Impact of the microbial origin and active microenvironment on the shape of biogenic elemental selenium nanomaterials

The role of the microbial origin and environment of the discharged nanomaterials in their shape change was investigated. Here, we show that the biogenic elemental selenium nanospheres (BioSe-Nanospheres) produced under mesophilic conditions (30 °C) by Escherichia coli K-12 remain spherically when exposed to heating (55 °C for 7 days), whereas those obtained by anaerobic granular sludge transform to biogenic elemental selenium nanorods (BioSe-Nanorods). The larger quantity of proteins present in the corona of the BioSe-Nanospheres produced by E. coli K-12 are responsible for their shape stability. However, the protein corona of BioSe-Nanospheres produced by E. coli K-12 was degraded by extracellular peptidases secreted upon co-incubation with Bacillus safensis JG-B5T bacteria, which led to their transformation to BioSe-Nanorods. This study consequently demonstrates that the shape of biogenic nanomaterials depends both on their microbial origin and microbial surrounding, which increases the complexity in determining their risk assessment.