Regulating mechanism of denitrifier Comamonas sp. YSF15 in response to carbon deficiency: Based on carbon/nitrogen functions and bioaggregation.

There is an urgent demand to investigate mechanisms for the improvement of denitrification in carbon-deficient environment, which will effectively reduce the eutrophication in water bodies polluted by nitrate. In this study, denitrifying bacterium Comamonas sp. YSF15 was used to explore the differences in different carbon source concentrations, with the complete genome, metabolomics, and other detecting methods. Results showed that strain YSF15 was able to achieve efficient denitrification, with complete pathways for denitrification and central carbon metabolism. The carbon deficiency prompted the bacteria to use extracellular amino acid-like metabolites initially, to alleviate inhibition and maintain bioactivity, which also facilitated glycogen storage. The biogenic inhibitors (tautomycin, navitoclax, and glufosinate) at extremely low level potentially favored the competitiveness and intraspecific utilization of extracellular polysaccharides (PS). Optimal solutions for bioaggregation in carbon-deficient condition are achieved by regulating the hydrophobicity, and hydrogen bond in extracellular metabolites. The strategy contributes to the maintenance of bioactivity and adaptation to carbon deficiency. Overall, this study provides a new perspective on understanding the denitrification strategies in carbon-deficient environment, and helps to improve the nitrate removal in low-carbon wastewater treatment.

Complex regulation in a Comamonas platform for diverse aromatic carbon metabolism.

Critical to a sustainable energy future are microbial platforms that can process aromatic carbons from the largely untapped reservoir of lignin and plastic feedstocks. Comamonas species present promising bacterial candidates for such platforms because they can use a range of natural and xenobiotic aromatic compounds and often possess innate genetic constraints that avoid competition with sugars. However, the metabolic reactions of these species are underexplored, and the regulatory mechanisms are unknown. Here we identify multilevel regulation in the conversion of lignin-related natural aromatic compounds, 4-hydroxybenzoate and vanillate, and the plastics-related xenobiotic aromatic compound, terephthalate, in Comamonas testosteroni KF-1. Transcription-level regulation controls initial catabolism and cleavage, but metabolite-level thermodynamic regulation governs fluxes in central carbon metabolism. Quantitative 13C mapping of tricarboxylic acid cycle and cataplerotic reactions elucidates key carbon routing not evident from enzyme abundance changes. This scheme of transcriptional activation coupled with metabolic fine-tuning challenges outcome predictions during metabolic manipulations.

Sediment-isolated Comamonas terrigena strain HJ-2: a novel nitrate-dependent ferrous-oxidizing bacterium with multifunction on pollutant transformation.

Microbially driven Fe(II) oxidation is vital for Fe-cycling processes. In the present study, a novel strain of nitrate-dependent Fe-oxidizing bacteria (FOB) was isolated from the riparian zone sediment of the Hanjiang River, China. It was identified as Comamonas terrigena strain HJ-2. The strain HJ-2 oxidized 2.80 mmol l-1 Fe(II) within 144 h to form Fe(III)/Fe(II) complex on the cell surface using 1.63 mmol l-1 nitrate as an electron acceptor. The formed nitrite from nitrate reduction chemically oxidized Fe(II). Surprisingly, this strain also reduced nitrilotriacetic iron to form 0.5 mmol l-1 Fe(II) in 120 h in anaerobic conditions primarily mediated by the NADH flavin oxidoreductase. Besides, the strain completely reduced 0.18 mmol l-1 nitrobenzene to aniline in 24 days and 15.6 µmol l-1 arsenate to arsenite in 7 days due to the existence of nitro and arsenate reductases. However, the Fe(II) inhibited the reduction of nitrate, nitrobenzene, and arsenate, possibly due to the impeding of transport of the solutes through the membrane or the synthesis of the related enzymes. These results provide new knowledge about the Fe(II)-cycling and the fate of some pollutants in the riparian zone. It also informed that some bacteria have universal functions on elements and contaminants transformation.

A Coculture of Enterobacter and Comamonas Species Reduces Cadmium Accumulation in Rice.

