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1. Bacterial Genetics

2. GENETICS-Study of genes their structure &
function, heredity & variation
Genomics-Study & analysis of nucleotides of
DNA
Nucleic acid-DNA and RNA

3. Bacterial DNA
 Single Haploid Chromosome
 Super coiled circular dsDNA=1mm
 Exception:
 2 chromosomes : Vibro cholerae

4. Nucleotides-Structural units of Nucleic acids
Nitrogenous bases-Purines(A,G) and
Pyrimidines(T,U,C) Nucleoside
Pentose sugar-Deoxyribose
Phosphate group

6. Bacterial DNA
 Ratio of A+T to G+C constant for each species
 Genetic information is stored as a code
 Codon-unit,triplet(3 bases)
 64 codon
 61 sense codon code for 20 AA
 AGA/AGG/CGA-arginine— code is degenerate
 3 codon UAA/UAG/UGA- nonsense codons

7.  Gene or cistron
 Segment of DNA carrying codons for a particular polypeptide synthesis
 Locus
 a large no of genes
 Genome
 large no of loci
 Letter---------word-----sentence—paragraph---
 Nucleotide—Codon-----Gene--------Locus---
 1000-3000 Gene
 580 -5200 kbp
 length1-1.3mm

8.  DNA Replication:
Bidirectional replication Rolling circle mechanism

9. RNA
 mRNA
 rRNA
 tRNA

11. Extra chromosomal elements
Plasmids
Free Circular dsDNA-In Cytoplasm for several
generations
Replicate independently
Episome-integrated form
Not essential for life of bacteria
Number: up to 40/cell
contain 50-100 genes

12. Extra chromosomal elements
Plasmids
Curing: process of eliminating plasmid from
bacteria
Spontaneous
induced
Acridine
Radiation
Thymine starvation
High temp

13. Classification
On the basis of ability to perform conjugation:
Conjugative/self transmissible plasmid
Non conjugative plasmid
Based on compatibility b/w plasmid:
Compatible
Incompatible

14. Classification
Based on function:
Fertility/F plasmid: contain tra gene: sex pili
expression
Resistance/R plasmid
Col plasmid
Virulence plasmid
Metabolic plasmid

15. Variation
 Phenotypic
 Genotypic

16. GENETIC TRANSFER
 Vertical
 Horizontal
 Transformation
 Transduction
 Lysogenic conversion
 Conjugation

17. Transformation
- Random uptake of free / naked DNA
incorporation into chromosome
 Natural – S. pneumoniae
 express DNA-binding proteins on cell surface
 natural competent state allows uptake of "naked DNA"

18. Transformation
- random uptake of free / naked DNA
incorporation into chromosome


19.  1928: Frederick Griffith (London): First demonstrated
bacterial transformation

20. An "S" or SMOOTH coat strain, which is
lethal to mice.

21. An “R" or rough coat strain, which is
NOT lethal to mice.

22. Griffith found that he could heat inactivate the
smooth strain.

23. heat-inactivated S strain,
mixed with the R strain, the mouse would die.
Thus there was some
Material in the heat-killed S strain that was responsible for
"transforming" the R strain into a lethal form.

24. GENETIC TRANSFER
 Vertical
 Horizontal
 Transformation
 Transduction
 Lysogenic conversion
 Conjugation

25. Transduction- Transfer of genetic
material through bacteriophage

27. Transduction 2 types:
Generalized:
Packaging error
3 outcome on transduction:
Abortive transduction: 70-90%
Stable gene transfer
Unstable gene transfer


28. Transduction 2 types:


29. Transduction 2 types:
Restricted/specialized
Defect in disintegration of lysogenic phage
2 outcome when transduced to new bacteria
Cross over
Integrated as prophage

30. Transduction 2 types:


31. Importance of transduction
Drug resistance: Pn resistance
in Staphylococci
Treatment: Genetic mapping,
inborn error of metabolism
Phage vectors used in
molecular transformation of
bacteria

32. Lysogenic Conversion
 In Lysogenic bact prophage acts as additional segment of bact
chromosome-new characters-lysogenic conversion eg. C.diphtheriae and its
bacteriophage
 Phage coded Toxins:
 Diphtheria toxin
 cholera toxin
 Verocytotoxin of E. coli
 Streptococcus pyrogenic exotoxin A & C
 Botulism toxin C & D

33.  Lysogenic conversion: Phage DNA itself behave as new genetic element
 Transduction: Phage act as vehicle carrying bacterial gene

34. GENETIC TRANSFER
 Vertical
 Horizontal
 Transformation
 Transduction
 Lysogenic conversion
 Conjugation

35. Bacterial Conjugation
 Transfer of genetic information from one bacterium (donor or male) to
another bacterium (recipient or female) bacterium by mating or contact with
each other & forming conjunction tube

37.  F+ F- Mating
 HFR conjugation
 F’ Conjugation
Col factor
R factor-RTF + r determinants

39. Colicinogenic (col) factor
 Bacteriocins are the antibiotic like substances produced by one
bacterium that inhibit other bacteria
 Bacteriocins produced by coliform bacteria are called as colicin
 Bacteria other than coliforms also produce similar kind of
substances e.g. pyocin, diphthericin

41. FATE OF DONOR DNA:

42. Bacterial Recombination
 Integration of Donor DNA to recipient chromosome
 General or Homologous
 Site specific

43. General or Homologous
 Recombination b/w similar DNA sequences
 Reciprocal:
 Exchange of pair of Homologous DNA sequence b/w donor & recipient
 Non Reciprocal:
 Bacterial transformation
 Donor ssDNA is inserted into host chromosome & replace piece of host DNA

44. Site specific
 Integration of bacteriophage DNA into Bacterial DNA is site specific
 Donor DNA not homologous with chromosome it joins

45. TRANSPOSONS

46. Genetic engineering
 Deliberate modification of organism genetic information by directly altering its genome
 Done using recombinant DNA technology
 Gene coding for desired property (protein) ---isolated from organism-----inserted to vector---
-cloned---desired property express

48. POLYMERASE CHAIN REACTION
 Kary Mullis-1983
 PCR is a DNA amplification system that produces a large amount of DNA in
vitro from small amounts of starting material. It amplifies a specific DNA
sequence (or gene) or interest.
 Primer mediated , temp dependant enzymatic amplification of specific target
sequence to detectable levels

49.  Target DNA
 Primers
 Polymerase Enzyme- Thermus aquaticus
 Nucleotide
 Thermocycler

50.  Denaturation-940C
 Annealing of primers-50-600C
 Extension of primers
30-40 cycles for 3 hrs- 106 copies
Detection-gel electrophoresis and ethidium bromide staining.

52. PCR in Diagnosis
Bacteria
Viruses
Fungi

53. DNA PROBES
 Radiolabelled or chromogenically labelled pieces of ss
DNA which can be used for the detection of homologous
DNA by hybridization.
 Hybridisation is the technique in which two single-strands
of nucleic acid come together to form a stable double-
stranded molecule.

54. Applications of DNA Probes
 In clinical microbiology :
 Direct detection of microbes in specimens
 To detect microbes which are difficult or impossible to culture
 Identification of culture isolates
 Strain identification
 To identify toxins, virulence factors
 Identification of resistant markers

55. BLOTTING TECHNIQUES
 SOUTHERN BLOT
 WESTERN BLOT
 NORTHERN BLOT
 EASTERN BLOT

56. Thank you