Salmonella Enteritidis is a major foodborne pathogen that can cause gastrointestinal infections in both humans and animals. As one of the key genes encoding the iron-sulfur cluster assembly, iscA plays a role in the transport of iron ions and energy metabolism. IscA is a conserved A-type iron-binding protein. [Objective] To study the role of iscA in the infection process of Salmonella by constructing an iscA-deleted mutant (ΔiscA) of Salmonella Enteritidis Z11. [Methods] The unmarked in-frame gene deletion method was employed to construct ΔiscA from the laboratory-preserved Salmonella Enteritidis Z11 strain. The wild type (WT) and ΔiscA were compared in terms of motility and biofilm formation. Additionally, the impact of IscA on the virulence of Salmonella Enteritidis was explored in both RAW264.7 cells and a mouse model. [Results] The deletion mutant ΔiscA was successfully constructed. No significant difference in the growth or biofilm formation was observed between ΔiscA and WT, indicating that the deletion of iscA did not affect the normal growth or biofilm formation of Salmonella Enteritidis. However, ΔiscA exhibited a significantly smaller zone of motility than WT at the time point of 6 h, suggesting that the loss of iscA reduced the motility of Salmonella Enteritidis Z11. In RAW264.7 cells, the adhesion and invasion of ΔiscA significantly decreased to 37% and 20%, respectively, of those of WT. Furthermore, the proliferation rate of ΔiscA in the cells was significantly lower than that of WT. Mouse infection experiments revealed that ΔiscA demonstrated reduced colonization in the jejunum and cecum compared with WT. [Conclusion] iscA is closely associated with the virulence of Salmonella Enteritidis. Its deletion affects the motility, adhesion, invasion, and proliferation, ultimately reducing the colonization in the host intestine and influencing the infection process of Salmonella Enteritidis.

Collagen is the most abundant protein in mammals, accounting for about one-third of human protein. As an important component of the connective tissue and extracellular matrix, collagen is essential for maintaining physiological functions and repairing injuries and has important applications in the fields of medicine, food, and beauty. The main methods for producing collagen are natural extraction, chemical synthesis, and biosynthesis. Natural extraction from animal connective tissue has ethical issues, unstable quality, and infectious disease risks. Chemical synthesis is costly and it is not easy to synthesize complex collagen structures. Biosynthesis enables the production of recombinant collagen for different purposes by genetic engineering in a more controllable, safer, and more precise manner. However, due to the complex structure of collagen, its biosynthesis depends on specific molecular chaperones and modifying enzymes, and thus the production of recombinant collagen is challenging. In addition, different types of collagen need to form particular tissue structures, such as fibril, reticular, or transmembrane structures, which further increases the difficulty of production. This article clarifies the multifunctionality of recombinant human collagen, reviews the latest progress and challenges in its biosynthesis, and looks forward to future development directions. This review aims to help researchers, engineers, and industry practitioners understand the research trends of recombinant collagen and promote its further development and commercialization in different application fields.

[Objective] Staphylococcusepidermidis is a coagulase-negative, Gram-positive coccobacillus that is widely found in the skin, breast milk, and blood. Bacteria in breast milk play a crucial role in the establishment of the gut microbiota in the intestinal tract and in the enhancement of immunity of infants. We then performed comparative genomic analyses to understand the genetic diversity and functional genes of breast milk-derived S. epidermidis. [Methods] We used the Illumina NovaSeq platform to sequence the genomes of 110 strains of S. epidermidis preliminarily isolated from healthy breast milk by our research team. We then performed comparative genomic analyses for the 110 strains and 263 skin, blood, and breast milk-derived S. epidermidis strains publicly available from the NCBI. [Results] The genome size of the 373 strains of S. epidermidis was (2.50±0.33) Mb, with the G+C content was (32.0±0.1)%, and the number of coding sequences (CDs) being 2 331±368. Differences existed in genome size and number of CDs among breast, blood, and skin isolates (P<0.05), with blood isolates having the largest genome size and the highest number of CDs. The phylogenetic tree showed that the S. epidermidis isolates of the same source had obvious aggregation, and the breast milk isolates and blood isolates were more closely related. There were differences in the number of virulence factors and drug resistance genes among the strains of three sources (P<0.05). The blood-derived strains exhibited the highest diversity of virulence and resistance genes, whereas the breast milk-derived strains displayed the lowest diversity of such genes. [Conclusion] S. epidermidis has undergone adaptive evolution to different habitats. Compared with skin- and blood-derived strains, breast milk-derived strains carry few genes related to biofilm synthesis, drug resistance, and virulence. This study gives new insights into the adaptive evolution of S. epidermidis and provides a theoretical basis for subsequent research on the genetic background of breast milk isolates.