The accumulation of cadmium (Cd) in plants is strongly impacted by soil microbes, but its mechanism remains poorly understood. Here, we report the mechanism of reduced Cd accumulation in rice by coculture of Enterobacter and Comamonas species. In pot experiments, inoculation with the coculture decreased Cd content in rice grain and increased the amount of nonbioavailable Cd in Cd-spiked soils. Fluorescence in situ hybridization and scanning electron microscopy detection showed that the coculture colonized in the rhizosphere and rice root vascular tissue and intercellular space. Soil metagenomics data showed that the coculture increased the abundance of sulfate reduction and biofilm formation genes and related bacterial species. Moreover, the coculture increased the content of organic matter, available nitrogen, and potassium and increased the activities of arylsulfatase, ß-galactosidase, phenoloxidase, arylamidase, urease, dehydrogenase, and peroxidase in soils. In subsequent rice transcriptomics assays, we found that the inoculation with coculture activated a hypersensitive response, defense-related induction, and mitogen-activated protein kinase signaling pathway in rice. Heterologous protein expression in yeast confirmed the function of four Cd-binding proteins (HIP28-1, HIP28-4, BCP2, and CID8), a Cd efflux protein (BCP1), and three Cd uptake proteins (COPT4, NRAM5, and HKT6) in rice. Succinic acid and phenylalanine were subsequently proved to inhibit rice divalent Cd [Cd(II)] uptake and activate Cd(II) efflux in rice roots. Thus, we propose a model that the coculture protects rice against Cd stress via Cd immobilization in soils and reducing Cd uptake in rice. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Quantitative proteomic analysis of the microbial degradation of 3-aminobenzoic acid by Comamonas sp. QT12.

A mab cluster associated with 3-aminobenzoic acid (3AB) degradation was identified in Comamonas sp. QT12. However, the cellular response of Comamonas sp. QT12 to 3-aminobenzoic acid remains unclear. In this study, label-free quantitative proteome analysis based on LC-MS/MS was used to study the protein expression difference of strain QT12 under the condition of using 3AB (3AB) and citric acid/ammonium chloride as substrates (3ABCon). A total of 2068 proteins were identified, of which 239 were significantly up-regulated in 3AB group, 124 were significantly down-regulated in 3AB group, 624 were expressed only in 3AB group, and 216 were expressed only in 3ABCon group in 3AB group. KEGG pathway analysis found that 83 pathways were up-regulated and 49 pathways were down-regulated, In GO analysis, 315 paths were up-regulated and 156 paths were down-regulated. There were 6 genes in the mab cluster that were only detected in the 3AB group.The mab cluster was found to be related to degradation of 3AB. By knockout, it was found that the growth rate of the mutant △orf7 and △orf9 were slowed down. HPLC results showed that the mutant △orf7 and △orf9 could still degrade 3AB, it was found that orf7, orf9 were not key genes about 3AB degradation and they could be replaced by other genes in strain QT12. These findings improve our understanding of the molecular mechanisms underlying the cellular response of 3AB degradation in Comamonas bacterium.

Genomic Analysis of Carbapenem-Resistant Comamonas in Water Matrices: Implications for Public Health and Wastewater Treatments.

