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Questions and Answers
What factor does NOT affect the length of the lag phase in bacterial growth?
What factor does NOT affect the length of the lag phase in bacterial growth?
- Synthesis of new enzymes
- Time to recover from shock
- Size of the inoculum
- Temperature of the medium (correct)
How is the generation time (G) of a bacterial culture defined?
How is the generation time (G) of a bacterial culture defined?
- Total time of the culture's life cycle
- Time required to exhaust nutrients
- Time taken for binary fission
- Time (t) per generation divided by the number of generations (n) (correct)
During which phase of growth do cells divide regularly through binary fission?
During which phase of growth do cells divide regularly through binary fission?
- Stationary phase
- Lag phase
- Decline phase
- Exponential (log) phase (correct)
Which factor is NOT a limitation for continued exponential growth in a batch culture?
Which factor is NOT a limitation for continued exponential growth in a batch culture?
What happens during the stationary phase of bacterial growth?
What happens during the stationary phase of bacterial growth?
Which statement accurately describes the exponential (log) phase?
Which statement accurately describes the exponential (log) phase?
What occurs if viable cells are counted during the stationary phase?
What occurs if viable cells are counted during the stationary phase?
Which of the following statements about the lag phase is true?
Which of the following statements about the lag phase is true?
What is the primary shape of cocci bacteria?
What is the primary shape of cocci bacteria?
Which of the following statements about the motility of bacterial cells is true?
Which of the following statements about the motility of bacterial cells is true?
What method is used for the preliminary identification of bacterial groups?
What method is used for the preliminary identification of bacterial groups?
What is Bergey's Manual of Determinative Bacteriology primarily used for?
What is Bergey's Manual of Determinative Bacteriology primarily used for?
Which arrangement is characteristic of streptococci?
Which arrangement is characteristic of streptococci?
Which type of bacteria is generally stained purple in a Gram stain?
Which type of bacteria is generally stained purple in a Gram stain?
Which type of bacteria is primarily motile?
Which type of bacteria is primarily motile?
Which characteristic is NOT used to differentiate bacterial shapes?
Which characteristic is NOT used to differentiate bacterial shapes?
What is the primary composition of the Gram-positive bacterial cell wall?
What is the primary composition of the Gram-positive bacterial cell wall?
What distinguishes a true capsule from a slime layer in procaryotes?
What distinguishes a true capsule from a slime layer in procaryotes?
What is the role of the cell wall in procaryotes?
What is the role of the cell wall in procaryotes?
Which component is found in the Gram-negative cell wall structure?
Which component is found in the Gram-negative cell wall structure?
What is located in the space between the inner and outer membranes in Gram-negative bacteria?
What is located in the space between the inner and outer membranes in Gram-negative bacteria?
Which of the following statements about bacterial capsules is true?
Which of the following statements about bacterial capsules is true?
What is the term for the less discrete structure that can embed a group of bacterial cells?
What is the term for the less discrete structure that can embed a group of bacterial cells?
What microscopy technique is suggested for viewing bacterial capsules like the hyaluronic acid capsule?
What microscopy technique is suggested for viewing bacterial capsules like the hyaluronic acid capsule?
What forms the interpeptide bridge in peptidoglycan structure?
What forms the interpeptide bridge in peptidoglycan structure?
Which component primarily forms the outer face of the outer membrane in Gram-negative bacteria?
Which component primarily forms the outer face of the outer membrane in Gram-negative bacteria?
What type of molecule is Lipid A considered in the structure of LPS?
What type of molecule is Lipid A considered in the structure of LPS?
How does the structure of the inner face of the outer membrane compare to that of the plasma membrane?
How does the structure of the inner face of the outer membrane compare to that of the plasma membrane?
What is the role of magnesium cations in the outer membrane structure?
What is the role of magnesium cations in the outer membrane structure?
What varies significantly among different species of Gram-positive bacteria?
What varies significantly among different species of Gram-positive bacteria?
In the context of LPS, what does the polysaccharide region consist of?
In the context of LPS, what does the polysaccharide region consist of?
What does the term 'amphiphilic' describe in the context of LPS?
What does the term 'amphiphilic' describe in the context of LPS?
What is the primary role of vacuoles in the hyphal cells?
What is the primary role of vacuoles in the hyphal cells?
Which of the following best describes the apical vesicular cluster (AVC)?
Which of the following best describes the apical vesicular cluster (AVC)?
What material is NOT typically found in the fungal cell wall?
What material is NOT typically found in the fungal cell wall?
How does hyphal growth correlate with vesicle positioning?
How does hyphal growth correlate with vesicle positioning?
What is one key function of the fungal cell wall?
What is one key function of the fungal cell wall?
What type of structures are ectoparasites and endoparasites classified as?
What type of structures are ectoparasites and endoparasites classified as?
Which chemical composition is a part of the fungal cell wall?
Which chemical composition is a part of the fungal cell wall?
What function do pigments like melanin serve in the fungal cell wall?
What function do pigments like melanin serve in the fungal cell wall?
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Study Notes
Bacterial Cell Forms and Characteristics
- Bacteria typically exhibit three shapes: rod (bacillus), sphere (coccus), and spiral (spirilla/spirochetes).
- Curved rods are referred to as vibrios.
- Bacteria can be classified as Gram-positive (purple) or Gram-negative (pink) based on staining.
- Bacilli may exist singularly or in chains; cocci can form chains (streptococci) or clusters (staphylococci).
- Spiral-shaped bacteria are usually motile, while cocci are generally non-motile.
Microscopic Identification and Classification
- Observations under a microscope, combined with environmental knowledge, help identify bacterial groups.
- Bergey's Manual of Determinative Bacteriology serves as a key for identifying bacteria based on morphology and physiological traits.
- Further classification requires biochemical tests that distinguish families and species.
Bacterial Cell Walls
- Almost all prokaryotes possess a cell wall to protect the protoplast.
- The cell wall structure varies between Gram-positive (thicker, composed mainly of peptidoglycan) and Gram-negative bacteria (thin and multilayered, with a periplasmic space).
- Gram-negative bacteria have an outer membrane made of lipopolysaccharides (LPS), consisting of a hydrophobic Lipid A component and a hydrophilic polysaccharide tail.
Capsules and Glycocalyx
- Many prokaryotes have polysaccharide capsules outside their cell wall, serving protective and functional roles.
- A true capsule is distinct, while a slime layer is a less organized matrix that supports cell aggregation.
- The glycocalyx capsule consists of tangled polysaccharide fibers.
Bacterial Growth Phases
- Lag Phase: Bacteria adjust and recover before division; factors like inoculum size and nutrient availability influence duration.
- Exponential Phase: Balanced growth with constant division rate; generation time (G) can be calculated using the formula G=t/n, where t is time and n is the number of generations.
- Stationary Phase: Growth ceases due to nutrient depletion, toxin accumulation, or space limitations; both cell dying and division may occur concurrently.
Fungal Structure and Growth
- Fungal cells are characterized by a protective wall that maintains shape and interfaces with the environment.
- The fungal wall contains chitin, glucans, proteins, and sometimes cellulose; it has various roles including nutrient storage and UV protection.
- Hyphal growth is linked to apical vesicular clusters (AVC), with vesicles aiding cell elongation and regeneration.
Fungal Wall Composition and Functions
- Contains polymeric fibrils (chitin, glucans) and amorphous matrix components.
- Old hyphal parts may accumulate pigments for protection against UV radiation and serve as nutrient reserves.
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