Dd - Bacterial Gene Transfer

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three different "bacterial genome" components

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• Bacterial chromosome - large DNA molecule, usually circular, contains all genes necessary for growth under normal conditions.
• Plasmids - small DNA molecules, usually circular, replicate independently from chromosome, encode genes for a variety of nonessential genes-- for example, those that make proteins that provide toxicity or antibiotic resistance.
• Bacterial viruses - a bacteriophage chromosome incorporated into the bacterial chromosome; this can influence the phenotype of the bacterial cell (see below, "lysogenic conversion").
 Example: diphtheria bacteria is only toxic if it stably acquires a particular viral gene.

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• Bacterial chromosome -

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large DNA molecule, usually circular, contains all genes necessary for growth under normal conditions.

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• Plasmids -

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small DNA molecules, usually circular, replicate independently from chromosome, encode genes for a variety of nonessential genes-- for example, those that make proteins that provide toxicity or antibiotic resistance.

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• Bacterial viruses

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- a bacteriophage chromosome incorporated into the bacterial chromosome; this can influence the phenotype of the bacterial cell (see below, "lysogenic conversion").
 Example: diphtheria bacteria is only toxic if it stably acquires a particular viral gene.

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• Gene acquisition methods:

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 Transposable elements:

 Bacteriophage conversion  Acquisition of plasmids  Acquisition of "pathogenicity islands"

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prophage

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viral DNA in the host chromosome

prophage can be induced to enter lytic state -->viral replication

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temperate phages

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dont kill host cells.

elicit lytic response --> phage multiplication and hoset cell lysis (lysogenic response)

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what does the repressor protein do in the lysogenic state

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the prophage encoded respressor protein maintains the lysogenic state and blocks expression of the phage genes that are required for viral DNA replication and lytic development

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lysogenic cycle

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integration of bacteriophage DNA into host bacteriums genome.

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lytic cycle

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main method of viral replication. results in destruction of infected cell

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conjugative transposon

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mobile elements for conjucation between pairs of cells

transferred DNA is the conjugative transposon itself.