Streptococcus suis is a major zoonotic pathogen that can infect both pigs and humans, causing severe diseases such as meningitis in humans. Its pathogenicity depends on the ability to rapidly adapt to environmental stress and host immune responses. Serine/threonine kinases and their corresponding phosphatases constitute a eukaryotic-like signal transduction system in bacteria and play a key regulatory role in S. suis serotype 2, closely related to its biological characteristics and pathogenic mechanisms. Through precise regulation of the phosphorylation and dephosphorylation of downstream substrates, serine/threonine kinases/phosphatases form complex signaling networks, thereby influencing various physiological and pathogenic processes of the bacterium. This article systematically reviews the currently known substrates of serine/threonine kinases in S. suis serotype 2, with a focus on elucidating how these kinases precisely regulate bacterial growth and division, capsule synthesis, stress tolerance, adhesion, invasion, and pathogenicity by modulating the phosphorylation status of functional substrates. This review aims to provide new perspectives for deciphering the pathogenic mechanism of S. suis serotype 2 and the development of novel antibacterial strategies.

Alzheimer’s disease (AD) is a complex neurodegenerative disorder characterized by progressive cognitive impairment. In recent years, the “gut-brain axis” has been recognized to play an important role in the pathogenesis of AD, with the gut microbiota-derived metabolites serving as key mediators of gut-brain communication. This review systematically summarizes the alterations and underlying molecular mechanisms of five classes of key metabolites—short-chain fatty acids, bile acids, indole derivatives, trimethylamine N-oxide, and lipopolysaccharides—during the progression of AD. This review not only provides new perspectives for understanding the pathological processes of AD but also lays a theoretical foundation for the development of diagnostic and therapeutic strategies based on microbiota modulation.

Ciliates of the family Balantidiidae widely parasitize the digestive systems of various invertebrates and vertebrates. Among them, Balantioides coli with cosmopolitan distribution is a major zoonotic pathogen. For a long time, due to the similar morphology of trophozoites of Balantidiidae ciliates from various hosts and the influences of various growing stages and host intestinal microenvironments on morphological characteristics, there have been some inconsistencies and confusions in their classification and nomenclature in literature. Recently, significant progress has been achieved in the study of the phylogenetic relationship and genetic diversity of Balantidiidae ciliates, providing new evidences for their taxonomic reconstruction. On the basis of a systematic review of literature and our findings, this article summarizes the taxonomic status and genetic diversity of Balantidiidae ciliates from different hosts in terms of the morphological characteristics, encystation ability, host specificity, and phylogenetic relationships. The existing evidence supports the division of the family Balantidiidae into two genera Balantidium and Balantioides and indicates that the ciliate infecting humans and various mammals should be classified as Balantioides coli. The related findings and understanding help clarify the taxonomy and nomenclature system of Balantidiidae ciliates and provide an important reference for studying the biological characteristics of Balantidiidae ciliates as well as the diagnosis and control of balantiosis in humans and animals.

Neopestalotiopsis cubana Maharachch. is the primary pathogen responsible for leaf spot and fruit ring rot in guava (Psidium guajava L.). The ADP-ribosylation factor-like protein 8 (Arl8) belonging to the ADP-ribosylation factor (Arf) superfamily is associated with lysosomal processes including localization, trafficking, and fusion. The function of Arl8 in phytopathogenic fungi remains poorly understood. Objective To elucidate the function of Arl8 in N. cubana. Methods An Arl8 gene was identified from the genome of N. cubana and designated as NecArl8. A NecArl8 knockout mutant (ΔNecArl8) and a complemented strain (ΔNecArl8-C) were generated via clustered regularly interspaced short palindromic repeats (CRISPR)-associated 9, (CRISPR/Cas9)-mediated genome editing. These strains were subsequently analyzed through phenotypic experiments and RNA-seq. Results ΔNecArl8 showed a reduction of 34.93% in sporulation capacity and significant increases of 5.74% and 7.39% in inhibition rates by salt and osmotic stresses, respectively. In addition, this mutant exhibited weakened pathogenicity, as indicated by a reduction of 5.74 mm in the average spot diameter. In contrast, the mutant displayed significantly enhanced resistance to oxidative stress, which showed an inhibition rate of -19.22%. After long-term culture, a large number of vacuolated cells were observed in the mutant. RNA-seq analysis was performed on ΔNecArl8 and the wild-type strain to identify differentially expressed genes. Transcriptomic analysis showed that 2 330 genes were significantly down-regulated and 1 355 genes were significantly up-regulated. Gene set enrichment analysis further revealed that transmembrane transport proteins were broadly suppressed, and the expression levels of 16 fungal-type vacuolar-related proteins were significantly down-regulated, suggesting that the structure and functions of fungal-type vacuoles were seriously damaged. The reverse transcription quantitative PCR (RT-qPCR) results showed the expression patterns of 9 randomly selected transmembrane transport genes were consistent with those obtained by transcriptome sequencing, indicating that the transcriptome data were highly reliable. Conclusion NecArl8 may affect the pathogenicity of N. cubana on guava by regulating function of transmembrane transport. This study lays a theoretical foundation for exploring the pathogenic mechanism of N. cubana and developing new control strategies.

