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排序方式: 共有771条查询结果,搜索用时 343 毫秒
91.
Bromoacetaldehyde (BAA) was used to study the secondary structure of DNA in lambda-phage particles. It was determined that about 1% of the adenines in the intraphage lambda-DNA reacts readily with BAA, thus, they are placed in DNA sites with disturbed complementary interactions. These adenines are close to the tryptophan residues of the phage protein. Fluorescence emission of epsilon A in the intraphage DNA is dramatically quenched. This, apparently, indicates the interaction between epsilon A and Trp- and/or Tyr- and/or Met-residues of phage protein. 相似文献
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The effects of co-evolution with lytic phage on bacterial virulence-related traits are largely unknown. In this study we investigate the incidence of the mucoid phenotype of the bacterium Pseudomonas fluorescens SBW25 in response to co-evolution with the lytic phage phi2 (φ2). The mucoid phenotype of Pseudomonas spp. is due to overproduction of alginate and is a considerable virulence factor contributing to the intractability of infections most notably in cystic fibrosis (CF) lung, but also in pathogenic infections of plants. Our data show that this phenotype can evolve as an adaptive response to phage predation and is favoured under specific abiotic conditions, in particular a homogenous spatial structure and a high rate of nutrient replacement. The mucoid phenotype remains partially sensitive to phage infection, which facilitates ‘apparent competition'' with phage-sensitive competitors, partially offsetting the costs of alginate production. Although P. fluorescens SBW25 is not a pathogen, several key characteristics typical of Pseudomonas aeruginosa clinical isolates from CF lung were noted, including loss of motility on mucoid conversion and a high rate of spontaneous reversion to the wild-type phenotype. Although the genetic mechanisms of this phenotype remain unknown, they do not include mutations at many of the commonly reported loci implicated in mucoid conversion, including mucA and algU. These data not only further our understanding of the potential role phage have in the ecology and evolution of bacteria virulence in both natural and clinical settings, but also highlight the need to consider both biotic and abiotic variables if bacteriophages are to be used therapeutically. 相似文献
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Jeong Seok Oh Hee Ho Park Tai Hyun Park 《Biotechnology and Bioprocess Engineering》2008,13(4):470-475
In a two-phase operation, E. coli containing λSNNU1 (Q
−
S
−) in the chromosome is typically cultured at 33°C and cloned gene expression is induced by elevating the temperature. At least
40°C is necessary for complete induction of cloned gene expression; however, temperatures above 40°C have been shown to inhibit
cloned gene expression. This suggests that a three-phase operation, which has an induction phase between the growth and production
phases, may result in higher gene expression. In this study, optimal temperature management strategies were investigated for
the three-phase operation of cloned gene expression in thermally inducible E. coli/bacteriophage systems. The optimal temperature for the induction phase was determined to be 40°C. When the temperature of
the production stage was 33°C, the optimal time period for the induction phase at 40°C was determined to be 60 min. In contrast,
when the temperature of the production phase was 37°C, the optimal period for the induction phase at 40°C was 20∼30 min. When
the three-phase temperature and temporal profile were set at a growth phase of 33°C, an induction phase at 40°C for 30 min,
and a production phase at 37°C, the highest level of cloned gene expression was achieved. 相似文献
98.
Aims: To study the efficacy of the lytic phage φS1 in eliminating Pseudomonas fluorescens in the early stage of biofilm formation, using an in situ and real time methodology for cell quantification.
Methods and Results: Cell adhesion and phage infection studies were carried out in a parallel plate flow chamber under laminar conditions. Cells were allowed to adhere until reaching 1·7–1·8 × 106 cells cm−2 and phage infection was performed with two different phage concentrations (2 × 109 PFU ml−1 and 1 × 1010 PFU ml−1 ). Phage concentration clearly affects the speed of infection. The less concentrated phage solution promoted a three times slower rate of cell removal but did not affect the overall percentage of cell removal. In fact, after a longer infection period the less concentrated phage solution reached the same 93% cell removal value.
Conclusions: Phages are efficient in the eradication of bacterial cells at the early stage of biofilm formation and their presence at the surface did not allow bacterial recolonization of the surface.
Significance and Impact of the Study: To date, no published studies have been made concerning in situ and real time quantification of cell removal from surfaces due to phage action. 相似文献
Methods and Results: Cell adhesion and phage infection studies were carried out in a parallel plate flow chamber under laminar conditions. Cells were allowed to adhere until reaching 1·7–1·8 × 10
Conclusions: Phages are efficient in the eradication of bacterial cells at the early stage of biofilm formation and their presence at the surface did not allow bacterial recolonization of the surface.
Significance and Impact of the Study: To date, no published studies have been made concerning in situ and real time quantification of cell removal from surfaces due to phage action. 相似文献
99.
Bhardwaj A Walker-Kopp N Wilkens S Cingolani G 《Protein science : a publication of the Protein Society》2008,17(9):1475-1485
A common objective in protein engineering is the enhancement of the thermodynamic properties of recombinant proteins for possible applications in nanobiotechnology. The performance of proteins can be improved by the rational design of chimeras that contain structural elements with the desired properties, thus resulting in a more effective exploitation of protein folds designed by nature. In this paper, we report the design and characterization of an ultra-stable self-refolding protein fiber, which rapidly reassembles in solution after denaturation induced by harsh chemical treatment or high temperature. This engineered protein fiber was constructed on the molecular framework of bacteriophage P22 tail needle gp26, by fusing its helical core to the foldon domain of phage T4 fibritin. Using protein engineering, we rationally permuted the foldon upstream and downstream from the gp26 helical core and characterized gp26-foldon chimeras by biophysical analysis. Our data demonstrate that one specific protein chimera containing the foldon immediately downstream from the gp26 helical core, gp26(1-140)-F, displays the highest thermodynamic and structural stability and refolds spontaneously in solution following denaturation. The gp26-foldon chimeric fiber remains stable in 6.0 M guanidine hydrochloride, or at 80 degrees C, rapidly refolds after denaturation, and has both N and C termini accessible for chemical/biological modification, thereby representing an ideal platform for the design of self-assembling nanoblocks. 相似文献
100.