STUDIES ON THE RELATIONSHIP BETWEEN VIRUS AND HOST CELL

1951 ◽  
Vol 29 (3) ◽  
pp. 144-148
Author(s):  
R. C. French ◽  
S. M. Lesley ◽  
A. F. Graham ◽  
C. E. van Rooyen
Keyword(s):  
Host Cell ◽  
Trichloroacetic Acid ◽  
E Coli ◽  
Breakdown Mechanism ◽  
Previous Infection ◽  
Per Se ◽  
T7 Phage ◽  
The Relationship

Infection of E. coli with T2r, T4r+, T4r, T5, T6r+, or T6r phages induces the formation of a mechanism which extensively degrades P32 labelled T2r+ phage adsorbed to the cell shortly afterwards, about 50% of the P32 being converted to a form soluble in 5% trichloroacetic acid. Each of the above viruses is as effi cient in this respect as a preliminary infection with T2r+ phage itself. Previous infection of the cells with Tl, T3, or T7 phages does not stimulate this mechanism to break down labelled T2r+ virus. When Tl, T3, or T7 phage, then T2r+ phage, and finally P32 labelled T2r+ phage were added to cells, with an interval of several minutes between each addition, the results indicated that adsorption of T2r+ to the cell was not sufficient per se to stimulate the breakdown of labelled phage. Apparently actual infection of the cell by T2r+ virus was required before the breakdown mechanism was induced.

STUDIES ON THE RELATIONSHIP BETWEEN VIRUS AND HOST CELL

1951 ◽  
Vol 29 (3) ◽  
pp. 128-143 ◽  
Author(s):  
S. M. Lesley ◽  
R. C. French ◽  
A. F. Graham ◽  
C. E. van Rooyen
Keyword(s):  
Cell Surface ◽  
Host Cell ◽  
Trichloroacetic Acid ◽  
Experimental Results ◽  
Multiple Infection ◽  
Cell Ratio ◽  
E Coli ◽  
Soluble Phosphorus ◽  
Breakdown Curve ◽  
The Relationship

Infection of E. coli with P32 labelled T2r+ bacteriophage resulted in the con version of a part of the isotope to a form soluble in 5% trichloroacetic acid. This acid soluble phosphorus was used as a measure of the breakdown of the virus. When the phage to cell ratio was less than unity a two step breakdown curve was obtained corresponding to the two cycles of infection in this type of experi ment. The heights of the steps represented 5 and 32% breakdown, the second rise commencing after about 25 min. Multiple infection of cells yielded a curve which rose without inflection to about 23% breakdown at 20 min. after which there was little further increase. When the addition of radioactive phage was preceded by sufficient nonradioactive phage to infect most of the cells in the culture, the amount of breakdown of labelled virus increased to about 55% within 20 min. at which time breakdown practically ceased. Control experi ments indicated that dead phage in the labelled preparations contributed little to the acid soluble P32 fraction in these experiments and that the breakdown resulted from infection of the cells by virus. It is suggested that infection of cells by phage stimulates some mechanism whereby phage adsorbed to the cell at a later time is broken down extensively at the cell surface. The experimental results are interpreted in the light of this concept.

Changes in the permeability of Escherichia coli during parasitization by Bdellovibrio bacteriovorus

1971 ◽  
Vol 17 (5) ◽  
pp. 689-697 ◽  
Author(s):  
S. F. Crothers ◽  
J. Robinson
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Host Cell ◽  
Culture Fluid ◽  
Infection Cycle ◽  
Bdellovibrio Bacteriovorus ◽  
E Coli ◽  
Hepes Buffer ◽  
Per Se ◽  
Ph Range

