Effect of gamma-ray irradiation on Escherichia coli motility
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Abstract The effects of ionizing radiation on bacteria are generally evaluated from the dose-dependent survival ratio, which is determined by colony-forming ability and mutation rate. The mutagenic damage to cellular DNA induced by radiation has been extensively investigated; however, the effects of irradiation on the cellular machinery in situ remain unclear. In the present work, we irradiated Escherichia coli cells in liquid media with gamma rays from 60Co (in doses up to 8 kGy). The swimming speeds of the cells were measured using a microscope. We found that the swimming speed was unaltered in cells irradiated with a lethal dose of gamma rays. However, the fraction of motile cells decreased in a dose-dependent manner. Similar results were observed when protein synthesis was inhibited by treatment with kanamycin. Evaluation of bacterial swimming speed and the motile fraction after irradiation revealed that some E. coli cells without the potential of cell growth and division remained motile for several hours after irradiation.Keywords:
Kanamycin
[Objective] To study the susceptibility of soybean cotyledonary node to kanamycin,so as to provide experimental basis for the genetic transformation and screening of soybean.[Method] With three different genotypes of soybean as test materials,their yellowing rate and differentiation rate were measured to study the impact of different concentration of kanamycin on the differentiation and shoots growth of soybean cotyledonary node.[Result] Different genotypes of soybean showed different degree of susceptibility to kanamycin,and the critical concentration of kanamycin for the differentiation of cotyledonary was 40 mg/L to Kennong 18,60 mg/L to Suinong 14 and Kennong 4;while the critical concentration of kanamycin for the rooting of shoots was 15 mg/L to Kennong 18,20 mg/L to Suinong 14 and Kennong 4.[Conclusion] The study laid foundation for the genetic transformation and screening of soybean.
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By genetic studies, it was tried to find the mechanism by which a bacterial fraction from different isolated clinical cultures resistant to 25 micrograms/ml of kanamycin can grow in media containing 500 micrograms/ml of kanamycin (at a frequency of about 10(-5)). This study was done in six clinical isolates of Escherichia coli resistant to more than three antibiotics. The results from the bacterial fraction (subpopulation) resistant to high concentrations of kanamycin in the level of resistance to aminoglycoside and non-aminoglycoside antibiotics, in the conjugation experiments, and in the percentage of resistant bacteria to 500 micrograms/ml of kanamycin when the subpopulations were subsequently cultivated in the absence of antibiotics suggest that genetic amplification occurred when one of the strains was growing in the presence of 500 micrograms/ml of kanamycin. Moreover, this strain increased its frequency of survival in high kanamycin concentrations when it was transduced by bacteriophage P1, propagated in cultures resistant to 500 micrograms/ml of kanamycin.
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Selection target plant with foreign gene from transgenic wheat progeny is the key step to wheat transformation. The selection effects to wheat of Xinong1376 and Xinong2611 with Kanamycin were studied. The results showed that non-transformation wheat could be refrained effectively by Kanamycin of 80 mg/L and there was a little difference of different wheat genotype to Kanamycin . By PCR analysis in the resistant seedling to Kanamycin of 80 mg/L, the frequency of PCR positive amounted to 90%.
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In an effort to optimize the antibacterial activity of kanamycin class aminoglycoside antibiotics, we have accomplished the synthesis and antibacterial assay of new kanamycin B analogues. A rationale-based glycodiversification strategy was employed. The activity of the lead is comparable to that of commercially available kanamycin. These new members, however, were found to be inactive against aminoglycoside resistant bacteria. Molecular modeling was used to provide the explanation. Thus, a new strategy for structural modifications of kanamycin class aminoglycosides is suggested.
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Three methods were developed to rapidly identify Bt-transgenic cotton plants with kanamycin-resistant gene as indirect selective marker.The first method was to culture uncoated seeds on the kanamycin containing medium(kan-medium),the difference between transgenic and non-transgenic plants was revealed after seeds germinated on the medium.According to the color of the cotyledons,kan-resistant plants were discovered at optimal concentration of 0.75 g·L-1.The second method was to paint kanamycin solution(kan-solution) on the cotyledons directly with optimal concentration at 4.0 g·L-1,by which after 4-7 days,plants with cotyledon normal green were considered as kan-resistant plants.The third one was that a pore was dug on cotyledons and dropped kan-solution in.The best concentration of the kan-solution was 2.0 g·L-1.All the plants could be rapidly screened out in 4-7 days after kanamycin treatment by the three methods.The efficacy of above methods for transgenic plant indirect identification were tested using PCR analysis with Bt-gene specific primers,giving a examination ratio of more than 90%.Moreover,all the seeds decorticated could be more easily identified with kanamycin treatments.
