Download Bacterial Genetics - Life Sciences Outreach Program

Summer 2008 Workshop
in Biology and Multimedia
for High School Teachers
Summer 2008 Workshop
Melissa Marchacos
Marlborough High School
Bacterial Genetics
Central Dogma
Recall a “new” old dogma:
DNA
RNA
Protein
Small Molecules
Referenced from Dr. Jon Clary
“An Ecological Approach to Microbes and Disease”
Harvard University, Cambridge
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Mechanisms of Genetic Transfer
1. Transformation
A. The uptake of “naked” DNA from the surrounding
environment
1. Free DNA (histones absent)
2. Plasmid DNA
b
Lysis
b
Recipient takes
b+
Recombination
b+
up fragment
a
+
Donor microbe
a
+
DNA fragments
a
a+
Recipient microbe
Recombinant
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Mechanisms of Genetic Transfer
2. Transduction
A. Viruses that infect bacteria; utilize syringe like
mechanism to introduce genome
http://en.wikipedia.org/wiki/Image:Transduction_%28genetics%29en.svg
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Transduction, cont.
Bacteriophages replicate in two manners
1. Lytic: T4 bacteriophages,
bacteriophages force host to burst,
releasing new bacteriophages
2. Lysogenic: incorporates genome into
host genome; replicates fairly harmlessly
with host
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://en.wikipedia.org/wiki/Phage
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://en.wikipedia.org/wiki/Phage
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Mechanisms of Genetic Transfer
3. Conjugation
A. The exchange of a plasmid
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
B. Usually occurs between same or
very similar species
C. Utilizes a pilus to connect the two
microbes
http://en.wikipedia.org/wiki/Image:Bacterial_Conjugation_en.png
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Conjugation, cont.
Plasmids
A. Small, double stranded, circular pieces of DNA
B. Replicate independently (self-replication) or within the host genome
(episomes)
Types of plasmids
1.
2.
3.
4.
5.
6.
Conjugative plasmids: transmitted during conjugation, carry a variety of information
R plasmids: resistance plasmids; protect against environmental factors, MDR (multiple
drug resistance) plasmid
Hfr plasmids: promotes genomic recombination
Col-plasmids: codes for proteins that kill other microbes
Degradative plasmids: contain sequencing that allows host to digest uncommon
substances (ex: toluene, salicylic acid)
Virulence plasmids: codes for altering the microbe into a pathogen
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.
Mutation
Types of mutations
1. Deletion
2. Insertion sequences
(transposons)
3. Frameshift mutations
4. Silent mutations
5. Missense mutations
6. Nonsense mutations
7. Mutagen induced
References
1. Campbell, Biology, 7e;
http://wps.aw.com/bc_campbell_biology_7/
2. Indiana University school of Medicine;
http://www1.indstate.edu/thcme/micro/bactGen/Bacgenet.h
tm
3. University of Miami Department of Molecular and Cellular
Biology; http://www.bio.miami.edu/
4. Wikipedia; http://en.wikipedia.org/wiki/Main_Page
Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.