Microbial mineralization of ring-substituted anilines through an ortho-cleavage pathway

Tetracycline hydrochloride degradation in polarity inverted microbial fuel cells: Performance, mechanisms and microbiology

Tetracycline antibiotics are widely used in veterinary medicine, human therapy and agriculture, and their presence in natural water raises environmental concerns. In this study, more than 94% of tetracycline hydrochloride (TCH) could be rapidly degraded within 48 h in polarity-inverted microbial fuel cells. The electrochemically active bacteria had the best electrochemical performance at 1 mg/L of TCH with the minimum internal resistance of 77.38 Ω. The electron-rich functional groups of TCH were continuously attacked and finally degradated into small molecules in three possible degradation pathways. Microbial community structure analysis showed that Comamonas and Shinella were enriched at the electrode as polarity-inverted bacteria. Genomic analysis showed that both direct and indirect electron transfer participated in the degradation of TCH in polarity-inverted microbial fuel cell (MFC) and the functional genes related to electrical conductivity in polarity-inverted MFC were more enriched on the electrode surface than non-polarity-inverted MFC. This study can facilitate further investigations about the biodegradation of TCH in polarity-inverted microbial fuel cell.

The Impact of Anti-Inflammatory Drugs on the Prokaryotic Community Composition and Selected Bacterial Strains Based on Microcosm Experiments

Non-steroidal anti-inflammatory drugs (NSAIDs) are increasingly recognized as potential environmental contaminants that may induce toxicity in aquatic ecosystems. This 3-week microcosm experiment explores the acute impacts of NSAIDs, including diclofenac (DCF), ibuprofen (IBU), and acetylsalicylic acid (ASA), on bacterial communities using a wide range of these substances (200-6000 ppm). The results showed that the NSAID-treated microcosms had higher cell count values than control samples, though the diversity of microbial communities decreased. The isolated heterotrophic bacteria mostly belonged to Proteobacteria, particularly Klebsiella. Next-generation sequencing (NGS) revealed that NSAIDs altered the structure of the bacterial community composition, with the proportion of Proteobacteria aligning with the selective cultivation results. Bacteria had higher resistance to IBU/ASA than to DCF. In DCF-treated microcosms, there has been a high reduction of the number of Bacteroidetes, whereas in the microcosms treated with IBU/ASA, they have remained abundant. The numbers of Patescibacteria and Actinobacteria have decreased across all NSAID-treated microcosms. Verrucomicrobia and Planctomycetes have tolerated all NSAIDs, even DCF. Cyanobacteria have also demonstrated tolerance to IBU/ASA treatment in the microcosms. The archaeal community structure was also impacted by the NSAID treatments, with Thaumarchaeota abundant in all microcosms, especially DCF-treated microcosms, while Nanoarchaeota is more typical of IBU/ASA-treated microcosms with lower NSAID concentrations. These results indicate that the presence of NSAIDs in aquatic environments could lead to changes in the composition of microbial communities.

Interpreting the degradation mechanism of triclosan in microbial fuel cell by combining analysis microbiome community and degradation pathway

Microbes play a dominant role for the transformation of organic contaminants in the environment, while a significant gap exists in understanding the degradation mechanism and the function of different species. Herein, the possible bio-degradation of triclosan in microbial fuel cell was explored, with the investigation of degradation kinetics, microbial community, and possible degradation products. 5 mg/L of triclosan could be degraded within 3 days, and an intermediate degradation product (2,4-dichlorophen) could be further degraded in system. 32 kinds of dominant bacteria (relative intensity >0.5%) were identified in the biofilm, and 10 possible degradation products were identified. By analyzing the possible involved bioreactions (including decarboxylation, dehalogenation, dioxygenation, hydrolysis, hydroxylation, and ring-cleavage) of the dominant bacteria and possible degradation pathway of triclosan based on the identified products, biodegradation mechanism and function of the bacteria involved in the degradation of triclosan was clarified simultaneously. This study provides useful information for further interpreting the degradation mechanism of organic pollutants in mixed flora by combining analysis microbiome community and degradation pathway.

Retrospect and prospect of aerobic biodegradation of aniline: Overcome existing bottlenecks and follow future trends

Aniline is a highly bio-toxic industrial product, even at low concentrations, whose related wastewater has been flowing out worldwide on a large scale along with human production. As a green technology, aerobic biological treatment has been widely applied in industrial wastewater and exhibited various characteristics in the field of aniline wastewater. Meanwhile, this technology has shown its potential of synchronous nitrogen removal, but it still consumes energy badly. In the face of resource scarcity, this review comprehensively discusses the existing research in aerobic biodegradation of aniline wastewater to find out the developmental dawn of aerobic biological treatment. Primarily, it put forward the evolution history details of aniline biodegradation from pure culture to mixed culture and then to simultaneous nitrogen removal. On this basis, it presented the existing challenges to further expand the application of aerobic biotechnology, including the confusions of aniline metabolic mechanism, the development of co-degradation of multiple pollutants and the lack of practical experience of bioreactor operation for aniline and nitrogen removal. Additionally, the prospects of the technological shift to meet the needs of an energy-conserving society was described according to existing experiences and feasibility. Including but not limiting to the development of multifunctional bacteria, the reduction of greenhouse gases and the combination of green technologies.

