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Bacterial Heredity and Variation
Heredity
The biological character between parental
generation and their off-spring is basically
identical, and the charact...
Variation
In general the term variation means the
difference in characteristics of organisms
belonging to the same species...
Section 1 bacteria variation
Morphological and Structure VariationMorphological and Structure Variation
a bacterial sphero...
Variation of bacteriaVariation of bacteria
Variation in morphology and structureVariation in morphology and structure
 lo...
VariationVariation
Variation in virulenceVariation in virulence
 Bovine TB-BCGBovine TB-BCG
13years, 230 generation13year...
 Bacillus diphtheriaeBacillus diphtheriae infected byinfected by
corynebacteriophage:corynebacteriophage: VirulenceVirule...
VariationVariation
Variation in drug resistanceVariation in drug resistance
 Penicillin resistant strains ofPenicillin re...
•Bacterial chromosomeBacterial chromosome
•PlasmidPlasmid
•BacteriophageBacteriophage
•Transposable elementsTransposable e...
The characteristic of bacterial genome:
A. Covalently closed circular DNA, naked
nucleic acid molecular and without histon...
The structure of operon
exon
modulating sequence
promoter
operator
The characteristic of bacterial
genome:
A. Covalently closed circular DNA, naked
nucleic acid molecular without histone.
B...
 SizeSize
 E.coliE.coli 13001300µµm, 4288genem, 4288gene
 Rolling-circle pattern ofRolling-circle pattern of
replicatio...
•Bacterial chromosomeBacterial chromosome
•PlasmidPlasmid
•BacteriophageBacteriophage
•Transposable elementsTransposable e...
Concept:
A circular, double-stranded
unit of DNA that replicates
within a cell independently of
the chromosomal DNA.
Plasm...
1.According to transfer properties1.According to transfer properties
Conjugative plasmidsConjugative plasmids:: Conjugativ...
• self-duplication, it is a replicon.
• The products encoded by plasmids assign
the host bacteria some characteristics, su...
Transitivity :
Conjugative plasmids —— transfer by
sexual pili
Nonconjugative plasmids——transferred
together with conjuga...
2.According to Genetic Information2.According to Genetic Information
Fertility plasmid (F factor)
————which contain only t...
Resistance plasmids ( R factors)
which contain genes that can build a
resistance against antibiotics or poisons.
Historica...
Tn9
Tn21
Tn 10
Tn8
RTF
R determinant
RTFRTF(( resistance transfer factor)
■■ Conjugative plasmidConjugative plasmid
■■ Tra...
Virulence plasmids, which turn the bacterium
into a pathogen.
Metabolism plasmids, which enable the digestion
of unusual s...
•Bacterial chromosomeBacterial chromosome
•PlasmidPlasmid
•BacteriophageBacteriophage
•Transposable elementsTransposable e...
Bacteriophage or phageBacteriophage or phage
Obligate intracellular parasites that
multiply inside bacteria , fungi, actin...
1. Morphous and sturcture :
The appearance of most phages likes a
tadpole, while the other’s likes a ball or
minute bar.
2...
T4 bacteriophages infectingT4 bacteriophages infecting E.coliE.coli..
 TailTail
Tail collarTail collar
TailTail Sheath
Tail coreTail core
Tail plateTail plate
Tail pins
Tail fiber
 Head
Core...
The appearance of E.coli T4 phage (TEM×390,000)(TEM×390,000)
3. Classification3. Classification
According toAccording to The fate of host bacteria infectedThe fate of host bacteria in...
Characteristics:Characteristics:
aa 、、 Large scaleLarge scale proliferate in host cellcell
bb 、、 Split or lyse host bacter...
②② Lysogenic or temperate phage
Phage that can either multiply via the
lytic cycle or enter a quiescent state in the
bacte...
Prophage: A prophage is a phage genome inserted as
part of the linear structure of the DNA chromosome of a
bacterium. Prop...
