Bacteriophage T4D Receptor and the Escherichia coli Cell Wall Structure: Binding of Endotoxin-Like Particles to the Cell Wall

A variety of degradative treatments have been used to investigate the nature of the structure and components of the cell walls of Escherichia coli B. The binding and localization of the endotoxin-like particles found on the cell walls were of special interest because some of them are associated with the site where the inner tail tube of bacteriophage T4D penetrates the cell wall. Modified cell walls were obtained by heating a suspension of bacterial cells originally in 0.1 M phosphate, pH 7.0, after the addition of 12.5 M NaOH to a final concentration of 0.25 M. With regard to the endotoxin-like particles, it was found that: (i) at least part of them still remained bound to the modified cell wall after the alkali treatment; (ii) the subsequent incubation of alkali-treated cell walls with lysozyme destroyed the bacterial form and released a complex of endotoxin-like particles together with a fibrous material; (iii) on the other hand, treatment with 45% phenol at 70°C removed the endotoxin-like particles from the surface of the alkali-treated cell walls, but most of the fibrous material was left on the cell wall; and (iv) incubation of alkali-treated cell walls with 5 mM ethylenediaminetetraacetic acid at 20°C also removed the endotoxin-like particles, but did not disrupt the rodlike bacterial form. However, if the ethylenediaminetetraacetic acid treatment was performed at 55°C, the bacterium-like form was destroyed. These differential sensitivities to ethylenediaminetetraacetic acid suggested that loosely bound divalent metal ions normally hold these endotoxin-like particles on the cell wall surface, but that probably more tightly bound metal ions are involved in the determination of cell shape. Analysis of the protein components of the alkalitreated cell walls showed that only one protein was present in significant amounts, and this protein had an electrophoretic mobility similar to that of the Braun lipoprotein. This protein was released from the alkali-treated cell walls upon heating with 2% sodium dodecyl sulfate at 100°C. Phospholipids were also absent from this structure. The distribution of the remaining cell wall components on the alkali-treated cell walls is discussed.     

Host Cell Deoxyribonucleic Acid Polymerase I and the Support of T4 Bacteriophage Growth

Ultraviolet irradiation of Escherichia coli polA(-) cells reduces their capacity to support the growth of T4 phage. There is no additional loss of capacity observed in pol tsA(-)recA(-) double mutants at the nonpermissive temperature. The reversion frequency of a T4 rII mutant after ultraviolet irradiation is not changed by the absence of host deoxyribonucleic acid polymerase I.     

Bacteriophage T4 Head Maturation: Release of Progeny DNA from the Host Cell Membrane

We have presented a new approach to studying bacteriophage T4 head maturation. Using a modified M-band technique, we have shown that progeny deoxyribonucleic acid (DNA) was synthesized on the host cell membrane throughout infection. This DNA was released from the membrane later in infection as the result of formation of the phage head; detachment of the DNA required the action of gene products 20, 21, 22, 23, 24, 31, 16, 17 and 49, known to be necessary for normal head formation. Gene products 2, 4, 50, 64, 65, 13 and 14, also involved in head morphogenesis were not required to detach progeny DNA from the membrane; the presence of the phage tail and tail fibers also was not required. DNA was released in the form of immature heads and initially was sensitive to deoxyribonuclease (DNase). Conversion to DNase resistance followed rapidly. The amount of phage precursors present at the time of DNA synthesis determined the time of onset and detachment rate of DNA from the M band as well as the kinetics by which the detached DNA become DNase resistant.     

Phage Receptor Material in Lactobacillus casei Cell Wall

A trichloroacetic acid (TCA)-soluble fraction, extracted using cold TCA, was derived from the cell wall of Lactobacillus casei strain S-1. It not only inhibited the adsorption of phage J-l but also desorbed these phages, in their active form, which had previously been adsorbed onto the cell walls. l-Rhamnose, one of the components of this TCA-soluble fraction, had an identical activity to this TCA-soluble fraction, on phage adsorption. This suggested that l-rhamnose is a part of phage receptor material in the cell wall of L. casei strain S-l; and the binding of the phage to the cell wall is reversible, even at 37 C.     

