Mineralization of 4-fluorocinnamic acid by a Rhodococcus strain

Biodegradation and Metabolic Pathway of 17β-Estradiol by Rhodococcus sp. ED55

Endocrine disrupting compounds (EDCs) in the environment are considered a motif of concern, due to the widespread occurrence and potential adverse ecological and human health effects. The natural estrogen, 17β-estradiol (E2), is frequently detected in receiving water bodies after not being efficiently removed in conventional wastewater treatment plants (WWTPs), promoting a negative impact for both the aquatic ecosystem and human health. In this study, the biodegradation of E2 by Rhodococcus sp. ED55, a bacterial strain isolated from sediments of a discharge point of WWTP in Coloane, Macau, was investigated. Rhodococcus sp. ED55 was able to completely degrade 5 mg/L of E2 in 4 h in a synthetic medium. A similar degradation pattern was observed when the bacterial strain was used in wastewater collected from a WWTP, where a significant improvement in the degradation of the compound occurred. The detection and identification of 17 metabolites was achieved by means of UPLC/ESI/HRMS, which proposed a degradation pathway of E2. The acute test with luminescent marine bacterium Aliivibrio fischeri revealed the elimination of the toxicity of the treated effluent and the standardized yeast estrogenic (S-YES) assay with the recombinant strain of Saccharomyces cerevisiae revealed a decrease in the estrogenic activity of wastewater samples after biodegradation.

Sediments in the mangrove areas contribute to the removal of endocrine disrupting chemicals in coastal sediments of Macau SAR, China, and harbour microbial communities capable of degrading E2, EE2, BPA and BPS

The occurrence of endocrine disrupting chemicals (EDCs) is a major issue for marine and coastal environments in the proximity of urban areas. The occurrence of EDCs in the Pearl River Delta region is well documented but specific data related to Macao is unavailable. The levels of bisphenol-A (BPA), estrone (E1), 17α-estradiol (αE2), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2) were measured in sediment samples collected along the coastline of Macao. BPA was found in all 45 collected samples with lower BPA concentrations associated to the presence of mangrove trees. Biodegradation assays were performed to evaluate the capacity of the microbial communities of the surveyed ecosystems to degrade BPA and its analogue BPS. Using sediments collected at a WWTP discharge point as inoculum, at a concentration of 2 mg l^-1 complete removal of BPA was observed within 6 days, whereas for the same concentration BPS removal was of 95% after 10 days, which is particularly interesting since this compound is considered recalcitrant to biodegradation and likely to accumulate in the environment. Supplementation with BPA improved the degradation of bisphenol-S (BPS). Aiming at the isolation of EDCs-degrading bacteria, enrichments were established with sediments supplied with BPA, BPS, E2 and EE2, which led to the isolation of a bacterial strain, identified as Rhodoccoccus sp. ED55, able to degrade the four compounds at different extents. The isolated strain represents a valuable candidate for bioremediation of contaminated soils and waters.

Aerobic degradation of 2- and 3-fluoroaniline in mixed culture systems and microbial community analysis

Among three monofluoroanilines, 2-fluoroaniline (2-FA) and 3-fluoroaniline (3-FA) exhibit relatively poor biodegradability. This work examined their degradation characteristics in a mixed culture system and also analyzed the microorganism community. After acclimation for 58 d and 43 d, the high removal efficiency of 100% of 2-FA and 95.3% of 3-FA was obtained by adding 25 mg L^-1 of 2-FA or 3-FA to the two reactors, respectively. In addition, the high defluorination rates of 2-FA and 3-FA were observed to be 87.0% and 89.3%, respectively. The degradation kinetics showed that the maximum specific degradation rates of 2-FA and 3-FA were (21.23 ± 0.91) mg FA (g•VSS·h)^-1, and (11.75 ± 0.99) mg FA (g•VSS·h)^-1, respectively. PCR-DGGE analysis revealed that the unique bacteria degrading 2-FA were mainly composed of six genera (Novosphingobium, Bradyrhizobium, Aquaspirillum, Aminobacter, Ochrobactrum, and Labrys), and five genera that degraded 3-FA (Ochrobactrum, Aquaspirillum, Lachnobacterium, Bradyrhizobium, and Variovorax). Analysis of the key catabolic enzyme activities indicated that the simultaneous hydroxylation and dehalogenation were involved in monooxygenase elimination of 2-FA and conversion of 3-FA to 4-fluorocatechol by dioxygenase, indicating that enriched mixed cultures were effective to metabolize 2-FA or 3-FA by unconventional pathways to prevent the accumulation of toxic metabolites.