1. The division of host cell is normal, and the
genome of phage is inherit to daughter cell
2. The host cell bear the comp...
Significance of LysogenySignificance of Lysogeny
Lysogenic conversionLysogenic conversion
Toxin production byToxin product...
•Bacterial chromosomeBacterial chromosome
•PlasmidPlasmid
•BacteriophageBacteriophage
•Transposable elementsTransposable e...
Transposable elementsTransposable elements
Transposable elements are a heterogeneous class
of genetic elements that can in...
Nature : DNA sequences in bacteria cell that
can change its position.
Transfer way :
The transfer or shift of the transpos...
ClassificationClassification ::
• Insertion sequenceInsertion sequence (( ISIS ))
• TransposonTransposon (( TnTn ))
• Bact...
1.1. Insertion sequenceInsertion sequence (( ISIS ))
DefinitionDefinition
Insertion sequences are transposable geneticInse...
StructureStructure
Insertion sequences are small stretches ofInsertion sequences are small stretches of
DNA that have repe...
2. Transposon2. Transposon (( TnTn ))
DefinitionDefinition
Transposons are transposable geneticTransposons are transposabl...
StructureStructure
The structure of a transposon is similar toThe structure of a transposon is similar to
that of an inser...
ImportanceImportance
Many antibiotic resistance genes are located onMany antibiotic resistance genes are located on
transp...
3 Transposable phage
Transposable phage is a temperate phage
with the competence of transposition
Section 3 The mechanisms
of bacterial variation
variation
Genotype
variation
Phenotype
variation
Gene mutation
Chromosome ...
Gene transfer and recombinationGene transfer and recombination
Basic conceptBasic concept
Gene transfer :Gene transfer :
T...
The main ways of gene transfer and
recombination :
Transformation
Conjugation
Transduction
Lysogenic conversion
Protoplast...
TransformationTransformation
Definition:Definition:
Transformation is gene transfer from theTransformation is gene transfe...
Injection
Bacterial
colonies
Rough
nonvirulent
(strain R)
Results
Mouse healthy
Smooth
virulent
(strain S)
Mouse dies
Heat...
The mechanism of transformation
Uptake of DNAbacteriolysis Recombination
The main ways of gene transfer and
recombination :
Transformation
Conjugation
Transduction
Lysogenic conversion
Protoplast...
TransductionTransduction
Definition:Definition:
Transduction is defined as the transfer ofTransduction is defined as the t...
TypesTypes of transduction:of transduction:
Generalized transductionGeneralized transduction
Transduction in which potenti...
• Infection of Donor
• Phage replication and degradation of host DNA
•Assembly of phages particlesAssembly of phages parti...
The fate of exogenous DNA in Generalized
Transduction:
1) Complete transduction
2) Abortive transduction
Bacteria
DNALytic...
• It is relatively easy.It is relatively easy.
• It is rather efficient, using the correct phage.It is rather efficient, u...
•Specialized transductiontransduction is transduction inis transduction in
which onlywhich only certain donorcertain donor...
Excision of theExcision of the
prophageprophage
• Replication andReplication and
release of phagerelease of phage
• Infec...
generalizedgeneralized Specialized
Vector virulent phage
or temperate phage in
lytic cycle
temperate phage
Target gene Any...
The main ways of gene transfer and
recombination :
Transformation
Conjugation
Transduction
Lysogenic conversion
Protoplast...
Lysogenic ConversionLysogenic Conversion
Definition:Definition:
The prophage DNA as a gene recombinedThe prophage DNA as a...
Example
Corynebacterium diphtheriae
(Does not produce diphthera toxin)
β-corynebacteria phageInfected with
Losogenic Coryn...
The main ways of gene transfer and
recombination :
Transformation
Conjugation
Transduction
Lysogenic conversion
Protoplast...
ConjugationConjugation
Definition:Definition:
Transfer of DNA from a donor to aTransfer of DNA from a donor to a
recipient...
1.Conjugation of F plasmid
The basic knowledge of F factor
• Function——encode sex pili
• Exist form:
F+
bacteria——contain ...