Comamonas spp. are Gram-negative bacteria that catabolize a wide range of organic and inorganic substrates. Comamonas spp. are abundant in aquatic and soil environments, including wastewater, and can cause opportunistic infections in humans. Because of their potential in wastewater bioaugmentation and bioremediation strategies, the identification of Comamonas species harboring genes encoding carbapenemases and other clinically important antibiotic resistance genes warrant further investigation. Here, we present an analysis of 39 whole-genome sequences comprising three Comamonas species from aquatic environments in South Australia that were recovered on media supplemented with carbapenems. The analysis includes a detailed description of 33 Comamonas denitrificans isolates, some of which carried chromosomally acquired blaGES-5, blaOXA, and aminoglycoside resistance (aadA) genes located on putative genomic islands (GIs). All blaGES-5- and blaOXA-containing GIs appear to be unique to this Australian collection of C. denitrificans. Notably, most open reading frames (ORFs) within the GIs, including all antimicrobial resistance (AMR) genes, had adjacent attC sites, indicating that these ORFs are mobile gene cassettes. One C. denitrificans isolate carried an IncP-1 plasmid with genes involved in xenobiotic degradation and response to oxidative stress. Our assessment of the sequences highlights the very distant nature of C. denitrificans to the other Comamonas species and its apparent disposition to acquire antimicrobial resistance genes on putative genomic islands. IMPORTANCE Antimicrobial resistance (AMR) poses a global public health threat, and the increase in resistance to "last-resort drugs," such as carbapenems, is alarming. Wastewater has been flagged as a hot spot for AMR evolution. Comamonas spp. are among the most common bacteria in wastewater and play a role in its bioaugmentation. While the ability of Comamonas species to catabolize a wide range of organic and inorganic substrates is well documented, some species are also opportunistic pathogens. However, data regarding AMR in Comamonas spp. are limited. Here, through the genomic analyses of 39 carbapenem-resistant Comamonas isolates, we make several key observations, including the identification of a subset of C. denitrificans isolates that harbored genomic islands encoding carbapenemase blaGES-5 or extended-spectrum ß-lactamase blaOXA alleles. Given the importance of Comamonas species in potential wastewater bioaugmentation and bioremediation strategies, as well as their status as emerging pathogens, the acquisition of critically important antibiotic resistance genes on genomic islands warrants future monitoring.

The role of nitrogen metabolism on polyethylene biodegradation.

Polyethylene (PE) is the most widely used plastic and its accumulation on natural environments has reached alarming levels causing severe damage to wildlife and human health. Despite the significance of this global issue, little is known about specific metabolic mechanisms behind PE biodegradation-a promising and sustainable remediation method. Herein, we describe a novel role of nitrogen metabolism in the fragmentation and oxidation of PE mediated by biological production of NOx in three PE-degrading strains of Comamonas, Delftia, and Stenotrophomonas. Resultant nitrated PE fragments are assimilated and then metabolized by these bacteria in a process assisted by nitronate monooxygenases and nitroreductases to support microbial growth. Due to the conservation of nitrogen metabolism genes, we anticipate that this oxidative mechanism is potentially shared by other nitrifier and denitrifier microbes.

Structural basis of terephthalate recognition by solute binding protein TphC.

Biological degradation of Polyethylene terephthalate (PET) plastic and assimilation of the corresponding monomers ethylene glycol and terephthalate (TPA) into central metabolism offers an attractive route for bio-based molecular recycling and bioremediation applications. A key step is the cellular uptake of the non-permeable TPA into bacterial cells which has been shown to be dependent upon the presence of the key tphC gene. However, little is known from a biochemical and structural perspective about the encoded solute binding protein, TphC. Here, we report the biochemical and structural characterisation of TphC in both open and TPA-bound closed conformations. This analysis demonstrates the narrow ligand specificity of TphC towards aromatic para-substituted dicarboxylates, such as TPA and closely related analogues. Further phylogenetic and genomic context analysis of the tph genes reveals homologous operons as a genetic resource for future biotechnological and metabolic engineering efforts towards circular plastic bio-economy solutions.

A cellulose degrading bacterial strain used to modify rice straw can enhance Cu(II) removal from aqueous solution.

The development of lignocellulose-based adsorbents for the removal of heavy metals from wastewater has attracted much recent attention. In this work, a high-yield cellulose bacterial strain Comamonas testosteroni FJ17 was evaluated for its capacity to modify rice straw towards increased Cu(II) removal. For optimum modification time (45.5 h), inoculum concentration (1.25%), and rice straw dose (12.6 g L-1) the optimized adsorption capacity was 28.4 mg g-1. After strain FJ17 modification the equilibrium adsorption percentage of rice straw for Cu(II) increased from 6.6 to 27.4% at an initial concentration of 100 mg L-1. This increase was attributed to an increase in rice straw surface modification, leading to improved adsorption ability. SEM-EDS indicated that, following strain FJ17 treatment, the surface of the rice straw became more disintegrated and the specific surface area consequentially increased from 1.9 to 3.7 m2 g-1. FTIR analysis also showed new functional groups (carbonyl) appearing, and CC and CH3CR functionality being enhanced after biomodification. Functional groups associated with the benzene ring, silicified polymer and carbohydrates were all involved in the adsorption process. Adsorption of Cu was well described by the Freundlich isotherm model (R2 > 0.98) where adsorption was endothermic with potential for both chemical and physical interactions to coexist. Reusability experiments showed that the removal efficiency of Cu(II) decreased from 96.9 to 73.2% after five cycles. Overall C.testosteroni-treated rice straw had significant potential as a heavy metal biosorbent.

