Resistance and resilience of soil bacterial community to zero-valent iron disposal of lindane contamination.

Zero-valent iron (ZVI, Fe) enables chemical reduction of environmental pollutants coupled with reactivity loss due to surface oxidation. During ZVI treatment process, however, microbial community stability in terms of resistance and resilience remains largely unclear. Here, we monitored bacterial community succession over a 4 weeks period in soil microcosms with or without 2% (w/w) Fe amendment. To simulate soil pollution, 100 μg g chlorinated pesticide lindane (γ-hexachlorocyclohexane) was added to the microcosms as a model contaminant. In addition to microbial activity as measured by soil organic carbon mineralization, bacterial abundance, diversity and composition were determined using qPCR and high-throughput sequencing of 16 S rRNA genes. Co-occurrence analysis was performed to reveal the interaction patterns within the bacterial communities. The results indicated that ZVI caused near-complete transformation of lindane, while in the microcosms without Fe amendment the pesticide was recalcitrant. ZVI strongly inhibited CO-efflux at the early stage of incubation, but the bacterial community appeared to be less sensitive to Fe amendment. The ratios of negative to positive correlations between network nodes suggested that Fe had marginal influence on community stability compared to the lindane treatments, which destabilized the bacterial community. Community succession occurred in the presence of ZVI, as exemplified by a dominancy transition from anaerobic to aerobic taxa. Yet, ZVI alleviated the stress of lindane on soil bacteria by improving community structure and increasing network complexity. Taken together, these findings demonstrate the stability of soil bacterial community under Fe stress, which might be conducive to functional recovery of soil microorganisms following ZVI remediation.