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1.
Annu Rev Biochem ; 86: 485-514, 2017 06 20.
Artigo em Inglês | MEDLINE | ID: mdl-28654327

RESUMO

Living organisms sense and respond to light, a crucial environmental factor, using photoreceptors, which rely on bound chromophores such as retinal, flavins, or linear tetrapyrroles for light sensing. The discovery of photoreceptors that sense light using 5'-deoxyadenosylcobalamin, a form of vitamin B12 that is best known as an enzyme cofactor, has expanded the number of known photoreceptor families and unveiled a new biological role of this vitamin. The prototype of these B12-dependent photoreceptors, the transcriptional repressor CarH, is widespread in bacteria and mediates light-dependent gene regulation in a photoprotective cellular response. CarH activity as a transcription factor relies on the modulation of its oligomeric state by 5'-deoxyadenosylcobalamin and light. This review surveys current knowledge about these B12-dependent photoreceptors, their distribution and mode of action, and the structural and photochemical basis of how they orchestrate signal transduction and control gene expression.


Assuntos
Proteínas de Bactérias/química , Cobamidas/metabolismo , Regulação Bacteriana da Expressão Gênica , Fotorreceptores Microbianos/química , Proteínas Repressoras/química , Fatores de Transcrição/química , Bacillus megaterium/genética , Bacillus megaterium/metabolismo , Bacillus megaterium/efeitos da radiação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cobamidas/química , Luz , Modelos Moleculares , Myxococcus xanthus/genética , Myxococcus xanthus/metabolismo , Myxococcus xanthus/efeitos da radiação , Fotoquímica , Fotorreceptores Microbianos/genética , Fotorreceptores Microbianos/metabolismo , Conformação Proteica , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Transdução de Sinais , Thermus thermophilus/genética , Thermus thermophilus/metabolismo , Thermus thermophilus/efeitos da radiação , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Genética , Vitamina B 12/química , Vitamina B 12/metabolismo
2.
Biosci Biotechnol Biochem ; 80(7): 1264-73, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26967471

RESUMO

Light is a ubiquitous environmental factor serving as an energy source and external stimulus. Here, I review the conserved molecular mechanism of light-inducible production of carotenoids in three nonphototrophic bacteria: Streptomyces coelicolor A3(2), Thermus thermophilus HB27, and Bacillus megaterium QM B1551. A MerR family transcriptional regulator, LitR, commonly plays a central role in their light-inducible carotenoid production. Genetic and biochemical studies on LitR proteins revealed a conserved function: LitR in complex with adenosyl B12 (AdoB12) has a light-sensitive DNA-binding activity and thus suppresses the expression of the Crt biosynthesis gene cluster. The in vitro DNA-binding and transcription assays showed that the LitR-AdoB12 complex serves as a repressor allowing transcription initiation by RNA polymerase in response to illumination. The existence of novel light-inducible genes and the unique role of the megaplasmid were revealed by the transcriptomic analysis of T. thermophilus. The findings suggest that LitR is a general regulator responsible for the light-inducible carotenoid production in the phylogenetically divergent nonphototrophic bacteria, and that LitR performs diverse physiological functions in bacteria.


Assuntos
Bacillus megaterium/efeitos da radiação , Proteínas de Bactérias/genética , Carotenoides/biossíntese , Proteínas de Ligação a DNA/genética , Regulação Bacteriana da Expressão Gênica , Streptomyces coelicolor/efeitos da radiação , Thermus thermophilus/efeitos da radiação , Bacillus megaterium/classificação , Bacillus megaterium/genética , Bacillus megaterium/metabolismo , Proteínas de Bactérias/metabolismo , Sequência de Bases , Proteínas de Ligação a DNA/metabolismo , RNA Polimerases Dirigidas por DNA/genética , RNA Polimerases Dirigidas por DNA/metabolismo , Luz , Família Multigênica , Filogenia , Plasmídeos/química , Plasmídeos/metabolismo , Regiões Promotoras Genéticas , Streptomyces coelicolor/classificação , Streptomyces coelicolor/genética , Streptomyces coelicolor/metabolismo , Thermus thermophilus/classificação , Thermus thermophilus/genética , Thermus thermophilus/metabolismo , Transcrição Genética , Vitamina B 12/metabolismo
3.
Carbohydr Polym ; 96(1): 365-70, 2013 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-23688493

