Complex Bilateral Interactions Determine the Fate of Polystyrene Micro- and Nanoplastics and Soil Protists: Implications from a Soil Amoeba

Abstract

Nano-and microplastics have become a serious global concern, threatening our living environments. Previous studies have shown that many organisms, including bacteria, animals, and plants, can be affected by microplastics. However, little is known about one ecologically important group of soil organisms, the protists. In this study, we investigated how polystyrene micro-and nanoplastics interacted with a soil amoeba Dictyostelium discoideum. The results showed that environmental concentrations of nano-and microplastics could negatively affect the soil amoeba's fitness and development. D. discoideum ingested both nano-and microplastics through phagocytosis but packed and excreted them during slug migration, which also promoted their biodegradation. Fourier transform infrared spectroscopy analyses revealed the formation of new oxygen-containing functional groups and the sign of possible oxidation of polystyrene. Also, nano-and microplastic exposure disrupted the nutrient and energy metabolisms of D. discoideum and affected the expression of key genes (e.g., cf45-1, dcsA, aprA, dymB, and gef B) related to morphogenesis and phagocytosis. In conclusion, our results show that nano-and microplastics have complex bilateral interactions with the soil amoeba, affecting each other's fate in the soil environment. This study provides new insights into how soil protists interact with nano-and microplastics in the soil ecosystem.

Environmental stress promotes the persistence of facultative bacterial symbionts in amoebae

“…This study used a model amoeba Dictyostelium discoideum QS9 for all experiments (Tian et al, 2022; Zhang et al, 2022). D. discoideum was grown from previously frozen spores on SM/5 agar plates (2 g glucose, 2 g BactoPeptone (Oxoid), 2 g yeast extract (Oxoid), 0.2 g MgCl 2 , 1.9 g KH 2 PO 4 , 1 g K 2 HPO 4 , and 15 g agar per liter) with food bacterium Klebsiella pneumoniae (obtained from the Dicty Stock Center) at 21°C.…”

“…Environmental pollutants, such as heavy metals, acid rain, and greenhouse gas, are a key challenge for life on Earth, affecting the growth and survival of organisms and acting as a strong selective force (Whitehead et al, 2017). Amoebae, an influential group of protists, can have complex relationships with environmental stressors (Wang et al, 2023; Wu et al, 2022; Yu et al, 2022; Zhang et al, 2022). In this study, we hypothesized that amoebae could protect their facultative bacterial symbionts from various environmental pollutants, promoting the persistence of facultative bacterial symbionts against environmental stress.…”

Protozoa as Hotspots for Potential Pathogens in the Drinking Water of a Subtropical Megacity: Diversity, Treatment, and Health Risk

“…One of them (UA010, PSF, 20 kDa) was the same as that in the drinking water treatment plant. Both the isolated amoeba and the model amoeba (Dictyostelium discoideum QS9) ,, were used in the assay. For the first experiment, a mixture of 2 × 10 5 amoeba spores and 1 mL K.…”

“…One of them (UA010, PSF, 20 kDa) was the same as that in the drinking water treatment plant. Both the isolated amoeba and the model amoeba (Dictyostelium discoideum QS9) 22,37,38 were used in the assay. For the first experiment, a mixture of 2 × 10 5 amoeba spores and 1 mL K. pneumoniae KpGe (OD 600 = 1.5) was plated on different medium surfaces, including plastic surface, agar plate, and 6 types of ultrafiltration membrane.…”

Soil Amoebae Affect Iron and Chromium Reduction through Preferential Predation between Two Metal-Reducing Bacteria

“…18 In theory, amebic predation and bacterial defense would influence the biogeochemical cycling of elements and energy flow in the soil ecosystem because their interactions could affect the bacterial community composition and activity. 19,20,73 However, few studies have tested this empirically, and how amoeba−bacterium interactions affect soil element cycling remains unknown. In fact, to our knowledge, there is no evidence that soil protists can directly affect the fate of metals in soils.…”