- Extensive loss of cell-cycle and DNA repair genes in an ancient lineage of bipolar budding yeasts. [Journal Article]
- PBPLoS Biol 2019; 17(5):e3000255
- Cell-cycle checkpoints and DNA repair processes protect organisms from potentially lethal mutational damage. Compared to other budding yeasts in the subphylum Saccharomycotina, we noticed that a line…
Cell-cycle checkpoints and DNA repair processes protect organisms from potentially lethal mutational damage. Compared to other budding yeasts in the subphylum Saccharomycotina, we noticed that a lineage in the genus Hanseniaspora exhibited very high evolutionary rates, low Guanine-Cytosine (GC) content, small genome sizes, and lower gene numbers. To better understand Hanseniaspora evolution, we analyzed 25 genomes, including 11 newly sequenced, representing 18/21 known species in the genus. Our phylogenomic analyses identify two Hanseniaspora lineages, a faster-evolving lineage (FEL), which began diversifying approximately 87 million years ago (mya), and a slower-evolving lineage (SEL), which began diversifying approximately 54 mya. Remarkably, both lineages lost genes associated with the cell cycle and genome integrity, but these losses were greater in the FEL. E.g., all species lost the cell-cycle regulator WHIskey 5 (WHI5), and the FEL lost components of the spindle checkpoint pathway (e.g., Mitotic Arrest-Deficient 1 [MAD1], Mitotic Arrest-Deficient 2 [MAD2]) and DNA-damage-checkpoint pathway (e.g., Mitosis Entry Checkpoint 3 [MEC3], RADiation sensitive 9 [RAD9]). Similarly, both lineages lost genes involved in DNA repair pathways, including the DNA glycosylase gene 3-MethylAdenine DNA Glycosylase 1 (MAG1), which is part of the base-excision repair pathway, and the DNA photolyase gene PHotoreactivation Repair deficient 1 (PHR1), which is involved in pyrimidine dimer repair. Strikingly, the FEL lost 33 additional genes, including polymerases (i.e., POLymerase 4 [POL4] and POL32) and telomere-associated genes (e.g., Repressor/activator site binding protein-Interacting Factor 1 [RIF1], Replication Factor A 3 [RFA3], Cell Division Cycle 13 [CDC13], Pbp1p Binding Protein [PBP2]). Echoing these losses, molecular evolutionary analyses reveal that, compared to the SEL, the FEL stem lineage underwent a burst of accelerated evolution, which resulted in greater mutational loads, homopolymer instabilities, and higher fractions of mutations associated with the common endogenously damaged base, 8-oxoguanine. We conclude that Hanseniaspora is an ancient lineage that has diversified and thrived, despite lacking many otherwise highly conserved cell-cycle and genome integrity genes and pathways, and may represent a novel, to our knowledge, system for studying cellular life without them.
- Comparison of the performance of pulsed and continuous UVC-LED irradiation in the inactivation of bacteria. [Journal Article]
- WRWater Res 2019 Jun 15; 157:218-227
- Ultraviolet light-emitting diode (UV-LED) is a newly emerging UV light source with a potential to replace the conventional chemical methods, mercury UV lamps and xenon lamps in water disinfection. UV…
Ultraviolet light-emitting diode (UV-LED) is a newly emerging UV light source with a potential to replace the conventional chemical methods, mercury UV lamps and xenon lamps in water disinfection. UV-LEDs are characterized by the diversity in wavelengths and can be turned on and off with a high and adjustable frequency, making them an attractive candidate for pulsed light (PL) disinfection apart from the conventional continuous wave (CW) operation. Previous studies on comparison between the PL and CW UV-LED irradiations for the inactivation of bacterium in water disinfection are limited and results conflict. In this work, PL and CW UV-LED in the C-spectral band (UVC-LED) irradiations were compared at equivalent fluence in the inactivation and subsequent photoreactivation of E. coli bacteria. In addition, effect of different driving currents and ambient temperatures on solder temperature of the PL and CW UVC-LED irradiation was also examined. Under the equivalent fluences, the PL and CW UVC-LED irradiations brought comparable inactivation efficiency and similar photoreactivation of the E. coli. Moreover, the PL UVC-LED exhibited a much lower solder temperature than the CW UVC-LED irradiation. On the other hand, CW UVC-LED irradiation, higher ambient temperature and higher driving current increased the solder temperature that resulted to a negative impact on the wavelength, full width at half maximum, optical power and irradiance, which are key factors in the UVC-LED disinfection efficiency. In all, this work reports the comparison between PL and CW in UVC-LED irradiation for inactivating E. coli bacteria and firstly revealed the photoreactivation of the E. coli after the PL UVC-LEDs irradiation.
