A defining feature of mycobacterial redox metabolism is the use of an unusual deazaflavin cofactor, F420 This cofactor enhances the persistence of environmental and pathogenic mycobacteria, including ...after antimicrobial treatment, although the molecular basis for this remains to be understood. In this work, we explored our hypothesis that F420 enhances persistence by serving as a cofactor in antimicrobial-detoxifying enzymes. To test this, we performed a series of phenotypic, biochemical, and analytical chemistry studies in relation to the model soil bacterium Mycobacterium smegmatis Mutant strains unable to synthesize or reduce F420 were found to be more susceptible to a wide range of antibiotic and xenobiotic compounds. Compounds from three classes of antimicrobial compounds traditionally resisted by mycobacteria inhibited the growth of F420 mutant strains at subnanomolar concentrations, namely, furanocoumarins (e.g., methoxsalen), arylmethanes (e.g., malachite green), and quinone analogues (e.g., menadione). We demonstrated that promiscuous F420H2-dependent reductases directly reduce these compounds by a mechanism consistent with hydride transfer. Moreover, M. smegmatis strains unable to make F420H2 lost the capacity to reduce and detoxify representatives of the furanocoumarin and arylmethane compound classes in whole-cell assays. In contrast, mutant strains were only slightly more susceptible to clinical antimycobacterials, and this appeared to be due to indirect effects of F420 loss of function (e.g., redox imbalance) rather than loss of a detoxification system. Together, these data show that F420 enhances antimicrobial resistance in mycobacteria and suggest that one function of the F420H2-dependent reductases is to broaden the range of natural products that mycobacteria and possibly other environmental actinobacteria can reductively detoxify.IMPORTANCE This study reveals that a unique microbial cofactor, F420, is critical for antimicrobial resistance in the environmental actinobacterium Mycobacterium smegmatis We show that a superfamily of redox enzymes, the F420H2-dependent reductases, can reduce diverse antimicrobials in vitro and in vivoM. smegmatis strains unable to make or reduce F420 become sensitive to inhibition by these antimicrobial compounds. This suggests that mycobacteria have harnessed the unique properties of F420 to reduce structurally diverse antimicrobials as part of the antibiotic arms race. The F420H2-dependent reductases that facilitate this process represent a new class of antimicrobial-detoxifying enzymes with potential applications in bioremediation and biocatalysis.
There is a well-established paradigm for degradation of protocatechuic acid via the β-ketoadipate pathway in a range of soil bacteria. In this study, we have found the existence of a second pathway ...for degradation of protocatechuic acid in
Rhodococcus jostii
RHA1, via hydroxyquinol (benzene-1,2,4-triol), which establishes a metabolic link between protocatechuic acid and hydroxyquinol. The presence of this pathway in a lignin-degrading
Agrobacterium
sp. strain suggests the involvement of the hydroxyquinol pathway in the metabolism of degraded lignin fragments.
Deletion of the
pcaHG
genes, encoding protocatechuate 3,4-dioxygenase in
Rhodococcus jostii
RHA1, gives a gene deletion strain still able to grow on protocatechuic acid as the sole carbon source, indicating a second degradation pathway for protocatechuic acid. Metabolite analysis of wild-type
R. jostii
RHA1 grown on medium containing vanillin or protocatechuic acid indicated the formation of hydroxyquinol (benzene-1,2,4-triol) as a downstream product. Gene cluster ro01857-ro01860 in
Rhodococcus jostii
RHA1 contains genes encoding hydroxyquinol 1,2-dioxygenase and maleylacetate reductase for degradation of hydroxyquinol but also putative mono-oxygenase (ro01860) and putative decarboxylase (ro01859) genes, and a similar gene cluster is found in the genome of lignin-degrading
Agrobacterium
species. Recombinant
R. jostii
mono-oxygenase and decarboxylase enzymes in combination were found to convert protocatechuic acid to hydroxyquinol. Hence, an alternative pathway for degradation of protocatechuic acid via oxidative decarboxylation to hydroxyquinol is proposed.
