Microbial Genetics

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Microbial Genetics
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Gene Transfer,Genetic Engineering,and
Genomics 1.   Genetic recombination.
2.   Genetic engineering. 3. Microbial
genomics.
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A. Genetic Terminology
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• Genotype
• The genetic compliment of an organism
• Types of genotypic changes
• Mutation
• Conjugation
• Transduction
• Transformation

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• Phenotype
• The genetic expression of an organism
• Types of phenotypic expressions
• Morphology
• Cultural
• Physiological

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B. The Bacterial Chromosome
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• 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

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• Loop domain structure allows for compaction of
  DNA

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• Replication of the chromosome
• DNA polymerase
• The semiconservative method
• Replication of a closed loop chromosome
• Okazaki fragments
• Rolling circle method

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• 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

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C. Bacterial Mutation
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• 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

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• 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

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• Induced mutations
• Chemical or Physical agents enhance mutation rate
• Mutagens
• Ultraviolet lightmechanism of action
• Chemicals
• Chromosomal changes

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• Mutation Type
• Point (substitution)
• (leu) (ser) (arg)
• Normal AAT AGT GCC
• (leu) (cyst) (arg)
• Mutant AAT TGT GCC

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• Mutation Type
• Frameshift (deletion)
• (leu) (ser) (arg)
• Normal AAT AGT GCC
• (leu) (val) (pro)
• Mutant AAT AGT GCC A

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• Mutation Type
• Frameshift (insertion)
• (leu) (ser) (arg)
• Normal AAT AGT GCC
• (leu) (glut) (cyst)
• Mutant AAT CAGT GCC

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• Repair Mechanisms
• DNA repair enzymes
• Many enzymes
• Constantly checking for errors
• Repair mechanisms
• Mismatch repair proofreads
• Damage repair
• Excision repair
• Dimer repair (UV light)

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Mismatch Repair
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Excision Repair
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• 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

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Sections A B repeating but reversed palindrome
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• Ames Test

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C. Bacterial Recombination
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• Transformation
• Description
• Griffith's experiments
• Modern interpretation Avery,McLeod McCarty
• Mechanism
• Competence

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• Conjugation
• Male and female cells
• Role of F factors (plasmids)
• High frequency of recombination strains
• Mechanism of Hfr conjugation
• Sexduction

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Simple Conjugation
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Hfr Conjugation
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• Transduction
• Description
• Role of the bacteriophage
• The lytic cycle
• Lysogeny
• Generalized transduction

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Lysogeny
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F. Control of protein synthesis
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• 1. Mechanism proposed by Jacob and Monod
• 2. The operon theory
• 3. Repressor-inductor model

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D. Genetic Engineering
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Genetic 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

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• History of Genetic Engineering
• Discovery of endonucleases
• Plasmids and sticky ends

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• 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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• E. Genomics

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• 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

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• 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

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• 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

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• 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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