Effect of biodegradation on haloacetic acid formation potentials of anthropogenic compounds during chlorination

During drinking water treatment processes, anthropogenic compounds act as important precursors of disinfection by-products such as haloacetic acids (HAAs). Several transformations in these precursors occur prior to the disinfection stage, such as partial biodegradation. We hypothesized that this partial biodegradation of anthropogenic compounds potentially affects their HAA formation potentials (HAAFPs). In this study, the HAAFPs of 51 anthropogenic compounds after short-term contact (less than 1 h) and long-term contact (24 h) with activated sludge were compared. Considerable changes were observed particularly in trichloroacetic acid (TCAA) formation potentials (FPs) of phenols, demonstrating that biodegradation should be considered in investigations of potential precursors of HAAs. Phenols with low HAAFPs, such as hydroquinone, show higher HAAFPs after biodegradation, but HAAFPs of most phenols and anilines decreased after biodegradation. Thus, biodegradation will most likely have a positive impact on water quality from the standpoint of HAAFP reduction. For most aliphatic compounds, changes in HAAFP were negligible, but the dichloroacetic acid (DCAA) FP of acrylic acid largely increased. This study illustrates that biodegradation may have a large effect on the HAAFPs of anthropogenic compounds.

Rapid aerobic visible-light-driven photo-reduction of nitrobenzene

Many strategies have been proposed to treat wastewater containing toxic contaminants, such as nitrobenzene, prior to discharge. Most of these degradation processes, especially biodegradation, undergo a limited step of nitrobenzene reduction into aniline and a subsequent fast step of aniline mineralization. The low efficiency of nitrobenzene reduction and the requirement of an anaerobic atmosphere limit the overall degradation performance. In this communication, eosin Y is reported as a potential homogeneous catalyst for the rapid photoreduction of nitrobenzene under aerobic conditions. As a result, a conversion (~10 min) of nitrobenzene (25 mg/L) into aniline driven by visible light was achieved. The reduction rate constants under aerobic conditions (0.30 min^-1) were even slightly higher than those under anaerobic conditions (0.28 min^-1), and the lifetime of the catalytic system was extended. Furthermore, the mechanism of nitrobenzene transformation was speculated based on the identification of intermediate products. To provide guidance for the practical application of this pretreatment strategy, the impact of pH value and widely existing heavy metal ions on photoreduction were also demonstrated. The results from this work provide a novel insight into the integrated control of organic pollutants produced in chemical industries.

Cometabolic degradation of p-chloroaniline by the genus Brevibacillus bacteria with extra carbon sources

In this study, we discovered and isolated a new genus Brevibacillus strain from effluent of dyeing and finishing factory containing highly toxic p-chloroanilines (PCA). Based on the morphological, physiological and biochemical characteristics, as well as 16S rDNA sequence, the strain was identified and denominated as Brevibacillus S-618. Co-metabolism effect was found with extra carbon sources including sodium succinate, sodium citrate, ammonium chloride and glucose which can efficiently promote the biodegradation process of PCA. Under the optimal growth conditions at temperature of 30 °C, pH˜7 and air-water ratio of 0.3 m³/m³·min, the degradation rate of PCA in a 2 L pilot bioreactor with high concentration of 180 mg/L increased from 86.7% to 100% within 72 h after adding sodium succinate. The release of chloride ions during the growth process of the strain was equivalent to the degradation amount of PCA. Meanwhile, the cleavage pathway of PCA degradation by Brevibacillus S-618 was proposed by analysis of enzyme activities of microorganism and intermediate products in the reaction. Benefiting from excellent degradation ability and unique characters in high pollutant contents, high efficient bioreactor can easily be scale up for industrial application. Our study provides a facile route for cost-effectively and environmental-friendly degrading hazardous chemicals.

Enhanced aniline degradation by Desulfatiglans anilini in a synthetic microbial community with the phototrophic purple sulfur bacterium Thiocapsa roseopersicina

Desulfatiglans anilini is a sulfate-reducing bacterium (SRB) capable of oxidizing aniline, although growth and aniline turnover rates are slow, making it difficult to analyze the metabolism of the strain. Therefore, this study was designed to investigate the effect of sulfide on growth of D. anilini cultures, in order to improve its growth and aniline turnover rates, and study the biochemical mechanisms of sulfide inhibition. Hydrogen sulfide was found to inhibit growth of D. anilini, regardless of whether the strain was grown with aniline or phenol, and complete inhibition was observed at 20mM hydrogen sulfide. For improving the growth of D. anilini with aniline, the sulfide-consuming phototrophic bacterium Thiocapsa roseopersicina was co-cultured in a synthetic microbial community with D. anilini using a co-cultivation device that continuously removed hydrogen sulfide from the culture. The doubling time of D. anilini with aniline was 15 days in the co-cultivation device, compared to 26 days in the absence of a sulfide-oxidizing partner. Moreover, the aniline degradation rate was significantly increased by a factor of 2.66 during co-cultivation of D. anilini with T. roseopersicina. The initial carboxylation reaction during aniline degradation was measured in cell-free extracts of D. anilini with carbon dioxide (CO₂) as a co-substrate in the presence of aniline and ATP. The effects of hydrogen sulfide on this aniline carboxylating system and on phenylphosphate synthase activity for phenol activation were studied, and it was concluded that hydrogen sulfide severely inhibited these enzyme activities.