F- F+
HfrF’
Conjugate with F+
Curing
Integrate
excision
Deviational excision
Curing
Integrate
Conjugate with F’
Transform ...
Autonomous (FAutonomous (F++
))
   Characteristics of FCharacteristics of F++
× F× F--
crosses:crosses:
• FF--
becomes Fbe...
Physiological States of F FactorPhysiological States of F Factor
Integrated (Hfr)Integrated (Hfr)
Characteristics ofCharac...
Physiological States of F FactorPhysiological States of F Factor
Autonomous with donor genes (F’)Autonomous with donor gen...
Structure of R FactorsStructure of R Factors
 RTF (resistance transfer factor)
 Conjugative plasmidConjugative plasmid
...
The main ways of gene transfer and
recombination :
Transformation
Conjugation
Transduction
Lysogenic conversion
Protoplast...
Protoplast fusion is a highly efficient method
for the direct transfer of expression vectors
from bacteria to other cell. ...
The protocol of Protoplast fusionProtoplast fusion
Bacteria A Bacteria B
Treat with lysozyme or penicilin
Protoplast A Pro...
Comparison among different ways of bacterial gene
transfer and recombanation
manner Origin of gene Transfer mechanism
tran...
Practical implicationsPractical implications
Application in diagnosis, treatment andApplication in diagnosis, treatment an...
The Ames
Test for
mutagenicity
Summary
• Definitions: phage, prophage,
transformation, conjugation,
transduction, lysogenic conversion
•
bacteria
• The f...
SummarySummary
1.Phage 2.Transposable elements1.Phage 2.Transposable elements
3.Lytic or virulent phage 4.Lysogenic or tem...
3 heredity and variation of bacteria
3 heredity and variation of bacteria
3 heredity and variation of bacteria
3 heredity and variation of bacteria
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3 heredity and variation of bacteria

  1. 1. Bacterial Heredity and Variation
  2. 2. Heredity The biological character between parental generation and their off-spring is basically identical, and the character can inherits from generation to generation stationary. The basic principle of heredity and variation
  3. 3. Variation In general the term variation means the difference in characteristics of organisms belonging to the same species in a natural population. It contains genotypical variation and phenotypical variation
  4. 4. Section 1 bacteria variation Morphological and Structure VariationMorphological and Structure Variation a bacterial spheroplast or protoplast originating from a normal bacterium following partial or complete removal of the cell wall.
  5. 5. Variation of bacteriaVariation of bacteria Variation in morphology and structureVariation in morphology and structure  lose capsule (Pneumococcus)lose capsule (Pneumococcus)  H-OH-O  Lose SporeLose Spore  L-formL-form
  6. 6. VariationVariation Variation in virulenceVariation in virulence  Bovine TB-BCGBovine TB-BCG 13years, 230 generation13years, 230 generation
  7. 7.  Bacillus diphtheriaeBacillus diphtheriae infected byinfected by corynebacteriophage:corynebacteriophage: VirulenceVirulence ↑ corynebacteriophage Virulent strainavirulent strain
  8. 8. VariationVariation Variation in drug resistanceVariation in drug resistance  Penicillin resistant strains ofPenicillin resistant strains of staphylococcusstaphylococcus aureusaureus Variation in enzyme activity Phenotypic Genotypic
  9. 9. •Bacterial chromosomeBacterial chromosome •PlasmidPlasmid •BacteriophageBacteriophage •Transposable elementsTransposable elements Section 2 Bacterial Genetic Elements
  10. 10. The characteristic of bacterial genome: A. Covalently closed circular DNA, naked nucleic acid molecular and without histone. B. Operon structure C. No intron, not need splicing after transcription D. There is no overlap in structural gene. Bacterial chromosomeBacterial chromosome
  11. 11. The structure of operon exon modulating sequence promoter operator
  12. 12. The characteristic of bacterial genome: A. Covalently closed circular DNA, naked nucleic acid molecular without histone. B. Operon structure C. No intron, not need splicing after transcription D. There is no overlap in structural gene.