Intimate communication between Comamonas aquatica and Fusarium solani in remediation of heavy metal-polluted environments.

Worldwide, humanity is facing a major environmental crisis with the disposal of heavy metal contaminated waste. The current study describes, for the first time, the interactions between gram-negative Comamonas aquatica and filamentous fungus Fusarium solani in removing heavy metal toxicity as an eco-friendly system. When combined, C. aquatica and F. solani grew well in a co-culture setup without showing any antagonistic indications. Monoculture versus co-culture setups were used to determine the metal tolerance concentration (MTC). Based on the metal tolerance concentration (MTC) values, cells of C. aquatica were able to tolerate 4, 5, 6, and 7 mM of Cr, Zn, Cu, and Ni, respectively. Moreover, C. aquatica withstood up to 6 mM of Pb. Although F. solani exhibited sensitivity to high concentrations of heavy metals in monoculture, the MTC of F. solani increased considerably in a co-culture setup. The results presented here revealed that F. solani facilitated the dispersion of C. aquatica and heightened bioavailability, whereas C. aquatica reduced the toxicity of heavy metals and promoted the growth of F. solani. Transmission electron microscopy (TEM) displayed different mechanisms for heavy metal removal by C. aquatica. Biosorption was evident for Cr and Pb, while transformation was recorded for Ni and Zn. Also, C. aquatica was able to reduce and accumulate Cu in cells.

Mineralization of the herbicide swep by a two-strain consortium and characterization of a new amidase for hydrolyzing swep.

BACKGROUND: Swep is an excellent carbamate herbicide that kills weeds by interfering with metabolic processes and inhibiting cell division at the growth point. Due to the large amount of use, swep residues in soil and water not only cause environmental pollution but also accumulate through the food chain, ultimately pose a threat to human health. This herbicide is degraded in soil mainly by microbial activity, but no studies on the biotransformation of swep have been reported. RESULTS: In this study, a consortium consisting of two bacterial strains, Comamonas sp. SWP-3 and Alicycliphilus sp. PH-34, was enriched from a contaminated soil sample and shown to be capable of mineralizing swep. Swep was first transformed by Comamonas sp. SWP-3 to the intermediate 3,4-dichloroaniline (3,4-DCA), after which 3,4-DCA was mineralized by Alicycliphilus sp. PH-34. An amidase gene, designated as ppa, responsible for the transformation of swep into 3,4-DCA was cloned from strain SWP-3. The expressed Ppa protein efficiently hydrolyzed swep and a number of other structural analogues, such as propanil, chlorpropham and propham. Ppa shared less than 50% identity with previously reported arylamidases and displayed maximal activity at 30 °C and pH 8.6. Gly449 and Val266 were confirmed by sequential error prone PCR to be the key catalytic sites for Ppa in the conversion of swep. CONCLUSIONS: These results provide additional microbial resources for the potential remediation of swep-contaminated sites and add new insights into the catalytic mechanism of amidase in the hydrolysis of swep.

Enhancement of the denitrification in low C/N condition and its mechanism by a novel isolated Comamonas sp. YSF15.

A novel denitrifying bacterium YSF15 was isolated from the Lijiahe Reservoir in Xi'an and identified as Comamonas sp. It exhibited excellent nitrogen removal ability under low C/N conditions (C/N = 2.5) and 94.01% of nitrate was removed in 18 h, with no accumulation of nitrite. PCR amplification and nitrogen balance experiments were carried out, showing that 68.92% of initial nitrogen was removed as gas products and the nitrogen removal path was determined to be NO3--N→NO2--N→NO→N2O→N2. Scanning electron microscopy and three-dimensional fluorescence spectroscopy were used to track extracellular polymeric substances (EPS). The results show that complete-denitrification under low C/N conditions is associated with EPS, which may provide a reserve carbon source in extreme environments. These findings reveal that Comamonas sp. YSF15 can provide novel basic materials and a theoretical basis for wastewater bioremediation under low C/N conditions.

