T6SS nuclease effectors in Pseudomonas syringae act as potent antimicrobials in interbacterial competition.

Type VI secretion system (T6SS) is a potent weapon employed by various Pseudomonas species to compete with neighboring microorganisms for limited nutrients and ecological niches. However, the involvement of T6SS effectors in interbacterial competition within the phytopathogen Pseudomonas syringae remains unknown. In this study, we examined two T6SS clusters in a wild-type P. syringae MB03 and verified the involvement of one cluster, namely, T6SS-1, in interbacterial competition. Additionally, our results showed that two T6SS DNase effectors, specifically Tde1 and Tde4, effectively outcompeted antagonistic bacteria, with Tde4 playing a prominent role. Furthermore, we found several cognate immunity proteins, including Tde1ia, Tde1ib, and Tde4i, which are located in the downstream loci of their corresponding effector protein genes and worked synergistically to protect MB03 cells from self-intoxication. Moreover, expression of either Tde1 or C-terminus of Tde4 in Escherichia coli cells induced DNA degradation and changes in cell morphology. Thus, our results provide new insights into the role of the T6SS effectors of P. syringae in the interbacterial competition in the natural environment. IMPORTANCE: The phytopathogen Pseudomonas syringae employs an active type VI secretion system (T6SS) to outcompete other microorganisms in the natural environment, particularly during the epiphytic growth in the phyllosphere. By examining two T6SS clusters in P. syringae MB03, T6SS-1 is found to be effective in killing Escherichia coli cells. We highlight the excellent antibacterial effect of two T6SS DNase effectors, namely, Tde1 and Tde4. Both of them function as nuclease effectors, leading to DNA degradation and cell filamentation in prey cells, ultimately resulting in cell death. Our findings deepen our understanding of the T6SS effector repertoires used in P. syringae and will facilitate the development of effective antibacterial strategies.

Efficient remediation of di-(2-ethylhexyl) phthalate and plant-growth promotion with the application of a phosphate-solubilizing compound microbial agent.

The ecotoxic endocrine-disrupting chemical di-(2-ethylhexyl) phthalate (DEHP) is ubiquitous in agricultural soil, posing a serious threat to human health. Here, we report efficient soil-borne DEHP degradation and plant growth promotion by a microbial organic fertilizer GK-PPB prepared by combining a recycled garden waste-kitchen waste compost product with ternary compound microbial agent PPB-MA, composed of Penicillium oxalic MB08F, Pseudomonas simiae MB751, and Bacillus tequilensis MB05B. The combination of MB08F and MB751 provided synergistic phosphorus solubilization, and MB05B enhanced the DEHP degradation capacity of MB08F via bioemulsification. Under optimal conditions (25.70 °C and pH 7.62), PPB-MA achieved a 96.81 % degradation percentage for 1000 mg L-1 DEHP within 5 days. The degradation curve followed first-order kinetics with a half-life of 18.24 to 24.76 h. A complete mineralization pathway was constructed after identifying the degradation intermediates of 2H-labeled DEHP. Evaluation in Caenorhabditis elegans N2 showed that PPB-MA eliminated the ecological toxicity of DEHP. A pakchoi (Brassica chinensis L.) pot experiment demonstrated that GK-PPB promoted phosphorus solubilization and plant growth, reduced soil DEHP residue, and decreased DEHP accumulation in pakchoi, suggesting its potential practical utility in environmentally responsible and safe cultivation of vegetables.

Copper oxide nanoparticles suppress retinal angiogenesis via inducing endothelial cell cuproptosis.

Background: Copper oxide nanoparticles (CuO NPs) exhibit antitumor activity; however, their potential as an antiangiogenesis agent is unknown. Materials & methods: The antiangiogenesis properties of CuO NPs were evaluated in vitro and in vivo and the underlying mechanism was examined using RNA sequencing and metabolomic analyses. Results: CuO NPs inhibited endothelial cell function in vitro. They also mitigated retinal vasculature development and alleviated pathological retinal angiogenesis in vivo. RNA sequencing and metabolomic analyses revealed that CuO NPs disrupt the tricarboxylic acid cycle and induce cuproptosis, which was further supported by evaluating cuproptosis-related metabolites and proteins. Conclusion: CuO NPs may be an effective antiangiogenic agent for the treatment of retinal angiogenesis.