Purification and characterization of hydroquinone dioxygenase from Sphingomonas sp. strain TTNP3

Hydroquinone-1,2-dioxygenase, an enzyme involved in the degradation of alkylphenols in Sphingomonas sp. strain TTNP3 was purified to apparent homogeneity. The extradiol dioxygenase catalyzed the ring fission of hydroquinone to 4-hydroxymuconic semialdehyde and the degradation of chlorinated and several alkylated hydroquinones. The activity of 1 mg of the purified enzyme with unsubstituted hydroquinone was 6.1 μmol per minute, the apparent Km 2.2 μM. ICP-MS analysis revealed an iron content of 1.4 moles per mole enzyme. The enzyme lost activity upon exposure to oxygen, but could be reactivated by Fe(II) in presence of ascorbate. SDS-PAGE analysis of the purified enzyme yielded two bands of an apparent size of 38 kDa and 19 kDa, respectively. Data from MALDI-TOF analyses of peptides of the respective bands matched with the deduced amino acid sequences of two neighboring open reading frames found in genomic DNA of Sphingomonas sp strain TTNP3. The deduced amino acid sequences showed 62% and 47% identity to the large and small subunit of hydroquinone dioxygenase from Pseudomonas fluorescens strain ACB, respectively. This heterotetrameric enzyme is the first of its kind found in a strain of the genus Sphingomonas sensu latu

Living with sulfonamides: a diverse range of mechanisms observed in bacteria

Sulfonamides are the oldest class of synthetic antibiotics still in use in clinical and veterinary settings. The intensive utilization of sulfonamides has been leading to the widespread contamination of the environment with these xenobiotic compounds. Consequently, in addition to pathogens and commensals, also bacteria inhabiting a wide diversity of environmental compartments have been in contact with sulfonamides for almost 90 years. This review aims at giving an overview of the effect of sulfonamides on bacterial cells, including the strategies used by bacteria to cope with these bacteriostatic agents. These include mechanisms of antibiotic resistance, co-metabolic transformation, and partial or total mineralization of sulfonamides. Possible implications of these mechanisms on the ecosystems and dissemination of antibiotic resistance are also discussed.info:eu-repo/semantics/publishedVersio

In-situ recovery of carboxylic acids from fermentation broths through membrane supported reactive extraction using membrane modules with improved stability

Membrane supported reactive extraction (MSE) coupled to back-extraction (MSBE) using a new type of Teflon (PTFE) capillary membrane contactor was studied for the in-situ removal of carboxylic acids from aqueous streams, e.g. fermentation broths. The use of microporous membranes as extraction interface helps avoiding emulsification problems, allows the use of extreme phase ratios, and protects microorganisms, as they are less affected by solvent toxicity during in-situ extractions. The use of PTFE capillary membranes is suitable for long-term use due its high chemical and thermal stability. A simple toxicity screening identified n-decanol with tri n-octyl amine (TOA) as a suitable solvent. MSE experiments were performed using membrane contactors (0.005 m2 to 0.15 m2), working with solvent to feed phase ratios down to 1:40 (mass based). The in-situ removal of lactic acid out of fermentation broths using lactobacillus plantarum led to a glucose conversion rate of 80 mol%. Additionally, a concentration factor up to 7.8 could be shown during back-extraction

Biotransformation of Sulfonamide Antibiotics in Activated Sludge: The Formation of Pterin-Conjugates Leads to Sustained Risk

The presence of antibiotics in treated wastewater and consequently in surface and groundwater resources raises concerns about the formation and spread of antibiotic resistance. Improving the removal of antibiotics during wastewater treatment therefore is a prime objective of environmental engineering. Here we obtained a detailed picture of the fate of sulfonamide antibiotics during activated sludge treatment using a combination of analytical methods. We show that pterin-sulfonamide conjugates, which are formed when sulfonamides interact with their target enzyme to inhibit folic acid synthesis, represent a major biotransformation route for sulfonamides in laboratory batch experiments with activated sludge. The same major conjugates were also present in the effluents of nine Swiss wastewater treatment plants. The demonstration of this biotransformation route, which is removal. related to bacterial growth, helps explain seemingly contradictory views on optimal conditions for sulfonamide More importantly, since pterin-sulfonamide conjugates show retained antibiotic activity, our findings suggest that risk from exposure to sulfonamide antibiotics may be less reduced during wastewater treatment than previously assumed. Our results thus further emphasize the inadequacy of focusing on parent compound removal and the importance of investigating biotransformation pathways and removal of bioactivity to properly assess contaminant removal in both engineered and natural systems