IMPORTANCE
There is a well-established paradigm for degradation of protocatechuic acid via the β-ketoadipate pathway in a range of soil bacteria. In this study, we have found the existence of a second pathway for degradation of protocatechuic acid in
Rhodococcus jostii
RHA1, via hydroxyquinol (benzene-1,2,4-triol), which establishes a metabolic link between protocatechuic acid and hydroxyquinol. The presence of this pathway in a lignin-degrading
Agrobacterium
sp. strain suggests the involvement of the hydroxyquinol pathway in the metabolism of degraded lignin fragments.
Polyethylene terephthalate (PET) is a plastic material that is widely used in beverage bottles, food packaging, and other consumer products, which is highly resistant to biodegradation. In this ...study, we investigated the effects of two insect gut symbionts, Xanthomonas sp. HY-74 and Bacillus sp. HY-75, during PET biodegradation. Both strains degraded PET-containing agar plates, and the sole nutrition source assay showed that HY-74 had different degradation rates depending on the presence of specific carbon and nitrogen sources, whereas HY-75 exhibited comparable degradation across all tested conditions. The two strains biodegraded the PET film with 1.57 ± 0.21% and 1.42 ± 0.46% weight loss after 6 weeks, respectively. Changes in the morphology and structure of the PET films, such as erosion, scratching, and surface roughening, were determined using scanning electron microscopy (SEM). Further, the two strains biodegraded PET powder, broke it into its degradation products, and changed the surface functional groups. This is the first study to investigate the biodegradation of PET by Hymenoptera gut-derived microbes and offers promising insights into the potential applications of insect gut symbionts in PET waste management.
Biodegradable polymers have been strongly recognized as an alternative to replace traditional petrochemical plastics, which have become a global problem due to their long persistence in the ...environment. In this work, the effect of the addition of titanium dioxide nanoparticles (TiOsub.2NP) on the morphology, physicochemical properties and biodegradation under industrial composting conditions of cassava starch-based nanocomposites obtained by extrusion at different screw speeds (80 and 120 rpm) were investigated. Films performed at 120 rpm (Ssub.120 and Ssub.120-TiOsub.2NP) showed completely processed starch and homogeneously distributed nanoparticles, leading to much more flexible nanocomposites than those obtained at 80 rpm. The incorporation of TiOsub.2NP led to an increase in storage modulus of all films and, in the case of Ssub.120-TiOsub.2NP, to higher strain at break values. From the Kohlrausch-Williams-Watts theoretical model (KWW), an increase in the relaxation time of the nanocomposites was observed due to a decrease in the number of polymer chains involved in the relaxation process. Additionally, Ssub.120-TiOsub.2NP showed effective protection against UV light, greater hydrophobicity and faster biodegradation in compost, resulting in a promising material for food packaging applications.
In the work described here, a two-layer biotrickling filter filled with new packing materials was used to remove H...S from air. The upper layer of the filter was packed with activated carbon-loaded ...polyurethane, whereas the lower layer was filled with modified organism-suspended fillers. The effects of inlet load, empty bed residence time (EBRT) from 79 s to 53 s, pH and contaminant starvation time were investigated. For loads of 15-50 g/(m... h), the average removal efficiency (RE) was higher than 96% under a consistent supply of pollutants. The critical elimination capacity was 39.95 g/(m... h) for an EBRT of 53 s with an RE of 99.9%. The two-layer BTF was capable of withstanding contaminant starvation periods for 1.5 d and 7 d with only a few hours of recovery time. The biodegradation kinetics was studied using Michaelis-Menten type equations under different EBRTs. At an EBRT of 66 s, the optimal kinetic constants r... and K... were 333.3 g/(m... h) and 0.93 g/m..., respectively. During the operation, the two-layer BTF performed well under various reasonable conditions. (ProQuest: ... denotes formulae/symbols omitted.) All rights reserved, Elsevier
Anaerobic biodegradation of toxic compounds found in industrial wastewater is an attractive solution allowing the recovery of energy and resources but it is still challenging due to the low kinetics ...making the anaerobic process not competitive against the aerobic one. In this review, we summarise the present state of knowledge on the anaerobic biodegradation process for phenol, a typical target compound employed in toxicity studies on industrial wastewater treatment. The objective of this article is to provide an overview on the microbiological and technological aspects of anaerobic phenol degradation and on the research needs to fill the gaps still hindering the diffusion of the anaerobic process. The first part is focused on the microbiology and extensively presents and characterises phenol-degrading bacteria and biodegradation pathways. In the second part, dedicated to process feasibility, anaerobic and aerobic biodegradation kinetics are analysed and compared, and strategies to enhance process performance, i.e. advanced technologies, bioaugmentation, and biostimulation, are critically analysed and discussed. The final section provides a summary of the research needs. Literature data analysis shows the feasibility of anaerobic phenol biodegradation at laboratory and pilot scale, but there is still a consistent gap between achieved aerobic and anaerobic performance. This is why current research demand is mainly related to the development and optimisation of powerful technologies and effective operation strategies able to enhance the competitiveness of the anaerobic process. Research efforts are strongly justified because the anaerobic process is a step forward to a more sustainable approach in wastewater treatment.