Performance and kinetics of triclocarban removal by entrapped Pseudomonas fluorescens strain MC46

This study investigated removal of triclocarban (TCC) from contaminated wastewater by Pseudomonas fluorescens strain MC46 entrapped in barium alginate. Appropriate entrapped cell preparation conditions (cell-to-entrapment material ratio and cell loading) for removing TCC were examined. The highest TCC removal by the entrapped and free cell systems at the initial TCC concentration of 10 mg/L was 72 and 45%, respectively. TCC was degraded to less toxic compounds. Self-substrate inhibition was found at TCC concentration of 30 mg/L. The kinetics of TCC removal by entrapped and free cells fitted well with Edwards model. Scanning and transmission electron microscopic observations revealed that entrapment matrices reduced TCC-microbe contact, which lessened TCC inhibition. A live/dead cell assay also confirmed reduced microbial cell damage in the entrapped cell system compared to the free cell system. This study reveals the potential of entrapment technology to improve antibiotic removal from the environment.

Anaerobic degradation of 2,4-dichlorophenoxyacetic acid by Thauera sp. DKT

Thauera sp. strain DKT isolated from sediment utilized 2,4-dichlorophenoxyacetic acid (2,4D) and its relative compounds as sole carbon and energy sources under anaerobic conditions and used nitrate as an electron acceptor. The determination of 2,4D utilization at different concentrations showed that the utilization curve fitted well with the Edward model with the maximum degradation rate as 0.017 ± 0.002 mM/day. The supplementation of cosubstrates (glucose, acetate, sucrose, humate and succinate) increased the degradation rates of all tested chemical substrates in both liquid and sediment slurry media. Thauera sp. strain DKT transformed 2,4D to 2,4-dichlorophenol (2,4DCP) through reductive side-chain removal then dechlorinated 2,4DCP to 2-chlorophenol (2CP), 4-chlorophenol (4CP) and phenol before complete degradation. The relative degradation rates by the isolate in liquid media were: phenol > 2,4DCP > 2CP > 4CP > 2,4D ≈ 3CP. DKT augmentation in sediment slurry enhanced the degradation rates of 2,4D and chlorophenols. The anaerobic degradation rates in the slurry were significantly slower compared to the rates in liquid media.

Aerobic Transformation of 2,4-Dinitrotoluene by Escherichia coli and Its Implications for the Detection of Trace Explosives

DNT (2,4-dinitrotoluene), a volatile impurity in military-grade 2,4,6-trinitrotoluene (TNT)-based explosives, is a potential tracer for the detection of buried landmines and other explosive devices. We have previously described an Escherichia coli bioreporter strain engineered to detect traces of DNT and have demonstrated that the yqjF gene promoter, the sensing element of this bioreporter, is induced not by DNT but by at least one of its transformation products. In the present study, we have characterized the initial stages of DNT biotransformation in E. coli, have identified the key metabolic products in this reductive pathway, and demonstrate that the main DNT metabolite that induces yqjF is 2,4,5-trihydroxytoluene. We further show that E. coli cannot utilize DNT as a sole carbon or nitrogen source and propose that this compound is metabolized in order to neutralize its toxicity to the cells.IMPORTANCE The information provided in this article sheds new light both on the microbial biodegradability of nitroaromatic compounds and on the metabolic capabilities of E. coli By doing so, it also clarifies the pathway leading to the previously unexplained induction of the E. coli yqjF gene by 2,4-dinitrotoluene, an impurity that accompanies 2,4,6-trinitrotoluene (TNT)-based explosives. Our improved understanding of these processes will serve to molecularly enhance the performance of a previously described microbial bioreporter of buried landmines and other explosive devices, in which the yqjF gene promoter serves as the sensing element.

Bioremediation of diuron contaminated soils by a novel degrading microbial consortium

Diuron is a biologically active pollutant present in soil, water and sediments. It is persistent in soil, water and groundwater and slightly toxic to mammals and birds as well as moderately toxic to aquatic invertebrates. Its principal product of biodegradation, 3,4-dichloroaniline, exhibits a higher toxicity than diuron and is also persistent in the environment. On this basis, the objective of the study was to determine the potential capacity of a proposed novel diuron-degrading microbial consortium (DMC) for achieving not only diuron degradation, but its mineralisation both in solution as well as in soils with different properties. The consortium was tested in a soil solution where diuron was the only carbon source, and more than 98.8% of the diuron initially added was mineralised after only a few days. The consortium was composed of three diuron-degrading strains, Arthrobacter sulfonivorans, Variovorax soli and Advenella sp. JRO, the latter had been isolated in our laboratory from a highly contaminated industrial site. This work shows for the first time the potential capacity of a member of the genus Advenella to remediate pesticide-contaminated soils. However, neither of the three strains separately achieved mineralisation (ring-¹⁴C) of diuron in a mineral medium (MSM) with a trace nutrient solution (NS); combined in pairs, they mineralised 40% of diuron in solution, but the most relevant result was obtained in the presence of the three-member consortium, where complete diuron mineralisation was achieved after only a few days. In the presence of the investigated soils in suspension, the capacity of the consortium to mineralise diuron was evaluated, achieving mineralisation of a wide range of herbicides from 22.9 to 69.0%.

