《微生物学》课程教学课件（PPT讲稿）chapter 8-4 Plasmids

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

F-Plasmid-Fertility plasmids 1s3 100KB Tn1000 Can be cured with 1000 acridine orange tra region s· compatibility(imc) Origin of replication (oriS) Transposable elements 75 25 tra region phi: phage inhibition Is (insertion sequence) rep: replication functions inc, rep, oris, phi

F-Plasmid-Fertility Plasmids • 100 KB • Can be cured with acridine orange • Incompatibility (inc) • Origin of replication (oriS) • Transposable elements (Tn) • tra region • phi: phage inhibition • IS (insertion sequence) • rep: replication functions

Cell to Cell transfer of plasmids Conjugative: Plasmids that govern their own transfer by cell-to-cell contact are called conjugative(not all plasmids are conjugative) Some conjugative plasmids can transfer genetic information between distintly related organisms (between gram-positive and gram-negative bacteria, between bacteria and plant cells, and between bacteria and fungi), it is important for evolution. Chromosome Plasmid Conjugation(接合作用)

Cell to Cell Transfer of Plasmids • Conjugative: Plasmids that govern their own transfer by cell-to-cell contact are called conjugative (not all plasmids are conjugative) • Some conjugative plasmids can transfer genetic information between distintly related organisms (between gram-positive and gram-negative bacteria, between bacteria and plant cells, and between bacteria and fungi), it is important for evolution. Conjugation (接合作用）

Plasmid biology Chromosome (a)Plasmid replication inde of chromosom (c)Cell-to-cell transfer during conjugation p Somes (a) Integration of plasmid into chromosome

Plasmid Biology Episomes

Plasmid Biology Growth cuning (b) Curing of plasmid

Plasmid Biology

Types of Plasmids and Their Biological significance The presence of plasmids in a cell can have a profound influence on the cells phenotype the ability of conjugation the ability of rhizobium to interact with plants the resistance to antibiotics and heavy metals the degradation of octane, camphor et al the production of enterotoxin the applications in genetic engineering

Types of Plasmids and Their Biological Significance • The presence of plasmids in a cell can have a profound influence on the cell’s phenotype: – the ability of conjugation – the ability of Rhizobium to interact with plants – the resistance to antibiotics and heavy metals – the degradation of octane, camphor et al – the production of enterotoxin – the applications in genetic engineering