Bdellovibrio bacteriovorus strain 6-5-S completed a typical infection cycle when incubated with E. coli ML 35 (lac i−z+y−) in 0.025 M Hepes buffer, pH 7.8, supplemented with 0.002 M CaCl2∙2H2O. Growth of this strain of B. bacteriovorus was optimal over the range of pH 7.5–8.5. No growth occurred at pH 6.5. The broad pH range may occur because a buffer per se is not required for growth and multiplication. The parasite failed to multiply in a two-membered culture unsupplemented with Ca2+ or Mg2+.Growth and multiplication of B. bacteriovorus in a two-membered culture were assessed by various parameters, including decrease in absorbance at 520 mμ, and release of materials absorbing at 260 mμ, and at 280 mμ. The onset of lysis of the host cell was accompanied by an increase in the release of materials absorbing at 260 mμ and at 280 mμ. The ratio of the absorbance of these materials at 280 and 260 mμ increased at the same time, from which it may be inferred that probably amino acids or proteins were being released.No β-galactosidase could be detected in the culture fluid of the two-membered culture. The infected E. coli cells were more permeable than uninfected cells to o-nitrophenyl-β-D-galactoside, and to the fluorescent dye 8-aniIino-1-naphthalenesulfonic acid.

The relationship between health effects in triathletes and microbiological quality of freshwater

1995 ◽  
Vol 31 (5-6) ◽  
pp. 19-26 ◽  
Author(s):  
G. J. Medema ◽  
I. A. van Asperen ◽  
J. M. Klokman-Houweling ◽  
A. Nooitgedagt ◽  
M. J. W. van de Laar ◽  
...  
Keyword(s):  
Water Quality ◽  
Geometric Mean ◽  
Microbiological Quality ◽  
Quality Parameters ◽  
Health Complaints ◽  
E Coli ◽  
Thermotolerant Coliforms ◽  
Microbiological Water Quality ◽  
The Relationship ◽  
Faecal Streptococci

This pilot study was carried out to determine the relationship between microbiological water quality parameters and the occurrence of health complaints among triathletes. Data were collected at an Olympic distance triathlon (n=314) and a run-bike-run (n=81; controls for exposure to fresh water). At the time of the triathlon, the concentrations of Escherichia coli , thermotolerant coliforms, faecal streptococci, entero- and reoviruses, F-specific RNA phages, Salmonella, Campylobacter, Aeromonas, Plesiomonas shigelloides, Pseudomonas aeruginosa and Staphylococcus aureus were examined over the swimming course. Information on the occurrence of health complaints during the competition and in the week thereafter was collected through a written questionnaire. The results show that triathletes and run-bike-runners are comparable with respect to factors other than water exposure (age, sex, training history, physical stress, lower intestinal health complaints during the competition) that may influence the occurrence of health complaints in the week after the competition. Triathletes and run-bike-runners reported gastro-intestinal (7.7% vs 2.5%), respiratory (5.5% vs 3.7%), skin/mucosal (2.6% vs 1.2%), general (3.5% vs 1.2%) and total symptoms (14.8% vs 7.4%) in the week after the event. The health risks for triathletes for all symptom groups are not significantly higher than for run-bike-runners. The geometric mean concentration of faecal indicator bacteria is relatively low: E. coli 170/100 ml; faecal streptococci 13/100 ml, enteroviruses were present at concentrations of 0.1/l. The group of triathletes was homogeneusly and relatively intensely exposed to water; they all swam in the same body of water at the same time and 75% reported to have swallowed freshwater. It was concluded that this study design is suitable to study the relationship between health complaints and microbiological water quality. In the summers of 1993 and 1994, a study will be carried out concerning several run-bike-runs and triathlons in freshwaters of different quality.

The effect of type of water supply on water quality in a developing community in South Africa

1997 ◽  
Vol 35 (11-12) ◽  
pp. 35-40 ◽  
Author(s):  
B. Genthe ◽  
N. Strauss ◽  
J. Seager ◽  
C. Vundule ◽  
F. Maforah ◽  
...  
Keyword(s):  
Water Quality ◽  
Water Supply ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
E Coli ◽  
Guideline Values ◽  
Developing Communities ◽  
Quality Guideline ◽  
And Control ◽  
The Relationship