Cyanuric Acid Biodegradation via Biuret: Physiology, Taxonomy, and Geospatial Distribution.

Cyanuric acid is an industrial chemical produced during the biodegradation of s-triazine pesticides. The biodegradation of cyanuric acid has been elucidated using a single model system, Pseudomonas sp. strain ADP, in which cyanuric acid hydrolase (AtzD) opens the s-triazine ring and AtzEG deaminates the ring-opened product. A significant question remains as to whether the metabolic pathway found in Pseudomonas sp. ADP is the exception or the rule in bacterial genomes globally. Here, we show that most bacteria utilize a different pathway, metabolizing cyanuric acid via biuret. The new pathway was determined by reconstituting the pathway in vitro with purified enzymes and by mining more than 250,000 genomes and metagenomes. We isolated soil bacteria that grow on cyanuric acid as a sole nitrogen source and showed that the genome from a Herbaspirillum strain had a canonical cyanuric acid hydrolase gene but different flanking genes. The flanking gene trtB encoded an enzyme that we show catalyzed the decarboxylation of the cyanuric acid hydrolase product, carboxybiuret. The reaction generated biuret, a pathway intermediate further transformed by biuret hydrolase (BiuH). The prevalence of the newly defined pathway was determined by cooccurrence analysis of cyanuric acid hydrolase genes and flanking genes. Here, we show the biuret pathway was more than 1 order of magnitude more prevalent than the original Pseudomonas sp. ADP pathway. Mining a database of over 40,000 bacterial isolates with precise geospatial metadata showed that bacteria with concurrent cyanuric acid and biuret hydrolase genes were distributed throughout the United States.IMPORTANCE Cyanuric acid is produced naturally as a contaminant in urea fertilizer, and it is used as a chlorine stabilizer in swimming pools. Cyanuric acid-degrading bacteria are used commercially in removing cyanuric acid from pool water when it exceeds desired levels. The total volume of cyanuric acid produced annually exceeds 200 million kilograms, most of which enters the natural environment. In this context, it is important to have a global understanding of cyanuric acid biodegradation by microbial communities in natural and engineered systems. Current knowledge of cyanuric acid metabolism largely derives from studies on the enzymes from a single model organism, Pseudomonas sp. ADP. In this study, we obtained and studied new microbes and discovered a previously unknown cyanuric acid degradation pathway. The new pathway identified here was found to be much more prevalent than the pathway previously established for Pseudomonas sp. ADP. In addition, the types of environment, taxonomic prevalences, and geospatial distributions of the different cyanuric acid degradation pathways are described here.

Degradation Mechanism of 4-Chlorobiphenyl by Consortium of Pseudomonas sp. Strain CB-3 and Comamonas sp. Strain CD-2.

Polychlorinated biphenyls (PCBs) are types of lasting environmental pollutants which are widely used in various industries. 4-chlorobiphenyl (4CBP) is a PCB which is harmful to the environment as well as humans. Two strains, CB-3 and CD-2, were isolated from the polluted soil of a chemical factory and could completely degrade 50 mg/L 4CBP within 12 h by co-culture. The consortium comprising strains CB-3 and CD-2 was effective in the degradation of 4CBP. 4CBP was degraded initially by strain CB-3 to accumulate 4-chlorobenzoate (4CBA) and further oxidised by strain CD-2. Based on 16S rRNA gene sequence analysis and phenotypic typing, strain CB-3 and strain CD-2 were identified as Pseudomonas sp. and Comamonas sp., respectively. The substrate spectra experiment showed that strain CB-3 could degrade PCBs with no more than three chlorine atoms. A gene cluster of biphenyl metabolism was found in the genome of strain CB-3. Besides, a dechlorination gene cluster and a gene cluster of protocatechuate (PCA) metabolic were found in the genome of strain CD-2. These gene clusters are supposed to be involved in 4CBP degradation. The ability of strains CB-3 and CD-2 to degrade 4CBP in soil was assessed by soil experiment, and 4CBP at the initial concentration of 10 mg/kg was 80.5% removed within 15 days.

