Bacterial Structures and Functions Quiz

Pili

• Pili are important for pathogens
• Pili facilitate biofilm formation, which is a slimy layer found in dental plaque
• Sex pili are longer than adhesion pili
• Sex pili participate in the transfer of genetic material from one cell to another
• Cells with sex pili are male or F+ cells
• The transfer of DNA is called conjugation

Capsule and Related Structures

• Capsules and slime layers are the outer layers of a bacteria cell
• Capsules and slime layers are typically composed of sugar polymers
• Capsules have a distinct outer edge whereas slime layers are less defined
• Capsule production commonly occurs in vivo
• Capsules protect bacteria from drying
• Capsules act as a secondary source of nutrition
• Capsules increase adhesion of bacteria to surfaces, such as S. mutans
• Capsules can protect bacteria from phagocytosis
• Some capsules are toxic or suppress the host’s defense system, which can contribute to disease

Bacterial Spores

• Spores are more resistant to disinfectants, drying, and heating compared to vegetative cells
• Moist heat at 121 °C for 10-20 minutes is required to kill spores
• Thermal resistance of spores is attributed to high contents of Ca2+ and dipicolinic acid
• Spores are resistant due to their impermeable cortex and outer coat and low water content
• Spores have low metabolic and enzymatic activity

Axial Filaments

• Axial filaments are composed of two fiber groups
• Axial filaments are found in spirochetes
• Spirochetes move by rotating around their longitudinal axis and bending along their length

Bacterial Growth and Physiology

• Bacteria grow by increasing in size and number

Definitions

• Bacterial growth is indicated by colonies on solid media and turbidity in a fluid media
• Generation time, or doubling time, is the time between every cell division
• The generation time of V. cholerae can be as short as 13 minutes
• The generation time of M. tuberculosis can be as long as 24 hours

Growth Requirements

• Nutrients such as carbon, nitrogen, and minerals are required for bacterial growth
• Oxygen is required for aerobic bacterial growth
• Carbon dioxide is required for bacterial growth
• An appropriate hydrogen ion concentration (pH) is required for bacterial growth
• A suitable temperature is required for bacterial growth

Bacterial Cytoplasm

• Cytoplasm is everything inside the bacterial cytoplasmic membrane
• Cytoplasm has a gel-like consistency
• The cytoplasm contains proteins, ribosomes, storage granules, plasmids, a circular genome (chromosome), nutrients, waste materials, and chemical intermediates

Flagella

• Flagella are long, rigid protein rods that allow for movement of bacteria
• Flagella are composed of flagellin protein
• Flagella are highly antigenic
• The number and arrangement of flagella is genetically determined
  • Monotrichous: one flagellum
  • Lophotrichous: multiple flagella at one end
  • Peritrichous: flagella surround the cell

Test your knowledge on pili, capsules, and bacterial spores. This quiz explores the structural features of bacteria and their significance in pathogenicity and biofilm formation. Learn how these components contribute to bacterial survival and interaction with hosts.