Bacterial genetics, extrachromosomal elements, mobile genetic elements, gene transfer.

Haploid prokaryotic genome

single double-stranded, circular DNA
(except in Streptomyces, Borrelia, Rhodobacter)

Supercoiled Structure

Exhibits negative supercoiling and, in archaea, positive supercoiling.

Content: DNA (60%), RNA (mainly mRNA), and nucleoid-associated proteins

Septal Mesosomes

The nucleoid is associated with septal mesosomes

Plasmids/Episome

Circular genetic elements independent of the bacterial chromosome

plasmids exist only in the autonomous state

Archaeal DNA Replication

The polymerase may have 3'-5' proofreading activity and reverse transcriptase activity.

Modification

Refers to a phenotypic change that occurs without altering the genotype

Mutation

refers to any permanent, heritable change in the information contained in the genome. A mutation is a change in the DNA base sequence

Spontaneous Mutation

A mutation that occurs naturally without external influence

Induced Mutation

A mutation that occurs as a result of exposure to external factors or agents, such as chemicals or radiation

Wild Type

a microorganism with natural, non-mutated traits

Episomes states

1. Autonomous State
2. Integrated State

Plasmids and episomes role

Conjugation (e.g., F-factor on episomes)
Defense against other strains and antibiotics (e.g., col and R factors on plasmids)
increasing virulence and tumor formation

Ribosome

protein and RNA-containing cellular components (ribonucleoproteins) consisting of two subunits

Sites of Protein Synthesis

rRNA (ribosomal RNA)
tRNA(transfer RNA)
mRNA (messenger RNA)

Insertion Sequences (jumping genes) and Transposons (TE) (mobile genetic elements)

Replicative (copy & paste) and Conservative (cut & paste) Transposons

• Transposase: Involved in sequence-specific and non-specific binding; sticky 5' and 3' ends; usually encoded by the transposon.
• Excision and Synthesis: At the excision site, synthesis occurs (using DNA polymerase and ligase).
• Gene Movement: Transfer of genes between bacterial chromosomes and plasmids.
• Insertion Sequences (700-2500 bp): Contain only the genes responsible for transposition.
• Composite Transposons: Contain additional genes and inverted repeat regions.
• Functions: moving information (genes) along the chromosome

Roles of Transposable elements

• In shaping the structure of chromosomes.
• In modulating the expression of genes.
• In converting RNA molecules to DNA.
• In changing positions of DNA sequence in genome.
• In carrying gene for enzyme that catalyzes transposition.
• In carrying antibiotic resistance genes

Transfer of genetic material between bacteria

transformation, conjugation and transduction