Region-Specific Recombination in Phage T4. III. the Effect of Host Mutations on Glucosylation-Dependent Recombination in Bacteriophage T4d

Mutations in the Escherichia coli genes recK, recL and (probably) uvrE and polA increase special (glucosylation-dependent), but not general recombination in bactriophage T4D.     

Role of the Host Cell in Bacteriophage Morphogenesis: Effects of a Bacterial Mutation on T4 Head Assembly

In certain bacterial mutants, called groE, T4 phage head assembly is blocked specifically, implying that the host plays a direct role in head assembly. The block occurs early in the assembly process at the level of action of T4 gene 31.     

乙烯对苹果果实细胞壁降解效应初探

以陕西主栽苹果品种'秦冠'为试材,研究了不同浓度乙烯利以及加热处理下苹果果实中与细胞壁代谢相关酶的活性变化及其与细胞壁组分降解的关系.结果表明:乙烯对各细胞壁酶活性的促进效应因乙烯利施用浓度不同而异.乙烯利浓度由10 mg/L增至1 000 mg/L时,果胶甲酯酶(PME)、多聚半乳糖醛酸酶(PG)和纤维素酶(CS)的活性先逐渐增强,而后又被抑制;木聚糖(Xyl)没有受到明显影响.加热处理可增进乙烯利的作用,如在60℃时,PME、PG、CS、Xyl活性分别是对照的1.5、2.7、1.1和1.5倍.PG活性的显著增加同时引起了果实可溶性糖含量的显著升高,但其他酶活性变化与可溶性糖含量无直接相关.     

Effect of Auxin on Cell Wall Degrading Enzymes

The effect of auxin on the activities of amylase, cellulase, β-1, 3- and/or β-l, 6-glucanase and hemieellulase were observed using etiolated barley coleoptile and pea epicotyl internode segments. The activities of β-1, 3- and/or β-l, 6-glueanase and hemicellulase of barley were increased by indole-3-acetic acid in a 3 hours' treatment. Amylase activity was not influenced by the auxin. Cellulase activity was not detected under the experimental conditions. 2, 4-Dichlorophenoxyacetic acid increased hemicellulase activity, but not cellulase and amylase activities, in pea epicotyl segments in 3 hours. Fungal β-1, 3-glucanase exogenously applied induced the elongation of barley coleoptile segments. The elongation induced by the enzyme was as high as that induced by indole-3-acetic acid at least for the first 1 to 3 hours.     

Permeability to Water of the Fibre Cell Wall Material of Two Hardwoods

The permeability to water of the fibre cell wall of birch (Betulapubescens Ehrh.) and lime (Tilia x vulgaris Hayne) wood, wasmeasured in wood slices in which most of the void space wasfilled with paraffin wax or a polymerizing silicone elastomer.An osmotic technique was used with solutes of molecular weightgreat enough to prevent their molecules from penetrating thepores in the water-swollen cell wall. The solutes used weredextran and polyethylene glycol with molecular weights of 40000 and 6000 respectively. Values for permeability k x 10²¹, as defined by the Darcy equation,ranged between 3.6 m² for the tangential direction in birch,to 27 m² for the longitudinal direction in birch. These resultsare in good agreement with previously measured values but areat least ten times less than theoretical values. It is calculatedthat total emptying or filling of a wood cell through the wallmight be possible in as little as 5 min under a pressure differenceof 0.1 MPa if other flow pathways were blocked. Key words: Betula pubescens, Tilia x vulgaris, Water permeability, Fibre cell wall     

Temporal Expression of Bacterial Proteins Instructs Host CD4 T Cell Expansion and Th17 Development

