|
Les phages infectent seulement une seule
bactérie spécifique. Certains phages sont virulents, c'est-à-dire qu'aussitôt
qu'ils infectent une cellule, elle se met immédiatement à se reproduire et, dans
un court laps de temps, le phage fait exploser la cellule ce qui dégage de
nombreux autres phages
|
Viruses exist in two distinct states. When not in contact with a host
cell, the virus remains entirely dormant. During this time there are
no internal biological activities occurring within the virus, and in
essence the virus is no more than a static organic particle. In this
simple, clearly non-living state viruses are referred to as 'virions'.
Virions can remain in this dormant state for extended periods of time,
waiting patiently to come into contact with the appropriate host. When
the virion comes into contact with the appropriate host, it becomes
active and is then referred to as a virus. It now displays properties
typified by living organisms, such as reacting to its environment and
directing its efforts toward self-replication. |
|
Las enzimas de los bacteriófagos pueden atacar a los estreptococos
El equipo de Vincent Fischetti, de la Universidad de Rockefeller, en
Nueva York, ha utilizado las enzimas que producen los bacteriófagos
para atacar a los estreptococos del grupo A, que, sobre todo, producen
infecciones de garganta que a veces evolucionan hacia fiebre reumática.
La técnica, de bajo coste, podría inaugurar una nueva vía antibiótica
contra muchas infecciones y además parece que no generaría
resistencias. |
Bacteriophage T4
A bacteriophage is a virus
which infects bacteria. In particular, the bacteriophage T4 is a virus which
infects E.Coli, a bacteria that has been used extensively for molecular biology
research. The bacteriophage T4 exemplifies the life cycle of viruses. It exists
as an inactive virion until one of its extended 'legs' comes into contact with
the surface of an E. Coli. Sensors on the ends of its 'legs' recognize binding
sites on the surface of the host's cell, and this triggers the bacteriophage
into action. The bacteriophage binds to the surface of the host, punctures the
cell with its injection tube, and then injects its own genetic blueprint. This
genetic information subverts the host cell's normal operation and sets the
cell's biosynthetic machinery to work creating replicas of the virus. These
newly created viruses escape from the cell and then float about dormant until
one happens to come into contact with a new host cell. |
|
A bacteriophage is a virus which
infects bacteria. In particular, the bacteriophage T4 is a virus which
infects E.Coli, a bacteria that has been used extensively for molecular
biology research. The bacteriophage T4 exemplifies the life cycle of
viruses. It exists as an inactive virion until one of its extended 'legs'
comes into contact with the surface of an E. Coli. Sensors on the ends of
its 'legs' recognize binding sites on the surface of the host's cell, and
this triggers the bacteriophage into action. The bacteriophage binds to
the surface of the host, punctures the cell with its injection tube, and
then injects its own genetic blueprint. This genetic information subverts
the host cell's normal operation and sets the cell's biosynthetic
machinery to work creating replicas of the virus. These newly created
viruses escape from the cell and then float about dormant until one
happens to come into contact with a new host cell.
A.
Definition - Bacteriophage
(phage) are obligate intracellular parasites that multiply inside bacteria
by making use of some or all of the host biosynthetic machinery (i.e.,
viruses that infect bacteria.).
There are
many similarities between bacteriophages and animal cell viruses. Thus,
bacteriophage can be viewed as model systems for animal cell viruses. In
addition a knowledge of the life cycle of bacteriophage is necessary to
understand one of the mechanisms by which bacterial genes can be transferred
from one bacterium to another.
At one time
it was thought that the use of bacteriophage might be an effective way to
treat bacterial infections, but it soon became apparent that phage are
quickly removed from the body and thus, were of little clinical value.
However, bacteriophage are used in the diagnostic laboratory for the
identification of pathogenic bacteria (phage typing). Although phage typing
is not used in the routine clinical laboratory, it is used in reference
laboratories for epidemiological purposes. Recently, new interest has
developed in the possible use of bacteriophage for treatment of bacterial
infections and in prophylaxis. Whether bacteriophage will be used in
clinical medicine remains to be determined.
