Genetics of Bacteria

Bacteria take advantage of several mechanisms by which DNA sequences can:

• Move from one DNA molecule to another,from one cell to another

• From one bacterial species to another

||These mechanisms have led to the evolution of ||These mechanisms have led to the evolution of multiple antibiotic-resistant bacteria.multiple antibiotic-resistant bacteria.

• Transformation• Many bacteria can acquire new genes (those found

laying around are called plasmids) by taking up DNA molecules from their surroundings The ability to deliberately transform the bacterium E. coli has made possible the cloning of many genes — including human genes — and the development of the biotechnology industry.

This is done by Plasmids

• Plasmids are molecules of DNA that are found in bacteria separate from the bacterial chromosome.

• They: • are small (a few thousand base pairs) • usually carry only one or a few genes • are circular • Sergio: This are not the ones from

Bioshock!

Some bacteria are capable of DNA transfer and genetic recombination.

Plasmid

• In E. coli, the F (fertility) plasmid can mobilize the chromosome for transfer to another

• cell in the process of conjugation.

• (transfer a portion of their chromosome to a recipient with which they are in direct contact )

• Video• Source

• Some types of bacteriophages can incorporate bacterial genes and transfer them into

• new host cells in the process of transduction

Transduction

• Bacteriophages are viruses that infect bacteria. In the process of assembling new virus particles, some host DNA may be incorporated in them. The virion head can hold only so much DNA so these viruses while still able to infect new host cells may be unable to lyze them.

• Instead the hitchhiker bacterial gene (or genes) may be inserted into the DNA of the new host, replacing those already there and giving the host an altered phenotype. Watch THIS!

• Concepts• Bacteria mutate spontaneously and

grow at an exponential rate • Conjugation is one means of

genetic recombination in bacteria • Rec proteins are essential to

bacterial recombination • F Factors are plasmids • Transformation is another process

leading to genetic recombination in bacteria

• Bacteriophages are bacterial viruses

• Transduction is virus-mediated bacterial DNA transfer

• Bacteriophages undergo intergenic recombination

• Intragenic recombination also occurs in Phage T4

• The different methods of gene transfer in bacteria generate Partial Diploid that permit the study of recombination and gene interaction.

• Watch this!

A partially diploid E. coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote). Source

• Cool Video

Questions!?Thought so. Be silent.