Pathogens can substantially alter gene expression within an infected host depending on metabolic or virulence requirements in different tissues, however, the effect of these alterations on host immunity are unclear. Here we visualized multiple CD4 T cell responses to temporally expressed proteins in Salmonella-infected mice. Flagellin-specific CD4 T cells expanded and contracted early, differentiated into Th1 and Th17 lineages, and were enriched in mucosal tissues after oral infection. In contrast, CD4 T cells responding to Salmonella Type-III Secretion System (TTSS) effectors steadily accumulated until bacterial clearance was achieved, primarily differentiated into Th1 cells, and were predominantly detected in systemic tissues. Thus, pathogen regulation of antigen expression plays a major role in orchestrating the expansion, differentiation, and location of antigen-specific CD4 T cells in vivo.     

Effect of Poxvirus Infection on Host Cell Deoxyribonucleic Acid Synthesis

Deoxyribonucleic acid (DNA) synthesis was studied in poxvirus-infected cells by measuring (14)C-thymidine incorporation into viral and host cell DNA. A complete separation of the two species of DNA was achieved by combining the previously used "Dounce method" with a separation method based on different reannealing properties of viral and vertebrate DNA. Shortly after infection of HeLa cells with poxviruses, a burst of viral DNA synthesis occurred in the cytoplasm, but a rapid inhibition of host-cell DNA synthesis in the nucleus was observed. This inhibition of cellular DNA synthesis was also found if an accumulation of viral DNA was prevented. At high multiplicites, ultraviolet-irradiated virus inhibited host-cell DNA synthesis to the same extent as fully infectious poxvirus. Under the same conditions, heating at 60 C for 15 min caused a decrease in the ability of cowpox virus to inhibit host-cell DNA synthesis, but did not produce the same effect on vaccinia virus strain WR.     

Effect of Oxygen on Host Cell Reactivation in Bacteroides fragilis

Host cell reactivation was induced by oxygen in Bacteroides fragilis. Chloramphenicol inhibited the induction of host cell reactivation. DNA and protein syntheses were not inhibited during oxygen-induced host cell reactivation.     

禽流感病毒NS1蛋白对细胞的影响

NS1蛋白为流感病毒非结构蛋白,只在病毒侵入宿主细胞后产生.目前NS1蛋白对细胞整体水平上的作用仍不清楚,为了解NS1蛋白在病毒感染细胞中的作用,构建了重组质粒pCMV-myc-NS1并将其转染A549细胞,利用双向电泳技术检测了受NS1蛋白调控的宿主蛋白,以期从蛋白质组水平上研究禽流感病毒与宿主细胞间的相互作用.同时,还检测了转染NS1对细胞增殖和细胞周期的影响.结果显示,NS1在细胞中的表达,能够明显引起宿主细胞代谢的变化,并通过阻滞细胞周期的正常进行而减缓细胞的增殖.     

Effect of the Specific Toxin in Helminthosporium victoriae on Host Cell Membranes

Helminthosporium victoriae toxin, which affects only hosts of the toxin-producing fungus, causes loss of electrolytes from roots, leaves, and coleoptiles of treated plants. Root hair cells lost the ability to plasmolyze after 20 minutes exposure to toxin in solution; comparable resistant cells retained plasmolytic ability during 3 hours exposure. Toxin stopped uptake of exogenous amino acids and Pi by susceptible but not by resistant tissue. Incorporation of ³²P into organic-P and ¹⁴C-amino acids into protein was blocked in susceptible but not in resistant tissue. Apparent free space increased in susceptible but not in resistant roots. The increase was evident within 30 minutes, and reached 80% free space after 2 hours exposure to toxin. When cell wall-free protoplasts were exposed to 0.16 μg toxin/ml, protoplasmic streaming stopped and all plasma membranes of susceptible protoplasts broke within 1 hour. Resistant protoplasts were not affected significantly. Data support the hypothesis of a primary lesion of toxin in the plasma membrane. Effects on synthesis could result from lack of transport of exogenous solutes to sites of synthesis. It is possible that all other observed effects of toxin are secondary to membrane damage.     

