Surface appendages: Bacterial Flagella and pili.pptx

Bacterial flagella and pili - Structure, arrangements, types and functions

1. Bacterial Flagella and pili Rithika . R Bp231510

2. Bacterial Flagella Thread-like or whip-like appendages intricately embedded in the Cell envelope.
Originated from the Cytoplasmic membrane. Helical and non-straight in nature.
Measures 20 – 30 μm in diameter and 15 µm in length.

3. Many times longer than Pili and Fimbriae. Made up of protein called Flagellin . Formation of Flagella is controlled by the gene present in the Nucleoid region .
Confers motility to the bacteria.

4. Structure of Bacterial Flagella A) FILAMENT Long thin appendage that extends from the cell surface. Composed of the protein Flagellin and is hollow. Flagellin proteins are transcribed in the cell cytoplasm and then transported across the cell membrane and cell wall.
Bacterial flagellar filament grows from its tip, adding more and more Flagellin units to extend the length until the correct size is reached. Flagellin units are guided into place by a Protein cap .

5. Structure of Bacterial Flagella B) Hook Curved coupler that attaches the filament to the Flagellar motor.
Length of Hook is longer in Gram positive bacteria than Gram negative bacteria.

6. Structure of Bacterial Flagella c) motor Spans both the Cell membrane and the Cell wall, with additional components for the Gram negative outer membrane.
Motor has two components: ( i ) Basal body , which provides the rotation (ii) Stator , which provides the torque necessary for rotation to occur. Basal body consists of a central shaft surrounded by Protein rings, two in the Gram positive bacteria and four in the Gram negative bacteria. Stator consists of “Mot” proteins that surround the rings embedded within the Cell membrane.

7. Arrangements of Flagella In Bacteria Atrichous Monotrichous Lopotrichous Amphitrichous Amphilopotrichous Peritrichous

8. i ) Atrichous Flagella is absent . Example : All non-motile bacteria

9. ii) Monotrichous Single Flagellum is present in one pole. Example: Pseudomonas aeruginosa and Vibrio cholerae

10. iii) Lopotrichous Tuft of Flagella at One pole. Example Pseudomonas fluorescence
Bartonella bacilliformis

11. iv) Amphitrichous Flagella at Both poles. Example : Aquaspirillum serpens

12. v ) Amphilopotrichous Tuft of Flagella at Both poles.

13. vi) Peritrichous Flagella all over the bacterial cell. Example – Escherichia coli, Proteus mirabilis and Salmonella typhi

14. Types of Bacterial Motility 1) Tumbling Motility – Listeria sp. 2) Gliding Motility – Mycoplasma sp. 3) Stately Motility – Clostridium sp .
4) Dartling Motility – Vibrio Cholerae and Campylobacter jejuni 5) Swarming Motility – C lostridium tetani and P roteus 6) Corkscrew Motility – Spirochetes

15. FUNCTIONS OF FLAGELLA of bacteria . Primarily responsible for motility Bacterial survival.
Bacterial Pathogenesis.
Signal Transduction .
Sensation.
Highly antigenic, possess H – antigens and helps in Serodiagnosis of Typhoid fever

16. Pili Hair like tubular microfibers like structure.
Present only on Gram negative bacteria.
Made up of protein called Pilin .
Longer than Fimbriae and shorter than Flagella.
Approximate length of Pili is 0.5 µm -2.0 μm . Number of Pili per cell is usually 1 to 10 per cell and randomly arranged on the surface of the bacteria. Pili are more rigid than Fimbriae.
Formation of Pili is controlled by the gene present in the Plasmids .

17. Types of pili Four types based on Hemagglutinating ability and Mannose sensitivity Type I – Mannose Sensitive ( Escherichia coli, Salmonella
sp., Shigella sp. And Klebsiella sp. ) Type II – Devoid of any Hemagglutinating or Adhesive properties ( Salmonella gallinarum & Salmonella pullorum ) Type III – Agglutinate RBC only after heating and mannose resistant ( Klebsiella sp. And Serratia sp.). Type IV – Mannose Resistant (Proteus sp. )

18. Functions of Pili Gene transfer mechanism ( Conjugation – the process of gene transfer through sex pili) Attachment (Act as Bacterial virulence factor because of its Antigenic nature ) Majority of the Pili can act as a Receptor for Viruses.