Transduction protein synthesis

1. Transduction
INSTRUCTOR : DR. KENTON HERNANDEZ
CENTRAL AMERICA HEALTH SCIENCE UNIVERSITY
BELIZE
PRESENTEDE BY : Gia K. Sharma

2. Contents
 Historical
 Transduction
 Mechanism
Bacteriophages and its life cycles
 Type of transduction
Generalized Transduction
Specialized Transduction
 Significance
2

3. historical
Lederberg & Zinder
Transduction was first discovered in 1952 by Joshua
Lederberg and Norton Zinder
Joshua Lederberg Norton zinder
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4. How transduction was discovered
 Studied in Salmonella typhimurium
 Plated two auxotrophic strains (LA-2 and LA-22)
individually on minimal medium, no cells grew.
 Plated a mixture of the two auxotrophic strains on
minimal medium, cells grew into colonies.
 Thus, genetic exchange was taking place between the
two cell types.
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5. U-tube Experiment
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6. Unexpected discovery
U-tube Experiment
 Performed U-tube experiment .
 Found that part of the cells on one side of the U-tube were
prototrophs (could grow in minimal medium).
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7. Types of Bacteriophage
Lytic or virulent – Phage that multiply within the
host cell, lyse the cell and release progeny phage
(e.g. T4)
Lysogenic or temperate phage: Phage that
can either multiply via the lytic cycle or enter a
quiescent state in the bacterial cell.
Expression of most phage genes repressed
Prophage – Phage DNA in the quiescent state
Lysogen – Bacteria harboring a prophage

9. Transduction
Definition: Gene transfer from a donor to a recipient by way of a
bacteriophage
Unlike transformation in which the naked DNA is transferred in
transduction DNA is carried by a bacteriophage.
or
In transduction, DNA is transferred from cell to cell through the
agency of viruses
NOTE :- All phages can be transducer and not all bacteria are
transducible

10. Transduction
• Types of transduction
1. Generalized - Transduction in which
potentially any donor bacterial gene can be
transferred.
2. Specialized- Transduction in which only
certain donor genes can be transferred

11. Mechanism of Transduction
Bacteriophage
Bacteriophage (phage): A virus that infects bacteria.
• Firstly Descovered in 1915 by Fredrick Twort and two years later by Felix d’Herelle.
• Means bacteria eater.
• A virus that infects certain type of bacteria and replicates within them
11

12. Phage Composition and Structure
 Composition
 Nucleic acid
 Protein
• Structure (T4)
– Size (80 X 100
nm)
– Head or
capsid
– Tail
Cor
e
Tail
Fibers
Base
Plate
Head/Capsi
d
Contractil
e Sheath

13. Bacteriophage - structure

14. Infection of Host Cells by Phages
 Irreversible attachment
Base plate
• Adsorption
–Tail fibers
– Receptor is LPS for
T4
• Nucleic acid
injection
• Sheath Contraction
• DNA uptake

16. Transduction has been found to occur in a variety
of prokaryotes, including certain species of the
Bacteria: Desulfovibrio, Escherichia, Pseudomonas,
Rhodococcus, Rhodobacter, Salmonella,
Staphylococcus, and Xanthobacter, as well as
Methanobacterium thermoautotrophicum.
EXAMPLES OF BACTERIA
16

17. Phages as DNA carriers
• Bacteriophages are natural vectors that
transduce DNA from one bacterial cell to
another.
• A bacteriophage cannot “live” or reproduce
without getting inside a bacterial cell

18. Types of bacterio-phage
Virulent: capable of causing infection and eventually
destruction and death of the bacterial cell. These follow the lytic
cycle. e.g. T4 host E.coli.
Temperate: does not cause destruptic infection instead
phage DNA is incorporated into bacterium DNA and is replicated
with it and after some cycle become virulent cause lysis.
 e.g. lambda phage.
18

19. Life cycle of bacteriophage 19

20. Transduction
 There are two types of transduction:
Generalized transduction:
A DNA fragment is transferred from one bacterium to another by a lytic
bacteriophage that is now carrying donor bacterial DNA due to an error in
maturation during the lytic life cycle.
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21. Generalised Transduction STEPS 21
1. A lytic bacteriophage adsorbs
to a susceptible bacterium.
2. The bacteriophage genome enters
the bacterium. The genome directs the
bacterium's metabolic machinery to
manufacture bacteriophage
components and enzymes

22. 22
3. Occasionally, a bacteriophage head or
capsid assembles around a fragment of
donor bacterium's nucleoid instead of a
phage genome by mistake.
steps in Generalised Transduction (cont’d)
4. The bacteriophages are released.

