Title: Microbial Genetics
1Microbial Genetics
2 Gene Transfer,Genetic Engineering,and
Genomics 1. Genetic recombination.
2. Genetic engineering. 3. Microbial
genomics.
3A. Genetic Terminology
4- Genotype
- The genetic compliment of an organism
- Types of genotypic changes
- Mutation
- Conjugation
- Transduction
- Transformation
5- Phenotype
- The genetic expression of an organism
- Types of phenotypic expressions
- Morphology
- Cultural
- Physiological
6B. The Bacterial Chromosome
7- Introduction
- DNA is arranged as a single molecule with no
histones present, and with no dominance or
recessiveness in the genes. - Bacterial chromosome is located in the nucleoid.
- In E. coli there are 4000 genes spread over 1.5mm
of DNA in less than 1 micrometer of space
8- Loop domain structure allows for compaction of
DNA
9- Replication of the chromosome
- DNA polymerase
- The semiconservative method
- Replication of a closed loop chromosome
- Okazaki fragments
- Rolling circle method
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11- Plasmids
- Fragments of DNA in the cytoplasm
- R Factors - confer drug resistance
- Bacteriocins -proteins toxic to other bacteria
and human cell - Many plasmids are found in Gram-Negative bacteria
12C. Bacterial Mutation
13- Permanent alteration in the DNA
- Example nonpathogenic Yersinia pestis
- have genes that cause them to remain in
- mid gut, pathogenic Y. pestis do not
have - these genes
- Types of mutations
- Spontaneous
- Induced
14- Spontaneous mutations
- Occurs every 106 to 1010 replications
- 1 mutation in every billion bacteria
- Example Neisseria gonorrhoeae penicillin
resistance original mutation was spontaneous - Example Salmonella strains antibiotic resistance
15- Induced mutations
- Chemical or Physical agents enhance mutation rate
- Mutagens
- Ultraviolet lightmechanism of action
- Chemicals
- Chromosomal changes
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18- Mutation Type
- Point (substitution)
- (leu) (ser) (arg)
- Normal AAT AGT GCC
- (leu) (cyst) (arg)
- Mutant AAT TGT GCC
19- Mutation Type
- Frameshift (deletion)
- (leu) (ser) (arg)
- Normal AAT AGT GCC
- (leu) (val) (pro)
- Mutant AAT AGT GCC A
20- Mutation Type
- Frameshift (insertion)
- (leu) (ser) (arg)
- Normal AAT AGT GCC
- (leu) (glut) (cyst)
- Mutant AAT CAGT GCC
21- Repair Mechanisms
- DNA repair enzymes
- Many enzymes
- Constantly checking for errors
- Repair mechanisms
- Mismatch repair proofreads
- Damage repair
- Excision repair
- Dimer repair (UV light)
22Mismatch Repair
23Excision Repair
24- Transposable genetic elements
- Insertion sequences
- Small DNA segments
- Provide no genetic information
- Located at several places on the chromosome
- Transposons
- Larger than Insertion sequences
- Provide information for protein synthesis
25Sections A B repeating but reversed palindrome
26 27C. Bacterial Recombination
28- Transformation
- Description
- Griffith's experiments
- Modern interpretation Avery,McLeod McCarty
- Mechanism
- Competence
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31- Conjugation
- Male and female cells
- Role of F factors (plasmids)
- High frequency of recombination strains
- Mechanism of Hfr conjugation
- Sexduction
32Simple Conjugation
33Hfr Conjugation
34- Transduction
- Description
- Role of the bacteriophage
- The lytic cycle
- Lysogeny
- Generalized transduction
35Lysogeny
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38F. Control of protein synthesis
39- 1. Mechanism proposed by Jacob and Monod
- 2. The operon theory
- 3. Repressor-inductor model
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41D. Genetic Engineering
42Genetic Engineering
- Genetic Engineering Was Born from Genetic
Recombination - Genetic engineering involves changing the genetic
material in an organism to alter its traits or
products - A recombinant DNA molecule contains DNA fragments
spliced together from 2 or more organisms
43- History of Genetic Engineering
- Discovery of endonucleases
- Plasmids and sticky ends
44- Modern applications
- Pharmaceutical production
- Insulin, interferon, hormones, vaccines etc.
- Genetically engineered plants
- Animal gene alterations
- Gene probes
- DNA fingerprinting
- The human genome initiative
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48 49- Microbial Genomes Have Been Sequenced
- Hundreds of microbial genomes have been sequenced
since the first in 1995 - Many of which are pathogens
- Segments of the Human Genome May Have Microbial
Ancestors - As many as 200 of the 35,000 human genes are
essentially identical to those of Bacteria - They were passed down from early ancestors of
humans
50- Microbial Genomics Will Advance Our Understanding
of the Microbial World - Knowing genomes of bacteria that cause food-borne
diseases can help us - develop detection methods
- make food safer
- It can help us identify microbes that cannot be
cultured in the lab - Environmental genomics helps us understand how
microbial communities function
51- Microbial Genomics Will Advance Our Understanding
of the Microbial World - Environmental genomics can help develop
bioremediation techniques - Genomics can help develop detection methods for
potential bioweapons organisms and other agents
of warfare
52- Comparative Genomics Brings a New Perspective to
- Defining Infectious Diseases
- Studying Evolution
Types of Genomics Functional genomics attempts
to discover the function of proteins coded for
in a genome how the genes interact, allowing the
microbe to grow and reproduce Comparative
genomics compares the DNA sequence of one microbe
to another similar or dissimilar organism
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