- Microorganisms inactivation by wavelength combinations of ultraviolet light-emitting diodes (UV-LEDs). [Journal Article]
- STSci Total Environ 2019 May 15; 665:1103-1110
- Ultraviolet light-emitting diode (UV-LED) is an emerging UV source with many special features due to the nature of semiconductor devices. One such feature is wavelength diversity that does not exist …
Ultraviolet light-emitting diode (UV-LED) is an emerging UV source with many special features due to the nature of semiconductor devices. One such feature is wavelength diversity that does not exist in conventional mercury based UV lamps, which provides opportunities to selectively combine multiple wavelengths for potentially additional effects by UV-LEDs. In this work, the inactivation of different microorganisms in water was investigated by UV-LEDs wavelength combinations. Various wavelength combinations, including simultaneous and sequential exposures, in different UV ranges such as UVC, UVB and UVA, were examined. These combinations were applied to the inactivation of indicator bacterium E. coli and coliphage MS2 in water. The results showed the effect of UV-LEDs multiple wavelengths depends on which wavelengths (UVC, UVB and UVA) are combined and the manner that different wavelengths (simultaneous, sequential) are used. Also, different microorganisms (bacteria, virus) respond differently to wavelength combinations. Combinations of UVC/UVB always achieved additive effect on microorganisms inactivation due to the same photochemical reaction induced by UVC/UVB on DNA. Combining UVA with UVC/UVB simultaneously or applying UVA after UVC/UVB reduced the inactivation of bacterium E. coli due to DNA repair and photoreactivation effect of UVA. However, applying extended UVA exposure before UVC significantly improved E. coli inactivation. For virus MS2 inactivation, only additive effect was observed under various wavelength combinations. This study presented a comprehensive work on UV-LEDs wavelength combinations, which is of significance on the application of UV-LEDs for water disinfection.
- Antibiotic resistant bacteria survived from UV disinfection: Safety concerns on genes dissemination. [Journal Article]
- CChemosphere 2019; 224:827-832
- Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are the emerging contaminants leading to a serious worldwide health problem. Although disinfection like ultraviolet (UV) irr…
Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are the emerging contaminants leading to a serious worldwide health problem. Although disinfection like ultraviolet (UV) irradiation could remove part of ARB and ARGs, there still are residual ARB and ARGs in the effluent of wastewater treatment plants. Conjugative transfer is main concern of the risk of ARGs and little is known about the effects of UV disinfection on the transfer ability of the non-inactivated ARB in the effluent which will enter the environment. Hence the influences of UV irradiation and reactivation on ARB conjugative transfer ability were studied under laboratory condition, focusing on the survival bacteria from UV irradiation and the reactivated bacteria, as well as their descendants. The experimental results imply that even 1 mJ/cm2 UV disinfection can significantly decrease the conjugative transfer frequency of the survival bacteria. However, viable but not culturable state cells induced by UV can reactivate through both photoreactivation and dark repair and retain the same level of transfer ability as the untreated strains. This finding is essential for re-considering about the post safety of UV irradiated effluent and microbial safety control strategies were required.
- UV-C irradiation compromises conidial germination, formation of appressoria, and induces transcription of three putative photolyase genes in the barley powdery mildew fungus, Blumeria graminis f. sp. hordei. [Journal Article]
- FBFungal Biol 2019; 123(3):218-230
- UV-C irradiation is known to compromise germination of Blumeria graminis conidia and to reduce powdery mildew infestation. However, only scarce information is available on the effects of UV-C irradia…
UV-C irradiation is known to compromise germination of Blumeria graminis conidia and to reduce powdery mildew infestation. However, only scarce information is available on the effects of UV-C irradiation on B. graminis appressorium formation. Applying a Formvar® resin-based in vitro system allowed for analyzing B. graminis germination and appressorium formation in absence of plant defense. UV-C irradiation more strongly affected the differentiation of appressoria than conidial germination. In vivo and in vitro, a single dose of 100 J m-2 UV-C was sufficient to reduce germination to less than 20 % and decrease appressorium formation to values below 5 %. UV-C irradiation negatively affected pustule size and conidiation. White light-mediated photoreactivation was most effective immediately after UV-C irradiation, indicating that a prolonged phase of darkness after UV-C treatment increases the efficacy of B. graminis control. UV-C irradiation increased transcript levels of three putative B. graminis photolyase genes, while mere white light or blue light irradiation did not contribute to the transcriptional up-regulation. Thus, UV-C irradiation effectively controls B. graminis infestation and proliferation by restricting prepenetration processes. Nevertheless, photoreactivation plays an important role in UV-C-based powdery mildew control in crops and hence has to be considered for planning specific irradiation schedules.