Efforts to provide water to developing communities in South Africa have resulted in various types of water supplies being used. This study examined the relationship between the type of water supply and the quality of water used. Source (communal taps, private outdoor and indoor taps) and point-of-use water samples were examined for heterotrophic plate counts (HPC), total and faecal coliforms, E. coli, and coliphages. Ten percent of samples were also analysed for enteric viruses, Giardia and Cryptosporidium. Approximately 320 households were included in a case-control study. In addition, a cross-sectional study was conducted. Both studies examined the relationship between different types of water facilities and diarrhoea among pre-school children. The source water was of good microbial quality, but water quality was found to have deteriorated significantly after handling and storage in both case and control households, exceeding drinking water quality guideline values by 1-6 orders of magnitude. Coliphage counts were low for all water samples tested. Enteric viruses and Cryptosporidium oocysts were not detected. Giardia cysts were detected on one occasion in case and control in-house samples. Comparisons of whether in-house water, after handling and storage, complied with water quality guideline values demonstrated households using communal taps to have significantly poorer quality than households using private outdoor or indoor taps for HPC and E. coli (χ2 = 14.9, P = 0.001; χ2 = 6.6, P = 0.04 respectively). A similar trend (although not statistically significant) was observed for the other microbial indicators. The cross-sectional study demonstrated an apparent decrease in health risk associated with private outdoor taps in comparison to communal taps. This study suggests that a private outdoor tap is the minimum level of water supply in order to ensure the supply of safe water to developing communities.

scholarly journals Exploring the taxonomical and functional profile of As Burgas hot spring focusing on thermostable β-galactosidases

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
María-Eugenia DeCastro ◽  
Michael P. Doane ◽  
Elizabeth Ann Dinsdale ◽  
Esther Rodríguez-Belmonte ◽  
María-Isabel González-Siso
Keyword(s):  
Microbial Community ◽  
Hot Spring ◽  
Functional Characterization ◽  
Tca Cycle ◽  
Maximal Activity ◽  
Sulfur Cycle ◽  
E Coli ◽  
Complex Microbial Community ◽  
Relationship Of ◽  
The Relationship

AbstractIn the present study we investigate the microbial community inhabiting As Burgas geothermal spring, located in Ourense (Galicia, Spain). The approximately 23 Gbp of Illumina sequences generated for each replicate revealed a complex microbial community dominated by Bacteria in which Proteobacteria and Aquificae were the two prevalent phyla. An association between the two most prevalent genera, Thermus and Hydrogenobacter, was suggested by the relationship of their metabolism. The high relative abundance of sequences involved in the Calvin–Benson cycle and the reductive TCA cycle unveils the dominance of an autotrophic population. Important pathways from the nitrogen and sulfur cycle are potentially taking place in As Burgas hot spring. In the assembled reads, two complete ORFs matching GH2 beta-galactosidases were found. To assess their functional characterization, the two ORFs were cloned and overexpressed in E. coli. The pTsbg enzyme had activity towards o-Nitrophenyl-β-d-galactopyranoside (ONPG) and p-Nitrophenyl-β-d-fucopyranoside, with high thermal stability and showing maximal activity at 85 °C and pH 6, nevertheless the enzyme failed to hydrolyze lactose. The other enzyme, Tsbg, was unable to hydrolyze even ONPG or lactose. This finding highlights the challenge of finding novel active enzymes based only on their sequence.

scholarly journals Cryo-EM structure of mycobacterial cytochrome bd reveals two oxygen access channels

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weiwei Wang ◽  
Yan Gao ◽  
Yanting Tang ◽  
Xiaoting Zhou ◽  
Yuezheng Lai ◽  
...  
Keyword(s):  
Rational Design ◽  
Pathogenic Bacteria ◽  
Structural Topology ◽  
Antimicrobial Drugs ◽  
E Coli ◽  
Cytochrome Bd ◽  
Cryo Electron Microscopy ◽  
Functional Mechanisms ◽  
The Relationship ◽  
Potential Oxygen

AbstractCytochromes bd are ubiquitous amongst prokaryotes including many human-pathogenic bacteria. Such complexes are targets for the development of antimicrobial drugs. However, an understanding of the relationship between the structure and functional mechanisms of these oxidases is incomplete. Here, we have determined the 2.8 Å structure of Mycobacterium smegmatis cytochrome bd by single-particle cryo-electron microscopy. This bd oxidase consists of two subunits CydA and CydB, that adopt a pseudo two-fold symmetrical arrangement. The structural topology of its Q-loop domain, whose function is to bind the substrate, quinol, is significantly different compared to the C-terminal region reported for cytochromes bd from Geobacillus thermodenitrificans (G. th) and Escherichia coli (E. coli). In addition, we have identified two potential oxygen access channels in the structure and shown that similar tunnels also exist in G. th and E. coli cytochromes bd. This study provides insights to develop a framework for the rational design of antituberculosis compounds that block the oxygen access channels of this oxidase.

