bacteriophage.ppt

7/25/2019 Bacteriophage.ppt

1/15

Bacteriophage Prokaryotes as host

Subcellular structure without metabolic machinery Double stranded DNA, single stranded DNA, RNA Virulent phage vs. template phage

MS2 Fd, M13T2

or lecture only BC Yang


2/15

Historical context

A century ago, Hankin (1896) reported that the waters ofthe anges and !u"na ri#ers in $ndia had "arked

anti%acteria& action (against Vibrio cholerae, restrict

epide"ic) which cou&d pass through a #ery fine porce&ain

fi&ter' this acti#ity was destroyed %y %oi&ing

dward *wort (191+) and e&i- d.Here&&e (191/)

independent&y reported iso&ating fi&tera%&e entities capa%&e

of destroying %acteria& cu&tures and of producing s"a&&

c&eared areas on %acteria& &awns

$t was d.Here&&e, a Canadian working at the 0asteur

$nstitute in 0aris, who ga#e the" the na"e

%acteriophages22 using the suffi- phage (1933)



3/15

Glossary

pfu4 p&a5ue for"ing unit

*it&e4 define pfu in a phage suspension

"oi4 "u&tip&icity of infection, the ration of

phage partic&es to %acteria

eop4 efficiency of p&ating, the ration of thep&a5ue titer to the nu"%er of phage partic&es

0rophage4 state of phage co2e-isting with host

ysogenic %acteria4 ter" of %acteria carrying

prophage

0hage con#ersion4 phenotype change in

&ysogenic %acteria



4/15

plaque 0&a5ues are c&ear 7ones for"ed

in a &awn of ce&&s due to &ysis %yphage

At a &ow "u&tip&icity of infection($) a ce&& is infected with asing&e phage and &ysed, re&easingprogeny phage which candiffuse to neigh%oring ce&&s andinfect the", &ysing these ce&&sthen infecting the neigh%oringce&&s and &ysing the", etc,

$t u&ti"ate&y resu&ts in a circu&ararea of ce&& &ysis in a tur%id &awnof ce&&s

:yna"icprocess gal-

gal+



5/15

One step growth

de"onstrate an ec&ipse period during which the :;A %eganrep&icating and there were no free phage in the ce&&, a period

of accu"u&ation of intrace&&u&ar phage, and a &ysis process

which re&eased the phage to go in search of new hosts

Ellis, E. L. and M. el!r"c# $%&'&(. )he Growth o*

Bacteriophage. . Gen. hysiol. '/0-'12.or lecture only BC Yang


6/15

Lytic cycle o* phage

%

'

2

0 /3



7/15

4inetics o* phage in*ection < "inAttach"ent of *3 to a suscepti%&eE. colice&&

1 "in$n=ect :;A into ce&& 12/ "in*ranscri%e and trans&ate ear&y genes

%&ock %acteria& :;A synthesis and degrade host chro"oso"a& :;A %&ock transcription of host ">;As %&ock trans&ation of host proteins s"a&& a"ounts of ear&y proteins produced (cata&ytic functions) transcription fro" sing&e phage geno"e

/21+ "in>ep&ication of phage :;A 1


8/15

5n*ection processes

1 Attach"ent of #irion to ce&&

3 ntry of #ira& nuc&eic acid into host ce&& (withor without other #irion co"ponents)

? ar&y #ira& proteins synthesi7ed (re5uiredfor geno"e rep&ication)

@ eno"e rep&ication

+ ate proteins synthesi7ed (capsid proteins)

6 Asse"%&y of progeny #irions/ >e&ease of infectious progeny #irions



9/15

6dsorption and 76 in8ection

A rando" co&&ision,

proteinprotein interaction

Affected %y CaBB, gBB, or

tryptonphanetc

>eceptor specific (outer

"e"%rane protein &a"B for

&a"%da' se- pi&i for )

76 is the 9a8or 9aterial

entering !acterial Lyso:9e li#e acti;ity, core

!oring through the cell

wall



10/15

e;elop9ental gene expressionassay !y protein synthesis

Early, in

5 minMiddle, in

10 minLate

In 25 min



11/15

Host gene shut-o**

A&tering >;A

po&y"erase acti#ity

Change the trans&ation

apparatus (trans&ationof the D3 phage >;A

with ri%oso"e of *@2

infected ce&&s reduced

%y 88E)

:egradation of host

:;AXP10



12/15

6sse9!ly o* phage


13/15

Lysogenic cycle

ysogenic Cyc&e4!ambda as an e"ample

lambda integrase and lambda repressor c#

synthesi$ed due to activation o% the

transcription o% their genes by c##. c# repressor turns o%% phage transcription

integrase cataly$es integration o% lambda

DNA into bacterial chromosome via shortsites o% homology &site'speci%ic

recombination( '''' prophage



14/15

>eturn to !e a #iller 0rophage4

Bacteriu" is now i""une to infection %y another phage,

%ecause repressor continuous&y produced 22222 new phage

:;A can %e in=ected into ce&& and is circu&ari7ed %ut is not

transcri%ed or rep&icated

0rophage can %e e-cised when host responsesyste" to potentia&&y &etha& situations4 if host :;A da"aged

one reaction %y host ce&& is to acti#ate a protease

protease a&so c&ea#es repressor

0hage :;A now transci%ed inc&uding a gene for an en7y"e

that cuts prophage :;A fro" %acteria& chro"oso"e

ytic cyc&e can start



15/15

6pplication o* phages

ode& syste" of"o&ecu&ar %io&ogy

C&oning and

e-pression 0hage disp&ay syste"

0hage typing

0hage therapy4 phage as natura&, se&f2

rep&icating, se&f2&i"iting anti%iotics


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