  13. 13.  SizeSize  E.coliE.coli 13001300µµm, 4288genem, 4288gene  Rolling-circle pattern ofRolling-circle pattern of replicationreplication
  14. 14. •Bacterial chromosomeBacterial chromosome •PlasmidPlasmid •BacteriophageBacteriophage •Transposable elementsTransposable elements Section 2 Bacterial Genetic Elements
  15. 15. Concept: A circular, double-stranded unit of DNA that replicates within a cell independently of the chromosomal DNA. Plasmids are most often found in bacteria and are used in recombinant DNA research to transfer genes between cells. PlasmidPlasmid
  16. 16. 1.According to transfer properties1.According to transfer properties Conjugative plasmidsConjugative plasmids:: ConjugativeConjugative plasmids contain so-plasmids contain so- calledcalled transfertransfer genesgenes, which perform the complex process, which perform the complex process ofof conjugationconjugation, the sexual transfer of plasmids to another, the sexual transfer of plasmids to another bacteriumbacterium Nonconjugative plasmids:Nonconjugative plasmids: Non-conjugativeNon-conjugative plasmids areplasmids are incapable of initiating conjugation, and therefore, theirincapable of initiating conjugation, and therefore, their movement to another bacterium, they must be transferredmovement to another bacterium, they must be transferred together with conjugative plasmids, during conjugation.together with conjugative plasmids, during conjugation. ClassificationClassification
  17. 17. • self-duplication, it is a replicon. • The products encoded by plasmids assign the host bacteria some characteristics, such as drug resistance, pathogenicity, etc. • It can be removed naturally. The rate of natural remove of plasmids is about 10-2 ~ 10-8 , and it can be removed by treatment with mega temperature, ultraviolet rays, etc. TheThe characteristic of plasmids ::
  18. 18. Transitivity : Conjugative plasmids —— transfer by sexual pili Nonconjugative plasmids——transferred together with conjugative or phage.
  19. 19. 2.According to Genetic Information2.According to Genetic Information Fertility plasmid (F factor) ————which contain only transferwhich contain only transfer genes.genes. Their only function is to initiate conjugation.Their only function is to initiate conjugation.
  20. 20. Resistance plasmids ( R factors) which contain genes that can build a resistance against antibiotics or poisons. Historically known as R-factors, before the nature of plasmids was understood.
  21. 21. Tn9 Tn21 Tn 10 Tn8 RTF R determinant RTFRTF(( resistance transfer factor) ■■ Conjugative plasmidConjugative plasmid ■■ Transfer genesTransfer genes R determinantR determinant ■■ Resistance genesResistance genes ■■ TransposonsTransposons
  22. 22. Virulence plasmids, which turn the bacterium into a pathogen. Metabolism plasmids, which enable the digestion of unusual substances, e.g., salicylic acid.
  23. 23. •Bacterial chromosomeBacterial chromosome •PlasmidPlasmid •BacteriophageBacteriophage •Transposable elementsTransposable elements Section 2 Bacterial Genetic Elements
  24. 24. Bacteriophage or phageBacteriophage or phage Obligate intracellular parasites that multiply inside bacteria , fungi, actinomycetes or sprirochete by making use of some or all of the host biosynthetic machinery. Also called phage, or bacterial virus. Definition:
  25. 25. 1. Morphous and sturcture : The appearance of most phages likes a tadpole, while the other’s likes a ball or minute bar. 2. Chemical composition : nucleic acid (genetic material)——dsDNA ssDNA +/- ssRNA dsRNA Proteins——mainly found in capsid.
  26. 26. T4 bacteriophages infectingT4 bacteriophages infecting E.coliE.coli..
  27. 27.  TailTail Tail collarTail collar TailTail Sheath Tail coreTail core Tail plateTail plate Tail pins Tail fiber  Head Core ( nucleic acid ) Capsid ( proteins ) phage
  28. 28. The appearance of E.coli T4 phage (TEM×390,000)(TEM×390,000)
  29. 29. 3. Classification3. Classification According toAccording to The fate of host bacteria infectedThe fate of host bacteria infected with phagewith phage ①① virulent phage Phage that can only multiply within bacteria and kill the cell by lysis.
