Effects of microplastics on common bean rhizosphere bacterial communities

Microplastic pollution in terrestrial ecosystems is a growing concern due to its potential influences on soil properties and crop growth. Little is known about the effects of microplastics on the microbiome in the rhizosphere. Here, we studied the effects of two types of microplastics (MPs), low density polyethylene (LDPE-MPs) and biodegradable microplastic (Bio-MPs) of poly-butylene-adipate-co-terephthalate (PBAT) mixed with polylactic acid (PLA), on rhizosphere bacterial communities of Phaseolus vulgaris at doses of 0.5 %, 1.0 % and 2.5 % (w/w, dry weight ratio between MPs and soil). Bio-MPs and LDPE-MPs showed significant higher α-diversity (Chao 1, ACE, Shannon and Simpson) than control. For each type of microplastic material, 2.5 % of LDPE-MPs and Bio-MPs showed lowest α-diversity as compared to doses of 0.5 % and 1.0 %, indicating 2.5 % dose of MPs might pose selective effect on rhizosphere bacterial communities. β-Diversity of 1.0 % and 2.5 % Bio-MPs were distinctive from the control and other treatments. Microplastics also affected the relative abundance at family level, i.e. as compared to control, Comamonadaceae was higher in all the MPs treatments, Rhizobiaceae was highest in 2.5 % LDPE-MPs and lowest in 2.5 % Bio-MPs. LefSe results showed, as compared to control, Bio-MPs induced more indictive taxa than LDPE-MPs. Our findings evidenced that LDPE-MPs and Bio-MPs exerted profound effects on rhizosphere bacterial communities, and these effects might have far-reaching effects on soil nutrient cycling and plant health in agroecosystems.