Key points
•
Review of phenol-degraders bacteria and biodegradation pathways.
•
Anaerobic phenol biodegradation kinetics for metabolic and co-metabolic processes.
•
Microbial and technological strategies to enhance process performance.
Graphical abstract
Biodiversity in Dead Wood Stokland, Jogeir N; Siitonen, Juha; Jonsson, Bengt Gunnar
04/2012
eBook, Book
Fossils document the existence of trees and wood-associated organisms from almost 400 million years ago, and today there are between 400,000 and 1 million wood-inhabiting species in the world. This ...is the first book to synthesise the natural history and conservation needs of wood-inhabiting organisms. Presenting a thorough introduction to biodiversity in decaying wood, the book studies the rich diversity of fungi, insects and vertebrates that depend upon dead wood. It describes the functional diversity of these organisms and their specific habitat requirements in terms of host trees, decay phases, tree dimensions, microhabitats and the surrounding environment. Recognising the threats posed by timber extraction and forest management, the authors also present management options for protecting and maintaining the diversity of these species in forests as well as in agricultural landscapes and urban parks.
RATIONALE As a by-product of oil sands extraction, large volumes of oil sands process water (OSPW) are generated, which are contaminated with a large range of water-soluble organic compounds. The ...acids are thought to be derived from hydrocarbons via natural biodegradation pathways such as alpha- and beta-oxidation of alkyl substituents, which could produce mono- and diacids, for example. However, while several monoacids ('O sub(2)' species) have been identified, the presence of diacids (i.e. 'O sub(4)' species) has only been deduced from results obtained via Fourier transform infrared (FTIR) spectroscopy, Fourier transform ion cyclotron resonance high-resolution mass spectrometry (FTICR-HRMS) and nuclear magnetic resonance ( super(1)H-NMR) spectroscopy and the structures have never been confirmed. METHODS An extract of an OSPW from a Canadian tailings pond was analysed and the retention times and the electron ionization mass spectra of some analytes were compared with those of bis-methyl esters of authentic diacids by gas chromatographygas chromatography/time-of-flight mass spectrometry (GCxGC/TOFMS) in nominal and accurate mass configurations. RESULTS Two diamondoid diacids (3-carboxymethyladamantane-1-carboxylic acid and adamantane-1,3-dicarboxylic acid) were firmly identified as their bis-methyl esters by retention time and mass spectral matching and several other structural isomers were more tentatively assigned. Diacids have substantially increased polarity over the hydrocarbon and monoacid species from which they probably derive: as late members of biodegradation processes they may be useful indicators of weathering and ageing, not only of OSPW, but potentially of crude oil residues more generally. CONCLUSIONS Structures of O sub(4) species in OSPW have been identified. This confirms pathways of microbial biodegradation, which were only postulated previously, and may be a further indication that remediation of OSPW toxicity can occur by natural microbial action. The presence and abundance of these diacids might therefore be useful as a measure of biodegradation and weathering. Copyright copy 2013 John Wiley & Sons, Ltd.
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