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61.
Fourier transform infrared (FT-IR) spectroscopy was used to investigate the radiation-induced effects on Kocuria rosea. Bacterial suspensions at the stationary phase were exposed to increasing doses of gamma radiation. In the region 1350-840cm(-1), assigned to phosphodiester backbone, nucleic acids, and sugar rings, the radical damaging effects were dose-dependent, with the first threshold at 2.75kGy and the second at 13.75kGy inducing more striking spectral variations. Postirradiation reincubation did not significantly affect the biomolecular response, except in the spectral range 1100-1000cm(-1). These observations suggest the occurrence of new phylogenetic characteristics for K. rosea following irradiation. Moreover, two-dimensional analysis was used to highlight correlated evolutions of molecular species as radical aggression increased. The results point to an evolutionary scheme during the time course of irradiation. Thus, one- and two-dimensional IR analyses are convenient means of investigating the metabolic events following oxidative stress generated by either chemical or physical agents. 相似文献
62.
Production of antibacterial substances by bifidobacterial isolates from infant stool active against Listeria monocytogenes 总被引:1,自引:0,他引:1
AIMS: This study aimed to characterize new isolates of human bifidobacteria, evaluate some of their probiotic potential and to screen these isolates for their effectiveness at inhibiting Listeria monocytogenes in vitro. METHODS AND RESULTS: Thirty-four Bifidobacterium isolates from infant faeces were identified by fructose-6-phosphate phosphoketolase and PCR. Six isolates, coded RBL67, RBL68, RBL69, RBL70, RBL85 and RBL86, showed higher antagonistic activity against L. monocytogenes. Neutralized culture supernatants of these strains did not inhibit L. monocytogenes when tested by agar diffusion method. However, the concentration of supernatant by speed-vac resulted in the formation of an inhibitory effect with supernatants from strains RBL67, RBL68 and RBL70. This effect was shown to be related to heat-stable proteinaceous compound(s) which were resistant to heating at 100 degrees C for 5 min but not to pronase-E, proteinase-K or trypsin. The extraction of the inhibitory compounds by methanol-acetone extraction procedure indicated that four strains (RBL67, RBL68, RBL69 and RBL70) were mostly soluble in acetone. However, strain RBL85 produced inhibitory substances that were soluble in methanol. CONCLUSION: Infant bifidobacterial isolates produce heat-stable proteinaceous compounds active against L. monocytogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: Production of antibacterial substances by bifidobacteria would improve intestinal bacterial ecology and inhibit intestinal pathogens. 相似文献
63.
An efficient protocol has been developed for direct shoot organogenesis from embryo axes derived from mature seeds of two different landraces of Bambara groundnut. Multiple shoots were initiated on several media containing different concentrations and combinations of benzylaminopurine (BAP) or thidiazuron (TDZ). Efficient regeneration occurred when the embryo axes were first plated for 6 days on a medium containing high concentrations of BAP (1 mg/l) and alpha-naphthaleneacetic acid (NAA, 1 mg/l) and then cut transversely and transferred onto a medium containing 1.5 mg/l BAP. Shoot regeneration frequency was 100% and from five to eight shoots per explant were obtained. The importance of using embryo explants and cytokinins in the culture media, with respect to controlling the development of a highly organogenic system, was demonstrated. Histological studies revealed that proliferating buds originated directly from the superficial layers of the explants without an intermediate callus phase. The regenerated shoots were rooted on a medium containing 1 mg/l NAA and then transferred to the greenhouse. Flow cytometric analyses and chloroplast counts of guard cells suggested that the regenerants were diploid. All were morphologically normal and fertile. The short duration, high efficiency and low frequency of somaclonal variation of this system make it well suited for wider biotechnological applications of Bambara groundnut-a neglected and under-utilized crop. 相似文献
64.