Salicylic acid (SA) is an important phenolic compound that plays a key role in plant defenses and is widely used in pharmaceuticals, cosmetics, and personal care products due to its significant anti-inflammatory and antimicrobial activities. Currently, the production of SA mainly relies on plant extraction and chemical synthesis, which suffers from complex processes, severe environmental pollution, and high dependence on petrochemical resources. With the rapid development of synthetic biology, metabolic engineering, and artificial intelligence (AI) technologies, the green synthesis of SA through intelligently designed microbial cell factories, empowered by machine learning algorithms and automated platforms, has become an important research direction to replace conventional production methods. This review systematically summarizes the microbial biosynthetic pathways of SA. With a focus on the intelligent design theme, this paper highlights the application of AI and synthetic biology tools in the discovery and utilization of natural SA-producing microbial resources and the rational reconstruction and optimization of the SA biosynthetic pathway in model microorganisms via intelligent metabolic engineering strategies. Furthermore, it introduces the key intelligent technologies for enhancing yields and the challenges faced. Finally, it discusses the future trends in this field.

Rice is one of the most widely cultivated and highest-yielding crops worldwide, and its yield stability is closely linked to global food security. As a typical mycorrhizal crop, rice exhibits enhanced growth and stress tolerance after colonization of arbuscular mycorrhizal fungi (AMF). Rhizosphere bacteria, a major component of the rhizosphere microbiome, interact synergistically with AMF, collectively contributing to enhanced nutrient acquisition and improved rice performance. This review summarizes recent advances in the interactions between AMF and rhizosphere bacteria. We highlight that their synergistic interactions regulate rice growth, nutrient acquisition, and stress tolerance, which contribute to the ecosystem stability and biodiversity of the rhizosphere. However, most available studies on the interactions between AMF and rhizosphere bacteria have been conducted under controlled conditions, which limits their applicability to the complex natural field environments. Therefore, this review proposes several suggestions for future research. First, utilize multi-omics technologies such as metagenomics and isotope tracing techniques to elucidate the molecular mechanisms underlying the AMF-bacterial interaction. Second, in practical applications, long-term field positioning trials should be conducted to screen out superior microbial agents that meet the requirements. Finally, optimize regulatory conditions to achieve large-scale propagation of AMF and overcome the bottleneck in AMF field propagation provides theoretical support for promoting the practical application of this technology in agricultural production.

Objective To overcome the limitations such as high costs and restricted substrate utilization of mono-culture fermentation, bacterium-alga co-culture based on resource complementarity offers a promising new avenue for ectoine production. This study investigated the co-culture conditions of Dunaliella pseudosalina ZBY-1 and Halomonas campaniensis XH26 and the variations in ectoine yield, aiming to elucidate the metabolic regulation mechanism of ectoine biosynthesis in the co-culture system. Methods Strains XH26 and ZBY-1 were co-cultured at different inoculation ratios (1/0, 1/5, 1/10, 1/15, and 1/20) to screen the ratio yielding the highest ectoine production. Targeted metabolomics analysis was performed on the co-culture group [H group (H)], the bacterial control group [XH26 group (X)], and the algal control group [ZBY-1 group (D)] to identify significant differential metabolites. Results The highest ectoine yield was achieved at a bacterium-to-alga ratio of 1:15, while the pigment content of the algal strain was lower than that of the control group. Metabolomics analysis identified 15 (H vs. D), 16 (H vs. X), and 16 (X vs. D) significant differential metabolites, including L-alanine, L-asparagine, L-aspartic acid, L-phenylalanine, malic acid, and pyruvic acid. Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis revealed that alanine, aspartate and glutamate metabolism, glyoxylate and dicarboxylate metabolism, and arginine biosynthesis were the significantly altered metabolic pathways. Conclusion The co-culture system exhibited an asymmetric pattern characterized by bacterial proliferation and algal inhibition. The co-culture system significantly activated the central carbon metabolic network of the bacteria. Notably, aspartic acid and glutamic acid were significantly accumulated in cells, serving as the direct carbon skeleton and amino donor, respectively, to directly promote the efficient synthesis of ectoine.

