Structure and Functions of Hydrocarbon-Degrading Microbial Communities in Bioelectrochemical Systems

Anna Espinoza-Tofalos,Federico Aulenta,Andrea Franzetti,Matteo Daghio,Enza Palma

doi:10.3390/w12020343

Abstract

Bioelectrochemical systems (BESs) exploit the interaction between microbes and electrodes. A field of application thereof is bioelectrochemical remediation, an effective strategy in environments where the absence of suitable electron acceptors limits classic bioremediation approaches. Understanding the microbial community structure and genetic potential of anode biofilms is of great interest to interpret the mechanisms occurring in BESs. In this study, by using a whole metagenome sequencing approach, taxonomic and functional diversity patterns in the inoculum and on the anodes of three continuous-flow BES for the removal of phenol, toluene, and BTEX were obtained. The genus Geobacter was highly enriched on the anodes and two reconstructed genomes were taxonomically related to the Geobacteraceae family. To functionally characterize the microbial community, the genes coding for the anaerobic degradation of toluene, ethylbenzene, and phenol were selected as genetic markers for the anaerobic degradation of the pollutants. The genes related with direct extracellular electron transfer (EET) were also analyzed. The inoculum carried the genetic baggage for the degradation of aromatics but lacked the capacity of EET while anodic bacterial communities were able to pursue both processes. The metagenomic approach provided useful insights into the ecology and complex functions within hydrocarbon-degrading electrogenic biofilms.

Highlights

Hydrocarbon pollution is a widespread phenomenon that affects human health and the environment, including air, water, and soil [1]
By using a shotgun metagenomic approach, we described the structure and functions of fiveIn microbial communities: wastewaters used approach, to inoculate bioelectrochemical systems, this study, by using a Two shotgun metagenomic wethe described the structure and functions of fivecommunities microbial communities: Two wastewaters used toofinoculate bioelectrochemical and three anodic operating in for the treatment aromaticthe hydrocarbons
Our results suggest that even if the two inocula carried the genetic baggage for hydrocarbon degradation, the lack of genes for direct electron transfer (EET) did not allow these strains to persist on the anode of a Bioelectrochemical systems (BESs)

Summary

Introduction

Hydrocarbon pollution is a widespread phenomenon that affects human health and the environment, including air, water, and soil [1] The removal of this class of contaminants from the environment is mandatory and can be achieved with physical-chemical or biological strategies [2]. Traditional bioremediation is often limited by several factors, such as (i) the need for long-term addition of suitable electron acceptors (oxygen, nitrate, sulfate, or other oxidized compounds); (ii) the consumption of added amendments by competitive biotic and abiotic reactions; and (iii) the accumulation of undesired side-products [4]. Some of these limitations could possibly be. In the remediation of organic substances, the co-localization of pollutants, microbes, and the electron acceptor may enhance the removal of the hazardous waste [11]

Methods

Results

Conclusion