Aeromonas hydrophila (A. hydrophila) is a highly harmful pathogenic bacterium in aquaculture, and its increasingly severe drug resistance poses a threat to global aquaculture and food safety. It is an urgent need to develop new antibacterial agents. Terpinen-4-ol is a natural plant monomer with broad-spectrum antibacterial activity, but its effect and mechanism against A. hydrophila remain unclear. In this study, the minimum inhibitory concentration (MIC) of terpinen-4-ol against A. hydrophila was 7.56 mM (1.17mg/mL), at which it effectively inhibited bacterial growth. Scanning electron microscopy (SEM) revealed morphological changes in treated A. hydrophila, including cell shrinkage, deformation, and flagellar detachment or loss. Detection of nucleic acid, protein, alkaline phosphatase (ALP), and β-galactosidase leakage, together with propidium iodide (PI) staining, showed that terpinen-4-ol caused intracellular content leakage and increased PI fluorescence intensity. Measurements of succinate dehydrogenase (SDH) activity and reactive oxygen species (ROS) levels revealed that terpinen-4-ol at 1 MIC reduced SDH activity by 55.7% and increased ROS levels by 5-fold. Crystal violet staining of biofilms further demonstrated that terpinen-4-ol at 1/2 MIC inhibited biofilm formation by 78.3%. In conclusion, terpinen-4-ol exerted its antibacterial effect on A. hydrophila by disrupting the integrity of the cell membrane and wall to cause the leakage of intracellular contents, interfering with bacterial metabolism, and inhibiting biofilm formation. This study provides potential strategies for controlling A. hydrophila infections in aquaculture and lays the foundation for future research into the antibacterial mechanism of terpinen-4-ol.

Tuberculosis (TB) remains a major global public health problem, emphasizing the necessity of identifying attenuation targets in Mycobacterium tuberculosis (Mtb) for the development of novel control strategies. In this context, plasma membrane transporters are critical determinants of Mtb virulence, including CtpF, a Ca2+ P-type ATPase, and MmpL7, a translocator of phthiocerol dimycocerosate (PDIM). In this study, we characterized in vitro the microbiological features of the MtbH37RvΔctpF and MtbH37RvΔmmpL7 strains. Both mutants displayed reduced colony roughness and hydrophobicity compared to MtbH37Rv, suggesting alterations in the composition of cell wall lipids. Chromatographic analyses confirmed changes in the lipid profiles; MtbH37RvΔctpF exhibited altered phosphatidylinositol mannosides and trehalose dimycolates profiles, whereas MtbH37RvΔmmpL7 showed accumulated PDIM intracellularly. Moreover, transcriptional analyses revealed the downregulation of PDIM biosynthesis and transport genes in both mutants. However, both strains retained the ability to secrete early secreted antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10), indicating that their immunostimulatory potential was preserved. These findings provide in vitro evidence that deletions of ctpF and mmpL7 alter envelope-associated traits commonly linked to mycobacterial virulence.

Phytopathogens are responsible for substantial yield losses in global agriculture. Significant use of chemical fungicides for controlling these pathogens often poses a threat to the environment. Thus, the application of fusaricidin-producing Paenibacillus offers a promising and eco-friendly alternative to conventional chemical control strategies. Fusaricidins possess a hexapeptide core linked to a consistent 15-guanidino-3-hydroxypentadecanoic acid tail, which is instrumental in membrane disruption and the eradication of a broad spectrum of pathogens. Recent genomic mining studies have identified the fusGFEDCBA gene cluster and elucidated the pivotal role of the KinB-Spo0A-AbrB signaling cascade in integrating environmental stimuli with the developmental regulation of fusaricidin biosynthesis. Beyond their direct antimicrobial effects, fusaricidins function as plant-defense elicitors, primarily activating systemic responses through salicylic acid (SA)-dependent pathways. In vitro, greenhouse, and field trials have demonstrated significant disease suppression and plant growth promotion across various crops. However, variability in field performance, challenges in formulation, and limited understanding of in-field stability and ecological interactions present significant barriers to commercialization. Through integrated molecular and applied research, these limitations and future directions are being addressed. Collectively, these insights position fusaricidins as promising candidates for sustainable plant disease management in agriculture. This review concentrates on the current understanding of fusaricidins, encompassing their chemical diversity, biosynthetic gene architecture, regulatory networks, mechanisms of antimicrobial action, and advancements toward field-level application.