IcmF2 of the type VI secretion system 2 plays a role in biofilm formation of Vibrio parahaemolyticus.

Vibrio parahaemolyticus possesses two distinct type VI secretion systems (T6SS), namely T6SS1 and T6SS2. T6SS1 is predominantly responsible for adhesion to Caco-2 and HeLa cells and for the antibacterial activity of V. parahaemolyticus, while T6SS2 mainly contributes to HeLa cell adhesion. However, it remains unclear whether the T6SS systems have other physiological roles in V. parahaemolyticus. In this study, we demonstrated that the deletion of icmF2, a structural gene of T6SS2, reduced the biofilm formation capacity of V. parahaemolyticus under low salt conditions, which was also influenced by the incubation time. Nonetheless, the deletion of icmF2 did not affect the biofilm formation capacity in marine-like growth conditions, nor did it impact the flagella-driven swimming and swarming motility of V. parahaemolyticus. IcmF2 was found to promote the production of the main components of the biofilm matrix, including extracellular DNA (eDNA) and extracellular proteins, and cyclic di-GMP (c-di-GMP) in V. parahaemolyticus. Additionally, IcmF2 positively influenced the transcription of cpsA, mfpA, and several genes involved in c-di-GMP metabolism, including scrJ, scrL, vopY, tpdA, gefA, and scrG. Conversely, the transcription of scrA was negatively impacted by IcmF2. Therefore, IcmF2-dependent biofilm formation was mediated through its effects on the production of eDNA, extracellular proteins, and c-di-GMP, as well as its impact on the transcription of cpsA, mfpA, and genes associated with c-di-GMP metabolism. This study confirmed new physiological roles for IcmF2 in promoting biofilm formation and c-di-GMP production in V. parahaemolyticus.

[Room-temperature solid-state synthesis of complexes of copper acetate and multi-nitrogen heterocyclic ligands].

At room temperature, sufficiently grinding the mixtures of copper acetate with 1,2,4-triazole and benzotriazole separately resulted in the proceeding of the solid state reaction. It was found that the acetate acid flowed during the grinding. The heterocycle ligand 1,2,4-triazole or benzotriazole replaced the acetate and coordinates to Cu (II) to form a mixed ligands complex. The elementary analysis results show that the compositions of products were consistent with Cu (C2H2N3)(Ac).H2O and Cu (C6H4N3)(Ac).H2O, respectively. Infrared spectra of both complexes have exhibited the characteristics of C=N vibrations [Cu(C2H2N3)(Ac).H2O, 1,513 cm-1; Cu(C6H4N3)(Ac).H2O, 1,446 cm-1] for heterocycle ligands, C=O [Cu(C2H2N3)(Ac).H2O, 1,570 and 1,406 cm-1; Cu(C6H4N3)(Ac).H2O, 1,604 and 1,422 cm-1] for acetate and O-H (-3,400 cm-1) for water, respectively. The solid state reaction provides a way which is rapid, mild and in the absence of solvent for synthesized new complexes.