Bacterial life-history trade-offs under biodegradable and conventional microplastics in cinnamon and lime concretion black soils

Microplastics (MPs) have emerged as a global environmental pollutant of growing concern, with soil serving as a critical sink for terrestrial MPs. However, the life-history trade-offs of soil bacteria to various MPs in different soils remain unclear. Here, we investigated the adaptive signatures of bacterial communities to two biodegradable and four conventional MPs in cinnamon soil and lime concretion black soil. Our results showed that bacterial diversity, composition, potential functional profiles, life-history strategies, resistance, and co-occurrence networks significantly changed under MP exposure, with soil type playing a key role. Specifically, poly (butylene succinate) (PBS), a biodegradable plastic, exerted a greater influence on bacterial diversity, community structure, and functional profiles than the other MPs in both soils. PBS MPs promoted the prevalence of copiotrophs (r-strategists), indicating reduced bacterial resistance relative to the control conditions, whereas most other MPs enhanced bacterial resistance. Moreover, PBS MPs significantly reduced the richness and evenness of both the oligotrophic and copiotrophic taxa. Co-occurrence network analysis revealed decreased stability of the overall bacterial networks, as well as oligotrophic and copiotrophic taxa, following the addition of MPs, particularly PBS. These changes may disrupt soil carbon cycling, thereby threatening soil carbon sequestration and climate regulation. Our findings provide critical insights into the bacterial life-history strategies under MP stress in different soils, useful for the risk assessment and management of MP pollution.