Research Article: Phylogenetic and functional diversity of metagenomic libraries of phenol degrading sludge from petroleum refinery wastewater treatment system

Date Published: March 27, 2012

Publisher: Springer

Author(s): Cynthia C Silva, Helen Hayden, Tim Sawbridge, Pauline Mele, Ricardo H Kruger, Marili VN Rodrigues, Gustavo GL Costa, Ramon O Vidal, Maíra P Sousa, Ana Paula R Torres, Vânia MJ Santiago, Valéria M Oliveira.


In petrochemical refinery wastewater treatment plants (WWTP), different concentrations of pollutant compounds are received daily in the influent stream, including significant amounts of phenolic compounds, creating propitious conditions for the development of particular microorganisms that can rapidly adapt to such environment. In the present work, the microbial sludge from a refinery WWTP was enriched for phenol, cloned into fosmid vectors and pyrosequenced. The fosmid libraries yielded 13,200 clones and a comprehensive bioinformatic analysis of the sequence data set revealed a complex and diverse bacterial community in the phenol degrading sludge. The phylogenetic analyses using MEGAN in combination with RDP classifier showed a massive predominance of Proteobacteria, represented mostly by the genera Diaphorobacter, Pseudomonas, Thauera and Comamonas. The functional classification of phenol degrading sludge sequence data set generated by MG-RAST showed the wide metabolic diversity of the microbial sludge, with a high percentage of genes involved in the aerobic and anaerobic degradation of phenol and derivatives. In addition, genes related to the metabolism of many other organic and xenobiotic compounds, such as toluene, biphenyl, naphthalene and benzoate, were found. Results gathered herein demonstrated that the phenol degrading sludge has complex phylogenetic and functional diversities, showing the potential of such community to degrade several pollutant compounds. This microbiota is likely to represent a rich resource of versatile and unknown enzymes which may be exploited for biotechnological processes such as bioremediation.

Partial Text

Wastewater treatment plants (WWTP) represent habitats of continuous change in chemical composition (Szczepanowski et al. 2008). In oil refineries, the wastewater influent differs daily in terms of concentrations and composition of pollutant compounds, including light fraction aliphatic and aromatic petroleum hydrocarbons, organochlorines originated from cooling liquids used in the industrial process (Stepnowski et al. 2002) and other compounds such as phenol, chlorides, sulphides, sodium hydroxide, ammonia and heavy metals (Braile 1979; Mariano 2001). Phenols and derivatives are prominent pollutants in these wastes. These compounds are widely used as raw materials in the petrochemical industry and in oil refineries, for example in the washing and conditioning of alkaline or acid products. The increasing presence of phenols in the environment represents a serious ecological problem due to toxicity hazard for living creatures, including micro-organisms (Ojumu et al. 2005; Barrios-Martinez et al. 2006). Besides, the presence of phenols reduces significantly the biological degradation of the other compounds.

This is the first report of a pyrosequencing approach for a broad phylogenetic and metabolic diversity analysis of metagenomic fosmid libraries derived from phenol degrading sludge samples of petroleum refinery WWTP. Sequencing of the metagenomic libraries has allowed us to have deeper insight to the complex metagenome of the phenol degrading sludge samples, with thousands of reads assigned to different taxa and metabolic categories driving the functioning of the microbial community in the membrane bioreactors.

The authors declare that they have no competing interests.




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