  30. 30. Characteristics:Characteristics: aa 、、 Large scaleLarge scale proliferate in host cellcell bb 、、 Split or lyse host bacteriaSplit or lyse host bacteria cc 、、 ProgenyProgeny Phage can infect othercan infect other sensitive cell, thussensitive cell, thus bacteriolysis cyclebacteriolysis cycle established.established.
  31. 31. ②② Lysogenic or temperate phage Phage that can either multiply via the lytic cycle or enter a quiescent state in the bacterial cell. • Prophage • Lysogen
  32. 32. Prophage: A prophage is a phage genome inserted as part of the linear structure of the DNA chromosome of a bacterium. Prophages are important agents of horizontal gene transfer. Lysogen (Lysogenic bacteria): a bacterium which contains in its genome the DNA of a virus which is lying dormant, passively letting itself be replicated by the bacterium whenever the bacterium replicates its own genome (a lysogenic virus), but able to reactivate and destroy the bacterium at a time of the virus's choosing (becomes a lytic virus).
  33. 33. 1. The division of host cell is normal, and the genome of phage is inherit to daughter cell 2. The host cell bear the competence of immunity to infect with relative phage. 3. The integrated prophage bring some new characters to its host cell. 4. The phage genome will deprive and enter to the lytic cycle spontaneously or induced by some factors, result in the lysis of the host cell. The characters of lysogenic bacteria
  34. 34. Significance of LysogenySignificance of Lysogeny Lysogenic conversionLysogenic conversion Toxin production byToxin production by CorynebacteriumCorynebacterium diphtheriaediphtheriae avirulent strain Virulent strain corynebacteriophage
  35. 35. •Bacterial chromosomeBacterial chromosome •PlasmidPlasmid •BacteriophageBacteriophage •Transposable elementsTransposable elements Section 2 Bacterial Genetic Elements
  36. 36. Transposable elementsTransposable elements Transposable elements are a heterogeneous class of genetic elements that can insert at new locations on chromosomes, plasmids and phages without the limitation of homologous recombination , it is also called jumping genes or movable genes. Definition
  37. 37. Nature : DNA sequences in bacteria cell that can change its position. Transfer way : The transfer or shift of the transposabletransposable elementelement was resulted by special recombinase coded by its own DNA sequence.
  38. 38. ClassificationClassification :: • Insertion sequenceInsertion sequence (( ISIS )) • TransposonTransposon (( TnTn )) • Bacteriophage MuBacteriophage Mu
  39. 39. 1.1. Insertion sequenceInsertion sequence (( ISIS )) DefinitionDefinition Insertion sequences are transposable geneticInsertion sequences are transposable genetic elements that carry only genes that areelements that carry only genes that are required for transposition.required for transposition.
  40. 40. StructureStructure Insertion sequences are small stretches ofInsertion sequences are small stretches of DNA that have repeated sequences at their endsDNA that have repeated sequences at their ends ,, which are involved in transposition. In betweenwhich are involved in transposition. In between the terminal repeated sequences there are genesthe terminal repeated sequences there are genes involved in transposition and sequences that caninvolved in transposition and sequences that can control the expression of the genes but no othercontrol the expression of the genes but no other nonessential genes are present.nonessential genes are present.
  41. 41. 2. Transposon2. Transposon (( TnTn )) DefinitionDefinition Transposons are transposable geneticTransposons are transposable genetic elements that carry one or more other geneselements that carry one or more other genes in addition to those for transposition.in addition to those for transposition.
