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Aims Vibrio parahaemolyticus is one of the most frequently occurred pathogens in mariculture. This study aimed to explore the mechanism of the impact of Ulva fasciata on the motility and biofilm formation of V. parahaemolyticus. Methods and Results The inhibitory effect of U. fasciata on a V. parahaemolyticus, isolated from clam maricultural sediment, was examined by co‐culture of them. The live U. fasciata significantly inhibited the swimming behaviour, twitching behaviour and biofilm formation of V. parahaemolyticus JF, with inhibition rates range of 2.48%–20.26%, 1.59%–39.18% and 28.3%–94.7% under different nitrate and phosphate levels, respectively. The results of transcriptome sequencing showed that 210 significantly differentially expressed genes (DEGs) were found in strain JF between the presence and absence of U. fasciata, including 90 upregulated genes and 120 downregulated genes. According to GO (Gene Ontology) function enrichment and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis, the downregulated genes of JF were partially enriched in flagella assembly (fliC, fliK, fliG, fliN, fliH, fliI, fliJ and fliA), bacterial chemotaxis (mCP, cheB, cheW and cheY) and biofilm formation (fliA/σ28 and eps), which explained the suppressed motility and biofilm formation of V. parahaemolyticus JF under U. fasciata stress. Conclusions Live U. fasciata significantly impaired the motility and biofilm formation of V. parahaemolyticus, which could occur in niches with either sufficient or inadequate nutrient (nitrate and phosphate) concentrations. The DEGs of V. parahaemolyticus modulated by U. fasciata were enriched mainly in the flagellar assembly, bacterial chemotaxis and biofilm pathways. Significance and Impact of the Study New information on how V. parahaemolyticus respond to U. fasciata regarding motility and adhesion behaviours, and the mechanism of that was firstly explored in this study. The results suggested that the seaweed U. fasciata has promising prospects as an environmentally friendly preventive measure to treat vibriosis in mariculture.

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The search for coplanar high‐energy insensitive explosives is a new direction in the research of energetic materials. A series of coplanar compounds based on the [1,2,4]triazolo[4,3‐b][1,2,4]triazine skeleton (ATTZ) were designed and studied using density functional theory. The research content includes density, detonation performance, shock sensitivity, bond‐dissociation energy, thermodynamic properties, and electrostatic potential. The formation of intramolecular hydrogen bonds between the energetic groups connected by these coplanar compounds and the introduction of coordinated oxygen on the parent to improve detonation performance are the highlights of this study. The results show that most of the compounds have good density, low sensitivity, and excellent detonation performance. And compound A11 shows a high density (d = 1.93 g/cm3), detonation velocity (D = 9.12 km/s1), and explosion pressure (P = 38.41 GPa), with the bond dissociation energy value of 253.4 kJ/mol. Designing coplanar compounds is an efficient approach to explore high‐energy insensitive explosives.