell wall of red algae. The biodegradation of agar affects marine ecological processes, such as nutrient recycling, succession of large seaweed communities, heavy metal pollution, and carbon sequestration. In addition, the degradation products of agar demonstrate great application potential in aquaculture, agriculture, medicine, health products, bioenergy, etc. Therefore, the biodegradation of agar and its ecological and application values have become research hotspots in recent years. This article reviews the research progress in the significance of agar degradation, microbial agarases, and agar metabolic pathways, providing theoretical support for the research on the ecological effects and comprehensive utilization of the agar from red algae.

[Objective] The application of Bacillus subtilis in soil can promote plant growth, while few studies have reported the bacteriophages infecting B. subtilis. Therefore, the isolation, biological characterization, and genome sequencing of bacteriophages infecting B. subtilis from soil will contribute to the application of B. subtilis and enrich the biological information of bacteriophages infecting B. subtilis. [Methods] B. subtilis SM13 was used as the host to isolate a bacteriophage strain Bac-S from soil. Biological characterization, whole genome sequencing, gene function annotation, and phylogenetic analysis were performed for this bacteriophage strain. [Results] Transmission electron microscopy showed that Bac-S had a head with the diameter of about 43 nm and a tail too short to be measured. The optimal multiplicity of infection of Bac-S was 0.1. The one-step growth curve showed that Bac-S had an incubation period of about 10 min and a burst size of 30 PFU/cell. Bac-S had a wide host spectrum and can infect hosts of different genera. The sequencing results showed that the genome of Bac-S was 150 019 bp, with the G+C content of 42.6% and 237 open reading frames (ORFs). The BLASTn comparison with the sequences in the NCBI database showed that Bac-S was similar to other bacteriophages infecting B. subtilis. [Conclusion] A bacteriophage strain infecting B. subtilis with a short incubation period, a wide host spectrum, tolerance to high temperature, and intolerance to UV light was isolated from soil. The biological and genetic characterization of this bacteriophage enriches our knowledge about the bacteriophages infecting B. subtilis.

[Objective] To investigate the biological role played by the glucoside transporter Lmo0738 in the virulence of Listeria monocytogenes. [Methods] The lmo0738-deleted mutant (Δlmo0738) and complementation mutant (CΔlmo0738) were constructed by homologous recombination. The growth, hemolytic activity, cellular adhesion and invasion, and intracellular migration of the wild type strain and the mutants were assessed by the growth curves, sheep red blood cell hemolysis assay, infection of human epithelial cells (Caco-2), and infection of mouse fibroblastic cells (L929), respectively. Additionally, the mRNA and protein levels of the virulence factor listeriolysin O (LLO) were determined by real-time quantitative reverse transcription PCR (RT-qPCR) and Western blotting, respectively. [Results] The L. monocytogenes strain with the deletion of lmo0738 demonstrated weakened growth and diminished hemolytic activity. Notably, Δlmo0738 exhibited significantly reduced cell adhesion, invasion, and intracellular migration compared with the wild type strain. In addition, the mRNA and protein levels of LLO were significantly down-regulated in Δlmo0738. [Conclusion] This study provides the evidence that the absence of lmo0738 attenuates the virulence of L. monocytogenes, laying a crucial foundation to illustrate the mechanism of the phosphotransferase system (PTS) in regulating the sugar catabolism and the infection mechanism of major food-borne pathogens including L. monocytogenes.

[Objective] We characterized the uterine microbiota in healthy felines and felines with pyometra, aiming to reveal the effect of pyometra on the uterine microbiota of felines and explore the potential pathogens causing pyometra. [Methods] High-throughput sequencing of the full-length 16S rRNA gene was employed to determine and compare the uterine microbiota in healthy felines and felines with pyometra. The key strains were isolated and identified by the culture method. [Results] The dominant bacterial genera in the uterus of healthy felines were Acinetobacter, Pseudomonas, Sphingomonas, and Weissella. The dominant bacterial genus and species in the uterus of felines with pyometra were Escherichia-Shigella and Escherichia coli, respectively. Functional prediction showed that pathways such as protein export, amino acid-related enzymes, protein processing in endoplasmic reticulum, and aminoacyl tRNA biosynthesis in the pyometra group were significantly reduced. The results of isolation and identification showed that the prevalent bacterial species in the uterus of felines with pyometra was E. coli. The isolates all belonged to the phylogroup B2 and were mostly tested positive for hylA, fimH, iroN, cnf1, papC, kpsMTII, and iutA. [Conclusion] We compared the uterine microbiota in healthy felines and felines with pyometra. The dominant bacteria in the uterus of healthy felines were mostly non-pathogenic, while those in the uterus of felines with pyometra changed significantly, with E. coli being dominant and carrying multiple virulence genes. The findings provide a theoretical basis for treating pyometra in felines.

