Exercise 12 Terms

Distinguish between brownian movement and true motility.

Brownian movement is a back and forth jiggling motion of the bacterial cells due to collisions with the water molecules, while true motility is movement in a definite direction to a new location

Brownian movement is directed motion

False, It is a back and forth motion due to collision with water molecules

proteus vulgaris is non-motile.

False, It is motile

A hanging drop preparation observes stained cells

False, the cells are unstained

List two functions of flagella

Flagella rotate and move cells towards more favorable environments and away from more harmful environments. The motion of flagella also helps pathogenic bacteria spread in the body.

Explain the observed differences in results for motile and nonmotile bacteria in motility agar medium.

Motile bacteria use their flagella to swarm through the soft agar and produce cloudiness away from the original streak line. Non-motile bacteria lack flagella and only show growth along the stab inoculation.

Positive chemotaxis occurs in the presence of

nutrient

Long protein extensions from the bacterial cell are called

flagella

Micrococcus luteus is motile or non-motile

growth along the stab line. Growth restricted near the surface

Distinguish between monotrichous, amphitrichous, lophotrichous, and peritrichous flagella arrangements in bacteria.

A monotrichous cell has one flagellum at each end of the cell. Bacteria with a single flagellum at each end are amphitrichous. Bacteria with a cluster of flagella at one end or both ends are lophotrichous. Bacteria with flagella found around the cell surface are peritrichous.

Explain the influence of oxygen on the observed results in motility agar medium and indicate which organism is most influenced by oxygen.

Motile bacteria such as Pseudomonas aeruginosa which are aerobes tend to swarm at the agar surface where oxygen is plentiful. They show less cloudiness inside the agar where the oxygen content is lower. Facultative bacteria such as Proteus vulgaris show swarming at the surface and swarming within the agar. Non-motile bacteria only show growth along the stab line at the surface and within the agar.

List three techniques to demonstrate motility and explain the results seen for each.

Three techniques to demonstrate the presence of flagella are the use of a prepared slide of flagella, inoculation of semi-soft motility agar and the hanging drop preparation. The flagella slide shows stained flagella extending from the cell surface. Motile organisms produce cloudiness in the motility agar on either side of the stab line. Hanging drop preparations show the random jiggling motion typical of brownian motion and the directed motion typical of true motility.