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Kanamycin can be used to select the transformed plants containing the nptⅡ gene.In order to assay the optimal screening concentration to nptⅡ gene,Kanamycin was smeared to the surface of the transformed soybean leaves of Jilinxiaoli No.1.It showed that 500 mg/L Km with 3 days' selecting was best.This method was compared with PCR as well,and the results suggested that the equivalent ratio was(90.8%) between the high-resistant plants and the resistant plants,87.1% between the sensitive plants and the hypersensitive plants.Accordingly,it is available to select the transformed soybean plants by smearing with Km.
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Kanamycin was fed to laying hens for 7 days at the dietary levels of 20, 1, 000, 4, 000, 8, 000 and 16, 000μg potency/g diet, respectively, and kanamycin content in the eggs laid on the 7 th day was analyzed microbiologically using Bacillus subtilis ATCC 6633. To the 40 hens fed 16, 000μg kanamycin/g for 7 days, kanamycin-free diet was fed for another 7 days and all of the eggs laid by 5 hens out of 40 during 14 days of experimental period were analyzed for kanamycin content. On 0, 1, 2, 3, 5 and 7 days after the withdrawal of dietary kanamycin, 5 hens each were sacrificed to get samples of the liver and bile for kanamycin analysis.No kanamycin was detected in the egg white tested. No kanamycin was detected in the egg yolk laid by the hens fed 20 and 1, 000μg kanamycin/g diet, respectively.During feeding the diet containing kanamycin, content of kanamycin in the egg yolk increased in proportion to the dietary kanamycin level over 1, 000μg/g and in proportion to the length of kanamycin feeding.After the withdrawal of dietary kanamycin, contents of kanamycin in the egg yolk, liver and bile increased or remained almost constant for 2 days, then decreased exponentially. The disappearance pattern of residual kanamycin in the body of laying hens was different from those of the antibiotics tested previously. Application of 3-compartment model to explain the pattern was discussed.
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Diets containing various levels from 20 to 16, 000μg potency of kanamycin per g diet were fed to meat-type male chicks of 4-week-old for 4 weeks, and 5 chicks each from each lot were sacrificed at the end of kanamycin feeding to get samples of the blood, breast muscle, liver and bile. Thereafter, to the rest of the chicks fed 16, 000μg kanamycin/g diet, kanamycin-free diet was fed, and 5 chicks each were sacrificed at 0, 3, and 6 hours and 1, 2, 3, 5, and 7 days. Content of kanamycin in the samples was determined microbiologically using Bacillus subtilis ATCC 6633.No residue was detected in the blood, muscle and liver of the chicks on 20μg of kanamycin/g diet.Except the residual kanamycin in the muscle, kanamycin contents in the blood, liver and bile at the end of kanamycin feeding were in proportion to dietary kanamycin levels. Residual kanamycin in the muscle increased after the withdrawal of dietary kanamycin, while those in the blood, liver and bile decreased rapidly.The disappearance pattern of residual kanamycin in the chick's body was peculiar and different from those of the antibiotics tested previously. Application of 3-compartment model to explain the disappearance pattern of kanamycin was discussed.
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Abstract Overuse of antibiotics has caused serious problems, such as appearance of super bacteria, whose accumulation in the human body through the food chain is a concern. Kanamycin is a common antibiotic used to treat diverse infections; however, residual kanamycin can cause many side effects in humans. Thus, development of an ultra-sensitive, precise, and simple detection system for residual kanamycin in food products is urgently needed for food safety. In this study, we identified kanamycin-binding aptamers via a new screening method, and truncated variants were analyzed for optimization of the minimal sequence required for target binding. We found various aptamers with high binding affinity from 34.7 to 669 nanomolar K d app values with good specificity against kanamycin. Furthermore, we developed a reduced graphene oxide (RGO)-based fluorescent aptasensor for kanamycin detection. In this system, kanamycin was detected at a concentration as low as 1 pM (582.6 fg/mL). In addition, this method could detect kanamycin accurately in kanamycin-spiked blood serum and milk samples. Consequently, this simple, rapid, and sensitive kanamycin detection system with newly structural and functional analysis aptamer exhibits outstanding detection compared to previous methods and provides a new possibility for point of care testing and food safety.
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