Bacterial Motility Activity PDF

Determination of Bacterial motility Module 6 Topic learning outcomes TLO14. Demonstrate wet mount and hanging-drop technique in characterizing movements of microorganisms. TLO15. Distinguish Brownian motion from true motility (self-propulsion). TLO16....

Determination of Bacterial motility Module 6 Topic learning outcomes TLO14. Demonstrate wet mount and hanging-drop technique in characterizing movements of microorganisms. TLO15. Distinguish Brownian motion from true motility (self-propulsion). TLO16. Perform culture method to determine motility of test microorganisms. Topic Outline Introduction Bacterial Motility True Motility Brownian Movement Tests to determine bacterial motility Wet Mount and Hanging Drop Technique Culture – based methods Bacterial Motility q The ability of an organism to move by itself is called motility. q Motility is closely linked with chemotaxis, the ability to orientate along certain chemical gradients. q Eukaryotic cells can move by means of different locomotor organelles such as cilia, flagella, or pseudopods. q Prokaryotes move by means of propeller-like flagella unique to bacteria or by special fibrils that produce a gliding form of motility. q Almost all spiral bacteria and about half of the bacilli are motile, whereas essentially none of the cocci are motile.  Arrangement of Flagella Monotrichous (Vibrio cholerae) Amphitrichous (Spirillium volutans) 5  Arrangement of Flagella Lophotrichous (Pseudomonas fluorescens) Peritrichous (Escherichia coli) 6  Components of Flagella and Types of Movement Flagella consist of: Filament – Composed of a protein called flagellin Hook – Base of filament near cell wall Basal Body – Anchors filament & hook to cell wall Types of movement : Run: straight line movement occurs when the flagella rotates counterclockwise Tumbles: turning the direction by clockwise movement of the flagella 7 Components of Flagella and Types of Movement 8  Types of Bacterial Motility Brownian Movement – results from the random motion of the water molecules bombarding the microbial cells and causing them to move e.g. Saccharomyces cerevisiae (yeast), Staphylococcus aureus (bacteria) True Motility – independent movement brought by different mechanisms for self-propulsion e.g. Bacillus megaterium, Escherichia coli 9 Tests to determine bacterial motility For non-pathogenic bacteria: Wet Mount Hanging Drop For pathogenic bacteria: Soft-agar stabbing (culture-based method)  Wet Mount Uses glass slides and cover slips Advantage/s: easier to prepare Disadvantage/s: tend to dry out quickly under the heat of the microscope light, thus, it is useful for short-term observation only  Hanging Drop Uses depression slides and cover slips Advantage/s: allows for longer-term observation and more reliable observation of motility Disadvantage/s: more complex to prepare Disadvantage of both wet mount and hanging drop: specimen is unstained, no contrast between specimen and background Solution: use stains that will not kill the cells or distort the cells and their structures, use phase contrast microscope Hanging Drop Hanging Drop Hanging Drop Hanging Drop Hanging Drop Hanging Drop  Soft-agar stabbing (culture-based method) Uses wire needle, alcohol lamp, and motility medium* in test tubes *Different modifications of the motility media are available and may be used depending on the purpose. Soft-agar stabbing (culture-based method) Results: Positive: Diffuse, hazy growths that spread throughout the medium rendering it slightly opaque. Negative: Growth that is confined to the stab-line, with sharply defined margins and leaving the surrounding medium clearly transparent. Positive Negative Soft-agar stabbing (culture-based method) Principle of the test (Source: Difco Manual) Motility Test Medium Bacterial motility can be observed directly from examination of the tubes following incubation. Growth spreads out from the line of inoculation if the organism is motile. Highly motile organisms provide growth throughout the tube. Growth of nonmotile organisms only occurs along the stab line. TTC (triphenyltetrazolium chloride) may be added to facilitate the detection of motility. TTC is a redox indicator that is colorless in the oxidized form but becomes an insoluble red precipitate when reduced. Determination of Bacterial motility Module 6 THANK YOU!