Source:
http://pathmicro.med.sc.edu/mayer/phage.htm
Links
|
Viruses straddle the definition
of life. They lie somewhere between supra molecular complexes and very
simple biological entities. Viruses contain some of the structures and
exhibit some of the activities that are common to organic life, but
they are missing many of the others. In general, viruses are entirely
composed of a single strand of genetic information encased within a
protein capsule. Viruses lack most of the internal structure and
machinery which characterize 'life', including the biosynthetic
machinery that is necessary for reproduction. In order for a virus to
replicate it must infect a suitable host cell. |
|
Bacteriophages,
first discovered around 1915, have played a unique role in viral biology.
They are perhaps the best understood viruses, yet at the same time, their
structure can be extraordinarily complex. The use of bacteriophages played
a prominent role in elucidating that DNA in viruses can reproduce through
two mechanisms: the lytic cycle and the lysogenic cycle.
|
|
T series of
DNA bacteriophages
The T series of bacteriophages had a
central role in the development of molecular biology. In 1944, at the
instigation of Max Delbruck, the phage group at Cold Spring Harbor agreed
to concentrate their research on 7 bacteriophages, all of which were
active against E. coli B, which had first been isolated by Demerec
and Fano. Up till this point, different scientists worked with different
phage - as a result, it was difficult to compare results.
This decision, while appearing
correct at the time, has been criticised since because it led to the
neglect of some other important aspects of bacteriophage biology, most
notably lysogeny. Nevertheless, the study of the T bacteriophage has
contributed a great deal to our understanding of molecular biology and
genetic regulation.
|
| The Pittsburgh
Bacteriophage Institute promotes and coordinates research on
bacteriophages locally, nationally, and internationally. Founded in 1993,
the Institute grew out of the strengths in bacteriophage research in the
Department of Biological Sciences at Pitt as well as in the corresponding
department at Carnegie-Mellon University. Members are currently found in
universities at numerous sites in North America, Europe, and Asia. In
Pittsburgh, the Institute operates the NIH-funded Pittsburgh Bacteriophage
Genome Project, sponsors meetings on bacteriophage research, fosters
collaborations among Institute members, and provides numerous other member
services. Administrative offices for the Institute are located on the
third floor of Crawford Hall. |
| The institute was founded by Georgian scientist Professor George Eliava
and his French-Canadian colleague Felix D'Herelle - the discoverer of
bacteriophages.
Major research trends:
-
a) Therapeutic bacteriophages (phages) for treatment
and prophylactics of different human and animal bacterial diseases, such
as: Staphylococcus, Streptococcus, E. coli, Pseudomonas, Proteus,
Salmonalla, Shigella, Serratia, Klebsialla, Enterobacter, Campilobacter,
Yersinia, Brucella, etc. Most of these phage have been widely applied in
clinics throughout the former Soviet Union.
b) Phage typing;
A number of original phage typing patterns have been elaborated for
epidemiology studies, in particular, Salmonella typhimurium, Salmonella
typhi, Salmonella paratyphy A,B, Sshigella, Proteus, Yersinia. The
patterns are destined for identification of source of infection routs of
its spread in environment. One of them is constructed for S. typhimurium
(I. Chirakadze, 1979). The scheme is adopted by the World Health
Organization and recommended for use in developing countries.
c) Study of bio-active substances of bacterial origin;
Hyaluronidase isolated from Staphylococcus aureus strain has been
successfully proved in clinical studies for treatment post-oprational
and burn scarms.
d) Research on endemic Caucasian lactic acid bacteria
has been started in 1995. A collection enumerating about 100
lactobacilli
and lactococci has been created, among them there are: Lactobacillus
delbrueki, ssp. Lactis, Lactobacillus acidophilus, Lactocacillus casei,
Streptococcus thermophilus, Enterococcus faecium, etc.
|
TEACHING
OBJECTIVES
To describe the general composition and structure of bacteriophage
To discuss the infectious process and the lytic multiplication cycle
To explain the lysogenic cycle and its regulation
In nature, the bacteriophage T4 contains about 168,800 bases
pairs of double stranded DNA.This genetic blueprint contains all of the
necessary information to create new bacteriophage T4. Our virtual bacteriophage
T4 also contains its own genetic information; it is made up of characters of
ascii VRML 2.0 code. At some point in the future evolution of cyberspace, our
virus will find an appropriate host and replicate itself. The virtual virus is
born, and the question of whether viruses are 'alive' is extended to the
question of whether virtual viruses are alive
|
Português
USA
