Contribution, Composition, and Structure of EPS by In Vivo Exposure to Elucidate the Mechanisms of Nanoparticle-Enhanced Bioremediation to Metals

Abstract

Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS–metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L–1) for 72 h. Cd–IONPs produced the highest concentrations of EPS proteins (136.3 mg L–1), while Cd induced the most production of polysaccharides (241.0 mg L–1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd–IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP–metal–EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP–metal–EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.

Microbiome enrichment from contaminated marine sediments unveils novel bacterial strains for petroleum hydrocarbon and heavy metal bioremediation

“…The blastp search against the SwissProt database identified in both MAGs the genetic basis for exopolysaccharide (EPS) biosynthesis, which may not only facilitate PAH degradation by enhancing the efficiency of all abovementioned PAH-degrading enzymes (Gutierrez et al, 2013;Alaba et al, 2018), but also confer metal-binding properties contributing to explain the observed ability of these strains to resist to and to sequester HMs (Amoozegar et al, 2012;Gupta and Diwan, 2017;Cao et al, 2022;Cheng et al, 2022). Specifically, a UDP-glucose 4-epimerase (e-value 0, score 1709, 97% identity), a UDP-glucose pyrophosphorylase (e-value 7.5 e − 180 , score 1300, 90% identity), and a poly-beta-1, 6-N-acetyl-D-glucosamine synthase (e-value 0, score 2011, 81% identity) were identified in A. xenomutans strain SRM1, with the latter two also present in H. alkaliantarctica strain SRM2 (respectively, e-value 2.6e − 165, score 1206, identity 77.3%, and e-value 0, score 1977, identity 86.1%).…”

“…Examples of this synergistic approach include microbial secretion -under mixed PAHs and HMs contamination -of enzymes with useful bioremediation activities (Chen et al, 2020) and of extracellular polysaccharides (EPSs). EPSs are particularly relevant targets for bioremediation studies, as they consist of a wide array of polymers and functional groups, that can simultaneously bind metals (thus enhancing HM extraction/removal from contaminated matrices) (Amoozegar et al, 2012;Ates, 2015;Little et al, 2014;Mohite et al, 2017;Gupta and Diwan, 2017;Cao et al, 2022;Cheng et al, 2022), and increase PAH solubilization and enzymatic degradation efficiency (Gutierrez et al, 2013;Alaba et al, 2018).…”

Emerging investigator series: metal nanoparticles in freshwater: transformation, bioavailability and effects on invertebrates

“…96 Thus, EPS can change the environmental behaviour of NPs and might subsequently influence their fate and toxicity in the environment. 39…”

“…96 Thus, EPS can change the environmental behaviour of NPs and might subsequently influence their fate and toxicity in the environment. 39 In addition to the EPS derived from natural water, the biomolecules secreted by organisms could also interact with the MNPs' surface and form a new identity (i.e., eco-corona) which affects the stability and toxicity of the MNPs toward organisms in the surrounding environment. For example, a recent study showed that AuNPs could interact with protein secreted by D. magna and produce protein-corona, reducing the AuNP aggregation and potentially detoxifying AuNPs to D. magna by shielding their surface attraction.…”

“…However, the majority of NP toxicity studies focused on ecotoxicity took apical endpoints, and only a few dealt with toxicity mechanisms. [36][37][38][39] AOPs span numerous levels of biological organization, from the molecular level to an organism level or even to population levels for ecotoxicology scenarios. 40 Since the AOP is an evidence-based framework, it is constantly updated following new evidence of toxicity mechanisms, improving its reliability and application.…”