Negative effects of poly(butylene adipate-co-terephthalate) microplastics on Arabidopsis and its root-associated microbiome

The degradable plastic poly(butylene adipate-co-terephthalate) (PBAT) is considered a potential replacement for low-density polyethylene (LDPE) as the main component of mulch film. However, it is not clear whether PBAT is harmful to the plant-soil system. Thus, we determined the effects of LDPE microplastics (LDPE-MPs) and PBAT microplastics (PBAT-MPs) on the growth of Arabidopsis. The inhibitory effect of PBAT-MPs was greater than that of LDPE-MPs on the growth of Arabidopsis. Transcriptome analysis showed that PBAT-MPs severely disrupted the photosynthetic system of Arabidopsis and increased the expression levels of genes in drug transport-related pathways. PBAT-MPs increased the relative abundances of Bradyrhizobium, Hydrogenophaga, and Arthrobacter in the bulk soil and rhizosphere soil. The abundances of Variovorax, Flavobacterium, and Microbacterium increased in the plant root zone only under PBAT-MPs. Functional prediction analysis suggested that microorganisms in the soil and plant root zone could degrade xenobiotics. Furthermore, the degradation products from PBAT comprising adipic acid, terephthalic acid, and butanediol were more toxic than PBAT-MPs. Our findings demonstrate that PBAT-MPs may be degraded by microorganisms to produce chemicals that are highly toxic to plants. Thus, biodegradable plastics may pose a great risk to the environment.