1. MICROBIAL GENETICS &
MICROBIAL INTERACTIONS
Last Lecture Sets for Examination 3
Monday, February 27, 2012

2. MICROBIAL GENETICS
Monday, February 27, 2012

3. TERMS IN MICROBIAL
GENETICS
Genome: All of the genetic material in a
cell
Genomics: The molecular study of
genomes
Genotype: The genes of an organism
Phenotype: Expression of the genes
Monday, February 27, 2012

4. OVERVIEW
Monday, February 27, 2012

5. IMPORTANT ENZYMES
Monday, February 27, 2012

6. REGULATION OF GENE
EXPRESSION
Monday, February 27, 2012

7. MUTATIONS
A change in the genetic material
Mutations may be neutral, beneficial, or
harmful
Mutagen: Agent that causes mutations
Spontaneous mutations: Occur in the absence
of a mutagen
Monday, February 27, 2012

8. TYPES OF MUTATIONS:
MISSENSE
Monday, February 27, 2012

9. TYPES OF MUTATIONS:
NONSENSE
Monday, February 27, 2012

10. TYPES OF MUTATIONS:
FRAMESHIFT
Monday, February 27, 2012

11. REPAIRING MUTATIONS
Ionizing radiation (X rays and gamma
rays) causes the formation of ions that
can react with nucleotides and the
deoxyribose-phosphate backbone
Nucleotide excision repairs mutations.
UV radiation causes thymine dimers
Light-repair separates thymine dimers.
Monday, February 27, 2012

12. MUTATIONS IN THE LAB
FREQUENCY: Spontaneous mutation rate = 1 in 109
replicated base pairs or 1 in 106 replicated genes AND
Mutagens increase to 10–5 or 10–3 per replicated gene
SELECTION:
Positive (direct) selection detects mutant cells because they
grow or appear different
Negative (indirect) selection detects mutant cells because
they do not grow.
Monday, February 27, 2012

13. CHARACTERIZING
MUTATIONS
Monday, February 27, 2012

14. CHARACTERIZING
MUTANTS
HYPOTHETICAL EXPERIMENT:
Using UV as mutagen you isolated colonies on your NA
plates, to verify possible effects on phenotypes, you
TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3
MINIMAL MEDIUM (MM)
- - -
MM + Penicillin
+ - -
MM + Erythromycin
- - +
MM + Rifampicin
- + +
MM + glycine
+ - -
MM + serine
- - -
MM + methionine
- + -
Monday, February 27, 2012

15. CHARACTERIZING
MUTANTS
TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3
MINIMAL MEDIUM (MM)
- - -
MMG + Penicillin
+ - -
MMG + Erythromycin
- - +
MMG + Rifampicin
- + +
MM + glycine
+ - -
MM + serine
- - -
MM + methionine
- + -
Monday, February 27, 2012

16. CHARACTERIZING
MUTANTS
TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3
MINIMAL MEDIUM (MM)
- - -
MMG + Penicillin
+ - -
MMG + Erythromycin
- - +
MMG + Rifampicin
- + +
MM + glycine
+ - -
MM + serine
- - -
MM + methionine
- + -
Do you believe that they are all mutants? Justify.
Monday, February 27, 2012

17. CHARACTERIZING
MUTANTS
TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3
MINIMAL MEDIUM (MM)
- - -
MMG + Penicillin
+ - -
MMG + Erythromycin
- - +
MMG + Rifampicin
- + +
MM + glycine
+ - -
MM + serine
- - -
MM + methionine
- + -
Do you believe that they are all mutants? Justify.
Which isolate(s) has mutations that resulted to antibiotic resistance? Justify.
Monday, February 27, 2012

18. CHARACTERIZING
MUTANTS
TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3
MINIMAL MEDIUM (MM)
- - -
MMG + Penicillin
+ - -
MMG + Erythromycin
- - +
MMG + Rifampicin
- + +
MM + glycine
+ - -
MM + serine
- - -
MM + methionine
- + -
Do you believe that they are all mutants? Justify.
Which isolate(s) has mutations that resulted to antibiotic resistance? Justify.
Which isolate(s) has mutations on the inability to produce an amino acid? Justify.
Monday, February 27, 2012

19. CHARACTERIZING
MUTANTS
TEST MEDIA ISOLATE 1 ISOLATE 2 ISOLATE 3
MINIMAL MEDIUM (MM)
- - -
MMG + Penicillin
+ - -
MMG + Erythromycin
- - +
MMG + Rifampicin
- + +
MM + glycine
+ - -
MM + serine
- - -
MM + methionine
- + -
Do you believe that they are all mutants? Justify.
Which isolate(s) has mutations that resulted to antibiotic resistance? Justify.
Which isolate(s) has mutations on the inability to produce an amino acid? Justify.
How will you name your isolate (E. coli) as a new strain?
Monday, February 27, 2012

20. MUTAGENICITY TEST: AMES
TEST
Monday, February 27, 2012

21. Monday, February 27, 2012

22. SINCE IT’S V-DAY....
Monday, February 27, 2012

23. SINCE IT’S V-DAY....
LET’S TALK ABOUT SEX!!!
Monday, February 27, 2012

24. SINCE IT’S V-DAY....
LET’S TALK ABOUT SEX!!!
Interested?
Monday, February 27, 2012

25. SINCE IT’S V-DAY....
LET’S TALK ABOUT SEX!!!
Interested?
Monday, February 27, 2012

26. SINCE IT’S V-DAY....
LET’S TALK ABOUT SEX!!!
Interested?
MICROBIAL GENETICS
Monday, February 27, 2012

27. GENE TRANSFERS
ENDPOINT: RECOMBINATION
Vertical gene transfer: Occurs during reproduction
between generations of cells
Horizontal gene transfer: The transfer of genes between
cells of the same generation
CONJUGATION, TRANSFORMATION,
TRANSDUCTION
Monday, February 27, 2012

28. CONJUGATION
Monday, February 27, 2012

29. CONJUGATION
Monday, February 27, 2012

30. TRANSFORMATION
Monday, February 27, 2012

31. TRANSDUCTION
Monday, February 27, 2012

32. EXTRACHROMOSOMAL
INHERITANCE: PLASMIDS
Conjugative plasmid: Carries genes for sex pili and transfer of the
plasmid
Dissimilation plasmids: Encode enzymes for catabolism of
unusual compounds
R factors: Encode antibiotic resistance
Monday, February 27, 2012

33. SOME METABOLIC ACTIVITIES
DETERMINED BY PLASMIDS
ORGANISM ACTIVITY
Pseudomonas spp degradation of camphor, toluene, octane, salicyclic acid
Bacillus stearothermophilus alpha amylase
Alcaligenes eutrophus utilization of hydrogen as oxidizable energy source
E. coli sucrose uptake and and metabolism, citrate uptake
Klebsiella spp nitrogen fixation
lactose utilization, galactose phosphotransferase system, citrate
Streptococcus (group N)
metabolism
Rhodospirillum rubrum synthesis of photosynthetic pigment
Flavobacterium spp nylon degradation
Monday, February 27, 2012

34. EXTRACHROMOSOMAL
INHERITANCE: TRANSPOSONS
Segments of DNA that can
move from one region of
DNA to another
Contain insertion
sequences for cutting and
resealing DNA
(transposase)
Complex transposons carry
other genes
Monday, February 27, 2012