  42. 42. StructureStructure The structure of a transposon is similar toThe structure of a transposon is similar to that of an insertion sequence. The extra genesthat of an insertion sequence. The extra genes are located between the terminal repeatedare located between the terminal repeated sequences. In some instances (compositesequences. In some instances (composite transposons) the terminal repeated sequencestransposons) the terminal repeated sequences are actually insertion sequences.are actually insertion sequences. IR IRTransposase Gene Extra genes
  43. 43. ImportanceImportance Many antibiotic resistance genes are located onMany antibiotic resistance genes are located on transposons. Since transposons can jump from onetransposons. Since transposons can jump from one DNA molecule to another, these antibioticDNA molecule to another, these antibiotic resistance transposons are a major factor in theresistance transposons are a major factor in the development of plasmids which can conferdevelopment of plasmids which can confer multiple drug resistance on a bacterium harboringmultiple drug resistance on a bacterium harboring such a plasmid. These multiple drug resistancesuch a plasmid. These multiple drug resistance plasmids have become a major medical problemplasmids have become a major medical problem because the indiscriminate use of antibiotics havebecause the indiscriminate use of antibiotics have provided a selective advantage for bacteriaprovided a selective advantage for bacteria harboring these plasmids.harboring these plasmids.
  44. 44. 3 Transposable phage Transposable phage is a temperate phage with the competence of transposition
  45. 45. Section 3 The mechanisms of bacterial variation variation Genotype variation Phenotype variation Gene mutation Chromosome aberration Gene recombination
  46. 46. Gene transfer and recombinationGene transfer and recombination Basic conceptBasic concept Gene transfer :Gene transfer : The process that DNA transfer from donor toThe process that DNA transfer from donor to recipient.recipient. Gene recombination :Gene recombination : The process thatThe process that exogenous DNA integrate with the chromosome of the recipientrecipient cell , result in the change of the genotype and become a recombinant bacteria.
  47. 47. The main ways of gene transfer and recombination : Transformation Conjugation Transduction Lysogenic conversion Protoplast fusion
  48. 48. TransformationTransformation Definition:Definition: Transformation is gene transfer from theTransformation is gene transfer from the donor cell DNA to a recipient cell. Certaindonor cell DNA to a recipient cell. Certain bacteria (bacteria (e.g.e.g. Bacillus, Haemophilus, Neisseria,Bacillus, Haemophilus, Neisseria, Pneumococcus) can take up DNA from thePneumococcus) can take up DNA from the environment and the DNA that is taken up canenvironment and the DNA that is taken up can be incorporated into the recipient'sbe incorporated into the recipient's chromosome.chromosome.
  49. 49. Injection Bacterial colonies Rough nonvirulent (strain R) Results Mouse healthy Smooth virulent (strain S) Mouse dies Heat-killed smooth virulent (strain S) Live strain S bacteria in blood sample from dead mouse Mouse diesMouse healthy + Rough nonvirulent (strain R) Heat-killed smooth virulent (strain S) Griffith’s experiment identifying the “transforming principle Pneumococcus transformation experiment
  50. 50. The mechanism of transformation Uptake of DNAbacteriolysis Recombination
  51. 51. The main ways of gene transfer and recombination : Transformation Conjugation Transduction Lysogenic conversion Protoplast fusion
  52. 52. TransductionTransduction Definition:Definition: Transduction is defined as the transfer ofTransduction is defined as the transfer of genetic information between cells through thegenetic information between cells through the mediation of phage particle.mediation of phage particle.
