Abstract
Current knowledge of the microbial diversity and metabolic pathways involved in hydrocarbon degradation in petroleum reservoirs is still limited, mostly due to the difficulty in recovering the complex community from such an extreme environment. Metagenomics is a valuable tool to investigate the genetic and functional diversity of previously uncultured microorganisms in natural environments. Using a function-driven metagenomic approach, we investigated the metabolic abilities of microbial communities in oil reservoirs. Here, we describe novel functional metabolic pathways involved in the biodegradation of aromatic compounds in a metagenomic library obtained from an oil reservoir. Although many of the deduced proteins shared homology with known enzymes of different well-described aerobic and anaerobic catabolic pathways, the metagenomic fragments did not contain the complete clusters known to be involved in hydrocarbon degradation. Instead, the metagenomic fragments comprised genes belonging to different pathways, showing novel gene arrangements. These results reinforce the potential of the metagenomic approach for the identification and elucidation of new genes and pathways in poorly studied environments and contribute to a broader perspective on the hydrocarbon degradation processes in petroleum reservoirs.
Highlights
Several studies have shown the ability of aerobic and anaerobic bacteria to degrade hydrocarbon compounds [1]
Understanding the microbial processes, in situ microorganisms and factors governing the biodegradation of crude oil hydrocarbons in vast oil reservoirs remains a challenge [6], because of the complex microbiological sampling and the inaccessibility of petroleum reservoirs, and because of the repeated isolation of the same species when cultivation techniques are employed [7]
There is only one previous study on aromatic hydrocarbon degradation in clones that can be used to evaluate our results (Vasconcellos et al [10]); in that study, degradation of more than 70% of the hexadecane by the metagenomic clones was detected after 28 days
Summary
Several studies have shown the ability of aerobic and anaerobic bacteria to degrade hydrocarbon compounds [1]. Traditional culturing techniques have been used to obtain valuable information on microbial interactions with hydrocarbons in the environment and have allowed the identification of many types of bacteria capable of utilizing hydrocarbons and the operons encoding these degradation pathways. Oil reservoirs constitute deep geological environments where microbial activities over millions of years have caused significant biodegradation of crude oils worldwide. Understanding the microbial processes, in situ microorganisms and factors governing the biodegradation of crude oil hydrocarbons in vast oil reservoirs remains a challenge [6], because of the complex microbiological sampling and the inaccessibility of petroleum reservoirs, and because of the repeated isolation of the same species when cultivation techniques are employed [7]
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