P. vortex-mediated strategies for polysaccharides decomposition

TECHNOLOGY ◽  
2015 ◽  
Vol 03 (02n03) ◽  
pp. 80-83
Author(s):  
Mark Polikovsky ◽  
Eshel Ben-Jacob ◽  
Alin Finkelshtein
Keyword(s):  
Degradation Products ◽  
Cellulose Degradation ◽  
Cellulose Hydrolysis ◽  
Industrial Applications ◽  
Biofuel Production ◽  
E Coli ◽  
Novel Approach ◽  
Textile Manufacture ◽  
Hydrolysis Of Cellulose ◽  
The Relationship

Cellulose hydrolysis has many industrial applications such as biofuel production, food, paper and textile manufacture. Here, we present a novel approach to cellulose hydrolysis using a consortium of motile bacteria, Paenibacillus vortex, that can swarm on solid medium carrying a non-motile recombinant E. coli cargo strain expressing the β-glucosidase and cellulase genes that facilitate the hydrolysis of cellulose. These two species cooperate; the relationship is mutually beneficial: the E. coli is dispersed over long distances, while the P. vortex bacteria gain from the supply of cellulose degradation products. This enables the use of such consortia in this area of biotechnology.

The relationship among freezing tolerance, vernalization requirement, Ppd alleles and winter hardiness in European wheat cultivars

2017 ◽  
Vol 155 (9) ◽  
pp. 1353-1370 ◽  
Author(s):  
A. GORASH ◽  
R. ARMONIENĖ ◽  
Ž. LIATUKAS ◽  
G. BRAZAUSKAS
Keyword(s):  
Molecular Markers ◽  
Western Europe ◽  
Complex Trait ◽  
Winter Hardiness ◽  
Photoperiod Sensitivity ◽  
The Other ◽  
Wheat Cultivars ◽  
Crucial Component ◽  
Per Se ◽  
The Relationship

SUMMARYWinter hardiness of wheat is a complex trait involving a system of structural, regulatory and developmental genes, which interact in a complex pathway. The objective of the present work was to study the relationship among the main traits determining the level of adaptation and the possibility for target manipulation of breeding material by using molecular markers and phenological parameters. Wheat cultivars from different ecoclimatic environments of Europe were included for analysis. Gene-specific assay showed that photoperiod sensitivity of the studied cultivars was determined by polymorphism in the Ppd-D1 allele. The study established the relationship among winter hardiness, LT50 (the temperature at which 50% of plants are killed), photoperiod sensitivity, vernalization duration and earliness per se genes in the environment of Lithuania. The cultivars from Northern and Western Europe exhibited stronger requirement for vernalization and photoperiod. Although the group of cultivars from the southern latitudes were characterized by earliness, they possessed a stronger level of LT50. The level of LT50 was found to be the most crucial component of winter hardiness, the other traits served as supplementary components.

Food Drive and Satiety in Yellow Mice

1957 ◽  
Vol 189 (1) ◽  
pp. 36-38 ◽  
Author(s):  
Guy Hollifield ◽  
William Parson
Keyword(s):  
Yellow Gene ◽  
Running Activity ◽  
Fasting And Refeeding ◽  
Ad Libitum ◽  
Per Se ◽  
Relationship Of ◽  
The Relationship ◽  
Ad Libitum Feeding ◽  
Reduced Activity

Spontaneous running activity during ad libitum feeding, fasting and refeeding was studied in inbred yellow mice. These studies suggest that the yellow gene per se is not associated with reduced activity and that inbred yellow mice have intact hypothalamic feeding centers. The relationship of these findings to obesity in yellow mice is discussed.

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