23. steps in Generalised Transduction (cont’d)
23
5. The bacteriophage carrying the
donor bacterium's DNA adsorbs to a
recipient bacterium
6. The bacteriophage inserts the donor
bacterium's DNA it is carrying into the
recipient bacterium .

24. 24steps in Generalised Transduction (contd)
7. The donor bacterium's DNA is exchanged for some
of the recipient's DNA.

25. Generalized Transduction
Release of phage
 Phage replication and degradation of host DNA
 Assembly of phages particles
 Infection of recipient
 Homologous recombination
 Infection of Donor
 Potentially any donor gene can transferred

26. Generalized Transduction

27. • Specialized transduction:
• A DNA fragment is transferred from one bacterium to another by a
temperate bacteriophage that is now carrying donor bacterial DNA due
to an error in spontaneous induction during the lysogenic life cycle.
• In specialized transduction the phage inserts its genome at the specific
site.
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28. Specialised Transduction
28
1. A temperate bacteriophage adsorbs
to a susceptible bacterium and injects
its genome .
2. The bacteriophage inserts its
genome into the bacterium's nucleoid
to become a prophage.

29. Steps in Specialised Transduction (cont’d)
29
3. Occasionally during spontaneous
induction, a small piece of the donor
bacterium's DNA is picked up as part
of the phage's genome in place of
some of the phage DNA which
remains in the bacterium's nucleoid.
4. As the bacteriophage replicates, the
segment of bacterial DNA replicates as
part of the phage's genome. Every
phage now carries that segment of
bacterial DNA.

30. Steps in Specialised Transduction (cont’d) 30
5. The bacteriophage adsorbs to a
recipient bacterium and injects its
genome.
6. The bacteriophage genome carrying
the donor bacterial DNA inserts into
the recipient bacterium's nucleoid.

31. Specialized Transduction
Lysogenic Phage
 Excision of the prophage
• Replication and release of
phage
• Infection of the recipient
• Lysogenization of the recipient
– Homologous recombination
also possible

32. Specialized Transduction
 In specialized or restricted transduction, the transducing
particle carries only specific portions of the bacterial
genome.
 Specialized transduction is made possible by an error in the
lysogenic life cycle.

33.  When a prophage is induced to leave the host chromosome,
excision is sometimes carried out improperly.
 The resulting phage genome contains portions of the
bacterial chromosome (about 5 to 10% of the bacterial DNA)
next to the integration site.
 A transducing phage genome usually is defective and lacks
some part of its attachment site. The transducing particle will
inject bacterial genes into another bacterium, even though
the defective phage cannot reproduce.

34.  The best-studied example of specialized transduction is the
lambda phage. The lambda genome inserts into the host
chromosome at specific locations known as attachment or att
sites.
 The phage att sites and bacterial att sites are similar and can
complex with each other.

35. 35
Significance of transduction
 It transfers genetic material from one bacterial cell to another and
alter the genetic characteristics.
 For example: In specialised transduction the gal gene, a cell
lacking ability to metabolize galactose could aquire the ability .
 It shows the evolutionary relationship between the prophage and
host bacterial cell.
 Prophage can exist in a cell for a long period suggests a similar
possible mechanism for the viral origin of cancer.
 It provides a way to study the gene linkage.

36. QUESTIONS

37. 1. In ______, the transducing particle
carries only specific portions of the
bacterial genome.
A. generalized transduction
B. generalized lysogenic phase of
transduction
C. specialized transduction
D.restricted lysogenic phase of
transduction

38. C . SPECIALIZED
TRANSDUCTION

39. 2. T4 is _____ type of
bacteriophage.
A. Lytic
B. Virulent
C. Only A
D. Both A and B

40. D. BOTH A and B

41. 3. Bacteriophages are _____
A. Bacteria that attacks viruses
B. viruses that attacks bacteria
C. they are free living viruses
D. all of above

42. B. VIRUSES that attacks
BACTERIA

43. 4. Genome of bacteria can be
______
A. DNA
B. RNA
C. Either DNA or RNA
D. BOTH DNA or RNA

44. C. Either DNA or RNA

45. 5. The protein coat on virus is
known as _____
A. Capsomere
B.Capsid
C. Conjugation
D. Pellicle

46. b. capsid

47. 6. In a bacteria virus , its DNA
is located in ____
A. Tail and sheath
B. Head
C. tentacles
D. Head and Tail

48. b. head