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Sharing of genetic information. Bacteria are successful because They carefully regulate their use of energy in metabolic processes by shutting down unneeded pathways at the biochemical and genetic levels.
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Sharing of genetic information • Bacteria are successful because • They carefully regulate their use of energy in metabolic processes by shutting down unneeded pathways at the biochemical and genetic levels. • They share genetic information with other bacteria, increasing their ability to adapt to their environment.
Genetic Recombination • Bacteria are asexual • With sexual reproduction, multiplication and gene recombination are linked. • In bacteria, they are separate • Bacteria acquire new DNA from mutation, phage infection, and transfer from other bacteria • Bacterial genotypes are somewhat fluid • Due to the ease of gene transfer, many genes can be widely distributed among many bacteria • One multicomponent organism?
Gene transfer • Ways that bacteria can acquire new genetic info • Transformation • Taking up of “naked DNA” from solution • Transduction • Transfer of DNA one to cell to another by a virus • Conjugation • “Mating”: transfer of DNA from one bacterium to another by direct contact.
Transformation Both G+ and Gram – bacteria can take up DNA. Cells in a state in which they can take up DNA are referred to as competent. DNA may be actively released by some cells, suggesting that DNA exchange is “intentional”. http://openwetware.org/images/0/0c/Competence2.jpg
Transformation requires homologous recombination New DNA must be similar. Successful transformation requires that donor and recipient be related.
Transduction: the vector is a virus • New DNA brought by a bacteriophage • Requires donor and recipient be related • Generalized transduction • Chopped up bacterial DNA is incorporated into a capsid • Phage binds to new host bacterium, but injects donor bacterial DNA instead • Specialized transduction • In lysogeny, virus DNA inserts. • If DNA excises, can take adjacent bacterial DNA with it • Upon infection of new host, new bacterial DNA added • Important in bacterial evolution
Gene transfer between bacteria-2 • Transduction: transfer of DNA via a virus.
Conjugation • A plasmid that can be spread by conjugation codes for a sex pilus. • Pilus attaches donor to recipient cell. • Shortening of pilus draws bacteria into contact • Channel opens thru cell wall of both bacteria • Copy of plasmid sent. http://parts.mit.edu/igem07/images/1/16/BU_conjugation.jpg
Conjugation and gene transfer • Sex pili bind specifically to surface molecules on bacteria • But many bacteria have similar molecules and can participate. • Homologous recombination is not needed • Plasmids remain in cytoplasm • Once the plasmid has been copied and sent, both donor and recipient bacteria have the genes. Recipient can now be a donor. • Several types of plasmids, incl R, can be widely spread