Objective To clarify the role and molecular mechanism of the host protein solute carrier family 25 member 6 (SLC25A6) during fowl adenovirus serotype-4 (FAdV-4) infection, thus providing a theoretical basis for elucidating the pathogenic mechanism of FAdV-4 and developing novel prevention and control strategies. Methods First, we confirmed that infection of LMH cells with FAdV-4 at different time points and multiplicities of infection (MOI) resulted in obvious cytopathic effects (CPE). Second, on the basis of the host protein SLC25A6 identified in previous screening, Western blotting was employed to examine the effect of FAdV-4 on the expression of endogenous SLC25A6 in cells. Subsequently, transfection experiments were performed to regulate the expression of SLC25A6 (overexpression or interference with endogenous expression). RT-qPCR and Western blotting were employed to analyze the effect of SLC25A6 on FAdV-4 replication from the aspects of mRNA level, protein level, and viral titer. Finally, co-immunoprecipitation (Co-IP) was employed to verify the interaction between SLC25A6 and the core capsid protein Hexon of FAdV-4. Results FAdV-4 significantly inhibited the expression of endogenous SLC25A6 in cells. The overexpression of SLC25A6 markedly inhibited FAdV-4 replication, while interference with endogenous SLC25A6 promoted viral replication. SLC25A6 could directly interact with the Hexon protein of FAdV-4. Conclusion The host protein SLC25A6 inhibits FAdV-4 replication through its interaction with the viral Hexon protein. The results provide a theoretical basis for further elucidating the pathogenic mechanism of FAdV-4 and developing novel prevention and control strategies.

Objective To address the limitations of current hair-loss treatments, we employed an in vitro human dermal papilla cell (HDPC) model and a telogen C57BL/6 mouse model to study the effects of Lactiplantibacillus plantarum CCFM1352 fermentation metabolites and bacterial preparations on the hair follicle cycle and decipher the associated molecular mechanisms. Methods HDPCs were treated with different concentrations of CCFM1352 fermentation metabolites or bacterial lysates in vitro, and cell viability as well as the expression of molecules related to Wnt/β-catenin signaling, anagen/catagen regulation, and apoptosis was assessed. Telogen C57BL/6 mice were administrated with the fermentation metabolites or heat-killed bacterial cells by gavage for 21 days, and changes in hair coverage, follicular structure, and associated signaling molecules were analyzed. Results CCFM1352 fermentation metabolites at a volume fraction of 10% increased the viability of HDPCs to 135.30%, up-regulated Wnt10b and FGF-7, down-regulated DKK1 and TGF-β1, and increased Bcl-2 and decreased Bax, inducing a favorable change pattern associated with the anagen phase. Continuous gavage of the fermentation metabolites promoted the transition of hair follicles from telogen to anagen, increased the hair coverage to 61.62%, and enhanced hair follicle density, dermal thickness, and β-catenin accumulation and nuclear translocation. However, the regulatory effects of bacterial lysate and heat-killed bacteria were weaker in both models and showed only limited improvements in some indices. Conclusion CCFM1352 fermentation metabolites could modulate Wnt/β-catenin-related molecules and the expression of key factors such as FGF-7, TGF-β1, Bcl-2, and Bax, which favors the transition of hair follicles from telogen to anagen and suggests an important role in promoting hair growth. This study provides experimental evidence for the application of bioactive metabolites from probiotics in the field of hair health.

Objective Planktonic bacteria are essential for marine ecosystem health, yet how mussel aquaculture influences planktonic microbial communities remains unclear. This study aims to clarify the effects of mussel aquaculture on the community structure, diversity, and assembly mechanisms of marine planktonic bacteria. Methods Sixty-eight water samples were collected from a mussel aquaculture area and surrounding areas in Shengsi, Zhejiang, during summer 2024. Integrated analyses of 16S rRNA gene amplicon sequencing data and environmental factors were performed. Results The alpha diversity of particle-attached bacteria (PAB) significantly reduced in the aquaculture area, whereas free-living bacteria (FLB) showed no significant change in alpha diversity but exhibited clear shifts in beta diversity and phylogenetic structure. Random forest analysis identified Pseudomonadales and Bdellovibrionaceae as indicator taxa within the aquaculture area, and their changes might be associated with organic matter inputs and altered nutrient conditions. Functional prediction indicated enhanced nitrogen cycling (especially nitrification and aerobic ammonia oxidation) and a shift toward reductive acetogenesis in carbon cycling, alongside suppressed methanogenesis in the aquaculture area. Microbial community assembly was governed mainly by deterministic processes (e.g., heterogeneous selection) in the aquaculture area but by stochastic processes in surrounding waters. Conclusion This study demonstrates that mussel aquaculture can reconfigure the structures, functions, and assembly mechanisms of planktonic bacterial communities, providing insights for ecological impact assessment of mariculture.