Analytical transport modelling of metabolites formed in dual-porosity media

Contaminants like nitroaromatic compounds can be degraded in the subsurface to similar or even more toxic metabolites. Degradation or transformation rates are dependent on physical, chemical and biological properties which can be different in sedimentological layers or other heterogeneous structures of aquifers. Sediments with low hydraulic conductivity can even consist of immobile water. These regions are only accessible by diffusion. Most modelling approaches accounting for immobile water regions focused on the mathematical description of the transport and decay of the parent compound. The objective of this study was to develop an analytical model to quantify the transport and formation of a metabolite in dual-porosity media describing the exchange between mobile and immobile water regions based on the metabolite's diffusion coefficient. Column experiments with a well-defined immobile water region were performed under anoxic conditions at three different water flow velocities. The model compound 4-Cl-nitrobenzene was reduced to 4-Cl-aniline (4-Cl-An) by surface-bound Fe (II) species within the immobile water region. Transport and formation of the metabolite were quantified with a modified solution of the single fissure dispersion model assuming additionally for the region with immobile water first-order metabolite production, irreversible sorption and an instantaneous equilibrium sorption. The number of unknown fitting parameters was reduced to two (sorption rate and retardation factor) by stepwise parameter estimation using tracer and parent compound data. Experimental results of the metabolite for each water flow velocity were successfully described with a first-order production term (λ _prod = 1.51 ± 0.08 h^-1), retardation factor (R _im = 2.94 ± 0.45) and first-order irreversible sorption rate (K _im = 0.39 ± 0.16 h^-1) within the immobile water region. Model results supported that 4-Cl-An was formed within the immobile water region. 4-Cl-An sorbed instantaneously onto the clay matrix while a fraction was irreversibly sorbed. Experimental results and the provided analytical solution help to improve the understanding about reactive transport and the formation of metabolites in dual-porosity media.

Natural production of fluorinated compounds and biotechnological prospects of the fluorinase enzyme

Fluorinated compounds are finding increasing uses in several applications. They are employed in almost all areas of modern society. These compounds are all produced by chemical synthesis and their abundance highly contrasts with fluorinated molecules of natural origin. To date, only some plants and a handful of actinomycetes species are known to produce a small number of fluorinated compounds that include fluoroacetate (FA), some ω-fluorinated fatty acids, nucleocidin, 4-fluorothreonine (4-FT), and the more recently identified (2R3S4S)-5-fluoro-2,3,4-trihydroxypentanoic acid. This largely differs from other naturally produced halogenated compounds, which totals more than 5000. The mechanisms underlying biological fluorination have been uncovered after discovering the first actinomycete species, Streptomyces cattleya, that is capable of producing FA and 4-FT, and a fluorinase has been identified as the enzyme responsible for the formation of the C-F bond. The discovery of this enzyme has opened new perspectives for the biotechnological production of fluorinated compounds and many advancements have been achieved in its application mainly as a biocatalyst for the synthesis of [¹⁸F]-labeled radiotracers for medical imaging. Natural fluorinated compounds may also be derived from abiogenic sources, such as volcanoes and rocks, though their concentrations and production mechanisms are not well known. This review provides an outlook of what is currently known about fluorinated compounds with natural origin. The paucity of these compounds and the biological mechanisms responsible for their production are addressed. Due to its relevance, special emphasis is given to the discovery, characterization and biotechnological potential of the unique fluorinase enzyme.

Multi-substrate biodegradation interaction of 1, 4-dioxane and BTEX mixtures by Acinetobacter baumannii DD1

This study evaluated substrate interactions during the aerobic biodegradation of 1, 4-dioxane and BTEX mixtures by a pure culture, Acinetobacter baumannii DD1, which is capable of utilizing 1, 4-dioxane for growth. A. baumannii DD1 could utilize BTEX as a sole carbon source, but could not utilize m-xylene and p-xylene. In binary mixtures, there was a lag of about 14 h before the degradation of BTE, and 1, 4-dioxane only started to be utilized when BTE was completely degraded by 1, 4-dioxane-grown DD1. Furthermore, the biodegradation rate of 1, 4-dioxane decreased from 73.33 to 40.74 mg/(h g dry weight) after the biodegradation of benzene. 1, 4-dioxane could not be degraded after the biodegradation of o-xylene in 80 h. DD1 could also not degrade m-xylene and p-xylene coexisting with 1, 4-dioxane. The ability of DD1 to degrade BTEX occurred in the following order: benzene > ethylbenzene > toluene > o-xylene > m-xylene = p-xylene. The biodegradation of 1, 4-dioxane was not activated in the mixture with o-xylene, primarily because of the accumulation of the specific toxic intermediate, 2, 3-dimethylphenol. The lag in BTE degradation was presumably because of the induction of enzymes necessary for BTE degradation. Additionally, SDS-PAGE analysis demonstrated that there were different proteins during the degradation of benzene and 1, 4-dioxane.

Cometabolism of Fluoroanilines in the Presence of 4-Fluoroaniline byRalstoniasp. FD-1

A strain ofRalstoniasp. FD-1 capable of using 4-fluoroaniline (4-FA) as the sole carbon and nitrogen source was investigated for its ability to utilize 4-FA isomers (2-FA, 3-FA) and homologs (2,4-DFA, 3,4-DFA, and 2,3,4-TFA). Both 4-FA and 3-FA could be mineralized as the sole carbon and nitrogen source by FD-1. 2-FA, 2,4-DFA, 3,4-DFA, and 2,3,4-TFA could not be degraded by FD-1, respectively, and were selected as secondary substrates for cometabolism with 500 mg/L 4-FA as growth substrate. Bacterial growth (OD600), F−concentrations, and fluoroanilines contents were measured to determinate the degradation ability of 4-FA isomers and homologs by FD-1. FD-1 growth was inhibited by 2,4-DFA, 3,4-DFA, and 2,3,4-TFA at higher concentrations (400 mg/L), except for 2-FA. Complete fluoroanilines degradation was achieved while incomplete defluorination was characterized by the stoichiometric fluoride release indicating partial degradation but not total mineralization. When fluoroaniline was supplied to the resting cells of strain FD-1, a relatively effective removal was showed. Strain FD-1 had broadened application prospect of toxicity and low nutrition fluoroanilines wastewater.

