Abstract
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.
Highlights
Wastewater treatment plants (WWTP) represent habitats of continuous change in chemical composition (Szczepanowski et al 2008)
The analysis of the carbohydrate metabolism category showed a high number of matches (9,387 sequences) related to genes involved in several subcategories for utilization of carbohydrates (Table 1). These results demonstrated the broad capability of microorganisms from refinery sludge to metabolize distinct sugar sources. 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
Summary
Wastewater treatment plants (WWTP) represent habitats of continuous change in chemical composition (Szczepanowski et al 2008). Several processes are used to eliminate phenolic compounds from industrial wastewater, but the biological treatments have been preferred for large-scale removal. This is not an easy task because of the proper toxicity of phenol towards microorganisms (BarriosMartinez et al 2006). The diversity of microbial communities has been accessed by means of cultivation-based techniques or optical microscopy (Henze et al 1997; Ojumu et al 2005; Chang et al 2005). Very useful for taxonomic, physiological and genetic studies, culturebased techniques are insufficient for a more precise characterization of the functional and phylogenetic diversity of microbial communities, since it is well known that only a small fraction (0.1 to 10%) of the microbial diversity in nature can be recovered in the laboratory (Torsvik et al 1990; Amann et al 1995)
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