  53. 53. TypesTypes of transduction:of transduction: Generalized transductionGeneralized transduction Transduction in which potentially any dornorTransduction in which potentially any dornor bacterial gene can be transferredbacterial gene can be transferred Specialized transduction Transduction in which only certain donor genes can be transferred
  54. 54. • Infection of Donor • Phage replication and degradation of host DNA •Assembly of phages particlesAssembly of phages particles • Release of phageRelease of phage • Infection of recipientInfection of recipient •Homologous recombinationHomologous recombination    Potentially any donor gene can be transferred Generalized TransductionGeneralized Transduction
  55. 55. The fate of exogenous DNA in Generalized Transduction: 1) Complete transduction 2) Abortive transduction Bacteria DNALytic bacterium Complete transduction Abortive transduction phage DNA Infected by phage integration Without integration
  56. 56. • It is relatively easy.It is relatively easy. • It is rather efficient, using the correct phage.It is rather efficient, using the correct phage. • It moves only a small part of the chromosomeIt moves only a small part of the chromosome which allows you to change part of a strain'swhich allows you to change part of a strain's genotype without affecting the rest of thegenotype without affecting the rest of the chromosome.chromosome. • The high frequency of transfer and the smallThe high frequency of transfer and the small region transferred allows fine-structure mappingregion transferred allows fine-structure mapping The application of generalized transductionThe application of generalized transduction
  57. 57. •Specialized transductiontransduction is transduction inis transduction in which onlywhich only certain donorcertain donor genesgenes can becan be transferred to the recipient.transferred to the recipient. •AnAn individual phage can only transfer certainindividual phage can only transfer certain genes.genes. • Specialized transduction is mediated bytransduction is mediated by lysogeniclysogenic or temperate phage and the genesor temperate phage and the genes that get transferred will depend on where thethat get transferred will depend on where the prophage hasprophage has inserted in the chromosome.inserted in the chromosome. Specialized transduction (( Lysogenic PhageLysogenic Phage ))
  58. 58. Excision of theExcision of the prophageprophage • Replication andReplication and release of phagerelease of phage • Infection of theInfection of the recipientrecipient • Lysogenization ofLysogenization of the recipientthe recipient • HomologousHomologous recombination alsorecombination also possiblepossible The mechanism ofThe mechanism of Specialized transductiontransduction
  59. 59. generalizedgeneralized Specialized Vector virulent phage or temperate phage in lytic cycle temperate phage Target gene Any dornor geneAny dornor gene Certain donor gene Time Bacteriolysis phase Lysogenic phase Cause Error assemble Error excisionexcision Difference between generalized transductiongeneralized transduction andand Restricted transductiontransduction
  60. 60. The main ways of gene transfer and recombination : Transformation Conjugation Transduction Lysogenic conversion Protoplast fusion
  61. 61. Lysogenic ConversionLysogenic Conversion Definition:Definition: The prophage DNA as a gene recombinedThe prophage DNA as a gene recombined with chromosome of host cell and assign somewith chromosome of host cell and assign some character to the host cell.character to the host cell.
  62. 62. Example Corynebacterium diphtheriae (Does not produce diphthera toxin) β-corynebacteria phageInfected with Losogenic Corynebacterium diphtheriae (Phage’S DNA integrated into host chromosome and encode diphthera toxin)
  63. 63. The main ways of gene transfer and recombination : Transformation Conjugation Transduction Lysogenic conversion Protoplast fusion
  64. 64. ConjugationConjugation Definition:Definition: Transfer of DNA from a donor to aTransfer of DNA from a donor to a recipient by direct physical contact between therecipient by direct physical contact between the cells. In bacteria there are two mating types acells. In bacteria there are two mating types a donor (male) and a recipient (female) and thedonor (male) and a recipient (female) and the directiondirection of transfer of genetic material is oneof transfer of genetic material is one way; DNA is transferred from a donor to away; DNA is transferred from a donor to a recipient.recipient.
  65. 65. 1.Conjugation of F plasmid The basic knowledge of F factor • Function——encode sex pili • Exist form: F+ bacteria——contain free F plasmid F’ bacteria——contain F plasmid with some host gene Hfr bacteria——(high frequency recombinant) F plasmid is integrate in host chromosome.
