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Ibuprofen (IBU) is a non-steroidal anti-inflammatory drug that is becoming increasingly recognized as an important micropollutant to be monitored in wastewater treatment plants (WWTP), since it has been detected in effluents at the µg L level. The IBU metabolites from biological degradation are not completely understood and can represent a threat to natural aquatic systems. P. medicamentivorans was previously isolated from WWTP sludge and found to be capable of IBU degradation. The aerobic biodegradation of ibuprofen by this organism was investigated in a batch lab-scale reactor for the identification of the metabolites formed. The metabolites were analysed and putatively identified by HPLC-DAD-MS/MS and GC-MS and biodegradation pathways were proposed. The toxicity and the biodegradability potential of the metabolites were also investigated. The results showed that IBU biotransformation was achieved by hydroxylation followed by the formation of a carboxylic acid in the IBU molecule and by the formation of a catechol, allowing the aromatic ring cleavage. Two biodegradation pathways were proposed: in one, the metabolites generated from the enzymatic action correspond to a less biodegradable chemical structure of the intermediate products (isobutylbenzene and 3-isobutylphenol), with comparatively higher toxicity; in the other mechanism, more oxidable chemical structures were formed with less toxicity and higher biodegradability. This suggests that the biodegradation of IBU by P. medicamentivorans can take place by more than one mechanism regarding the enzymes formed by this Gram-positive bacterium, with subsequent oxidation of the parent compound to overall more soluble and less toxic compounds to fish, daphnia and green algae.

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A Gram-positive, aerobic, non-motile, non-endospore-forming rod-shaped bacterium with ibuprofen-degrading capacity, designated strain I11 T , was isolated from activated sludge from a wastewater treatment plant. The major respiratory quinone was demethylmenaquinone DMK-7, C 18 : 1 cis9 was the predominant fatty acid, phosphatidylglycerol was the predominant polar lipid, the cell wall contained meso-diaminopimelic acid as the diagnostic diamino acid and the G+C content of the genomic DNA was 74.1 mol%. On the basis of 16S rRNA gene sequence analysis, the closest phylogenetic neighbours of strain I11 T were Patulibacter ginsengiterrae CECT 7603 T (96.8 % similarity), Patulibacter minatonensis DSM 18081 T (96.6 %) and Patulibacter americanus DSM 16676 T (96.6 %). Phenotypic characterization supports the inclusion of strain I11 T within the genus Patulibacter (phylum Actinobacteria). However, distinctive features and 16S rRNA gene sequence analysis suggest that is represents a novel species, for which the name Patulibacter medicamentivorans sp. nov. is proposed. The type strain is I11 T (5DSM 25962 T 5CECT 8141 T ).

The use of mixed microbial cultures enriched for biological mercury removal is explored in this paper, focusing on the ecological shifts occurring throughout acclimatization to mercury and on the long-term stability of four microbial enrichments. The 16S rRNA genetic profiles obtained by denaturing gradient gel electrophoresis (DGGE) revealed that the glucose and ethanol cultures had similar profiles, whereas the acetate cultures diverged into a totally dissimilar cluster. Quantification of the merA gene copies in each enrichment showed higher values for the glucose culture, followed by the ethanol and then the acetate cultures, which was consistent with the mercury removal performance throughout the study. Isolates were obtained from the four cultures and analyzed with respect to their genetic (16S rRNA) and functional (merA) phylogenies in order to identify mercury-resistant species enriched with different carbon sources. All mercury-resistant isolates obtained from the glucose and ethanol cultures belonged to the Gammaproteobacteria, whereas acetate cultures also contained members of other phyla, with differences in merA sequences. Higher phylogenetic than functional diversity of the isolates, together with increasing merA copies even after culture stabilisation, highlight the role of horizontal gene transfer in the acclimatization process.