Paranosema locustae, an environmentally friendly biocontrol agent, holds significant potential for managing locusts. However, its application is affected by various environmental factors. Understanding the resistance differences of P. locustae under different conditions is essential for its application in biocontrol. [Objective] To study the effects of different environmental conditions on the energy metabolism and stress responses of P. locustae, providing a theoretical foundation for its environmental adaptability. [Methods] Spores of P. locustae were exposed to three controlled experimental environments: a dry environment at 40 °C (40 °C GR), a wet environment at 20 °C (20 °C SR), and ultraviolet irradiation under dry conditions (≥100 µW/cm²) (ZW) for varying time periods. We employed a microplate reader, laser confocal microscopy, and differential interference contrast microscopy to assess the survival curves of infected locusts and the spore germination rate, ATP level, protein content, reactive oxygen species (ROS) level, and trehalose level of P. locustae. [Results] In the 20 °C SR group, P. locustae showed a decrease in the germination rate and notable rises in ATP and active oxygen (ROS) levels, and the median survival time of infected locusts increased. The 40 °C GR group showed no significant changes in the ATP level, ROS level, spore germination rate, or the survival curve of infected locusts compared with the control group. The ZW group showed increases in the ATP and ROS levels, but no significant change in the germination rate or the survival curve of infected locusts. Conclusions Dry spores of P. locustae exhibit greater resistance to environmental stress, while prolonged exposure to liquid conditions leads to a decrease or even loss of spore viability. These findings provide insights for the preservation and application of P. locustae formulations, establishing a theoretical basis for revealing its environmental adaptability.

Leaf photosynthesis forms the foundation of plant energy and material cycles. Mycorrhizal fungi, as a crucial component associated with roots, play a significant role in regulating the nutrient absorption, water utilization, and stress resistance of plants and are key ecological factors affecting the function and stability of forest ecosystems. However, at present, knowledge is limited regarding the effects of different mycorrhizal types on the photosynthetic capacity of woody plants and their responses to environmental changes. Objective To explore the differences in photosynthetic capacity among woody plants with different mycorrhizal types and their responses to changes in leaf characteristics and environmental factors. [Methods] According to the China Plant Trait Database and available articles, we identified three mycorrhizal types of woody plants, which included arbuscular mycorrhiza (AM), ectomycorrhiza (ECM), and AM+ECM. On this foundation, a database of woody plant traits for different mycorrhizal types in China was established, with the data of each sample encompassing photosynthetic capacity, photosynthetic physiology, leaf structure, nutrient characteristics, and environmental factors. [Results] The woody plants with ECM had higher photosynthetic capacity than those with AM. Mycorrhizal types significantly influenced the relationship between leaf traits and photosynthetic capacity. The photosynthetic capacity of woody plants was primarily affected by the stomatal conductance and transpiration rate of leaves. In addition, the photosynthetic capacity of plants with AM were influenced by leaf area, specific leaf area (SLA), and nitrogen and phosphorous content. The photosynthetic capacity of plants with AM+ECM were affected by SLA, specific leaf weight, and carbon and phosphorous content, while that of plants with ECM was influenced by the vapor pressure deficit. The maximum net photosynthetic rate and maximum electron transport rate of plants with ECM were more susceptible to temperature and precipitation than plants with AM and AM+ECM. [Conclusion] Mycorrhizal types significantly affect the maximum net photosynthetic rate of woody plants, and leaf characteristics primarily influence the maximum net photosynthetic rate by regulating the maximum electron transport rate. Moreover, the effects of environmental factors on the morphological and physiological traits of woody plant leaves depend on mycorrhizal types.