RESUMO

Microbial levan, a natural polymer of fructose, was produced and purified by alcohol precipitation from culture supernatants of Bacillus megaterium type 1 grown in an optimized liquid sucrose medium. GPC analysis showed that the yield of the major fraction of levan having molecular weight ~5000 D increased with increase in sucrose concentration in the broth. Levan subjected to (60)Co-gamma radiation as well as acid hydrolysis was investigated by rheometry, UV-visible spectrophotometry and gel permeation chromatography (GPC) techniques. Unlike most of the polysaccharides, levan powder exhibited good radiation degradation stability up to 150 kGy. Gamma irradiation of 10% levan aqueous solution at 250 kGy yielded 63.0% fructo-oligosaccharide (FOS) with an average molecular weight of 1250 D. Acid hydrolysis of levan using 0.5 N HCl for 60 min treatment time gave rise to the desired FOS with lower yield (23.1%) as compared to that obtained in gamma radiolysis process.


Assuntos
Bacillus megaterium/metabolismo , Frutanos/efeitos da radiação , Raios gama , Oligossacarídeos/química , Bacillus megaterium/efeitos da radiação , Carga Bacteriana , Frutanos/biossíntese , Tamanho da Partícula , Viscosidade
4.
Photochem Photobiol ; 89(1): 2-4, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22946878

RESUMO

This article is a highlight of the study by Maclean et al. in this issue of Photochemistry and Photobiology describing the sporicidal effects 405 nm visible light alone on endospores of the Clostridium and Bacillus genera. 1.73 kJ cm(-2) was capable of reducing endospore colony-forming units by up to 4-log(10). These findings have never been previously demonstrated and may be incorporated into decontamination methods that span medical, military and food preparatory applications.


Assuntos
Bacillus cereus/efeitos da radiação , Bacillus megaterium/efeitos da radiação , Clostridium difficile/efeitos da radiação
5.
Photochem Photobiol ; 89(1): 120-6, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-22803813

RESUMO

Resistance of bacterial endospores to treatments, including biocides, heat and radiation is a persistent problem. This study investigates the susceptibility of Bacillus and Clostridium endospores to 405 nm visible light, wavelengths which have been shown to induce inactivation of vegetative bacterial cells. Suspensions of B. cereus endospores were exposed to high-intensity 405 nm light generated from a light-emitting diode array and results demonstrate the induction of a sporicidal effect. Up to a 4-log(10) CFU mL(-1) reduction in spore population was achieved after exposure to a dose of 1.73 kJ cm(-2). Similar inactivation kinetics were demonstrated with B. subtilis, B. megaterium and C. difficile endospores. The doses required for inactivation of endospores were significantly higher than those required for inactivation of B. cereus and C. difficile vegetative cells, where ca 4-log(10) CFU mL(-1) reductions were achieved after exposure to doses of 108 and 48 J cm(-2), respectively. The significant increase in dose required for inactivation of endospores compared with vegetative cells is unsurprising due to the notorious resilience of these microbial structures. However, the demonstration that visible light of 405 nm can induce a bactericidal effect against endospores is significant, and could have potential for incorporation into decontamination methods for the removal of bacterial contamination including endospores.


Assuntos
Bacillus cereus/efeitos da radiação , Bacillus megaterium/efeitos da radiação , Clostridium difficile/efeitos da radiação , Bacillus cereus/fisiologia , Bacillus megaterium/fisiologia , Carga Bacteriana , Clostridium difficile/fisiologia , Luz , Dispositivos Ópticos , Esporos Bacterianos/fisiologia , Esporos Bacterianos/efeitos da radiação
6.
J Appl Microbiol ; 111(3): 663-70, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21714839

RESUMO

AIMS: To determine the effects of Mn levels in Bacillus megaterium sporulation and spores on spore resistance. METHODS AND RESULTS: Bacillus megaterium was sporulated with no added MnCl(2) and up to 1 mmol l(-1) MnCl(2). The resultant spores were purified and loosely bound Mn removed, and spore Mn levels were found to vary c. 100-fold. The Mn level had no effect on spore γ-radiation resistance, but B. megaterium spores with elevated Mn levels had higher resistance to UVC radiation (as did Bacillus subtilis spores), wet and dry heat and H(2)O(2). However, levels of dipicolinic acid and the DNA-protective α/ß-type small, acid-soluble spore proteins were the same in spores with high and low Mn levels. CONCLUSIONS: Mn levels either in sporulation or in spores are important factors in determining levels of B. megaterium spore resistance to many agents, with the exception of γ-radiation. SIGNIFICANCE AND IMPACT OF THE STUDY: The Mn level in sporulation is an important factor to consider when resistance properties of B. megaterium spores are examined, and will influence the UV resistance of B. subtilis spores, some of which are used as biological dosimeters.