Enrichment of a mixed microbial culture of PHA-storing microorganisms by using fermented hardwood spent sulfite liquor.

Pulp and paper factories produce several residues that can be explored and valorized through polyhydroxyalkanoate (PHA) production via a three-step process. The objective of this work was focused on the selection step. Acidified hardwood spent sulfite liquor (HSSL), a fermented waste stream from a pulp and paper factory, was used to select a mixed microbial culture (MMC) in a sequencing batch reactor (SBR) operated for 156 days under different operational conditions. The MMC adapted to the imposed conditions, revealing its robustness whenever the operational parameters were changed. Feast-to-Famine ratio was kept below or equal to 0.2, with constant production of a copolymer of P(3HB-co-3 HV), and with storage contents values over 30 %. Changes in the operational conditions, namely cycle length, and organic load rate (OLR), successfully led to the selection of an MMC with a stable accumulation capacity and an increased biomass concentration. Next Generation Sequencing analysis was performed on samples collected during the SBR operational period. The analysis of the microbial composition of the MMC showed a rise in PHA-accumulating bacteria over time. Acidovorax and Comamonas species were found mainly to drive the PHA storage process during the first two periods of operation. After an increase in the OLR, in the last period, a shift towards Comamonas dominance occurred, suggesting a higher tolerance to the inhibitory compounds of the HSSL for this genus.

Comamonas sp. 3ah48 is a dibenz[a,h]anthracene-degrading bacterium that is tolerant to heavy metals.

Industrialization often causes polycyclic aromatic hydrocarbon (PAH) and heavy metal contamination of soil and water. In this study, we isolated a bacterium from bottom mud water around a park of Kawasaki Port, Japan, that degrades the 5-ring PAH dibenz[a,h]anthracene (DBA). The strain, Comamonas sp. 3ah48, degraded 29% of DBA (30 µg ml-1 ) in 7 days, and the degradation level increased drastically, to 59%, by the addition of glutamate to the medium. The strain also degraded 40, 14, 15 and 19% of pyrene (Pyr), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF) and benzo[g,h,i]perylene (BghiP) respectively. Benzo[a]pyrene (BaP) was degraded only when glutamate was added to the medium. Strain 3ah48 retained its degradation levels in the presence of 2 mmol l-1 Co2+ , Zn2+ or Cr2+ , at almost the same level as that without metal, and increased the DBA degradation level to 57% in the presence of 2 mmol l-1 Cu2+ , suggesting the possibility of the presence of laccase. SIGNIFICANCE AND IMPACT OF THE STUDY: Sixteen polycyclic aromatic hydrocarbons (PAHs) are listed as priority pollutants by the United States Environmental Protection Agency (USEPA). Information about the biodegradation of one of those PAHs, dibenz[a,h]anthracene (DBA), is limited. The present study focuses on DBA degradation by Comamonas sp. 3ah48 strain isolated around Kawasaki Port, Japan. Comamonas sp. 3ah48, cultured with the addition of glutamate to the medium, was found to increase the degradation level of DBA and to degrade DBA even in the presence of high concentrations of heavy metals.

Performance and Microbial Community Analysis of Bioaugmented Activated Sludge System for Indigo Production from Indole.

Indole is a typical nitrogen-containing aromatic pollutant in coking wastewater, and it can be used for the microbial production of indigo, one of the oldest dyestuffs. In this study, the activated sludge system bioaugmented with two indigo-producing bacterial strains, wild strain Comamonas sp. MQ and recombinant Escherichia coli (ND_IND), was constructed to investigate indigo bioproduction from indole. During the operation, the bioaugmentation could promote the production of indigo, especially in early stages, and the indigo yields gradually increased from 17.5 ± 0.4 to 44.3 ± 0.5 mg/L with the increase of influent indole (80 to 282 mg/L). Illumina MiSeq sequencing revealed that the microbial community could have a noticeable shift driven by the bioaugmentation and high indole pressure. The indigenous bacteria could be more responsible for indigo production, and the dominant genera Comamonas, Diaphorobacter, Paracoccus, Aquamicrobium, Pseudomonas, and Truepera could be the key functional taxa. Based on FAPROTAX (Functional Annotation of Prokaryotic Taxa) analysis, the nitrogen metabolism-related functional groups could play important roles in indole biotransformation and indigo biosynthesis. This study should provide insights into microbial production of indigo by microbial communities.