Degradation of 3-fluoroanilne by Rhizobium sp. JF-3

The interest of fluoroanilines in the environment is due to their extensive applications in industry and their low natural biodegradability. A pure bacterial strain capable of degrading 3-fluoroaniline (3-FA) as the sole source of carbon and energy was isolated from a sequencing batch reactor operating for the treatment of 3-FA. The strain (designated as JF-3) was identified by 16S rRNA gene analysis as a member of the genus Rhizobium. When grown in 3-FA medium at concentrations of 100-700 mg/L, strain JF-3 almost completely removed 3-FA within 72 h. However, the obvious cell growth inhibition was observed in cultures treated with 3-FA concentrations greater than 500 mg/L. The degradation kinetics of 3-FA were consistent with Haldane's model with the maximum degradation rate as 67.66 mg/(g dry cell h). The growth kinetics of strain JF-3 followed Andrew's model with the maximum growth rate as 30.87 h^-1. Also, strain JF-3 was able to degrade 4-fluoroaniline, aniline, and catechol, but hardly grew on 2-fluoroaniline, 2,4-dfluoroaniline, 2,3,4-trifluoroaniline, 3-fluorocatechol, and 4-fluorocatechol. Additionally, it was able to grow over a wide pH range (pH 6-10), and also showed tolerance to salinity with lower than 1.0%. This result, in combination with the enzyme assays and analysis of metabolite intermediates, indicated an unconventional pathway for 3-fluoroaniline metabolism that involved conversion to 3-aminophenol and resorcinol by monooxygenase, and which was subsequently metabolized via the ortho-cleavage pathway. To our knowledge, this is the first report on the utilization of 3-FA as a growth substrate by Rhizobium sp.

Enantioselective degradation of ofloxacin and levofloxacin by the bacterial strains Labrys portucalensis F11 and Rhodococcus sp. FP1

Fluoroquinolones are a class of antibiotics widely prescribed in both human and veterinary medicine of high environmental concern and characterized as environmental micropollutants due to their ecotoxicity and persistence and antibacterial resistance potential. Ofloxacin and levofloxacin are chiral fluoroquinolones commercialized as racemate and in enantiomerically pure form, respectively. Since the pharmacological properties and toxicity of the enantiomers may be very different, understanding the stereochemistry of these compounds should be a priority in environmental monitoring. This work presents the biodegradation of racemic ofloxacin and its (S)-enantiomer levofloxacin by the bacterial strains Labrys portucalensis F11 and Rhodococcus sp. FP1 at a laboratory-scale microcosm following the removal and the behavior of the enantiomers. Strain F11 could degrade both antibiotics almost completely when acetate was supplied regularly to the cultures. Enrichment of the (R)-enantiomer was observed in FP1 and F11 cultures supplied with ofloxacin. Racemization was observed in the biodegradation of the pure (S)-ofloxacin (levofloxacin) by strain F11, which was confirmed by liquid chromatography - exact mass spectrometry. Biodegradation of ofloxacin at 450 µg L^-1 by both bacterial strains expressed good linear fits (R² > 0.98) according to the Rayleigh equation. The enantiomeric enrichment factors were comprised between - 22.5% to - 9.1%, and - 18.7% to - 9.0% in the biodegradation of ofloxacin by strains F11 and FP1, respectively, with no significant differences for the two bacteria under the same conditions. This is the first time that enantioselective biodegradation of ofloxacin and levofloxacin by single bacteria is reported.

