Flagella and bacterial structure

Question 1

What is bacterial flagella?

Answer 1

• They are structures of loco- motion which are long filamentous appendages that propel bacteria.
• They are too small to be seen with a light microscope without staining
• Bacteria that lacks flagella are referred to as atrichous (without projection)

Question 2

What is flagella staining ?

Answer 2

It is a tedious and delicate staining procedure using mordant and stain carbol fuchsin to build up the diameters of flagella until they become visible under light microscope

Question 3

What are the different types of flagella ?

Answer 3

• Flagella may be peritrichous ( distributed over the entire cell )
  or Polar ( at one end or both the ends of the cell )
  If polar, flagella may be
• monotrichous = a single flagellum at one pole
• Lophotrichous = a tuft of flagella coming from one pole
• Amphitrichous = flagella at both poles of the cell.

Question 4

Explain the structure of flagella

Answer 4

Flagellum has three basic parts:
- the filament = long, outermost region
- Filament is attached to a slightly wider hook = that anchors the filament and basal body
- Basal body = anchors the flagellum of the cell wall and plasma membrane
Basal body is composed of a small central rod inserted into a series of rings.

• Gram -ve bacteria = has two pairs of rings
  i) outer pair of rings ( various portions of cell wall)
  ii) inner pair of rings (Plasma membrane)
• Gram +ve bacteria = only inner pair is present

Question 5

Explain the run and tumble phenomena

Answer 5

• in anti-clockwise direction : bacteria run in a single direction
• in clockwise direction : bacteria tumbles and changes its direction