[Objective] To study the composition, functional characteristics, and vertical distribution features of microbial communities of three different habitats in the Yellow River Delta wetland ecosystem, and provide theoretical support and potential microbial resources for targeted restoration and sustainable management of wetland ecology. [Methods] By using 16S rRNA gene amplicon sequencing and metabolomics analyses, we compared the composition and structures of soil bacterial communities in three habitats (vegetation-covered area, bare land, and biohabitat), and analyzed the characteristics of bacterial communities at varying soil depths as well as the potential interactions between habitat-specific bacteria and metabolites. [Results] The dominant phyla in the three habitats were Proteobacteria and Bacteroidota. The dominant phyla specific to the shallow and deep soil layers were Gemmatimonadota and Firmicutes, respectively. The unidentified MBNT15 in the vegetation-covered area, Halomonas in the bare land, and unidentified Rhodobacteraceae and Woeseia in the biohabitat showed significantly different abundance between different depths, and Bacillus was enriched in the deeper soil layer of all the three habitats. Metabolomic analysis revealed that the vegetation-covered area showed higher levels of sphinganine, 3-indoleacrylic acid, 2,4-dihydroxybenzoic acid, and perfluorooctanoic acid. Deoxycholic acid had the highest level in the bare land, while sulfamethoxazole was the highest in the biohabitat, which had lower level of l-tryptophan. Correlation analysis revealed that in the vegetation-covered area, Micrococcus luteus and Pseudomonas geniculata showed significantly positive correlations with sphinganine and perfluorooctanoic acid. Saccharospirillum salsuginis had significantly positive correlations with 3-indoleacrylic acid and 2,4-dihydroxybenzoic acid. In the bare land, Bacillus horikoshii showed a significantly positive correlation with deoxycholic acid. In the biohabitat, Halomonas ventosae had a significantly positive correlation with l-tryptophan, while Halomonas korlensis showed a significantly positive correlation with sulfamethoxazole. [Conclusion] Our study demonstrated that varying soil depths significantly impact the structure of microbial communities, and the structural and functional characteristics of soil microbial communities exhibit habitat specificity. The enriched bacteria such as M. luteus in the vegetation-covered area may promote plant growth and enhance stress resistance by regulating metabolites. The enriched Bacillus in the bare land plays a role in decomposing bird feces. The unique bacteria such as H. ventosae in the biohabitat demonstrate the potential for maintaining the ecological health of crab habitats through metabolite regulation. These findings offer new insights into the microbial regulation and management of wetland ecosystems.

[Objective] Phosphate-solubilizing bacteria (PSB) can increase available phosphorus by promoting the transformation of different phosphorus forms in soil. However, the phosphate-solubilizing ability of PSB is influenced by soil texture. Therefore, we studied the changes of phosphorus fractions in red soil with different textures and treated with PSB, with the aims of improving the efficient utilization of soil phosphorus. [Methods] We collected the rhizosphere soil samples of four main Camellia oleifera varieties (‘Huashuo’ ‘Huaxin’ ‘Huajin’ and ‘Changlin No. 40’) in Liuyang City, Hunan Province. PSB strains were isolated, purified, screened, and identified by plate coating, transparent circle method, molybdenum-antimony anti-spectrophotometric method, and 16S rRNA gene sequencing, and a batch of highly efficient PSB strains were obtained. The phosphate-solubilizing abilities of the obtained PSB strains were investigated with different phosphorus sources (iron phosphate, aluminum phosphate, calcium phosphate, and calcium phytate). PSB were inoculated into the red soil samples added with 0, 20% and 40% perlite (0%PR, 20%PR and 40PR%) to clarify the changes in phosphorus fractions in the red soil samples with different textures. [Results] A total of 57 strains of PSB were isolated from the rhizosphere of C. oleifera, of which strains CL37, HS5, and CL36 exhibited stronger phosphate-solubilizing abilities. The three strains were identified by 16S rRNA gene sequencing and named Pantoea sp. CL37, Burkholderia sp. HS5, and Burkholderia sp. CL36, respectively. The three strains showed significant differences in their ability to solubilize different phosphorus sources, with the highest solubilizing ability for calcium phytate and calcium phosphate. Compared with CK, the inoculation of PSB increased the available phosphorus (AP) in soil by 8.90%-54.60% and 1.90%-56.00% in 20%PR and 40%PR, respectively. The inoculation with PSB increased Fe-P, Resin-P, NaHCO₃-Pi, and NaOH-Pi, which showed a tendency of first increasing and then decreasing along with the increase in the addition of perlite in red soil. Meanwhile, PSB decreased the content of HCl-Pi and Residual-P, and the decrease in HCl-Pi was more pronounced in 20%PR than in 0%PR and 40%PR. Of all treatments, the inoculation with HS5 led to the highest increases in Fe-P, Resin-P, NaHCO₃-Pi, and NaOH-Pi in the soil samples analyzed. Correlation analysis and random forest analysis suggested that AP was mainly affected by Resin-P, Al-P, NaOH-Pi, acid phosphatase, urease, pH, and NaOH-Po. [Conclusion] The phosphate-solubilizing pathways of PSB vary in red soil with different textures. Strain HS5 has a strong phosphorus-transforming ability and is more conducive to phosphorus transformation in the red soil with 20%PR.