- UV-A screening in Cladophora sp. lowers internal UV-A availability and photoreactivation as compared to non-UV screening in Ulva intestinalis. [Journal Article]
- PPPhotochem Photobiol Sci 2019 Feb 13; 18(2):413-423
- In the Baltic Sea, two co-occurring green macroalgae Cladophora sp. and Ulva intestinalis grow in the upper eulittoral. Due to regular and high sunlight exposure in their habitat, both species need r…
In the Baltic Sea, two co-occurring green macroalgae Cladophora sp. and Ulva intestinalis grow in the upper eulittoral. Due to regular and high sunlight exposure in their habitat, both species need resistance mechanisms to protect themselves against ultraviolet-B (UV-B)-induced DNA damage. While Cladophora sp. possesses efficient screening of UV-B and ultraviolet-A (UV-A) radiation, U. intestinalis was recently shown to have higher DNA repair by UVA-driven photoreactivation than Cladophora sp. [F. Pescheck and W. Bilger, Mar. Biol., 2018, 165, 132]. In the present study, the hypothesis that the screening of UV-A radiation limits internal UV-A availability for photoreactivation in Cladophora sp. was tested. Both species had identical and much lower fractions of damaged DNA when sampled in situ under direct sunlight as expected based on a photophysical prediction. To quantify the effect of UV-A screening spectrally and physiologically, in vivo UV screening spectra were determined and the UV-A photon flux dependency of photoreactivation was investigated for both species. Identical intrinsic photoreactivation rates were revealed by the applied correction for internal UV-A photon flux density and under irradiation with visible radiation which is not screened by the UV absorbing compounds in Cladophora sp. Natural sunlight was weighted with in vivo action spectra for DNA damage induction and light-dependent repair. The resulting spectrum was further corrected for the apparent UV screening spectra of both species to calculate the species-specific internal ratios of DNA damaging and photoreactivating photons. This photophysical modelling improves the understanding of UV damage and tolerance mechanisms in the two co-occurring green macroalgae under solar irradiation.
- Visible-light-driven photocatalytic inactivation of bacteriophage f2 by Cu-TiO2 nanofibers in the presence of humic acid. [Journal Article]
- JEJ Environ Sci (China) 2019; 77:383-391
- Pathogenic viruses in drinking water are great threats to public health. Visible-light-driven photocatalysis is a promising technology for virus inactivation. However, the existing photocatalytic ant…
Pathogenic viruses in drinking water are great threats to public health. Visible-light-driven photocatalysis is a promising technology for virus inactivation. However, the existing photocatalytic antiviral research studies have mostly been carried out in single-component systems, neglecting the effect of natural organic matter, which exists widely in actual water bodies. In this paper, electrospun Cu-TiO2 nanofibers were prepared as photocatalysts, and their photocatalytic antiviral performance in the presence of humic acid (HA) was comprehensively studied for the first time. The properties of the reaction mixture were measured during the reaction. In addition, the safety, reliability and stability of photocatalytic disinfection in the mixed system were evaluated. The results showed that the virus removal efficiency decreased with the increase of the HA concentration. The type of reaction solution, such as PBS buffer solution or water, did not affect the removal efficiency noticeably. Under acidic conditions, the electrostatic forces between photocatalysts and viruses were strengthened, leading to higher virus removal efficiency. As the reaction time went on, the pH value in the solution increased first and then tended to be stable, the conductivity remained stable, and the dissolved oxygen increased first and then decreased. The safety test showed that the concentration of Cu ions released into the solution was lower than specified by the international standards. No photoreactivation was observed, and the addition of HA significantly reduced the reutilization efficiency of the photocatalysts.