MALDI-TOF MS for the Identification of Cultivable Organic-Degrading Bacteria in Contaminated Groundwater near Unconventional Natural Gas Extraction Sites

Groundwater quality and quantity is of extreme importance as it is a source of drinking water in the United States. One major concern has emerged due to the possible contamination of groundwater from unconventional oil and natural gas extraction activities. Recent studies have been performed to understand if these activities are causing groundwater contamination, particularly with respect to exogenous hydrocarbons and volatile organic compounds. The impact of contaminants on microbial ecology is an area to be explored as alternatives for water treatment are necessary. In this work, we identified cultivable organic-degrading bacteria in groundwater in close proximity to unconventional natural gas extraction. Pseudomonas stutzeri and Acinetobacter haemolyticus were identified using matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF MS), which proved to be a simple, fast, and reliable method. Additionally, the potential use of the identified bacteria in water and/or wastewater bioremediation was studied by determining the ability of these microorganisms to degrade toluene and chloroform. In fact, these bacteria can be potentially applied for in situ bioremediation of contaminated water and wastewater treatment, as they were able to degrade both compounds.

Bacterial degradation of moxifloxacin in the presence of acetate as a bulk substrate

Fluoroquinolones constitute a group of emerging pollutants and their occurrence in different environmental compartments is becoming object of increasing public concern due to their ecotoxicological effects and the potential to develop resistant bacteria. This study aimed to investigate the biodegradation of moxifloxacin (MOX), for which studies in the literature are very scarce. An activated sludge (AS) consortium and three bacterial strains able to degrade fluoroaromatic compounds - strains F11, FP1 and S2 - were tested. Biodegradation studies were conducted using acetate as a bulk carbon source. Strain F11 showed the highest biodegradation capacity, being able to completely consume and dehalogenate 7.5 μM of the target antibiotic when daily co-supplemented with acetate present as a readily degradable organic substrate in wastewaters. MOX could be used by strain F11 as a sole nitrogen source but the presence of an external nitrogen source in the culture medium was essential for complete biodegradation. Strain F11 was capable of completely consuming MOX in a range between 2 and 11 μM, although stoichiometric fluoride release was not obtained for the highest tested concentration. The antibacterial activity of residual MOX and of the metabolic products potentially resultant from the biodegradation process was investigated by agar diffusion tests, demonstrating that MOX biodegradation is associated with the elimination of the antibacterial properties of the target antibiotic and of the produced metabolites, which is an important result, as the activity of antibiotics and/or their metabolites in the environment, even at low levels, may lead to the development of resistant bacterial strains. Overall, the results obtained in this study suggest that strain F11 is a promising microorganism for the treatment of waters contaminated with MOX, where it could be used for bioaugmentation/bioremediation purposes. To the best of our knowledge, this is the first study reporting complete removal and dehalogenation of MOX by a single microorganism.

Spontaneous release of fluoride during the dioxygenolytic cleavage of 5-fluorosalicylate by the salicylate 1,2-dioxygenase from Pseudaminobacter salicylatoxidans BN12

The alpha-Proteobacterium Pseudaminobacter salicylatoxidans BN12 forms a peculiar gentisate 1,2-dioxygenase (SDO) that oxidatively cleaves gentisate (2,5-dihydroxybenzoate) and additionally 1-hydroxy-2-naphthoate, salicylate and various amino-, chloro-, fluoro-, hydroxy- and methylsalicylates. In the present study, the conversion of 5-fluorosalicylate by this enzyme was analysed using various analytical techniques. Spectrophotometric assays showed that the conversion of 5-fluorosalicylate by the purified enzyme resulted in the formation of a new unstable intermediate showing an absorbance maximum at λmax = 292 nm. The analysis of the enzymatic reaction by HPLC showed that two main products with absorbance maxima at λmax = 292-296 nm were formed from 5-fluorosalicylate. The same two products (although in different relative proportions) were also formed when the SDO transformed 5-chlorosalicylate or when a purified 5-nitrosalicylate 1,2-dioxygenase from Bradyrhizobium sp. JS329 oxidized 5-nitrosalicylate. A whole cell system with recombinant Escherichia coli cells overexpressing the SDO activity was established in order to produce larger amounts of the reaction products. The reaction products were subsequently identified by (1)H-NMR and mass spectrometry as stereoisomers of 2-oxo-3-(5-oxofuran-2-ylidine)propanoic acid. The release of fluoride in the course of the dioxygenolytic cleavage reaction was confirmed by ion-chromatography and (19)F-NMR.