ABSTRACT
The growing contamination of arsenic and plastics has severely effects on the soil fauna health, including shifts of gut microbiota community. A few studies have focused on effects of microplastics and metal(loid) in soil and fauna gut microbiome. However, the environmental effect of nanoplastics and arsenic on the earthworm gut microbiota, especially on arsenic biotransformation in the gut, remain largely unknown. Here, a microcosm study was performed to explore the effects of nanoplastics and arsenic on the microbiota characteristics in earthworm Metaphire vulgaris gut using Illumina high throughput sequencing, and to investigate changes in the gut microbiota-mediated arsenic biotransformation genes (ABGs) by using high-throughput quantitative PCR. Our results demonstrated that the concentration of arsenic in the earthworm body tissues after exposure to arsenic and nanoplastics was significantly lower from that with arsenic alone exposure. Moreover, the clearly different bacterial community was observed in the soil compared with the earthworm gut, which was dominated by Proteobacteria, Actinobacteria, and Firmicutes at phylum level. Arsenic exposure significantly disturbed bacterial community structure in the earthworm gut, but exposure to nanoplastics did not induce gut microbiota changes. More interestingly, nanoplastics can relieve adverse effect of arsenic on the gut microbiota possibly by adsorbing arsenic. In addition, a total of 16 ABGs were detected, and predominant genes involved in arsenic reduction and transport process were observed in the earthworm guts. In short, this study provides a new picture of the effects of nanoplastics and arsenic on the gut microbiota and arsenic biotransformation in soil fauna gut.
Subject(s)
Arsenic , Gastrointestinal Microbiome , Oligochaeta , Animals , Microplastics , Plastics , SoilABSTRACT
We conducted a 12-month fine root decomposition experiment under 19-year-old Mytilaria laosensis and Cunninghamia lanceolate plantations to explore the dynamics of nutrient concentration and microbial community composition. The aim of this study was to provide insights into nutrient cycling under plantations with different tree species. Our results showed that the initial concentrations of phosphorus (P) and potassium (K) were significantly higher in the fine root of M. laosensis than those in C. lanceolata, which significantly decreased with decomposition. Nitrogen (N) concentration in fine roots of both species increased with decay time. The variation of N concentration in fine root of C. lanceolata lagged behind that in M. laosensis. During the decomposition, magnesium (Mg) concentration in fine root of C. lanceolata showed no significant changes, but that of M. laosensis decreased at the initial decay stage and increased thereafter and was significantly lower than that of C. lanceolata at the 8th month. The ratio of fungi to bacteria (F/B) of both species decreased at the initial stage and then increased, with significantly higher F/B in fine root of M. laosensis than that of C. lanceolate after one-year decay. Redundancy analysis (RDA) showed that changes in N and K concentrations and C/N ratio explained 37.2%, 14.5% and 14.8% of the variations in microbial community composition of C. lanceolata fine root respectively. However, during the decay of M. laosensis fine root, concentrations of Mg and K were key factors, accounting for 35.9% and 17.6% of the variations in microbial community composition, respectively. We concluded that other nutrients beyond N, such as Mg, might also be an important factor affecting root decomposition in different tree species.
