Microbial genetics for exam 3
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MICROBIAL GENETICS & MICROBIAL INTERACTIONS
Last Lecture Sets for Examination 3
Monday, February 27, 2012
MICROBIAL GENETICS
Monday, February 27, 2012
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
OVERVIEW
Monday, February 27, 2012
IMPORTANT ENZYMES
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REGULATION OF GENE EXPRESSION
Monday, February 27, 2012
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
TYPES OF MUTATIONS: MISSENSE
Monday, February 27, 2012
TYPES OF MUTATIONS: NONSENSE
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TYPES OF MUTATIONS: FRAMESHIFT
Monday, February 27, 2012
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
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
CHARACTERIZING MUTATIONS
Monday, February 27, 2012
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
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
CHARACTERIZING MUTANTS
Do you believe that they are all mutants? Justify.
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
CHARACTERIZING MUTANTS
Do you believe that they are all mutants? Justify.
Which isolate(s) has mutations that resulted to antibiotic resistance? Justify.
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
CHARACTERIZING MUTANTS
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.
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
CHARACTERIZING MUTANTS
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?
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
MUTAGENICITY TEST: AMES TEST
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Monday, February 27, 2012
SINCE IT’S V-DAY....
Monday, February 27, 2012
LET’S TALK ABOUT SEX!!!
SINCE IT’S V-DAY....
Monday, February 27, 2012
LET’S TALK ABOUT SEX!!!
Interested?
SINCE IT’S V-DAY....
Monday, February 27, 2012
LET’S TALK ABOUT SEX!!!
Interested?
SINCE IT’S V-DAY....
Monday, February 27, 2012
LET’S TALK ABOUT SEX!!!
Interested?
MICROBIAL GENETICS
SINCE IT’S V-DAY....
Monday, February 27, 2012
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
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CONJUGATION
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CONJUGATION
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TRANSFORMATION
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TRANSDUCTION
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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
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
Streptococcus (group N) lactose utilization, galactose phosphotransferase system, citrate metabolism
Rhodospirillum rubrum synthesis of photosynthetic pigment
Flavobacterium spp nylon degradation
Monday, February 27, 2012
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
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