A bioflocculant-supported dissolved air flotation system for the removal of suspended solids, lipids and protein matter from poultry slaughterhouse wastewater.

In this study, two previously identified isolates, i.e. Comamonas aquatica (BF-3) and Bacillus sp. BF-2, were determined to be suitable candidates to utilise in a bioflocculant-supported dissolved air flotation (Bio-DAF) system as a pretreatment system for poultry slaughterhouse wastewater (PSW). A 2% (v/v) (bioflocculant:PSW) strategy was used for the DAF to reduce total suspended solids (TSS), lipids and proteins in the PSW, by supplementing the bioflocculants produced and the co-culture (C. aquatica BF-3 and Bacillus sp. BF-2) directly into the DAF. The Bio-DAF was able to reduce 91% TSS, 79% proteins and 93% lipids when the DAF system was operating at steady state, in comparison with a chemical DAF operated using 2% (v/v) alum that was able to only reduce 84% TSS, 71% proteins and 92% lipids. It was concluded that the Bio-DAF system worked efficiently for the removal of suspended solids, lipids and proteins, achieving better results than when alum was used.

NRVS Studies of the Peroxide Shunt Intermediate in a Rieske Dioxygenase and Its Relation to the Native FeII O2 Reaction.

The Rieske dioxygenases are a major subclass of mononuclear nonheme iron enzymes that play an important role in bioremediation. Recently, a high-spin FeIII-(hydro)peroxy intermediate (BZDOp) has been trapped in the peroxide shunt reaction of benzoate 1,2-dioxygenase. Defining the structure of this intermediate is essential to understanding the reactivity of these enzymes. Nuclear resonance vibrational spectroscopy (NRVS) is a recently developed synchrotron technique that is ideal for obtaining vibrational, and thus structural, information on Fe sites, as it gives complete information on all vibrational normal modes containing Fe displacement. In this study, we present NRVS data on BZDOp and assign its structure using these data coupled to experimentally calibrated density functional theory calculations. From this NRVS structure, we define the mechanism for the peroxide shunt reaction. The relevance of the peroxide shunt to the native FeII/O2 reaction is evaluated. For the native FeII/O2 reaction, an FeIII-superoxo intermediate is found to react directly with substrate. This process, while uphill thermodynamically, is found to be driven by the highly favorable thermodynamics of proton-coupled electron transfer with an electron provided by the Rieske [2Fe-2S] center at a later step in the reaction. These results offer important insight into the relative reactivities of FeIII-superoxo and FeIII-hydroperoxo species in nonheme Fe biochemistry.

Cometabolic Degradation of Dibenzofuran and Dibenzothiophene by a Naphthalene-Degrading Comamonas sp. JB.

Comamonas sp. JB was used to investigate the cometabolic degradation of dibenzofuran (DBF) and dibenzothiophene (DBT) with naphthalene as the primary substrate. Dehydrogenase and ATPase activity of the growing system with the presence of DBF and DBT were decreased when compared to only naphthalene in the growing system, indicating that the presence of DBF and DBT inhibited the metabolic activity of strain JB. The pathways and enzymes involved in the cometabolic degradation were tested. Examination of metabolites elucidated that strain JB cometabolically degraded DBF to 1,2-dihydroxydibenzofuran, subsequently to 2-hydroxy-4-(3'-oxo-3'H-benzofuran-2'-yliden)but-2-enoic acid, and finally to catechol. Meanwhile, strain JB cometabolically degraded DBT to 1,2-dihydroxydibenzothiophene and subsequently to the ring cleavage product. A series of naphthalene-degrading enzymes including naphthalene dioxygenase, 1,2-dihydroxynaphthalene dioxygenase, salicylaldehyde dehydrogenase, salicylate hydroxylase, and catechol 2,3-oxygenase have been detected, confirming that naphthalene was the real inducer of expression the degradation enzymes and metabolic pathways were controlled by naphthalene-degrading enzymes.