[Objective] To explore the physiochemical response mechanism of a model algal strain Chlamydomonas reinhardtii that hyper-accumulates oils to exposure of naphthenic acids (NAs). [Methods] The impacts of a typical NA, cyclohexanecarboxylic acid (CHCA), on the physiochemical parameters, including growth, photosynthetic activity, pH value of the culture, uptake of nitrogen and phosphorus, and biochemical constituents (lipids, carbohydrates, proteins, and pigments), of C. reinhardtii with high initial cell density under high light-nitrogen repletion (HL+N) and high light-nitrogen deprivation (HL-N) conditions were studied. [Results] The exposure to CHCA prominently promoted the uptake of phosphorus by C. reinhardtii under HL+N, while significantly inceasing the relative abundance of saturated C16:0 and decreasing the relative abundance of polyunsaturated C18:3n3. In contrast, CHCA treatment significantly inhibited the photosynthetic activity and phosphorus uptake but did not affect the fatty acid profile of C. reinhardtii under HL-N stress. In addition, the growth, pH value of the culture, and content of lipids, carbohydrates, proteins, and pigments, in C. reinhardtii under both HL+N and HL-N conditions all remained relatively constant when subjected to CHCA exposure. [Conclusion] The tolerance of microalgae to environmental stress can be visualized by growth curves, photosythetic activity, uptake of nitrogen and phosphorus, and key biochemical constituents. HL+N improves the tolerance of C. reinhardtii to NAs by promoting the uptake of phosphorus and altering the fatty acid profile, while the case was contrary under HL-N. These findings are beneficial for establishing strategies on effective cultivation of microalgae that highly tolerate NAs.

[Objective] The rhizosphere microorganism-plant combined approach has high application potential for the remediation of heavy metal-contaminated soil. This study observed the effects of adding exogenous plant growth-promoting bacteria (PGPB) on the growth and molybdenum (Mo) accumulation of alfalfa (Medicago sativa), aiming to provide theoretical references for plant-microbial remediation of Mo-contaminated soil. [Methods] The endophytic bacteria were isolated from dominant plants of Mo tailing and they were identified based on morphological characteristics and molecular evidence. The plant growth-promoting (PGP) properties of molybdate-reducing strains were determined. By adding exogenous PGPB into the soil, we investigated the effects of adding exogenous PGPB on the biomass, physiological activity, and Mo accumulation of alfalfa. [Results] Two molybdate-reducing strains M9 and M13 were obtained and identified as Serratia plymuthica based on morphological characteristics, 16S rRNA gene sequence, and gyrB sequence. M9 and M13 had the abilities to fix nitrogen, solubilize phosphorus, solubilize potassium, and secrete indole-3-acetic acid (IAA), siderophores, and 1-amino cyclopropane-1-carboxylic acid (ACC) deaminase. Under Mo stress, the inoculation of M9, M13, and M9+M13 significantly promoted the growth of alfalfa, increasing the plant height, root length, and fresh weight of alfalfa compared with the non-inoculation control group. At the same time, the inoculation increased the chlorophyll content and peroxidase (POD) activity while decreasing the malondialdehyde (MDA) content in alfalfa. M9 and M13 significantly affected the Mo accumulation of alfalfa. The Mo content in the above-ground and under-ground parts of alfalfa inoculated with M9, M13, and M9+M13 significantly decreased compared with that in the non-inoculation control group. The decreased enrichment factor of Mo in alfalfa indicated that inoculation with molybdate-reducing strains reduced the uptake and transport of Mo in alfalfa. [Conclusion] The molybdate-reducing strains M9 and M13 can promote the growth and reduce the Mo content of alfalfa in Mo-contaminated soil. This finding can provide theoretical reference for revealing the mechanism of microbial-enhanced Mo remediation by plants as well as the joint remediation of Mo-contaminated soil by plants and microorganisms.

Aeromonas hydrophila is a pathogen that can infect both fish and mammals, including humans. [Objective] To construct the tolA-deleted strain of A. hydrophila ATCC 7966 and use this strain to explore the biological functions of tolA. [Methods] We constructed the tolA-deleted strain AhΔtolA by homologous recombination and characterized the physiological phenotype of AhΔtolA. Transcriptome sequencing was performed to compare the gene expression between the wild type (WT) and AhΔtolA. [Results] The cell morphology of AhΔtolA was changed. The deletion of tolA significantly enhanced the sensitivity to sodium deoxycholate and oxidative stress, while significantly reducing the biofilm formation and the expression levels of several virulence genes. The yield of outer membrane vesicles was significantly increased in AhΔtolA. Transcriptomic analysis data showed that a total of 300 differentially expressed genes (DEGs) were screened between WT and AhΔtolA, including171 genes with up-regulated expression and 129 genes with down-regulated expression. GO enrichment analysis showed that the DEGs were mainly enriched in the oxidation-reduction process, metabolic process, outer membrane, and oxidoreductase activity. KEGG pathway enrichment analysis showed that the DEGs were mainly enriched in the biosynthesis of secondary metabolites, microbial metabolism in diverse environments, biosynthesis of cofactors, and biosynthesis of amino acids. [Conclusion] This study gives an insight into the roles of tolA in A. hydrophila and provides information about the metabolic pathways involving tolA. These results provide a theoretical reference for the prevention and control of A. hydrophila.