Plasticizer Degradation by Marine Bacterial Isolates: A Proteogenomic and Metabolomic Characterization

Abstract

Many commercial plasticizers are toxic endocrine-disrupting chemicals that are added to plastics during manufacturing and may leach out once they reach the environment. Traditional phthalic acid ester plasticizers (PAEs), such as dibutyl phthalate (DBP) and bis­(2-ethyl hexyl) phthalate (DEHP), are now increasingly being replaced with more environmentally friendly alternatives, such as acetyl tributyl citrate (ATBC). While the metabolic pathways for PAE degradation have been established in the terrestrial environment, to our knowledge, the mechanisms for ATBC biodegradation have not been identified previously and plasticizer degradation in the marine environment remains underexplored. From marine plastic debris, we enriched and isolated microbes able to grow using a range of plasticizers and, for the first time, identified the pathways used by two phylogenetically distinct bacteria to degrade three different plasticizers (i.e., DBP, DEHP, and ATBC) via a comprehensive proteogenomic and metabolomic approach. This integrated multi-OMIC study also revealed the different mechanisms used for ester side-chain removal from the different plasticizers (esterases and enzymes involved in the β-oxidation pathway) as well as the molecular response to deal with toxic intermediates, that is, phthalate, and the lower biodegrading potential detected for ATBC than for PAE plasticizers. This study highlights the metabolic potential that exists in the biofilms that colonize plasticsthe Plastisphereto effectively biodegrade plastic additives and flags the inherent importance of microbes in reducing plastic toxicity in the environment.

Food or just a free ride? A meta-analysis reveals the global diversity of the Plastisphere

“…For many plastics, these chemicals are not only additives but are also likely intermediates of both biotic and abiotic degradation. Cyclic and noncyclic dicarboxylic acids, for example, are the most commonly identified intermediates for the abiotic degradation of PE, PP, PS, and PET [137] and are also intermediates of biotic PET [138] and polyester [48] as well as plastic additive (plasticizer) [37] degradation. It has been suggested that the microbial community that is likely able to use these more labile chemicals is only present at earlier time points [31].…”

“…Microbial members of the Plastisphere have been found to be: (i) different from communities that colonize other surfaces [25][26][27]; (ii) not different from communities that colonize other surfaces [28]; (iii) only different from communities colonizing other surfaces under specific environmental conditions [29,30] or at specific time points [31]; (iv) more diverse than other microbial communities [32]; (v) less diverse than other microbial communities [33,34]; (vi) potentially degrading the plastics that they colonize [35,36]; (vii) capable of degrading plastic additives [33,37,38]; and (viii) pathogenic and/or carrying antimicrobial resistance genes [39][40][41][42]. The marine Plastisphere has been heavily reviewed within the last year, e.g., [18,[43][44][45][46], and there are also several recent reviews on plastic biodegradation, e.g., [47][48][49].…”

A Multi-OMIC Characterisation of Biodegradation and Microbial Community Succession Within the PET Plastisphere

“…BHET1 exposed to PET suggests that, while it is capable of PET hydrolysis, it is not as e cient at using the BHET as the community is. No degradation intermediates were detected when each of the three bacteria were incubated with terephthalic acid suggesting: i) that the toxicity of terephthalic acid limits degradation of this compound when no other carbon source is present, as we previously found for phthalic acid [54]; or ii) the degradation pathway of terephthalic acid has no bottleneck that produces an accumulation of detectable levels of the intermediate in the culture supernatant.…”

Putative degraders of low‐density polyethylene‐derived compounds are ubiquitous members of plastic‐associated bacterial communities in the marine environment

“…This might be due to their ability to degrade LDPE‐related hydrocarbons as indicated by their enrichment in our laboratory incubations with LDPE as the sole carbon source after 1 year. However, whether they have the ability to degrade the LDPE hydrocarbon backbone, associated plastic additives (Wright et al ., 2020) or passively released compounds (Romera‐Castillo et al ., 2018) remains unknown. Furthermore, it is important to note that only duplicate samples were collected in the in situ incubations in the northern Adriatic, precluding rigorous statistical analyses.…”