Assuntos
Bacillus megaterium/efeitos dos fármacos , Bacillus megaterium/efeitos da radiação , Temperatura Alta , Peróxido de Hidrogênio/farmacologia , Manganês/metabolismo , Bacillus megaterium/metabolismo , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/metabolismo , Bacillus subtilis/efeitos da radiação , Proteínas de Bactérias/análise , Raios gama , Ácidos Picolínicos/análise , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/metabolismo , Esporos Bacterianos/efeitos da radiação , Raios Ultravioleta
7.
Appl Environ Microbiol ; 77(10): 3368-79, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21441336

RESUMO

Raman spectroscopy and differential interference contrast (DIC) microscopy were used to monitor the kinetics of nutrient and nonnutrient germination of multiple individual untreated and wet-heat-treated spores of Bacillus cereus and Bacillus megaterium, as well as of several isogenic Bacillus subtilis strains. Major conclusions from this work were as follows. (i) More than 90% of these spores were nonculturable but retained their 1:1 chelate of Ca²+ and dipicolinic acid (CaDPA) when incubated in water at 80 to 95°C for 5 to 30 min. (ii) Wet-heat treatment significantly increased the time, T(lag), at which spores began release of the great majority of their CaDPA during the germination of B. subtilis spores with different nutrient germinants and also increased the variability of T(lag) values. (iii) The time period, ΔT(release), between T(lag) and the time, T(release), at which a spore germinating with nutrients completed the release of the great majority of its CaDPA, was also increased in wet-heat-treated spores. (iv) Wet-heat-treated spores germinating with nutrients had higher values of I(release), the intensity of a spore's DIC image at T(release), than did untreated spores and had much longer time periods, ΔT(lys), for the reduction in I(release) intensities to the basal value due to hydrolysis of the spore's peptidoglycan cortex, probably due at least in part to damage to the cortex-lytic enzyme CwlJ. (v) Increases in T(lag) and ΔT(release) were also observed when wet-heat-treated B. subtilis spores were germinated with the nonnutrient dodecylamine, while the change in I(release) was less significant. (vi) The effects of wet-heat treatment on nutrient germination of B. cereus and B. megaterium spores were generally similar to those on B. subtilis spores. These results indicate that (i) some proteins important in spore germination are damaged by wet-heat treatment, (ii) the cortex-lytic enzyme CwlJ is one germination protein damaged by wet heat, and (iii) the CaDPA release process itself seems likely to be the target of wet-heat damage which has the greatest effect on spore germination.


Assuntos
Bacillus cereus/efeitos da radiação , Bacillus megaterium/efeitos da radiação , Bacillus subtilis/efeitos da radiação , Temperatura Alta , Esporos/efeitos da radiação , Água , Bacillus cereus/química , Bacillus cereus/crescimento & desenvolvimento , Bacillus megaterium/química , Bacillus megaterium/crescimento & desenvolvimento , Bacillus subtilis/química , Bacillus subtilis/crescimento & desenvolvimento , Cálcio/análise , Microscopia de Interferência , Ácidos Picolínicos/análise , Análise Espectral Raman , Esporos/química , Esporos/crescimento & desenvolvimento , Fatores de Tempo
8.
Appl Environ Microbiol ; 76(6): 1796-805, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20097820

RESUMO

Dual-trap laser tweezers Raman spectroscopy (LTRS) and elastic light scattering (ELS) were used to investigate dynamic processes during high-temperature treatment of individual spores of Bacillus cereus, Bacillus megaterium, and Bacillus subtilis in water. Major conclusions from these studies included the following. (i) After spores of all three species were added to water at 80 to 90 degrees C, the level of the 1:1 complex of Ca(2+) and dipicolinic acid (CaDPA; approximately 25% of the dry weight of the spore core) in individual spores remained relatively constant during a highly variable lag time (T(lag)), and then CaDPA was released within 1 to 2 min. (ii) The T(lag) values prior to rapid CaDPA release and thus the times for wet-heat killing of individual spores of all three species were very heterogeneous. (iii) The heterogeneity in kinetics of wet-heat killing of individual spores was not due to differences in the microscopic physical environments during heat treatment. (iv) During the wet-heat treatment of spores of all three species, spore protein denaturation largely but not completely accompanied rapid CaDPA release, as some changes in protein structure preceded rapid CaDPA release. (v) Changes in the ELS from individual spores of all three species were strongly correlated with the release of CaDPA. The ELS intensities of B. cereus and B. megaterium spores decreased gradually and reached minima at T(1) when approximately 80% of spore CaDPA was released, then increased rapidly until T(2) when full CaDPA release was complete, and then remained nearly constant. The ELS intensity of B. subtilis spores showed similar features, although the intensity changed minimally, if at all, prior to T(1). (vi) Carotenoids in B. megaterium spores' inner membranes exhibited two changes during heat treatment. First, the carotenoid's two Raman bands at 1,155 and 1,516 cm(-1) decreased rapidly to a low value and to zero, respectively, well before T(lag), and then the residual 1,155-cm(-1) band disappeared, in parallel with the rapid CaDPA release beginning at T(lag).


