Study Questions
- List 8 major structural differences between prokaryotes and eukaryotes and/or draw a picture of each cell type that shows these differences (don’t forget to label the structures).
- is it important for us to know that there are differences between prokaryotes and eukaryotes?
- Using the correct pronunciation, shout out “Escherichia coli”. Which part of its name refers to the species? What is the plural of species?
- Can you describe and or draw (with labels) several different phenotypic features of bacteria?
- Describe one technique that could be used to determine the genotype (or partial genotype) of a microorganism.
- Bacteria that are shaped like baseballs are referred to as __________ (or if there is only one, it is called a ________). Bacteria that are shaped like hot dogs are referred to as _____ or __________.
- A clinical specimen is sent to the clinical microbiology lab to be tested for the presence of Chlamydia. A few days later the lab report states that the specimen was positive for chlamydial antigens. What did the lab use to detect the Chlamydia-specific antigens?
- Draw a diagram outlining the steps of the Gram staining procedure and how Gram-positive and Gram-negative cells appear microscopically at each step. Use colored pencils, crayons, or highlighters!
- Draw a picture of Gram-negative and a Gram-positive cells and label all of the major structural features of each (include everything in the cytoplasm and cell wall). Put a green + next to the structures they both have and a red X next to structures that they do not have in common.
- Peptidoglycan is present on the outside of Gram-____________ bacteria.
- The outermost layer of Gram-negative bacterial cell walls is called the _______________.
- Gram-negative cells do / do not (circle one) have peptidoglycan present in their cell walls.
- Lipopolysaccaride (LPS) is unique to Gram-__________bacteria and is called an _______. The unit of LPS that is responsible for its toxic effects is ____________. Why is LPS toxic even after autoclaving?
- Where is the periplasmic space in Gram-negative bacteria?
- Draw a simple diagram of the structure of peptidoglycan, including the alternating NAG and NAM molecules and the peptide cross links.
- What is the function of peptidoglycan?
- Add to your diagram in #15, the site(s) at which lysozyme acts to compromise cell wall structure.
- Teichoic acid is found in the cell wall of Gram-______________bacteria.
- What are some of the functions of the outer membrane of Gram-negative bacteria and how does it affect the general “vulnerability” of Gram-negative bacteria to antibiotics and harsh environmental conditions?
- Describe the location and general structure of the cytoplasmic membranes of Gram-positive and Gram-negative cells. How is it similar and how is it different from the cytoplasmic membrane of eukaryotic cells?
- Bacterial capsules are composed of ___________________.
- The 4 most important things I need to remember about bacterial capsules are:
- Compare and contrast flagella and pili with respect to structure, functions, and roles in pathogenesis.
- Describe the structure of spores, including the unique calcium chelator found in their outer coat. Under what conditions do spores form and germinate?
- The only two medically-important genera that produce spores are __________________ and _____________________. They are both Gram-____________ Â Â ____________.
- Are the same procedures that inactivate bacteria effective in inactivating spores? If not, what procedures must be used to inactivate spores?
Frequently Asked Questions
What are the major structural differences between prokaryotic and eukaryotic cells?
Prokaryotic cells are simpler and smaller than eukaryotic cells. They lack a nucleus and membrane-bound organelles, and typically have a single circular chromosome. Eukaryotic cells have a defined nucleus, multiple linear chromosomes, and complex organelles like mitochondria and the endoplasmic reticulum. These differences affect cellular processes and are crucial for understanding cell biology.
How do you pronounce Escherichia coli and what part of the name refers to the species?
Escherichia coli is pronounced as 'ESH-uh-RIK-ee-uh KOH-lai'. In binomial nomenclature, the first part of the name 'Escherichia' refers to the genus, while 'coli' specifies the species. Understanding this helps in classifying and identifying bacteria in microbiology.
What is the function of peptidoglycan in bacterial cells?
Peptidoglycan provides structural support to bacterial cell walls, maintaining their shape and protecting against osmotic pressure. It consists of sugar molecules and peptides that form a mesh-like layer, crucial for bacterial integrity. This structure is targeted by antibiotics like penicillin to disrupt cell wall synthesis.
Why is lipopolysaccharide (LPS) considered toxic, and how is it unique to Gram-negative bacteria?
LPS is a component of the outer membrane of Gram-negative bacteria and acts as an endotoxin. It triggers strong immune responses and can cause symptoms like fever and shock. The toxic effects are due to its lipid A component. LPS remains active even after autoclaving, presenting challenges in sterilization.
What are bacterial capsules made of, and why are they important?
Bacterial capsules are usually composed of polysaccharides (sugars), forming a protective layer around the cell. They help bacteria evade the host immune system, adhere to surfaces, and resist desiccation. Capsules increase bacterial virulence, making infections harder to treat.
What is the difference between bacterial flagella and pili?
Flagella are long, whip-like structures used for bacterial motility, allowing bacteria to swim through liquid environments. Pili are shorter, hair-like structures used for attachment to surfaces and for DNA transfer between bacteria (conjugation). Both structures play roles in bacterial pathogenesis and colonization.
How does Gram staining differentiate between Gram-positive and Gram-negative bacteria?
Gram staining is a technique that classifies bacteria based on their cell wall structure. Gram-positive bacteria retain the crystal violet stain, appearing purple under a microscope, due to their thick peptidoglycan layer. Gram-negative bacteria do not retain the stain and appear pink after counterstaining, due to their thinner peptidoglycan and outer LPS layer.
What conditions lead to spore formation in bacteria, and which bacteria are known for this?
Spores form in response to harsh conditions such as nutrient depletion, allowing bacteria to survive until favorable conditions return. Bacillus and Clostridium are two medically important genera that produce spores. These spores are highly resistant, requiring special methods like autoclaving to inactivate.