Transcript Bacterial Form and Function

Motility of bacterial
cell
Motility
•
Types of bacterial motility
–
–
–
•
run or swim - when a bacterium moves in one direction
for a length of time
tumbles - periodic, abrupt random changes in direction
swarming - rapid wavelike growth across a solid culture
medium
Mechanism of flagellar movement - relative
rotation of the rings in the basal body of the
flagellum
Antigenicity
–
flagellar or H antigen - useful in the serological
identification of serotypes of Salmonella organisms
Evidence of motility
Two ways by which motility can be demonstrated:
• direct or microscopic
– hanging drop preparation or wet mount preparation by dark field
mycroscope
– Distinguishes:
• Brownian movement - when the bacteria show molecular movement
• true motility - if a bacterium describes a rotatory, undulatory or
sinuous movement
• indirect or macroscopic
– Stab inoculation of the semisolid media
• nonmotile - growth is limited at the point of inoculation
• motile - growth is diffuse or moves away from the line of inoculation;
turbidity of the medium
Detection of Motility
• Direct
• Indirect
Presence motile bacteria
Hanging drop method
• Place a very small drop of bacterial culture in the
center of cover slip
• Place a small drop of vaseline at each cornre of the
depression side of the cavity slide
• Invert the slide (cavity side) over the cover slip
• The cover slip adhere to the glass slide and when
the cover slip is inverted the hanging drop is
suspended in the well
• Bring the edge of the hanging drop into the focus
with 10x objective before turning to the high power
• Objective to observe motility.