During anaerobic treatment, several microorganisms mediate a series of reactions to convert reduced compounds (electron donors) into methane. Inhibitors such as long chain fatty acids (LCFAs) can affect several anaerobic microbial populations and decrease the treatment efficiency. The effects of three C18 LCFAs on hydrogenotrophic methanogens in a flocculated mixed anaerobic culture were assessed in this study. The reaction half-life and the hydrogen versus time profiles were used to characterize the inhibition process. The half-life values and profiles were similar for controls and cultures exposed to LCFAs for 1 h. The hydrogen inhibition was a function of the exposure time and the LCFA concentration except for cultures exposed to stearic acid (SA). A statistical analysis of the reaction half-life for cultures incubated with 1,500 and 2,000 mg L(-1) LCFAs for 48 h, revealed the following inhibition trend: linoleic acid (LA) > oleic acid (OA) > SA. After 48 h of exposure, no clear inhibition trend was observed for cultures inoculated with LCFA mixtures; however, at levels of 1,500 and 2,000 mg L(-1), the reaction half-life values were less than that observed for cultures fed with only LA. Based on the reaction half-life data, all of the LCFAs except SA at threshold levels of approximately 1,500 mg L(-1) inhibited hydrogen metabolism. The greatest inhibition and, hence, the largest amount of accumulated hydrogen was observed in cultures fed with 2,000 mg L(-1) LA and incubated for 48 h.

One new limonoid, toonaciliatone A (1), and one new tirucallane-type triterpenoid, toonaciliatine A (4), along with three known compounds, methyl-3β-acetoxy-1-oxomelic-14(15)-enate (2), perforin A (3), and cholest-14-ene-3,7,24,25-tetrol-21,23-epoxy-21-methoxy-4,4,8-trimethyl-3-(3-methyl-2-butenoate) (5), were isolated from the leaves of Toona ciliata. The structures of the new compounds were established by spectroscopic methods.

Symbiotic microorganisms are ubiquitous on the body surface or internal tissues of invertebrates, providing them with benefits. Developing symbiotic relationships requires synchronization of developmental stages and physical proximity of partners. Therefore, the identification of metabolites that coordinate the reproduction of symbiotic partners is essential. This study demonstrates that palmitoleic acid (C16: 1) coordinates bilateral propagation by regulating the synchronization of reproduction between the invasive pinewood nematode (PWN) and its newly associated blue-stain fungus, Sporothrix sp.1. When the PWN fed on Sporothrix sp.1, there was a significant increase in lipid metabolism gene expression and metabolite abundance. Through further investigations, it highlighted a significant enhancement in the reproduction of the PWN through direct acquisition of C16: 1, which was abundantly present in Sporothrix sp.1. Furthermore, the PWN biosynthesized C16: 1 through the involvement of the stearoyl-CoA 9-desaturase gene fat-5 and its hormone nuclear receptor nhr-80, which was clarified to promote the egg-laying capacity of females. Moreover, it is worth noting that the production of C16: 1 was significantly higher by the associated fungus Sporothrix sp.1 to enhance sporulation during the spore formation phase compared to the hypha growth phase. Thus, by coordinating the fecundity and spore production, the key lipid metabolite C16: 1 facilitates the rapid and successful colonization of a mutually beneficial symbiotic relationship between the invasive PWN and the native Sporothrix sp.1 within the host. This finding emphasizes the significant role of metabolite sharing and its function in promoting partner synchronization within symbiotic relationships.

Anthropogenic activities and climate change have accelerated biological invasions, leading to profound ecological, economic, social, and health impacts. The invasive species fall webworm (Hyphantria cunea) has been reported to have outbreaks in areas with climate anomalies and human settlements in recent years, highlighting the necessity to explore the species’ suitable habitat and associated future changes. We built an ensemble species distribution model using Random Forest, MaxEnt, and Support Vector Machine, achieving excellent predictive performance (AUC = 0.996). Our results identify human settlement density as the dominant driving factor, with a contribution > 50%, far exceeding climatic and forest structure variables. Therefore, densely urbanized regions such as Beijing–Tianjin–Hebei, the Liaodong Peninsula, and the North China Plain comprise the current highly suitable areas. Future climate projections suggest a continued expansion of the suitable habitat for H. cunea, with the most pronounced growth expected under the high-emission pathway (SSP5-8.5), where human activity is greatest. Such a correlation indicates that highly urbanized regions should be given priority for corresponding monitoring and control measures. As climate warming continues, northeastern China will face escalating invasion risks. Conversely, some regions within the Yangtze River Delta may become less suitable for the habitation of H. cunea. These findings provide insightful guidance for region-specific surveillance, quarantine measures, and the precision management of H. cunea in China.

Pine wilt disease poses a serious threat to pine forest health, and efficient biocontrol agents are urgently needed. Bacillus velezensis YG4-2 is a pine endophytic bacterium with strong nematicidal activity against Bursaphelenchus xylophilus, but the effect of oxygen conditions on its activity remains unclear. In this study, we compared the growth, nematicidal activity, and extracellular metabolite profiles of YG4-2 under aerobic and anaerobic conditions. Aerobic cultivation significantly increased bacterial biomass and enhanced the nematicidal activity of both bacterial cultures and cell-free supernatants. LC-MS/MS-based untargeted metabolomics revealed clear metabolic differences between the two oxygen conditions, with 19 metabolites significantly upregulated under aerobic conditions. Activity validation showed that kynurenic acid exhibited the strongest nematicidal activity among the tested candidate metabolites. Targeted LC-MS/MS further confirmed the accumulation of kynurenic acid in aerobic culture supernatants, with an estimated concentration of 0.38 ng/mL, and no obvious signal was detected under anaerobic conditions. These results suggest that oxygen enhances the nematicidal activity of YG4-2 by promoting growth and regulating extracellular metabolite production, with kynurenic acid as a potential oxygen-responsive active metabolite.