Chapter&& Microbial genetics 8. 4 Plasmids 8.5 Genetic Conjugation, Transformation transduction 8.6 Transposons and Insertion sequences
Chapter8 Microbial genetics 8.4 Plasmids 8.5 Genetic Conjugation, Transformation, transduction 8.6 Transposons and Insertion Sequences
8. 4 Plasmids Circular genetic elements that reproduce autonomously and have an extra-chromosomal existence. ·1-1000 KB in size Typical plasmid 1/20 of chromosome Most are circular double-stranded DNA. some linear ds dna Transmitted from cell to cell via conjugation process Some can integrated into chromosome Can carry a variety of genes for production of toxin, resistance to antibiotics and heavy metals et al
8.4 Plasmids • 1-1000 KB in size • Typical plasmid 1/20 of chromosome • Most are circular double-stranded DNA, some linear ds DNA • Transmitted from cell to cell via conjugation process • Some can integrated into chromosome • Can carry a variety of genes for production of toxin, resistance to antibiotics and heavy metals et al. Circular genetic elements that reproduce autonomously and have an extra-chromosomal existence:
Plasmid Conjugative: plasmids which govern their own transfer by cell-to-cell contact are called conjugative Tra region: a set of genes within the plasmid that control the transmissability by conjugation Hfr(high frequency of recombination): strains of bacteria that transfer large amounts of chromosomal dna during conjugation Supercoil: plasmids isolated from the cells are in supercoiled configuration Curing of plasmids: elimination of plasmids from host cel Plasmid separation: by ultracentrifugation or electrophores by various treatments
Plasmid • Conjugative: plasmids which govern their own transfer by cell-to-cell contact are called conjugative • Tra region: a set of genes within the plasmid that control the transmissability by conjugation • Hfr (high frequency of recombination): strains of bacteria that transfer large amounts of chromosomal DNA during conjugation • Supercoil: plasmids isolated from the cells are in supercoiled configuration • Plasmid separation: by ultracentrifugation or electrophoresis • Curing of plasmids: elimination of plasmids from host cells by various treatments
Plasmids Replication: Most plasmids of gram-positive bacteria replicate by a rolling circle mechanism Copy number: The number of plasmids in a cell, can range from only 1-3 copies to 100 copies. Incompatibility: Two different types of Plasmids can not coexist in a cell pl Episomes: Plasmids having the ability to integrate into host chromosome
Plasmids • Replication: Most plasmids of gram-positive bacteria replicate by a rolling circle mechanism. • Copy number: The number of plasmids in a cell, can range from only 1-3 copies to 100 copies. • Incompatibility: Two different types of plasmids can not coexist in a cell. • Episomes: Plasmids having the ability to integrate into host chromosome
Col plasmids Bacteria also harbor plasmids with genes that may give them a competitive advantage in the microbial word Bacteriocins are bacterial protein that destroy other bacteria. Usually act only against closely related strains
Col plasmids • Bacteria also harbor plasmids with genes that may give them a competitive advantage in the microbial word. • Bacteriocins are bacterial protein that destroy other bacteria. Usually act only against closely related strains