Aerobic degradation study of three fluoroanilines and microbial community analysis: the effects of increased fluorine substitution

The fate of fluorinated compounds in the environment, especially polyfluorinated aromatics, is a matter of great concern. In this work, 4-Fluoroaniline (4-FA), 2,4-Difluoroanilines (2,4-DFA), and 2,3,4-Trifluoroanilines (2,3,4-TFA), were chosen as the target pollutants to study their biodegradability under aerobic conditions. The required enriched time of the mixed bacterial culture for degrading 4-FA, 2,4-DFA, and 2,3,4-TFA was 26, 51, and 165 days, respectively, which suggested that the longer enrichment time was required with the increase of fluorine substitution. At the initial concentrations of 100-200 mg L(-1), the 4-FA, 2,4-DFA, and 2,3,4-TFA could be degraded completely by the mixed bacterial culture. The maximum specific degradation rates of 4-FA, 2,4-DFA, and 2,3,4-TFA were 22.48 ± 0.55, 15.27 ± 2.04, and 8.84 ± 0.93 mg FA (g VSS h)(-1), respectively. Also, the three FAs enriched cultures showed certain potential of degrading other two FAs. The results from enzyme assay suggested the expression of meta-cleavage pathways during three FAs degradation. The denaturing gradient gel electrophoresis analysis revealed that unique bacterial communities were formed after FAs enrichment and these were principally composed of β-Proteobacteria, Oscillatoriophycideae, δ-Proteobacteria, α-Proteobacteria, Thermales, Xanthomonadales, Deinococci, Flavobacteriia, and Actinobacteridae. The Shannon-Wiener indexes in three FAs enriched culture decreased with the increase of fluorine substitution, indicating the significant effect of fluorine substitution on the microbial diversity. These findings supply important information on the fate of three FAs under aerobic environment, and the bacterial communities in their degradation systems.

Aerobic degradation of N-methyl-4-nitroaniline (MNA) by Pseudomonas sp. strain FK357 isolated from soil

N-Methyl-4-nitroaniline (MNA) is used as an additive to lower the melting temperature of energetic materials in the synthesis of insensitive explosives. Although the biotransformation of MNA under anaerobic condition has been reported, its aerobic microbial degradation has not been documented yet. A soil microcosms study showed the efficient aerobic degradation of MNA by the inhabitant soil microorganisms. An aerobic bacterium, Pseudomonas sp. strain FK357, able to utilize MNA as the sole carbon, nitrogen, and energy source, was isolated from soil microcosms. HPLC and GC-MS analysis of the samples obtained from growth and resting cell studies showed the formation of 4-nitroaniline (4-NA), 4-aminophenol (4-AP), and 1, 2, 4-benzenetriol (BT) as major metabolic intermediates in the MNA degradation pathway. Enzymatic assay carried out on cell-free lysates of MNA grown cells confirmed N-demethylation reaction is the first step of MNA degradation with the formation of 4-NA and formaldehyde products. Flavin-dependent transformation of 4-NA to 4-AP in cell extracts demonstrated that the second step of MNA degradation is a monooxygenation. Furthermore, conversion of 4-AP to BT by MNA grown cells indicates the involvement of oxidative deamination (release of NH2 substituent) reaction in third step of MNA degradation. Subsequent degradation of BT occurs by the action of benzenetriol 1, 2-dioxygenase as reported for the degradation of 4-nitrophenol. This is the first report on aerobic degradation of MNA by a single bacterium along with elucidation of metabolic pathway.

Isolation, identification and characterization of a novel Ralstonia sp. FD-1, capable of degrading 4-fluoroaniline

A gram-negative strain, designated as FD-1, isolated from aerobic activated sludge was capable of metabolizing 4-fluoroaniline (4-FA) as its sole carbon and nitrogen source and energy supply. According to the Biolog GNIII detection method 17 of 71 carbon substrates were easily utilized, while 12 of 23 substrates did not inhibit strain FD-1. The 16S rDNA sequence from strain FD-1 was 99 % similar to Ralstonia sp., suggesting that it belonged to the genus Ralstonia. The optimal conditions for growth and 4-FA degradation were pH 7 and 30 °C. The tolerance to 4-FA were 1,250 mg/L, while the tolerance to salinity was 15 g/L. Catechol 2,3-dioxygenase activity was detected and degradation intermediates were analyzed by liquid chromatography mass spectrometry leading to a proposed degradation pathway and suggesting that extradiol cleavage was involved in 4-FA degradation. This is the first report on the degradation of 4-FA by a bacterium from the Ralstonia genus.

