Flagella Slender rigid structures Approx. 20 nm across and up to 20 m long Used for locomotion (Hair is 57-120 m across)

Flagella distribution Bacteria differ regarding the arrangement of flagella Monotrichous = one Polar = located at the end Amphitrichous = one on each pole

Flagella distribution Lophotrichous = tuft at one or both ends Peritrichous = spread evenly over the entire surface Arrangement can be useful in identification

Flagella ultrastructure Composed of three parts: Filament Hook Basal body Some bacteria have sheaths surrounding their flagella

Flagella ultrastructure

Flagella ultrastructure

Flagella ultrastructure C-ring contains proteins involved in the rotation of the flagella

Flagella ultrastructure Gram negative Gram positive Have four rings Have two rings

Flagella synthesis Involves more than 20 genes Mechanism related to type III secretion systems Filament is a hollow tube composed of flagellin and ending with a capping protein

Flagella synthesis The hook is made of different protein subunits Basal body is composed of several different proteins

Flagella synthesis Other proteins are involved in the transport of subunits across the membrane Protein subunits travel down the hollow filament and are incorporated into the end of the growing flagella

Flagella synthesis

Chemotaxis Rotation of flagella propels cell through the environment E. coli flagella can rotate 270 rps V. alginolyticus flagella can rotate 1,100 rps

Chemotaxis Rotation of flagella in counter-clockwise direction usually results in running/swimming Rotation in opposite direction results in tumbling (random movement)

Chemotaxis When in the presence of a gradient of attractant, amount of time spent in run vs. tumble mode increases

Chemotaxis Exact mechanism of flagella movement not yet understood Basal body may rotate within a membrane bound ring of proteins (rotor and stator)

Chemotaxis Rotation is driven by proton and sodium ion gradients and not ATP

Chemotaxis Controlled by a two-component phosphorelay system Chemicals bind to chemoreceptor on cell surface Che A = sensor kinase Che Y = response regulator

Chemotaxis Different levels of phosphorylation of proteins in response to the presence of attractant or repellent influences the direction of rotation

Chemotaxis Attractant Repellent

Archaeal flagella Are quite different from bacterial flagella Subunits may be added to filament from the cytoplasmic side (like pili)

Pili/fimbriae Conjugation pili differ from other pili/fimbriae Conjugation pili are usually wider and longer than other pili/fimbriae (9-10 nm wide vs. 3-10 nm wide)

Pili/fimbriae Are composed primarily of a single protein Many have special adhesive proteins located on the tip Can aid in attachment to various surfaces

Pili/fimbriae Many pathogenic bacteria are dependent on pili/fimbriae for their ability to cause disease e.g. urinary tract and kidney infections Pili also help bacteria to attach to surfaces in the environment Attachment often followed by production of a slime layer/biofilm

Pili/fimbriae Unlike flagella, pilus subunits are added to the growing rod from the bottom Outer membrane complex required in gram-negative bacteria

Pili/fimbriae Some pili/fimbriae are responsible for a type of motility referred to as twitching motility (Type IV pili) Caused by extension and retraction of adherent pili