Flagella is a LASH or Whip like appendage , arising from Cellbody of Prokaryotic and Eukaryotic Organisms
Main Function of the Flagella is Locomotion , but other than that it also functions as a Sensory Organelle.
● Motility -Movement
● Swarming occurs with some bacteria
– Spreads across petri dishes
– Proteus species is the most evident
● This motility of bacteria occur in 2 different phenomenon :
~ Phototaxis – Movement of bacteria in response to Light This phototaxis is again of 2 types –
* Positive Phototaxis : Towards light
* Negative Phototaxis : Away from light
~ Chemotaxis – Movement of bacteria in response to light
This Chemotaxis is again of 2 types –
* Positive Chemotaxis : Towards Chemical
* Negative Chemotaxis : Away from Chemicals
Arrangement of Bacterial Flagella
● How many flagella does a bacteria have ?
● How are they arranged ?
● Do all Bacteria have flagella ?
● How does a flagella look like ?
● How does it help in movement of a bacteria ?
Classification of Bacteria based on arrangement of flagella . . .
● ATRICHOUS : Absence of Flagella
● MONOTRICHOUS : Presence of a Single Flagella at one end
● LOPHOTRICHOUS : Presence of “tuft” of Flagella at one end
● AMPHITRICHOUS : Presence of a single Flagella at both ends
● PERITRICHOUS : Presence of Flagella all over the cell surface .
Examples of the bacteria based on the arrangement of flagella . . .
Atrichous : Lactobacilli ,Diptheria bacillus
Monotrichous : Vibrio cholerae
Lophotrichous : Pseudomonas
Amphitrichous : Spirillum
Peritrichous : Bacillus
Structure of a Flagella -Prokaryotes
● Flagellum , consists of a Basal body , Hook and a Main Filament .
● Basal Body or Basal Granule :200 to 500 A in diameter ,
● In gram -ve bacteria , basal ring has 2 sets of rings , i.e.,
~ Proximal set
~ Distal set
● Each set has 2 rings,and the four rings are- M-ring , S ring , P ring , L ring .
● The arrangement of these rings are from inside to outside .
● M-ring is anchored to Plasma membrane , and P- ring to the Peptidoglycan layer of the cell-wall.
● M-ring provides the “movement” to the flagella.
● The S-ring is the Static- ring .
● The P-ring is attached to the Peptidoglycan layer , and the L-ring to the Lipopolysaccharide layer of the membrane of the gram -ve .
● While in Gram +ve , there are only a only single set of rings ,No attachment to cell wall is seen .
● The inner rings are attached to the p.membrane.
● The Hook,penetrates the cell-wall,and connects main Filament and Basal body .
● It allows the axis of the helix to point directly away from the cell.
Main Filament :
● The filament consists entirely of Protein, called “Flagellin”.
● This protein is either free or consists of very
low amounts of amino acid residues.
● These residues are of : – Proline, Histidine, Cysteine, Tryptophan