Metabolism of 2-chloro-4-nitroaniline via novel aerobic degradation pathway by Rhodococcus sp. strain MB-P1

2-chloro-4-nitroaniline (2-C-4-NA) is used as an intermediate in the manufacture of dyes, pharmaceuticals, corrosion inhibitor and also used in the synthesis of niclosamide, a molluscicide. It is marked as a black-listed substance due to its poor biodegradability. We report biodegradation of 2-C-4-NA and its pathway characterization by Rhodococcus sp. strain MB-P1 under aerobic conditions. The strain MB-P1 utilizes 2-C-4-NA as the sole carbon, nitrogen, and energy source. In the growth medium, the degradation of 2-C-4-NA occurs with the release of nitrite ions, chloride ions, and ammonia. During the resting cell studies, the 2-C-4-NA-induced cells of strain MB-P1 transformed 2-C-4-NA stoichiometrically to 4-amino-3-chlorophenol (4-A-3-CP), which subsequently gets transformed to 6-chlorohydroxyquinol (6-CHQ) metabolite. Enzyme assays by cell-free lysates prepared from 2-C-4-NA-induced MB-P1 cells, demonstrated that the first enzyme in the 2-C-4-NA degradation pathway is a flavin-dependent monooxygenase that catalyzes the stoichiometric removal of nitro group and production of 4-A-3-CP. Oxygen uptake studies on 4-A-3-CP and related anilines by 2-C-4-NA-induced MB-P1 cells demonstrated the involvement of aniline dioxygenase in the second step of 2-C-4-NA degradation. This is the first report showing 2-C-4-NA degradation and elucidation of corresponding metabolic pathway by an aerobic bacterium.

Carbon and nitrogen isotope effects associated with the dioxygenation of aniline and diphenylamine

Dioxygenation of aromatic rings is frequently the initial step of biodegradation of organic subsurface pollutants. This process can be tracked by compound-specific isotope analysis to assess the extent of contaminant transformation, but the corresponding isotope effects, especially for dioxygenation of N-substituted, aromatic contaminants, are not well understood. We investigated the C and N isotope fractionation associated with the biodegradation of aniline and diphenylamine using pure cultures of Burkholderia sp. strain JS667, which can biodegrade both compounds, each by a distinct dioxygenase enzyme. For diphenylamine, the C and N isotope enrichment was normal with ε(C)- and ε(N)-values of -0.6 ± 0.1‰ and -1.0 ± 0.1‰, respectively. In contrast, N isotopes of aniline were subject to substantial inverse fractionation (ε(N) of +13 ± 0.5‰), whereas the ε(C)-value was identical to that of diphenylamine. A comparison of the apparent kinetic isotope effects for aniline and diphenylamine dioxygenation with those from abiotic oxidation by manganese oxide (MnO(2)) suggest that the oxidation of a diarylamine system leads to distinct C-N bonding changes compared to aniline regardless of reaction mechanism and oxidant involved. Combined evaluation of the C and N isotope signatures of the contaminants reveals characteristic Δδ(15)N/Δδ(13)C-trends for the identification of diphenylamine and aniline oxidation in contaminated subsurfaces and for the distinction of aniline oxidation from its formation by microbial and/or abiotic reduction of nitrobenzene.

Biodegradation of aniline in an alkaline environment by a novel strain of the halophilic bacterium, Dietzia natronolimnaea JQ-AN

Dietzia natronolimnaea JQ-AN was isolated from industrial wastewater containing aniline. Under aerobic conditions, the JQ-AN strain degraded 87% of the aniline in a 300 mg L(-1) aniline solution after 120 h of shake flask incubation in a medium containing sodium acetate. This strain had an unusually high salinity tolerance in minimal medium (0-6% NaCl, w/v). The optimal pH for microbial growth and aniline biodegradation was pH 8.0. Two liters of simulated aniline wastewater was created in a reactor at pH 8.0 and 3% NaCl (w/v), and biodegradation of aniline was tested over 7 days at 30 °C. For the initial concentrations of 100, 300, and 500 mg L(-1), 100%, 80.5% and 72% of the aniline was degraded, respectively. Strain JQ-AN may use an ortho-cleavage pathway for dissimilation of the catechol intermediate.

Moraxella species are primarily responsible for generating malodor in laundry

Many people in Japan often detect an unpleasant odor generated from laundry that is hung to dry indoors or when using their already-dried laundry. Such an odor is often described as a "wet-and-dirty-dustcloth-like malodor" or an "acidic or sweaty odor." In this study, we isolated the major microorganisms associated with such a malodor, the major component of which has been identified as 4-methyl-3-hexenoic acid (4M3H). The isolates were identified as Moraxella osloensis by morphological observation and biochemical and phylogenetic tree analyses. M. osloensis has the potential to generate 4M3H in laundry. The bacterium is known to cause opportunistic infections but has never been known to generate a malodor in clothes. We found that M. osloensis exists at a high frequency in various living environments, particularly in laundry in Japan. The bacterium showed a high tolerance to desiccation and UV light irradiation, providing one of the possible reasons why they survive in laundry during and even after drying.