- Two Photolyases Repair Distinct DNA Lesions and Reactivate UVB-Inactivated Conidia of an Insect Mycopathogen under Visible Light. [Journal Article]
- AEAppl Environ Microbiol 2019 Feb 15; 85(4)
- Fungal conidia serve as active ingredients of fungal insecticides but are sensitive to solar UV irradiation, which impairs double-stranded DNA (dsDNA) by inducing the production of cytotoxic cyclobut…
Fungal conidia serve as active ingredients of fungal insecticides but are sensitive to solar UV irradiation, which impairs double-stranded DNA (dsDNA) by inducing the production of cytotoxic cyclobutane pyrimidine dimers (CPDs) and (6-4)-pyrimidine-pyrimidine photoproducts (6-4PPs). This study aims to elucidate how CPD photolyase (Phr1) and 6-4PP photolyase (Phr2) repair DNA damage and photoreactivate UVB-inactivated cells in Beauveria bassiana, a main source of fungal insecticides. Both Phr1 and Phr2 are proven to exclusively localize in the fungal nuclei. Despite little influence on growth, conidiation, and virulence, singular deletions of phr1 and phr2 resulted in respective reductions of 38% and 19% in conidial tolerance to UVB irradiation, a sunlight component most harmful to formulated conidia. CPDs and 6-4PPs accumulated significantly more in the cells of Δphr1 and Δphr2 mutants than in those of a wild-type strain under lethal UVB irradiation and were largely or completely repaired by Phr1 in the Δphr2 mutant and Phr2 in the Δphr1 mutant after optimal 5-h exposure to visible light. Consequently, UVB-inactivated conidia of the Δphr1 and Δphr2 mutants were much less efficiently photoreactivated than were the wild-type counterparts. In contrast, overexpression of either phr1 or phr2 in the wild-type strain resulted in marked increases in both conidial UVB resistance and photoreactivation efficiency. These findings indicate essential roles of Phr1 and Phr2 in photoprotection of B. bassiana from UVB damage and unveil exploitable values of both photolyase genes for improved UVB resistance and application strategy of fungal insecticides.IMPORTANCE Protecting fungal cells from damage from solar UVB irradiation is critical for development and application of fungal insecticides but is mechanistically not understood in Beauveria bassiana, a classic insect pathogen. We unveil that two intranuclear photolyases, Phr1 and Phr2, play essential roles in repairing UVB-induced dsDNA lesions through respective decomposition of cytotoxic cyclobutane pyrimidine dimers and (6-4)-pyrimidine-pyrimidine photoproducts, hence reactivating UVB-inactivated cells effectively under visible light. Our findings shed light on the high potential of both photolyase genes for use in improving UVB resistance and application strategy of fungal insecticides.
- Photolyases and Cryptochromes in UV-resistant Bacteria from High-altitude Andean Lakes. [Journal Article]
- PPPhotochem Photobiol 2019; 95(1):315-330
- "High-altitude Andean Lakes" (HAAL) are pristine environments harboring poly-extremophilic microbes that show combined adaptations to physical and chemical stress such as large daily ambient thermal …
"High-altitude Andean Lakes" (HAAL) are pristine environments harboring poly-extremophilic microbes that show combined adaptations to physical and chemical stress such as large daily ambient thermal amplitude, extreme solar radiation levels, intense dryness, alkalinity, high concentrations of arsenic (up to 200 ppm) and dissolved salts. In this work, we compared the UV resistance profiles, pigment content and photoreactivation abilities of three UV-resistant bacteria isolated from distinct niches from HAALs, that is Acinetobacter sp. Ver3 (water, Lake Verde; 4400 m), Exiguobacterium sp. S17 (stromatolite, Lake Socompa, 3570 m) and Nesterenkonia sp. Act20 (soil, Lake Socompa, 3570 m). UV resistance ability of HAAL's strains indicate a clear adaptation to high radiation exposure encountered in their original habitat, which can be explained by genetic and physiological mechanisms named as the UV-resistome. Thus, the UV-resistome depends on the expression of a diverse set of genes devoted to evading or repairing the damage it provoked direct or indirectly. As pigment extraction and photoreactive assays indicate the presence of photoactive molecules, we characterized more in detail proteins with homology to photolyases/cryptochromes members (CPF). Phylogenetic analyses, sequence comparison and 3D modeling with bona fide CPF members were used to prove the presence of functional domains and key residues in the novel proteins.
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- Methotrexate-Induced Toxic Epidermal Necrolysis: A Rare Case Report and Review of Literature. [Case Reports]
- IJIndian J Crit Care Med 2018; 22(10):740-742
- Acute lymphoblastic leukemia (ALL) is the most common malignancy in pediatric patients, and it is characterized by the presence of malignant lymphoblasts within the bone marrow and peripheral blood. …
Acute lymphoblastic leukemia (ALL) is the most common malignancy in pediatric patients, and it is characterized by the presence of malignant lymphoblasts within the bone marrow and peripheral blood. The treatment of ALL involves induction, consolidation, reinduction, and maintenance therapy. Consolidation therapy in ALL-Berlin-Frankfurt-Münster 90 protocol involves the use of high-dose methotrexate (HDMTX, 5 g/m2) over 24 h as continuous infusion. The adverse effects due to HDMTX include renal dysfunction in 2%-12% patients, which can lead to increased systemic MTX exposure, leading to further myelosuppression, mucositis, hepatotoxicity, skin toxicity, and, in severe cases, multiorgan failure. Dermatologic toxicity due to MTX includes morbilliform drug rash, photoreactivation, photoenhancement, and skin hyperpigmentation. Stevens-Johnson syndrome and toxic epidermal necrolysis (TEN) are rare and possibly fatal reaction which can occur with MTX. Here, we describe a patient with B-cell ALL who developed TEN after administration of HDMTX.