Assuntos
Bacillus cereus/efeitos da radiação , Bacillus megaterium/efeitos da radiação , Bacillus subtilis/efeitos da radiação , Temperatura Alta , Viabilidade Microbiana/efeitos da radiação , Esporos/efeitos da radiação , Bacillus cereus/química , Bacillus cereus/fisiologia , Bacillus megaterium/química , Bacillus megaterium/fisiologia , Bacillus subtilis/química , Bacillus subtilis/fisiologia , Luz , Análise Espectral Raman/métodos , Esporos/química , Esporos/fisiologia
9.
Rev Argent Microbiol ; 39(3): 170-6, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17987854

RESUMO

Different natural antimicrobials affected viability of bacterial contaminants isolated at critical steps during a beer production process. In the presence of 1 mg/ml chitosan and 0.3 mg/ml hops, the viability of Escherichia coli in an all malt barley extract wort could be reduced to 0.7 and 0.1% respectively after 2 hour- incubation at 4 degrees C. The addition of 0.0002 mg/ml nisin, 0.1 mg/ml chitosan or 0.3 mg/ml hops, selectively inhibited growth of Pediococcus sp. in more than 10,000 times with respect to brewing yeast in a mixed culture. In the presence of 0.1 mg ml chitosan in beer, no viable cells of the thermoresistant strain Bacillus megaterium were detected. Nisin, chitosan and hops increased microbiological stability during storage of a local commercial beer inoculated with Lactobacillus plantarum or Pediococcus sp. isolated from wort. Pulsed Electric Field (PEF) (8 kV/cm, 3 pulses) application enhanced antibacterial activity of nisin and hops but not that of chitosan. The results herein obtained suggest that the use of these antimicrobial compounds in isolation or in combination with PEF would be effective to control bacterial contamination during beer production and storage.


Assuntos
Bacillus megaterium/isolamento & purificação , Cerveja/microbiologia , Quitosana/farmacologia , Campos Eletromagnéticos , Escherichia coli/isolamento & purificação , Humulus , Microbiologia Industrial/métodos , Lactobacillus plantarum/isolamento & purificação , Nisina/farmacologia , Pediococcus/isolamento & purificação , Extratos Vegetais/farmacologia , Bacillus megaterium/efeitos dos fármacos , Bacillus megaterium/crescimento & desenvolvimento , Bacillus megaterium/efeitos da radiação , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/efeitos da radiação , Fermentação , Conservação de Alimentos , Lactobacillus plantarum/efeitos dos fármacos , Lactobacillus plantarum/crescimento & desenvolvimento , Lactobacillus plantarum/efeitos da radiação , Testes de Sensibilidade Microbiana , Pediococcus/efeitos dos fármacos , Pediococcus/crescimento & desenvolvimento , Pediococcus/efeitos da radiação , Temperatura
10.
Rev. argent. microbiol ; 39(3): 170-176, jul.-sep. 2007. graf, tab
Artigo em Inglês | LILACS | ID: lil-634554

RESUMO

Different natural antimicrobials affected viability of bacterial contaminants isolated at critical steps during a beer production process. In the presence of 1 mg/ml chitosan and 0.3 mg/ml hops, the viability of Escherichia coli in an all malt barley extract wort could be reduced to 0.7 and 0.1% respectively after 2 hour- incubation at 4 °C. The addition of 0.0002 mg/ml nisin, 0.1 mg/ml chitosan or 0.3 mg/ml hops, selectively inhibited growth of Pediococcus sp. in more than 10,000 times with respect to brewing yeast in a mixed culture. In the presence of 0.1mg ml chitosan in beer, no viable cells of the thermoresistant strain Bacillus megaterium were detected. Nisin, chitosan and hops increased microbiological stability during storage of a local commercial beer inoculated with Lactobacillus plantarum or Pediococcus sp. isolated from wort. Pulsed Electric Field (PEF) (8 kV/cm, 3 pulses) application enhanced antibacterial activity of nisin and hops but not that of chitosan. The results herein obtained suggest that the use of these antimicrobial compounds in isolation or in combination with PEF would be effective to control bacterial contamination during beer production and storage.