Escherichia coli heat shock protein DnaK: production and consequences in terms of monitoring cooking 总被引:1,自引:0,他引:1
Seyer K Lessard M Piette G Lacroix M Saucier L 《Applied and environmental microbiology》2003,69(6):3231-3237
Through use of commercially available DnaK proteins and anti-DnaK monoclonal antibodies, a competitive enzyme-linked immunosorbent assay was developed to quantify this heat shock protein in Escherichia coli ATCC 25922 subjected to various heating regimens. For a given process lethality (F(70)(10) of 1, 3, and 5 min), the intracellular concentration of DnaK in E. coli varied with the heating temperature (50 or 55 degrees C). In fact, the highest DnaK concentrations were found after treatments at the lower temperature (50 degrees C) applied for a longer time. Residual DnaK after heating was found to be necessary for cell recovery, and additional DnaK was produced during the recovery process. Overall, higher intracellular concentrations of DnaK tended to enhance cell resistance to a subsequent lethal stress. Indeed, E. coli cells that had undergone a sublethal heat shock (105 min at 55 degrees C, F(70)(10) = 3 min) accompanied by a 12-h recovery (containing 76,786 +/- 25,230 molecules/cell) resisted better than exponentially growing cells (38,500 +/- 6,056 molecules/cell) when later heated to 60 degrees C for 50 min (F(70)(10) = 5 min). Results reported here suggest that using stress protein to determine cell adaptation and survival, rather than cell counts alone, may lead to more efficient heat treatment. 相似文献
65.
Identification of two human nuclear proteins that recognise the cytosine-rich strand of human telomeres in vitro 总被引:4,自引:2,他引:2
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Lacroix L Liénard H Labourier E Djavaheri-Mergny M Lacoste J Leffers H Tazi J Hélène C Mergny JL 《Nucleic acids research》2000,28(7):1564-1575
Most studies on the structure of DNA in telomeres have been dedicated to the double-stranded region or the guanosine-rich strand and consequently little is known about the factors that may bind to the telomere cytosine-rich (C-rich) strand. This led us to investigate whether proteins exist that can recognise C-rich sequences. We have isolated several nuclear factors from human cell extracts that specifically bind the C-rich strand of vertebrate telomeres [namely a d(CCCTAA)n repeat] with high affinity and bind double-stranded telomeric DNA with a 100× reduced affinity. A biochemical assay allowed us to characterise four proteins of apparent molecular weights 66–64, 45 and 35 kDa, respectively. To identify these polypeptides we screened a λgt11-based cDNA expression library, obtained from human HeLa cells using a radiolabelled telomeric oligonucleotide as a probe. Two clones were purified and sequenced: the first corresponded to the hnRNP K protein and the second to the ASF/SF2 splicing factor. Confirmation of the screening results was obtained with recombinant proteins, both of which bind to the human telomeric C-rich strand in vitro. 相似文献
66.
Garat Chrystelle; Carter Ethan P.; Matthay Michael A. 《Journal of applied physiology》1998,84(5):1763-1767
Because the availability of transgenic micemakes it possible to examine the contribution of single genes to invivo function, we developed a simple in situ mouse model that can beused to quantify isosmolar alveolar epithelial fluid clearance (AFC). Mice were killed, a tracheostomy was done, and then a test solution ofa 5% isosmolar albumin solution with 0.1 µCi of125I-labeled albumin was instilledvia the trachea into the distal air spaces of both lungs. Afterinstillation, the lungs were inflated to 7 cmH2O with 100%O2 and maintained at 37°C byplacing the animals under an infrared lamp. AFC was measured by theprogressive increase in concentration of labeled and unlabeled proteinover 1 h. The results indicated the following.1) Basal, unstimulated AFC in mouselungs was significantly faster than in ex vivo rat lungs (27 ± 5%in in situ mice vs. 11 ± 3% in ex vivo rat lungs; P < 0.05).2) Comparison of equivalent doses(104 M) of -adrenergicagonist (isoproterenol) and2-adrenergic agonists(terbutaline and salmeterol) indicated that stimulated clearanceoccurred only in presence of isoproterenol.3) Because atenolol, a specific1-antagonist, abolished theeffect of isoproterenol, the -adrenergic stimulation appears to bemediated by 1-receptors. Therate of AFC in nonperfused mouse lungs was significantly faster than inprior studies of nonperfused lungs in rats and sheep. Interestingly,the stimulated clearance rate in mice was similar to the fast rates ofAFC that we recently reported in patients recovering from hydrostaticpulmonary edema. This in situ model is a unique experimentalpreparation that can be readily used to quantify isosmolar epithelialfluid clearance in mice. 相似文献
67.