Effect of Alfalfa Wilts on the Hydroxyproline Content in Cell Wall

The Hyp content was studied in cell wall of alfalfa susceptible and resistant strains on the 3rd, the 7th and on the 14th day after inoculation with Verticillium albo-atrum or Corynebacterium michiganense pv. insidiosum. The changes of Hyp content after inoculation with both pathogens were markedly expressed in alfalfa roots. Resistant plants of R 337 strain responded to inoculation with V. albo-atrum or C. michiganense pv. insidiosum by the decrease of Hyp content mainly on the 3rd and on the 7th day. On the 14th day after inoculation Hyp content practically did not differ from that of the control. Susceptible plants of S 354 and S 321 srains responded to inoculation with wilt pathogens by the slight decrease of Hyp content at the 3rd day after inoculation. A significant increase of Hyp content was found on the 7th and mainly on the 14th day after inoculation in comparison with control plants. The cell wall Hyp content was also determined with 7 R-strains and 7 S-strains at 120 days after inoculation with both pathogens. In each R and S strain two categories of plants were used for chemical analyses: Wilt-free plants (0 to 1 classes) and diseased, wilted plants (2 to 6 classes). In the resistant alfalfa strains no differences in Hyp content between the wilt-free and diseased plants were found. In the susceptible alfalfa strains the Hyp content was significantly higher in roots of diseased plants comparing with the wilt-free ones. Only negligible changes in Hyp content were registered in the overground parts of all inoculated alfalfa strains.     

细胞壁缺陷对白喉棒状杆菌致病性影响的研究

检测白喉棒状杆菌稳定L型对动物的致病性,探讨细胞壁缺陷对白喉棒状杆菌致病性的影响及其可能的分子机制。采用氨苄青霉素在非高渗培养基内诱导并获得产毒性白喉棒状杆菌稳定L型纯培养物。收集白喉棒状杆菌稳定L型纯培养物及其代谢产物,将收集的高于细菌型10 000倍浓度的白喉棒状杆菌稳定L型纯培养物及其代谢产物皮内注射家兔,观察局部注射部位皮肤或全身的病理改变。分别采用对流免疫电泳(CIEP)和SDS-不连续聚丙烯酰胺凝胶电泳(SDS-PAGE)检测白喉棒状杆菌稳定L型可溶性代谢产物中的白喉毒素蛋白质。结果显示,白喉棒状杆菌稳定L型不能引起动物局部或全身发生异常表现,在其可溶性代谢产物中并未检测到白喉毒素蛋白质。提示细胞壁缺陷变异可影响白喉棒状杆菌产生白喉毒素蛋白质,从而使其丧失了产生外毒素致病的作用。     

Bacterial Characteristics Determining the Potential Host Range of Bacteriophage T4

Many members of the Enterobacteriaceae, but not other gram-negative organisms, apparently carry a specific recognition site for the T4 tail tube on their cytoplasmic membranes.     

Regulatory Networks of the T4SS Control: From Host Cell Sensing to the Biogenesis and the Activity during the Infection

Delivery of effectors, DNA or proteins, that hijack host cell processes to the benefit of bacteria is a mechanism widely used by bacterial pathogens. It is achieved by complex effector injection devices, the secretion systems, among which Type 4 Secretion Systems (T4SSs) play a key role in bacterial virulence of numerous animal and plant pathogens. Considerable progress has recently been made in the structure–function analyses of T4SSs. Nevertheless, the signals and processes that trigger machine assembly and activity during infection, as well as those involved in substrate recognition and transfer, are complex and still poorly understood. In this review, we aim at summarizing the last updates of the knowledge on signaling pathways that regulate the biogenesis and the activity of T4SSs in important bacterial pathogens.