《微生物学》课程教学课件（PPT讲稿）Chapter 1 Special structure

Chapter 1 The structure and function of prokaryotes Special structure Pili and fimbriae Flagella The bacterial endospore

Special structure • Pili and fimbriae • Flagella • The bacterial endospore Chapter 1 The structure and function of prokaryotes

Pili and fimbriae G-", short, fine, hairlike appendages that are not involved in motility Fimbriae/fimbria: 1000piece/cell adhesion to host epithelium Sex pili/pilus: 1-10piece/cell, sexual conjugation, they are genetically determined by sex factors or conjugative plasmids and are required for bacterial mating. Receptors of some bacterial viruses

Pili and fimbriae G-, short, fine, hairlike appendages that are not involved in motility. Fimbriae/fimbria:1000piece/cell, adhesion to host epithelium Sex pili/pilus: 1-10piece/cell, sexual conjugation, they are genetically determined by sex factors or conjugative plasmids and are required for bacterial mating. Receptors of some bacterial viruses

Fimbriae and pilli Vinus covered pilus

Fimbriae and Pilli

FLAGELLA Some bacteria are motile Locomotory organelles-flagella Taste environment Respond to food/poison Chemotaxis Flagella embedded in cell membrane project as strand Flagellin(protein) subunits move cell by propeller like action

FLAGELLA • Some bacteria are motile • Locomotory organelles- flagella • Taste environment • Respond to food/poison – Chemotaxis – Flagella – embedded in cell membrane – project as strand – Flagellin (protein) subunits – move cell by propeller like action

The majority of motile prokaryotes move by means offlagella 4

The majority of motile prokaryotes move by means of flagella

Flagellar arrangements Peritrichous Polar/monotrichous Lophotrichous Amphitrichous

Flagellar Arrangements Amphitrichous Peritrichous Polar/monotrichous Lophotrichous

Flagellar ultrastructure Filament: from cell surface to the tip Basal body: embedded in the cell Hook: link the filament to its basal body Basal body The e coli Flagellar G Structure s(peptidoglycan) M(plasma membrane) G L(out membrane) P(peptidoglycan layer) S-M(contact the plasma membrane)

Flagellar ultrastructure Filament: from cell surface to the tip Basal body: embedded in the cell Hook: link the filament to its basal body Basal body: G+ : S (peptidoglycan), M(plasma membrane) G-: L (out membrane), P (peptidoglycan layer), S-M(contact the plasma membrane) The E. coli Flagellar Structure

The mechanism of flagellar movement Rotatal moⅴ ement Fk counterclock wiae: forward on Directio of rotation clockwise tumble Enlargement E co 3um of

The mechanism of flagellar movement Rotatal movement counterclockwiae: forward on clockwise: tumble

Bacteria-bound experiment ce flagella antibody Glass lide

Glass lide cell flagella antibody Bacteria-bound experiment

Bacterial behavior Chemotaxis. phototaxis and Other taxes Prokaryotes encounter gradients of physical and chemical agents in nature, and the motility machinery in the cell is designed to respond in a positive or negative way to these gradients by directing the movement of the cell either toward or away from the signal molecule respectively Such directed movements are called taXes Chemotaxis: a response to chemicals Phototaxis: a response to ligl ht

Bacterial Behavior Chemotaxis, Phototaxis, and Other Taxes • Prokaryotes encounter gradients of physical and chemical agents in nature, and the motility machinery in the cell is designed to respond in a positive or negative way to these gradients by directing the movement of the cell either toward or away from the signal molecule, respectively. • Such directed movements are called TAXES. • Chemotaxis: a response to chemicals. • Phototaxis: a response to light