M. Turgis J. Han M. Millette S. Salmieri J. Borsa M. Lacroix 《Letters in applied microbiology》2009,48(6):657-662
Aims: In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces.
Methods and Results: Ground beef samples inoculated with Salmonella Typhi (106 CFU g−1 ) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a 60 Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D 10 value in the absence/presence of antimicrobial compound.
Conclusions: Depending on the compound tested, the addition of antimicrobial compound decreased the D10 value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef.
Significance and Impact of the Study: These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi. 相似文献
Methods and Results: Ground beef samples inoculated with Salmonella Typhi (10
Conclusions: Depending on the compound tested, the addition of antimicrobial compound decreased the D
Significance and Impact of the Study: These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi. 相似文献
68.
Violaine Garcia‐Fernandez Mathieu Amy André Lacroix Giorgio Malacarne Gérard Leboucher 《Ethology : formerly Zeitschrift fur Tierpsychologie》2010,116(7):662-670
Females invest differently in their eggs depending on the quality of their mates. In oscines, female investment is influenced by the quality of male song. In domestic canaries Serinus canaria, as well as in black‐capped chickadees Poecile atricapillus, females pay attention not only to the intrinsic quality of male song but can also gather information, by eavesdropping on male–male singing interactions, on the relative quality of males. During these interactions, overlapping the song of the rival is more threatening than alternating. Moreover eavesdropping female canaries have been shown to prefer the overlapping song rather than the overlapped song. The present study was designed to assess the effect of the information gathered by eavesdropping on female investment in eggs. First, we broadcasted overlapping interactions to female canaries. Then, we broadcasted to each female one of the two songs previously heard and collected eggs. Females exposed to overlapping songs laid eggs with greater yolk ratio than females exposed to overlapped songs. In contrast, yolk testosterone quantity and concentration were not affected by the treatment. Moreover, we found a variation between eggs with regard to the testosterone deposited in yolk: both quantity and concentration increased with laying order. Our results suggest that female canaries use information gathered by eavesdropping to differentially allocate resources into the eggs. They suggest that singing interactions could influence chick quality via female investment. 相似文献
69.
Loïc Lesobre Frédéric Lacroix Eric Le Nuz Yves Hingrat Toni Chalah Michel Saint Jaime 《Journal of avian biology》2010,41(2):117-127
Behavioural studies have led to the perception that lekking species experience a high male reproductive skew as a consequence of females’ selective mate choice. In addition, observations suggest that females copulate only once and therefore polyandry seems unlikely as females are supposed to choose the best male available. In order to analyse the mating strategy of the Houbara bustard, an endangered lekking species under reinforcement in eastern Morocco, we used microsatellite data to perform paternity analyses. None of our observations followed common expectations under a lek mating system: we found no male reproductive skew suggesting no apparent selective female mate choice and no apparent male benefit from lekking. In contrast, a high level of polyandry (60 % of the nests) was recorded suggesting that sperm competition may operate. In addition, we present another case of conspecific brood parasitism in a lekking species and this was an unexpected alternative strategy for a species presenting high parental cost and low fecundity. The increasing number of studies contradicting common assumptions on lekking species suggests that alternative breeding strategies such as males pursuing an off‐lek mating strategy, female polyandry and even conspecific brood parasitism might be more widespread in lekking species than previously thought. 相似文献
70.
Valeria Mozzetti Franck Grattepanche Déborah Moine Bernard Berger Enea Rezzonico Leo Meile Fabrizio Arigoni Christophe Lacroix 《Microbial cell factories》2010,9(1):60