  66. 66. F- F+ HfrF’ Conjugate with F+ Curing Integrate excision Deviational excision Curing Integrate Conjugate with F’ Transform of F plasmid
  67. 67. Autonomous (FAutonomous (F++ ))    Characteristics of FCharacteristics of F++ × F× F-- crosses:crosses: • FF-- becomes Fbecomes F++ while Fwhile F++ remains Fremains F++ • Low transfer of donor chromosomal genesLow transfer of donor chromosomal genes Physiological States of F FactorPhysiological States of F Factor
  68. 68. Physiological States of F FactorPhysiological States of F Factor Integrated (Hfr)Integrated (Hfr) Characteristics ofCharacteristics of HfrHfr × F- crosses:× F- crosses: • FF-- rarely becomes Hfr while Hfr remains Hfrrarely becomes Hfr while Hfr remains Hfr • High transfer of certain donor chromosomal genesHigh transfer of certain donor chromosomal genes
  69. 69. Physiological States of F FactorPhysiological States of F Factor Autonomous with donor genes (F’)Autonomous with donor genes (F’) Characteristics of F’ x F- crosses:Characteristics of F’ x F- crosses: • F- becomes F’ while F’ remains F’F- becomes F’ while F’ remains F’ • High transfer of donor genes on F’ and lowHigh transfer of donor genes on F’ and low transfer of other donor chromosomal genestransfer of other donor chromosomal genes
  70. 70. Structure of R FactorsStructure of R Factors  RTF (resistance transfer factor)  Conjugative plasmidConjugative plasmid  Transfer genesTransfer genes Tn9 Tn21 Tn 10 Tn8 RTF R determinant  R determinantR determinant  Resistance genesResistance genes  TransposonsTransposons
  71. 71. The main ways of gene transfer and recombination : Transformation Conjugation Transduction Lysogenic conversion Protoplast fusion
  72. 72. Protoplast fusion is a highly efficient method for the direct transfer of expression vectors from bacteria to other cell. It involves digesting bacterial cell walls with lysozyme or penicilin to produce protoplasts and then fusing the two protoplasts in the presence of polyethylene glycol. Protoplast fusionProtoplast fusion
  73. 73. The protocol of Protoplast fusionProtoplast fusion Bacteria A Bacteria B Treat with lysozyme or penicilin Protoplast A Protoplast BProtoplast A Protoplast B Treat with polyethylene glycol Recombinant fusion Incubation Recombinant bacteria
  74. 74. Comparison among different ways of bacterial gene transfer and recombanation manner Origin of gene Transfer mechanism transformation Donor Intake directly Generalized transduction Lysogenic bacteria virulent phage or temperate phage in lytic cycle Restricted transduction Lysogenic bacteria Defective phage infection Lysogenic Conversion Temperate phage Temperate phage infection Conjugation “Male” bacteria Sex pili communication Protoplast fusion Protoplast Protoplast fusion
  75. 75. Practical implicationsPractical implications Application in diagnosis, treatment andApplication in diagnosis, treatment and prevention of infectious diseasesprevention of infectious diseases Eg. L-formEg. L-form PCRPCR Detection of mutagenicityDetection of mutagenicity Application in genetic engineeringApplication in genetic engineering
  76. 76. The Ames Test for mutagenicity
  77. 77. Summary • Definitions: phage, prophage, transformation, conjugation, transduction, lysogenic conversion • bacteria • The forms of genetic recombination
  78. 78. SummarySummary 1.Phage 2.Transposable elements1.Phage 2.Transposable elements 3.Lytic or virulent phage 4.Lysogenic or temperate phage3.Lytic or virulent phage 4.Lysogenic or temperate phage 5.Transformation 6.Transduction5.Transformation 6.Transduction 7.Conjugation 8.Lysogenic conversion7.Conjugation 8.Lysogenic conversion 9.Protoplast fusion 10.Ames Test9.Protoplast fusion 10.Ames Test 11.11. Briefly describe types of genetic materials in bacteria . Briefly describe types of genetic materials in bacteria .  12.Briefly describe the differences between generalized-transduction12.Briefly describe the differences between generalized-transduction and specialized (restricted)-transduction.and specialized (restricted)-transduction. 13. Briefly describe the  forms of genetic recombination in bacteria.13. Briefly describe the  forms of genetic recombination in bacteria. 14.Describe the practical implications of bacterial heredity and14.Describe the practical implications of bacterial heredity and variations.variations.

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