Physiological characterization of a phenanthrene degrading co-culture of Sphingobium sp. AM and Burkholderia sp Bk in PAH mixtures: challenging genomic data.

NIETO, FESTA S, MORELLI I.S.; COPPOTELLI BM.

worldwide online

Congreso; World Microbe Forum brings together two of the biggest events in the microbial sciences ASM Microbe 2021 and FEMS2021, 20-24 junio 2021 Online Worldwide; 2021

ASM-ISME

Environmental contamination with polycyclic aromatic hydrocarbon (PAH) involved mixture of compounds with distinct chemical structure and resistance to biodegradation. Phenanthrene degrading strains Sphingobium sp. AM, Burkholderia sp Bk were used to design a coculture (DSC_AB) capable of degrading 99% of phenanthrene as a sole carbon and energy source (SCES). A complete phenanthrene degradation pathway and several PAH-degrading enzymes were found to be codified in AM and Bk genomes (LRUK01 and NHOM01), suggesting the ability to degrade other PAH. The goal of this research was to study and compare the degradation of different PAH as SCES and in mixture with phenanthrene (Phe) in DSC_AB, AM and BK monocultures and confirm genomic data. Anthracene (Ant), dibenzothiophene (Dib), fluorene (Flu) and pyrene (Pyr) degradation were determined in minimum medium with 100 ppm of each PAH as SCES or in mixture with 200 ppm of Phe (GC-FID). The growth of each strain in DSC_AB was assessed by colony count during PAH degradation. DSC_AB was able to degrade Ant, Dib and Flu as SCES after 15 days (45%, 93% and 95% respectively), however non-growth was observed in these cultures. An increase in the final degradation of Ant was observed when supplemented in mixture (67%). Despite the final concentration of Dib and Flu was not affected by the presence of Phe, the degradation kinetics differed particularly at day four when DSC_AB degraded 66% and 40% of Dib and Flu as SCES in comparison with an 86% and 92% in mixture. The increase in PAH degradation in mixtures could be explained by different mechanisms (e.g. induction of specific enzymes, unspecificity of Phe enzymes, etc.). No Pyr degradation was observed as a SCES or in mixture. Phe degradation was not significantly affected in presence of Dib and Flu but decreased with Ant and Pyr. An increase in colony count of AM or Bk was observed in DSC_AB in mixtures. The reported results showed that PAH degradation by the DSC_AB was equally or more efficient compared to monocultures of AM and Bk strains, suggesting that the degrading ability is more than the sum of each monoculture performance. This highlights the importance of considering the interaction between populations during the design of an inoculant for bioremediation strategy. It was demonstrated that PAH interaction in mixtures could affect their degradation and that the growth observed in mixture was supported by Phe. Future metaproteomic assays would help to elucidate the mechanisms responsible for the stimulation of the degradation of one PAH in the presence of the other.