Diferentes antimicrobianos naturales disminuyeron la viabilidad de bacterias contaminantes aisladas en etapas críticas del proceso de producción de cerveza. En un extracto de malta, el agregado de 1 mg/ml de quitosano y de 0,3 mg ml de lúpulo permitió reducir la viabilidad de Escherichia coli a 0,7 y 0,1%, respectivamente, al cabo de 2 horas de incubación a 4 °C. El agregado de 0,0002 mg/ml de nisina, 0,1 mg/ml de quitosano o de 0,3 mg/ml de lúpulo inhibió selectivamente (10.000 veces más) el crecimiento de Pediococcus sp. respecto de la levadura de cerveza en un cultivo mixto. El agregado de 0,1 mg/ml de quitosano permitió disminuir la viabilidad de una cepa bacteriana termorresistente, Bacillus megaterium, hasta niveles no detectables. Por otra parte, el agregado de nisina, quitosano y lúpulo aumentó la estabilidad microbiológica durante el almacenamiento de cervezas inoculadas con Lactobacillus plantarum y Pediococcus sp. aislados de mosto de cerveza. La aplicación de campos eléctricos pulsantes (CEP) (3 pulsos de 8kV/cm) aumentó el efecto antimicrobiano de la nisina y del lúpulo, pero no el del quitosano. Los resultados obtenidos indicarían que el uso de antimicrobianos naturales en forma individual o en combinación con CEP puede constituir un procedimiento efectivo para el control de la contaminación bacteriana durante el proceso de elaboración y almacenamiento de la cerveza.


Assuntos
Bacillus megaterium/isolamento & purificação , Cerveja/microbiologia , Quitosana/farmacologia , Campos Eletromagnéticos , Escherichia coli/isolamento & purificação , Humulus , Microbiologia Industrial/métodos , Lactobacillus plantarum/isolamento & purificação , Nisina/farmacologia , Pediococcus/isolamento & purificação , Extratos Vegetais/farmacologia , Bacillus megaterium/efeitos dos fármacos , Bacillus megaterium/crescimento & desenvolvimento , Bacillus megaterium/efeitos da radiação , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/efeitos da radiação , Fermentação , Conservação de Alimentos , Lactobacillus plantarum/efeitos dos fármacos , Lactobacillus plantarum/crescimento & desenvolvimento , Lactobacillus plantarum/efeitos da radiação , Testes de Sensibilidade Microbiana , Pediococcus/efeitos dos fármacos , Pediococcus/crescimento & desenvolvimento , Pediococcus/efeitos da radiação , Temperatura
11.
Water Environ Res ; 79(5): 507-13, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17571840

RESUMO

Escherichia coli (E. coli) and Bacillus megaterium bacteria were frozen at -15 degrees C using a freezer and a spray freezing method. The frozen Bacillus spores were also exposed to UV and free chlorine. An average of 4.7-log inactivation was obtained from the spray ice with 2-day storage time, while the freezer freezing only caused 0.84-log reduction with the same storage time. Significantly higher inactivation levels were observed for the E. coli cells with 2-day storage compared with those without storage. The spray freezing was found more effective in killing the E. coli cells, while more cells were sublethally injured by the freezer freezing. Freezing did not kill the Bacillus megaterium spores, but affected their response to UV and chlorine. Greater inactivation levels were observed at higher free chlorine doses or longer contact time, and the UV fluence-response curve showed initial rapid kill followed by tailing for the frozen spores.