Biodegradation pathways of chloroanilines by Acinetobacter baylyi strain GFJ2

The Acinetobacter baylyi strain GFJ2 was isolated from soil that was potentially contaminated with herbicides. It exhibited complete biodegradations of 4-chlroaniline (4CA) and 3,4-dichloroaniline (34DCA), a wide range of monohalogenated anilines (chloro-, bromo-, and fluoro-anilines) and other dichloroanilines. An in-depth investigation of the biodegradation pathway revealed that a dechlorination reaction may be involved in 34DCA biodegradation, which forms 4CA as the first intermediate. By detecting the transient intermediates and characterizing the relevant enzymes, this investigation is also the first to report that A. baylyi strain GFJ2 has two distinct 4CA degradation pathways that yield 4-chlorocatechol (4CC) and aniline as the first intermediate in each route, which are further metabolized through an ortho-cleavage pathway. Analysis of biodegradation kinetics analysis illustrated that A. baylyi GFJ2 utilized aniline and 4CC at significantly slower rates than it used 4CA, suggesting that the transformations of aniline and 4CC were probably the limiting steps during 4CA biodegradation. Our results suggest the potential application of A. baylyi strain GFJ2 in bioremediation and waste treatment, and the kinetic data provide the insights into the degradation mechanism, dynamics and possible limitations of the biodegradation which include substrate and product inhibitions.

Identification of wastewater bacteria involved in the degradation of triclocarban and its non-chlorinated congener

Triclocarban (TCC) is an antimicrobial additive of personal care products that is only partially degraded during wastewater treatment. Bacteria responsible for its transformation are unknown. We obtained wastewater bacteria capable of using as the sole carbon source TCC or its non-chlorinated analog, carbanilide (NCC). Enrichments established using activated sludge amended with TCC and NCC, respectively, were maintained for 1 year through successive transfers. Enrichments displayed exponential growth after 2 weeks, reaching stationary phase after 1 month. The NCC enrichment was shown to accumulate aniline. Denaturing gradient gel electrophoresis of amplified 16S rRNA genes indicated markedly reduced community richness compared to the inoculum and a single, prominent taxonomic unit emerged in both chlorinated and non-chlorinated carbanilide enrichment cultures. Cloned 16S rRNA genes showed both enrichments were dominated by a single genotype related to uncharacterized organisms within the Alcaligenaceae. Of ∼30 sequences from each enrichment, no other organisms were detected in the TCC enrichment while, a small, flanking community of alpha proteobacteria was detected in the NCC enrichment. Study results demonstrate that growth of wastewater bacteria on TCC and its lower chlorinated analog can be linked to bacteria within the family Alcaligenaceae. These organisms are promising agents for the bioremediation of hazardous phenylurea pollutants.

Biodegradation of 2-chloroaniline, 3-chloroaniline, and 4-chloroaniline by a novel strain Delftia tsuruhatensis H1

A new strain Delftia tsuruhatensis H1 able to degrade several chloroanilines (CAs) as individual compounds or a mixture was isolated from a CA-degrading mixed bacterial culture. The isolated strain could completely degrade 3-CA and 4-CA as growth substrates, while concurrently metabolize 2-CA by growing on other CA compounds. The strain could also efficiently degrade all the three CA components when presented as a mixture. Following CA consumption, stoichiometric amounts of chloride were released and small amount of soluble metabolites accumulated in the medium, indicating that the loss of CA was mainly via mineralization and incorporation into cell material. The additions of yeast extract, citrate or succinate appeared to accelerate CA degradation. In contrast, aniline strongly inhibited the CA degradation. The strain H1 could also decompose other substituted aniline compounds such as 3,4-dichloroaniline, 4-methylaniline, 2,3-dichloroaniline and 2,4-dichloroaniline. The elimination of these CA compounds seemed to occur via an ortho-cleavage pathway.

Characterization of a Pseudomonas sp. Capable of Aniline Degradation in the Presence of Secondary Carbon Sources

Pseudomonas strain K1 is a gram-negative rod which grows aerobically on minimal media containing aniline with a doubling time of 2 h at 30 degrees C. The half-saturation parameter for aniline metabolism by aniline-grown cells was 3.8 mumol . liter. Concentrations of aniline as low as 50 nM were metabolized. Neither substituted anilines nor other aromatic compounds (other than aromatic amino acids) supported growth. Cells grew as fast on aniline as on nonaromatic substrates such as lactate. The aromatic ring was cleaved via the meta pathway. Catechol 2,3-oxygenase activity was induced by aniline, even in cultures containing alternative carbon sources such as lactate. Cultures grown on a mixture of aniline and lactate mineralized aniline in the presence of the second substrate. Lactate-grown cultures lacked catechol oxygenase activity, and resting cells from these cultures did not respire aniline. Resting cells from aniline-grown cultures exhibited high respiratory activity upon the addition of aniline or catechol, some activity with toluidine, and no activity after addition of a wide variety of other aromatic compounds, including dihydroxybenzylamine, chloroanilines, ethylanilines, aminophenols, aminobenzoates, and dihydroxybenzoates. Although substituted anilines were not metabolized, 3-or 4-chloroaniline did induce the enzymes for aniline oxidation.

Degradation of o-chloronitrobenzene as the sole carbon and nitrogen sources by Pseudomonas putida OCNB-1

A bacterial strain that utilized o-chloronitrobenzene (o-CNB) as the sole carbon, nitrogen and energy sources was isolated from an activated sludge collected from an industrial waste treatment plant. It was identified as Pseudomonas putida based on its morphology, physiological, and biochemical characteristics with an automatic biometrical system and the 16S rRNA sequence analysis. Microcosm study showed that the biodegradation of o-CNB was optimized at culture medium pH 8.0 and 32 degrees C. At these conditions, the strain degraded 85% of o-CNB at a starting concentration of 1.1 mmol/L in 42 h. o-Chloroaniline was identified as the major metabolite with high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The study showed that o-CNB degradation by Pseudomonas putida OCNB-1 was initiated by aniline dioxyenase, nitrobenzene reductase and catechol-1,2-dioxygenase.