Comparative genomics reveals a novel genetic organization of the sad cluster in the sulfonamide-degrader 'Candidatus Leucobacter sulfamidivorax' strain GP

Microbial communities recurrently establish metabolic associations resulting in increased fitness and ability to perform complex tasks, such as xenobiotic degradation. In a previous study, we have described a sulfonamide-degrading consortium consisting of a novel low-abundant actinobacterium, named strain GP, and Achromobacter denitrificans PR1. However, we found that strain GP was unable to grow independently and could not be further purified.; Previous studies suggested that strain GP might represent a new putative species within the Leucobacter genus (16S rRNA gene similarity < 97%). In this study, we found that average nucleotide identity (ANI) with other Leucobacter spp. ranged between 76.8 and 82.1%, further corroborating the affiliation of strain GP to a new provisional species. The average amino acid identity (AAI) and percentage of conserved genes (POCP) values were near the lower edge of the genus delimitation thresholds (65 and 55%, respectively). Phylogenetic analysis of core genes between strain GP and Leucobacter spp. corroborated these findings. Comparative genomic analysis indicates that strain GP may have lost genes related to tetrapyrrole biosynthesis and thiol transporters, both crucial for the correct assembly of cytochromes and aerobic growth. However, supplying exogenous heme and catalase was insufficient to abolish the dependent phenotype. The actinobacterium harbors at least two copies of a novel genetic element containing a sulfonamide monooxygenase (sadA) flanked by a single IS1380 family transposase. Additionally, two homologs of sadB (4-aminophenol monooxygenase) were identified in the metagenome-assembled draft genome of strain GP, but these were not located in the vicinity of sadA nor of mobile or integrative elements.; Comparative genomics of the genus Leucobacter suggested the absence of some genes encoding for important metabolic traits in strain GP. Nevertheless, although media and culture conditions were tailored to supply its potential metabolic needs, these conditions were insufficient to isolate the PR1-dependent actinobacterium further. This study gives important insights regarding strain GP metabolism; however, gene expression and functional studies are necessary to characterize and further isolate strain GP. Based on our data, we propose to classify strain GP in a provisional new species within the genus Leucobacter, 'Candidatus Leucobacter sulfamidivorax'

Biodegradation of sulfamethoxazole and other sulfonamides by Achromobacter denitrificans PR1

This study aimed to isolate and characterize a microbial culture able to degrade sulfonamides. Sul-famethoxazole (SMX)-degrading microorganisms were enriched from activated sludge and wastewater.The resultant mixed culture was composed of four bacterial strains, out of which only Achromobacterdenitrificans PR1 could degrade SMX. This sulfonamide was used as sole source of carbon, nitrogen andenergy with stoichiometric accumulation of 3-amino-5-methylisoxazole. Strain PR1 was able to removeSMX at a rate of 73.6 ± 9.6 molSMX/gcell dry weighth. This rate more than doubled when a supplement ofamino acids or the other members of the mixed culture were added. Besides SMX, strain PR1 was able todegrade other sulfonamides with anti-microbial activity. Other environmental Achromobacter spp. couldnot degrade SMX, suggesting that this property is not broadly distributed in members of this genus.Further studies are needed to shed additional light on the genetics and enzymology of this process.info:eu-repo/semantics/publishedVersio

Biodeterioration Affecting Efficiency and Lifetime of Plastic-Based Photovoltaics