Assuntos
Bacillus megaterium , Cloro/farmacologia , Desinfecção/métodos , Escherichia coli , Congelamento , Viabilidade Microbiana/efeitos dos fármacos , Viabilidade Microbiana/efeitos da radiação , Raios Ultravioleta , Bacillus megaterium/efeitos dos fármacos , Bacillus megaterium/efeitos da radiação , Contagem de Colônia Microbiana , Resistência a Medicamentos , Escherichia coli/efeitos dos fármacos , Escherichia coli/efeitos da radiação , Modelos Biológicos
12.
Microbiology ; 151(Pt 3): 775-87, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15758224

RESUMO

Isolation and subsequent knockout of a recA-homologous gene in Bacillus megaterium DSM 319 resulted in a mutant displaying increased sensitivity to mitomycin C. However, this mutant did not exhibit UV hypersensitivity, a finding which eventually led to identification of a second functional recA gene. Evidence for recA duplicates was also obtained for two other B. megaterium strains. In agreement with potential DinR boxes located within their promoter regions, expression of both genes (recA1 and recA2) was found to be damage-inducible. Transcription from the recA2 promoter was significantly higher than that of recA1. Since a recA2 knockout could not be achieved, functional complementation studies were performed in Escherichia coli. Heterologous expression in a RecA null mutant resulted in increased survival after UV irradiation and mitomycin C treatment, proving both recA gene products to be functional in DNA repair. Thus, there is evidence for an SOS-like pathway in B. megaterium that differs from that of Bacillus subtilis.


Assuntos
Bacillus megaterium/enzimologia , Proteínas de Bactérias/genética , Reparo do DNA , Regulação Bacteriana da Expressão Gênica , Recombinases Rec A/genética , Resposta SOS em Genética , Bacillus megaterium/genética , Bacillus megaterium/efeitos da radiação , Proteínas de Bactérias/biossíntese , Sequência de Bases , Dano ao DNA , Dados de Sequência Molecular , Recombinases Rec A/biossíntese , Raios Ultravioleta
13.
Radiat Res ; 162(4): 464-8, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15447035

RESUMO

We measured the X-ray transmission spectra of several biologically related samples in the phosphorus K-shell edge absorption region. These include red phosphorus, hydrated sodium phosphate (Na(3)PO(4).12 H(2)O), deoxyribonucleic acid (DNA), adenosine triphosphate (ATP), diolylphosphatidyl choline (DOPC), and Bacillus megaterium spores. Red phosphorus essentially displays an edge-jump. All other spectra are similar in form and energy position: Each is dominated by a narrower, more intense first peak and a broader but less intense second peak. The corresponding K-shell edge absorption thresholds are shifted toward higher energy relative to that for red phosphorus, as expected for increasing degrees of phosphorus oxidation. The B. megaterium spectrum has aspects common to both the phosphate and DNA spectra and is therefore interpreted as a composite of spectra arising from DNA, ribonucleic acid (RNA) and phosphates within the spore. The B. megaterium spore spectrum provides information for resonant radiation damage studies in the phosphorus K-shell edge absorption region by identifying candidate photoexcitations. In addition, the absorption spectra will be useful in X-ray microscopy and macromolecular crystallography studies at the phosphorus K-shell edge.


Assuntos
Bacillus megaterium/efeitos da radiação , DNA/efeitos da radiação , Fósforo/análise , Trifosfato de Adenosina/química , Trifosfato de Adenosina/efeitos da radiação , Cristalização , DNA/metabolismo , Relação Dose-Resposta à Radiação , Microanálise por Sonda Eletrônica , Oxigênio/metabolismo , Fosfatos/efeitos da radiação , Fosfatidilcolinas/efeitos da radiação , Fósforo/metabolismo , Fótons , Espectrometria de Fluorescência , Espectrofotometria , Esporos Bacterianos/efeitos da radiação , Raios X
14.
Appl Microbiol Biotechnol ; 65(2): 193-9, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-14872291

RESUMO

The Bacillus megaterium genes uvrB and uvrA, encoding two subunits of the (A)BC excinuclease, which is responsible for nucleotide excision repair, were isolated and functionally characterized. RNA analyses revealed co-transcription of both genes probably forming a bicistronic operon. Expression of uvrB and uvrA was inducible by the DNA-damaging agent mitomycin C. This finding agrees with the presence of a potential DinR box within the uvrBA promoter. Single inactivation of uvrB or uvrA as well as the parallel knockout of both genes resulted in mutants highly sensitive to UV irradiation. Thus, this locus represents an attractive target for generating biologically safe containment strains of B. megaterium.