[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.

Depression is a prevalent affective disorder exerting negative impacts on an individual's emotional and cognitive functions and is commonly complicated with other diseases. As depression is affecting increasingly younger populations, it poses a serious challenge to the mental health initiatives in China. In recent years, the relationship between depressive symptoms and gut microbiota has garnered increasing attention, fueled by the deepening research on gut microbiota. Lactulose, a medication aimed at promoting gut health and known for its potential benefits on emotional and cognitive functions, has sparked interests regarding its clinical application in ameliorating depressive symptoms. This article reviews the clinical research findings on the efficacy of lactulose in alleviating depressive symptoms and outlines the potential mechanisms through which lactulose may mitigate these symptoms. Furthermore, this article offers a perspective on the mitigation of depressive symptoms through the gut-brain axis.

[Objective] To improve the culture medium components of Parvimonas micra, increase the number of live cells, and develop a demonstration method for culturing fastidious bacteria. [Methods] Biochemical analysis was conducted on a strain of P. micra to screen the potential substrates that could promote bacterial growth. A single-factor experiment was carried out for each substrate with three concentrations. The substrate with a significant bacterial enrichment effect was further optimized for concentration, and thus a new culture medium was obtained. [Results] The single-factor experiment results showed that the substrates with significant bacterial enrichment effects included L-serine, L-threonine, and glycyl-L-glutamine. In the medium with the addition of 4.8 g/L L-serine, the live cell count of P. micra reached 3.6×10⁸ CFU/mL, representing a 4.2-fold increase compared with that in the basic medium with tryptone soya broth (TSB) and fetal bovine serum (FBS). Furthermore, the improved culture medium was applied to the culture of another P. micra strain, demonstrating a significant growth-promoting effect. [Conclusion] This study proves that using biochemical identification plates to screen medium supplements is a fast and efficient method, providing a reference for the enlargement culture of fastidious bacteria.

Anaerobic digestion (AD) of biomass waste combined with waste activated sludge (WAS), which is characterized by great stability, low energy consumption, and biogas production, can effectively reduce the volume and improve the dehydration of WAS and thus has been widely applied in methane production. However, the AD process is susceptible to external factors such as microplastics (MPs) or nanoplastics (NPs), which can lead to reduced efficiency or even collapse of AD. The AD system needs the interdependence and interaction of the microbial community to keep stable operation in a dynamic equilibrium state, in which phages play a key role. Phages can not only regulate the structure of the microbial community in the sludge and direct the energy flow but also attach to MPs and NPs with bacteria and archaea for transmission. Nevertheless, the effects of MPs and NPs on such a process were underestimated in previous studies. In this paper, we summarize the research progress in the effects of different types and sizes of MPs and NPs on AD systems, with focus on the ecological connections among microbial communities, especially bacteria, archaea, and phages, in anaerobic systems. Furthermore, we put forward novel viewpoints about the effects of MPs and NPs on microbial communities and make an outlook on the future research directions in this field.

Listeria monocytogenes, a major zoonotic food-borne intracellular pathogen, is ubiquitous in the natural environment and easily contaminates animal-derived food products. The consumption of the contaminated food can cause severe listeriosis in both humans and animals, with the mortality rate reaching up to 30%. The antimicrobial therapy is the only feasible approach for treatingL.monocytogenes infection sinceL.monocytogenes is susceptible to multiple antimicrobials. However, the reports of multidrug-resistant strains are increasing due to the selective pressure exerted by the irrational use of antimicrobials or disinfectants. The antimicrobial resistance mechanisms ofL.monocytogenes are complex. Efflux pump proteins are crucial in bacteria and participate in various biological processes. Specifically, they can influence bacterial sensitivity to antibiotics, facilitate the efflux of toxic compounds, and affect bacterial virulence. Over the last two decades, scholars have conducted research on the efflux pumps-mediated resistance ofL.monocytogenes, identifying several efflux pump proteins associated with the efflux of antibiotics or toxic compounds. Additionally, some efflux pumps are involved in the virulence expression process ofL.monocytogenes. This paper reviews the research advances in the functions and regulatory mechanisms of efflux pumps in multidrug-resistantL.monocytogenes. It provides a theoretical foundation for probing into the environmental adaption mechanisms ofL.monocytogenes, curbing the spread of this pathogen, and identifying new drug targets for combating infections.