Bacterial GeneticsBacterial GeneticsSupplemental instruction

Designed by Pyeongsug Kim ©2010 sibio@att.net

Fall 2010For Dr. Wright’s Bio 7/27 Class

Picture from http://www.buildinggreentv.com/node/7088 http://steveaoki.dimmak.com/blog/2009/11/useless-information-4-bacteria/ http://www.scienceclarified.com/As-Bi/Bacteria.html

Designed by Pyeongsug Kim, ©2009Picture from Dr. Wright’s Bio27 Slides

___________: Duplication of a DNA molecule.; its encoded information can be passed on to future generation.

___________: synthesis of RNA from a DNA template.

___________: formation of a protein (amino acid sequence) from RNA sequence.

Transcription

Translation

Replication

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Bacterial genomeBacterial genome

Picture from http://en.wikipedia.org/wiki/Plasmid http://scienceprofonline.googlepages.com/microbiologymicrobialgenetics

Many bacteria have…..• Single, circular DNA

• Plasmids Small, circular double-stranded DNA Can encode a variety of genes not essential bacterial genes may give new properties conjugation

• Operons a group of genes expressed together a functioning unit of DNA sequence -promoter -operator -structural genes

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•Repressor binds to operator blocks transcription. •Corepressor binds to the repressor alters its shape enabling the repressor to bind to the operator. Transcription OFF!

•Inducer binds to the repressor alters its shape preventing the repressor to bind to the operator. Transcription ON!

Picture from Dr. Wright’s Bio27 Slides

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Lactose operonLactose operon (lac operon) (lac operon)

-inducible operon -Lactose as a inducer. -Genes are expressed(turn on) only if lactose(inducer) is present.

If Lactose present genes are expressed. transcription on!

If Lactose is absent genes are not expressed. transcription off!

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TryptophanTryptophan operon operon (trp operon)(trp operon)

-Repressible operon -Tryptophan as a corepressor. -Genes are not expressed(turn off) if tryptophan(corepressor) is present.

Picture from http://departments.oxy.edu/biology/bio130/lectures_2000/11-17-00_lecture.htm

MutationsMutations(rare)(rare)

-One or more amino acid is changed as a result. Bases (nucleotides) are changed or substituded-may be induced by radiation or chemical(mutanogens).

-Mutations can have a significant effect on genetic diversity.-New traits acquisition of resistance can be transmitted to other microbes.-Antimicrobial (Drug) Resistance

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Bacteria proliferate rapidly by binary fission.

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MutagensMutagens -Chemicals or radiation that changes the genetic material induced mutation• Base analogs -incorporated into DNA replace normal base with base analog(similar base) Base substitution• Intercalating agents -inserted(intercalated) b/w base pairs replace normal base with base analog -Frame shift mutation addition or subtraction of base pairs• Transposons -Random insertion into any gene. The gene inactivated. -Common in lab.

MutagensMutagens (cont’d) (cont’d)

-Radiation UV ~base subsitution

X Rays ~deletion of base

Designed by Pyeongsug Kim, ©2009Picture from http://en.wikipedia.org/wiki/Radiation

Ames test Ames test -uses bacteria to test chemicals…. “Is this chemical mutagen? Carcinogens?”-more rapid and inexpensive-More colonies than control plate (than normal) “This is mutagen!”

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Gene transmission in bacteriaGene transmission in bacteria

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transformation, transduction and conjugation

____________ - uptake of “naked” DNA

____________- by bacteriophages

____________- bacterial cells come in direct contact with each other. - Plasmid is often transferred

Transformation

Transduction

Conjugation

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Transduction

Designed by Pyeongsug Kim, ©2009Picture from Dr. Wright’s Bio27 Slides http://www.nature.com/nrm/journal/v2/n7/box/nrm0701_538a_BX1.html

AB C

TransductionTransductionConjugation

A:B:C:

B

TransformationConjugationTransduction

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A

A:B:C:

C

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Transformation, Transduction and Conjugation

Which one can be performed in Laboratory?

ALL

Which one can cause antibiotic resistace?

ALL

Picture from http://oceanexplorer.noaa.gov/explorations/04etta/background/antimicrobial/media/antimicrobial2.html

Transduction