Assuntos
Bacillus megaterium/efeitos da radiação , Proteínas de Bactérias/fisiologia , DNA Helicases/genética , DNA Bacteriano/efeitos da radiação , Raios Ultravioleta , Bacillus megaterium/enzimologia , Bacillus megaterium/genética , Proteínas de Bactérias/genética , Dano ao DNA , DNA Helicases/fisiologia , Reparo do DNA , Mitomicina/farmacologia , Mutação , Óperon/genética , Transcrição Genética
15.
J Food Prot ; 66(7): 1233-40, 2003 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-12870758

RESUMO

Advantage is taken in many sterilization processes, especially for food packaging materials, of the synergy between H2O2 and UV irradiation for spore killing. The nature of the synergy is currently not well defined in terms of targets and mechanisms. We found that under some experimental conditions, the synergistic killing of spores of Bacillus megaterium ATCC 19213 appeared to be mainly UV-enhanced peroxide killing, while under other conditions, it appeared to be mainly peroxide-enhanced UV killing. Lethal combinations of H2O2 and UV irradiation for spores resulted in only modest increases in auxotrophic mutations among survivors, indicative of little DNA damage, in contrast to higher mutation levels after dry-heat damage at 115 degrees C. However, the combination of UV light and peroxide did lead to major inactivation of glucose 6-phosphate dehydrogenase, an enzyme that was used to monitor the damage to bacterial protein. Synergistic UV-H2O2 killing was reduced by agents such as pyruvate, thiosulfate, and iron or copper cations, which appeared to act at least in part by reacting chemically with H2O2, and was only slightly affected by the use of UV light at a wavelength of 222 nn rather than 254 nm. Hydrogen peroxide treatment can precede UV irradiation for synergistic killing by some hours with an interim of drying for spores of Bacillus subtilis A, a spore type used commonly for the validation of aseptic processes. Synergistic killing of dried spores or those in suspensions was accelerated at higher temperatures (50 degrees C) rather than at lower temperatures (25 degrees C).


Assuntos
Bacillus megaterium/efeitos dos fármacos , Bacillus megaterium/efeitos da radiação , Irradiação de Alimentos , Peróxido de Hidrogênio/farmacologia , Raios Ultravioleta , Bacillus megaterium/crescimento & desenvolvimento , Proteínas de Bactérias , Contagem de Colônia Microbiana , Dano ao DNA , Relação Dose-Resposta a Droga , Relação Dose-Resposta à Radiação , Sinergismo Farmacológico , Embalagem de Alimentos , Tolerância a Radiação , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/crescimento & desenvolvimento , Esporos Bacterianos/efeitos da radiação
16.
J Appl Microbiol ; 91(1): 176-81, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11442728

RESUMO

AIMS: To provide data on the interaction of radiation dose (x1) and microbial contamination load (x2), as predictor variables, on the percentage of vials exhibiting growth of Bacillus megaterium spores (y). METHODS AND RESULTS: The influence of a wide range of spore loads (1-50 000 spores of B. megaterium vial-1) and gamma radiation doses (0.2-10 kGy) on the contaminated samples was determined. Each contamination load was studied by adding the specified number of spores to 100 vials containing nutrient broth and exposing them to various doses of gamma radiation. Curves representing the number of contaminated vials against the dose of radiation were sigmoidal in shape and the data showed an indirect relationship. Data were analysed by regression analysis which revealed a significant correlation (R2=0.85). The relationship among the tested variables is exponential and can be described by the following equation: y = 1 - (1 - e(0.0173x(1)))(x(2)) It was also estimated that, for each increase of 1 in the number of spores per vial, there is an increase of 1 in the number of contaminated vials. CONCLUSION: The two variables (x1 and x2) have great influence on the radiation sterilization efficiency and the proposed mathematical model is valid for the prediction of this efficiency. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of the present investigation can be of useful industrial application and can help to set acceptance and rejection limits for the production of materials vulnerable to microbial contamination.


Assuntos
Bacillus megaterium/efeitos da radiação , Raios gama , Bacillus megaterium/fisiologia , Relação Dose-Resposta à Radiação , Doses de Radiação , Esporos Bacterianos/crescimento & desenvolvimento , Esporos Bacterianos/efeitos da radiação
17.
J Agric Food Chem ; 48(4): 1340-4, 2000 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10775394

RESUMO

Three spices, chili, black pepper, and turmeric, were tested for the effect of their aqueous extracts on the sensitivity of three bacteria, Escherichia coli, Bacillus megaterium, and Bacillus pumilusspores, to gamma-radiation. It was found that the extracts of the three spices offered protection to these organisms against inactivation by gamma-radiation. These spice extracts were also tested for their protection of naked plasmid DNA. Radiation-induced degradation of plasmid pUC18 DNA was reduced in the presence of the spice extracts. The maximum protection was offered by the chili extract followed by that of black pepper and turmeric. The two known antioxidants, curcumin and piperine from turmeric and black pepper, respectively, were shown to protect the plasmid DNA from the degradation by gamma-radiation. Experiments with the plasmid pUC18 DNA indicated that the spice extracts probably protected microorganisms by protecting their DNA. These studies indicated the importance of spices among ingredients in food as dose-modifying factors during radiation processing.