The low environmental impact of electricity generation using solar cells crucially depends on high energy-conversion efficiencies, long lifetimes, and a minimal energy and material demand during production. Emerging thin-film photovoltaics such as perovskites on plastic substrates could hold promises to fulfill all these requirements. Under real-world operating conditions, photovoltaic operation is challenged by biological stressors, which have not been incorporated for evaluation in any test. Such stressors cause biodeterioration, which impairs diverse, apparently inert materials such as rock, glass, and steel and therefore could significantly affect the function and stability of plastic-based solar cells. Given that different photovoltaic technologies commonly use similar materials, the biodeterioration mechanisms reviewed here may possibly affect the efficiency and lifetimes of several technologies if they occur sufficiently faster (during the expected lifetime of photovoltaics). Once the physical integrity of uppermost module layers is challenged by biofilm growth, microbially mediated dissolution and precipitation reactions of photovoltaic functional materials are very likely to occur. The biodeterioration of substrates and seals also represents emission points for the release of potentially harmful photovoltaic constituents to the environment. Upon exposure to the natural environment, not even diamonds are forever. In real-world operating conditions, photovoltaics are affected by biodeterioration through biofilm growth that impairs diverse, apparently inert materials, such as rock, glass, and steel. Biodeterioration goes beyond obstructing incoming light and affecting energy conversion; it challenges the physical integrity of substrates. This phenomenon may thus heavily degrade primarily plastic-based thin-film photovoltaics. Following initial degradation, functional layers can undergo microbially mediated dissolution and precipitation, thereby affecting the lifetimes of such solar cells. Biofilm development also influences how potentially harmful photovoltaic constituents (e.g., lead from perovskites) are released to the environment. Despite the considerable potentiality of these detrimental effects, however, they are yet to be systematically studied. Given that different types of solar cells commonly use similar materials, the biodeterioration mechanisms reviewed here may affect several technologies. This paper provides a comprehensive review of the colonization of photovoltaics by sub-aerial biofilms and their potential negative impacts on photovoltaics. We discuss why abiotic laboratory tests for PV efficiency and lifetime poorly reflect the stress PVs suffer in outdoor conditions. We then summarize the knowledge on soiling as well as microbial-, algal-, and fungal growth on PVs. This is followed by a discussion of the physical mechanisms that affect PV efficiency via soiling and photon competition as well as chemical and biological mechanisms (plastic degradation, microbially induced dissolution, and precipitation reactions) that can affect active layers and thus the lifetime of PVs in the field. Solar cells are subjected to various physical, chemical, and biological stressors in the field. Here, a perspective on the potential detrimental effects of biofilm growth on solar cells is given. Soiling and photon competition affect the photovoltaic performance of all cells, while a suite of biochemical mechanisms (“biodeterioration”) may affect the efficiency and lifetime of plastic-based solar cells in particular. Further, biodeterioration might provide a pathway for the entry of harmful solar cell components to the environment.</p

Arsenic mobilization from historically contaminated mining soils in a continuously operated bioreactor : Implications for risk assessment

Concentrations of soil arsenic (As) in the vicinity of the former Złoty Stok gold mine (Lower Silesia, southwest Poland) exceed 1000 μg g-1 in the area, posing an inherent threat to neighboring bodies of water. This study investigated continuous As mobilization under reducing conditions for more than 3 months. In particular, the capacity of autochthonic microflora that live on natural organic matter as the sole carbon/electron source for mobilizing As was assessed. A biphasic mobilization of As was observed. In the first two months, As mobilization was mainly conferred by Mn dissolution despite the prevalence of Fe (0.1 wt % vs 5.4 for Mn and Fe, respectively) as indicated by multiple regression analysis. Thereafter, the sudden increase in aqueous As[III] (up to 2400 μg L-1) was attributed to an almost quintupling of the autochthonic dissimilatory As-reducing community (quantitative polymerase chain reaction). The aqueous speciation influenced by microbial activity led to a reduction of solid phase As species (X-ray absorption fine structure spectroscopy) and a change in the elemental composition of As hotspots (micro X-ray fluorescence mapping). The depletion of most natural dissolved organic matter and the fact that an extensive mobilization of As[III] occurred after two months raises concerns about the long-term stability of historically As-contaminated sites.</p