Genetics of Bacteria

Bacterial Chromosomes One double-stranded, circular molecule of DNA. Found in nucleoid region, which is a dense region of DNA. Many bacterial also contain extrachromosomal DNA, in the form of a plasmid, which is a small double-stranded ring of DNA. DNA is replicated bidirectionally from a single origin of replication, and is then followed by Binary Fission.

Binary Fission Asexual reproduction via Mitosis that is used by most bacteria to rapidly reproduce. It produces a clone, which is genetically identical to the parent.

Genetic Recombination in Bacteria Produces new bacterial strains with different genetics. 3 Types: oTransformation oTransduction oConjugation

Transformation Change of a bacterial cell’s genotype by the uptake of foreign DNA plasmid from its surrounding environment when the bacteria is stressed. Process can be induce in a lab very easily. Used in biotech industry to produce copies of genes and so bacterial cells can produce proteins of other species. Ex: Insulin, Human Growth Hormone

Transduction Transfer of DNA from one bacteria to another by a bacteriophage. 2 Types: Generalized and Specialized.

Generalized Transduction Occurs when random pieces of host cell DNA are packaged within a phage capsid during the Virus Lytic Cycle. Phage within host cell (donor cell) DNA infects a new host (recipient cell). Donor cell’s DNA recombines with the recipient cell’s DNA. Results in a recombinant bacterial cell with a genotype different from the donor and recipient cells.

Specilized Transduction Occurs when a prophage (virus) excises from the bacterial chromosome & carries adjacent bacterial genes with it. Carried out only by temperate phages.

Conjugation Direct transfer of genes between 2 cells that are temporarily joined. Physical connection (pili). Bacterial version of sex. F-factor: –F = fertility. –Codes for sex pili = male. –If F-factor is carried in a plasmid = F plasmid. HFr: –F-factor integrates into chromosome.

Conjugation (Continued) Conjugation bridge usually breaks before entire chromosome and tail end of F-factor can be transferred. As a result: –Only some bacterial genes are donated. –F- cell does not become F+ cell because only part of the F-factor is transferred.