Assuntos
Alcaloides , Bacillus/efeitos da radiação , Escherichia coli/efeitos da radiação , Extratos Vegetais/farmacologia , Tolerância a Radiação/efeitos dos fármacos , Especiarias , Antioxidantes/farmacologia , Bacillus/efeitos dos fármacos , Bacillus megaterium/efeitos dos fármacos , Bacillus megaterium/efeitos da radiação , Benzodioxóis , Curcuma , Curcumina/farmacologia , Relação Dose-Resposta à Radiação , Escherichia coli/efeitos dos fármacos , Raios gama , Piperidinas/farmacologia , Plasmídeos/efeitos dos fármacos , Plasmídeos/efeitos da radiação , Alcamidas Poli-Insaturadas
18.
Curr Microbiol ; 35(2): 71-6, 1997 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-9216879

RESUMO

A xylose-regulated plasmid expression system for producing high levels of recombinant proteins in Bacillus megaterium has recently been described [Appl Microbiol Biotechnol 35:594, 1991]. Using an antibiotic resistance protein as the expressed protein, we have been able to select mutant plasmids that produce increased levels of heterologous protein. The mutant plasmids show increased segregational stability and have lost the ability to be transformed into Escherichia coli. The same selection protocol has been used to isolate a mutant strain producing high levels of the Bacillus sphaericus mosquitocidal binary toxin. This strain shows toxicity to Culex quinquefasciatus larvae that is comparable toB. sphaericus 2362 and higher than a B. megaterium strain with the original expression plasmid. This approach may be generally useful for high-level regulated protein expression in B. megaterium.


Assuntos
Bacillus megaterium/genética , Toxinas Bacterianas/genética , Animais , Bacillus megaterium/metabolismo , Bacillus megaterium/efeitos da radiação , Toxinas Bacterianas/metabolismo , Toxinas Bacterianas/toxicidade , Bioensaio , Clonagem Molecular , Culex/efeitos dos fármacos , Relação Dose-Resposta a Droga , Larva/microbiologia , Mutagênese , Plasmídeos , Proteínas Recombinantes/biossíntese , Raios Ultravioleta
19.
Acta Biochim Biophys Hung ; 24(3): 283-90, 1989.
Artigo em Inglês | MEDLINE | ID: mdl-2562104

RESUMO

These experiments were aimed at the better understanding of the mechanism of the enhancement of radiation damage brought about by acetone in spores of Bacillus megaterium. Particularly, the intention was to examine the extent of involvement of water content in this action of acetone. The radiosensitization of acetone increased with increasing oxygen concentration and ultimately became zero at 2.1% O2 in N2. The extent of sensitization increased with rising concentration of acetone up to the first peak (50% acetone in water) under anaerobic condition. Further increase in acetone concentration resulted a maximum response seen at 90% acetone in water. To investigate the role of hydroxyl radical in the radiation sensitization caused by acetone two different types of hydroxyl radical scavengers (t-butanol and iso-propanol) were used.


Assuntos
Acetona/farmacologia , Radiossensibilizantes , Esporos Bacterianos/efeitos da radiação , Água/farmacologia , 1-Propanol , Bacillus megaterium/efeitos da radiação , Butanóis , Raios gama , Hidróxidos , Radical Hidroxila , Oxigênio
20.
Artigo em Inglês | MEDLINE | ID: mdl-3025119

RESUMO

As an extension of results obtained from radiation studies on caffeine both in other laboratories and more recently in this laboratory using the bacterial spore as the test system, six compounds with chemical structures closely resembling that of caffeine were tested as radiation modifiers. Of these compounds, purine, adenine and hypoxanthine resembled caffeine in sensitizing spores to radiation, while theobromine, xanthine and theophylline did not. These responses are discussed in relation to the electron sequestration hypothesis of cellular sensitization to high-energy radiation.


Assuntos
Purinas/farmacologia , Tolerância a Radiação/efeitos dos fármacos , Bacillus megaterium/efeitos da radiação , Cafeína/farmacologia , DNA/metabolismo , Hidróxidos , Radical Hidroxila , Oxigênio/farmacologia , Esporos Bacterianos/efeitos da radiação
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