Isolation and characterization of aniline-degrading Rhodococcus sp. strain AN5

A pure culture using aniline as a sole source of carbon and energy was isolated by selective enrichment culturing on a minimum salt medium (MSM) from the Nanjing Chemical Plant, Nanjing, Jiangsu Province, China. An analysis of the 16S rRNA gene sequence and morphological and physiological characteristics showed that this strain was a member of the genus Rhodococcus, and it was designated as strain AN5. Its optimal conditions for aniline biodegradation were 30 degrees C (pH 7.0). Due to the water insolubility of aniline, growth of strain AN5 at various aniline concentrations was studied via spectrophotometry and microcalorimetry in different culture mediums. Strain AN5 not only utilized aniline as its sole carbon and energy resources, but also degraded phenol, benzoic acid and naphthalin. Glucose, peptone and ammonium sulfate, when utilized as its secondary carbon and nitrogen sources, had no active effect on the aniline biodegradation. Such findings would be valuable in the application of strain AN5 to depurate industrial waste water.

Biodegradation of 4-chloroaniline by bacteria enriched from soil

4-Chloroaniline has been released into the environment due to extensive use in chemical industries and intensive agriculture; hence, it becomes one of the hazardous pollutants in the priority pollutant list. In this study, three gram-negative bacteria were enriched and isolated from agricultural soil as 4-chloroaniline-degrading bacteria. They were identified as Acinetobacter baumannii CA2, Pseudomonas putida CA16 and Klebsiella sp. CA17. They were able to utilize 4-chloroaniline as a sole carbon and nitrogen source without stimulation or cocultivation with aniline or another cosubstrate. The biodegradation in these bacteria was occurred via a modified ortho-cleavage pathway of which the activity of chlorocatechol 1, 2-dioxygenase was markedly induced. They grew well on 0.2-mM 4-chloroaniline exhibiting a 60-75% degradation efficiency and equimolar liberation of chloride. The isolates were able to survive in the presence of 4-chloroaniline at higher concentrations (up to 1.2 mM). 2-Chloroaniline, 3-chloroaniline and aniline, but not 3, 4-dichloroaniline, were also growth substrates for these isolates. The results of cosubstrate supplementation illustrated the suitable conditions of each isolate to improve growth rate and 4-chloroaniline biodegradation efficiency. These results suggest that these isolates have a potential use for bioremediation of the site contaminated with 4-chloroaniline.

Microbial transformation of aniline derivatives: regioselective biotransformation and detoxification of 2-phenylenediamine by Bacillus cereus strain PDa-1

A bacterial isolate, strain PDa-1, grew well on basal medium supplemented with 2-phenylenediamine, sucrose, and ammonium nitrate and completely transformed 2-phenylenediamine. The isolate was identified as Bacillus cereus. The product formed from 2-phenylenediamine was identified by EI-MS and NMR as 2-aminoacetanilide; whole cells converted 2-phenylenediamine to the product with a 76% molar yield. Whole cells also showed a broad substrate specificity toward 20 of 26 tested arylamines with substituent groups of various size and positions. Especially 2-aminobenzoic acid, 4-aminosalicylic acid, 5-aminosalicylic acid, and 2-aminofluorene were converted completely to the corresponding product with an aminoacetyl group. Cell extracts of strain PDa-1 had a high arylamine N-acetyltransferase activity. The partially purified enzyme converted 2-phenylenediamine to 2-aminoacetanilide. Strain PDa-1 constitutively expressed the enzyme in the absence of 2-phenylenediamine. Effects of 2-phenylenediamine and 2-aminoacetanilide on growth indicated that this enzyme probably plays a role in the detoxification of toxic arylamines in this strain.

Chromosome-encoded gene cluster for the metabolic pathway that converts aniline to TCA-cycle intermediates in Delftia tsuruhatensis AD9

Delftia tsuruhatensis AD9 was isolated as an aniline-degrading bacterium from the soil surrounding a textile dyeing plant. The gene cluster involved in aniline degradation was cloned from the total DNA of strain AD9 into Escherichia coli JM109. After shotgun cloning, two recombinant E. coli strains showing aniline oxidation activity or catechol meta-cleavage activity were obtained by simple plate assays. These strains contained 9.3 kb and 15.4 kb DNA fragments, respectively. Sequence analysis of the total 24.7 kb region revealed that this region contains a gene cluster (consisting of at least 17 genes, named tadQTA1A2BRD1C1D2C2EFGIJKL) responsible for the complete metabolism of aniline to TCA-cycle intermediates. In the gene cluster, the first five genes (tadQTA1A2B) and the subsequent gene (tadR) were predicted to encode a multi-component aniline dioxygenase and a LysR-type regulator, respectively, while the others (tadD1C1D2C2EFGIJKL) were expected to encode meta-cleavage pathway enzymes for catechol degradation. In addition, it was found that the gene cluster is surrounded by two IS1071 sequences, indicating that it has a class I transposon-like structure. PFGE and Southern hybridization analyses confirmed that the tad gene cluster is encoded on the chromosome of strain AD9 in a single copy. These results suggest that, in strain AD9, aniline is degraded via catechol through a meta-cleavage pathway by the chromosome-encoded tad gene cluster. The tad gene cluster showed significant similarity in nucleotide sequence and genetic organization to the plasmid-encoded aniline degradation gene cluster of Pseudomonas putida UCC22.