Functional Anatomy of Prokaryotic Cells Flashcards
What are the basic shapes of bacteria?
- Coccus (spherical)
- Bacillus (rod shaped)
- Spiral
What are the 5 arrangements of cocci after division?
- Diplococci
- Streptococci
- Tetrad
- Sarcinae
- Staphylococci
What are the 4 arrangements of bacilli after division?
- Single bacillus
- Diplobacilli
- Streptobacilli
- Coccobacillus
What are the 3 shapes of spiral bacteria?
- Vibrio
- Spirillum
- Spirochete
How do spirilla more and how about spirochetes?
- Spirilla move via flagella
2. Spirochetes move via axial filaments
Give an example of a common pleomorphic bacterium
Corynebacterium
What is glycocalyx? What is it composed of?
- The bacterial glycocalyx is a viscous, gelatinous polymer
2. Composed of polysaccharide, polypeptide or both.
What are the two forms of glycocalyx on the outside of bacterial cells?
- If glycocalyx is firmly attached to the cell wall, it is a Capsule
- If glycocalyx is loosely attached to the cell wall, it is a slime layer
Why are bacterial capsules virulent sometimes?
Or: Importance of glycocalyx/capsule (4 key points)
- Capsules often protect pathogenic bacteria from phagocytosis, thus, can adhere to host cell surface and colonize easily
- Glycocalyx (capsule) can be a source of nutrition (sugar) when energy stores are low
- Glycocalyx can protect a cell against dehydration
- Viscosity of glycocalyx may inhibit the movement of nutrients out of the cell
Give some examples of common encapsulated bacteria
- Bacillus anthracis (some are not encapsulated)
- Streptococcus pneumoniae
- Streptococcus mutans (cause dental caries)
- Klebsiella
Some bacteria have flagella, what are the 4 arrangements?
- Monotrichous (a single polar flagellum)
- Amphitrichous (a tuft of flagella at each end of the cell)
- Lophotrichous (2 or more flagella at one pole of the cell)
- Peritrichous (flagella distributed over the entire cell)
What is Taxis? What are the two common forms?
- Taxis is a stimulus that a bacterium move toward or away from
- Two forms: chemotaxis and phototaxis
- - Chemotaxis: ex. O2, ribose, galatose
- - Phototaxis: light
Why is it important to perform flagella stain?
The Flagellar (H) protein functions as antigens in Gram (-) bacteria
Name two common spirochetes, and diseases they cause
- Treponema pallidum: Syphilis
2. Borrelia burgdorferi: Lyme disease
What other two appendage structures besides flagella do many Gram (-) bacteria have and their functions
- Fimbriae: enable cells to adhere to surfaces, including the surfaces of other cells
- - Example: Neisseria gonorrhoea - Pili: join bacterial cells in preparation for the transfer of DNA from one cell to another
What is the major function of bacterial cell wall?
To prevent bacterial cells from rupturing when placed in hypotonic solutions
– Cell wall can cause disease in some species, so it is the site of action of some antibiotics
What is the composition of bacterial cell wall? What is its importance in Gram stains?
- Peptidoglycan (aka. Murein) – a repeating disaccharide attached by polypeptides
- Recall Gram Stain materials
How does Penicillin interfere w/ peptidoglycan?
Interferes w/ the final linking of the peptidoglycan rows
In addition of Peptidoglycan, what other compounds are usally found in the Gram (+) cell wall?
- Teichoic Acids
- - consist of alcohol and phosphate - Waxy lipids, such as mycolic acid (important for acid-fast stain)
- - Ex. Mycobacterium
What is the importance of Teichoid Acid?
- Negatively charged due to phosphate groups, so teichoid acid can bind and regulate the movement of positive ions into and out of the cell
- Teichoid acid provides much of the wall’s Antigenic specificity
What special compound is found in the outer mem. of Gram (-) bacteria and it’s composition
- Lipopolysaccharides (LPS)
- LPS:
- - O polysaccharide: functions as antigens
- - Lipid A: an endotoxin that is toxic when in the bloodstream or GI tract
What is the importance of LPS to Gram (-) bacteria?
- LPS is strong negatively charged: lyses cells and promotes phagocytosis
- LPS provides a barrier to certain antibiotics (ex. Penicillin), digestive enzymes (ex. Lysozymes) and certain dyes
How does lysozyme act on cell walls in Gram (+) and Gram (-) bacteria?
- Gram (+): Lysozyme catalyzes hydrolysis of the bonds b/w the sugar backbone of peptidoglycan in Gram (+) bacteria
- Gram (-): the outer mem. usually remains after treating w/ lysozyme.
- - Treat bacteria w/ EDTA, which weakens ionic bonds in the outer mem and thereby damages it, giving Lysozyme access to the peptidoglycan layer.
Gram (-) bacteria are not as susceptible to penicillin, what kind of antibiotics work?
Beta-Lactam antibiotics
