bacteria

What are the general characteristics of a prokaryotic cell?

- Prokaryotic cells are simple, lack a true nucleus, and have no membrane-bound organelles. Their DNA is found in the nucleoid region.

What are the three common shapes of bacteria? Give examples of each.

Which one moves ?

-Cocci (spherical): Streptococcus (chains), Staphylococcus (clusters)
- Bacilli (rod-shaped): E. coli, Bacillus anthracis
- Spirilli (spiral-shaped): Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme disease)

What layers make up the bacterial envelope?

- Capsule (outer layer), Cell Wall, Cytoplasmic (plasma) membrane.

What organelles are typically found inside?

- Nucleoid (DNA), Ribosomes, Plasmids, Inclusions, Granules, and Endospores (in some).

What is the bacterial capsule made of? What is the cell wall made of?

- Capsule: Polysaccharides that protect against desiccation and immune attack.
- Cell wall: Peptidoglycan (murein), gives rigidity and shape.

What layer will be thick in a Gram-positive cell?

- Peptidoglycan layer (cell wall) is thick in Gram-positive bacteria (stains purple).

Where are the pili found? What are the functions of the pili?

- Found on the bacterial surface.
- Functions: Attachment to host tissues, conjugation (sex pili), virulence (colonization), and hemagglutination.

What are endospores, and what do they do?

- Dormant, resistant structures produced under stress by Bacillus and Clostridium species.
- Allow survival in harsh conditions (heat, desiccation, chemicals).

How does bacterial DNA recombine?

- Through transformation, transduction, and conjugation.

What is DNA transformation?

- Uptake of naked DNA from the environment and incorporation into the bacterial genome.

What occurs with bacterial conjugation?

- Direct DNA transfer via a mating bridge using an F plasmid (fertility factor).

What is bacterial transduction?

- Gene transfer via bacteriophages (viruses that infect bacteria).

What is an F plasmid? What is its role?

- Small circular DNA carrying genes for conjugation. Enables DNA transfer between cells.

What is an HFr cell?

- “High frequency recombination” cell; F factor integrated into the chromosome for frequent recombination events.

What do transposons do?

- Mobile DNA segments that move between genome locations, can carry resistance genes (“jumping genes”).

What do operons do?

- Gene clusters controlled by a single promoter; regulate gene expression (inducible or repressible).

What factors determine the virulence of a bacteria?

- Adherence, persistence, invasion, toxigenicity, and ability to evade the immune system.

What are the stages of bacterial infection?

1. Transmission from external source via entry portal.
2. Evasion of host defenses (skin, stomach acid).
3. Adherence to mucous membranes via pili or glycocalyx.
4. Colonization and growth at adherence site.
5. Disease: Toxin production, invasion, and inflammation.

What factors determine adherence?

- Pili, glycocalyx, capsule formation, and spikes for attachment.

How do exotoxins and endotoxins differ?

- Exotoxins: Secreted by Gram + or - bacteria; specific effects (e.g., tetanus, cholera); not fever-inducing.
- Endotoxins: Part of Gram-negative cell wall (lipopolysaccharides); cause fever, shock (e.g., septic shock).

Mechanisms of antibiotic action:

- Inhibit cell wall synthesis, protein synthesis, nucleic acid synthesis, or metabolic pathways.

Examples of antibiotic-resistant bacteria:

- MRSA (Methicillin-resistant Staph aureus), VRE (Vancomycin-resistant Enterococcus), ESBL-producing E. coli, MDR-TB.

Reasons for antibiotic resistance:

- Overuse/misuse of antibiotics, plasmid transfer, mutation, and horizontal gene transfer.