Question

1. What are the possible flagellar arrangements on bacteria?
2. Describe the basic structure of peptidoglycan.
3. What is the difference between gram positive and gram negative cell wall structure? Know the procedure and sequence of performing a gram stain, and what is happening to the bacterial cell after each step.
4. What is the significance of a bacterial cell wall? (why is it so important?)
5. How can hypertonic solutions be used to inhibit bacterial growth?
6. What are the 3 types of motility seen in microbial eukaryotes? Which one is shared by bacteria?
7. How does the flagellar movement differ in eukaryotes and bacteria?
8. What is the evidence supporting the endosymbiotic theory?
9. Know how the planes of division determine the arrangement of bacterial cells.

Answer 1

The possible flagellar arrangements on bacteria are:

1. Atrichous : Flagella absent.

2. Monotrichous: Single flagellum occurs at or near one end of bacterium.

3. Amphitrichous: A flagellum at each of the two ends.

4. Lophotrichous: A group or tuft of flagella only at one end.

5. Cephalotrichous: A tuft of flagella at both the ends.

6. Peritrichous: Number of flagella distributed all over the surface.

Q2.

Peptidogylcan forms the structural network of the bacterial cell wall.

Its also called as murein or mucopolypeptide.

It consists of long glycan strands formed of repeating units of N-Acetyl glucosamine (NAG) and N-acetyl muranic acid (NAM) cross-linked by small peptide chains.

Q3. Gram positive cell wall consists of a single layer. Outer membrane is absent while Gram negative cell wall is double layered.

The lipid content of gram positive cell wall is quite low compared to the lipid content of gram negative cell wall.

Bacteria with gram positive cell wall are more susceptible to antibiotics compared to gram negative ones etc.

Q4.

Gram staining procdure:

The bacterial smear is first heat fixed.

This is followed by the application of primary stain of crystal voilet to heat fixed smear.

Iodide is added ,it binds cystal voilet within the cell.

After sometime addition of acetone or alcohol is done which decolorises the smear. Counterstaining with Safranin is followed.

Those bacteria that stain purple are called gram positive amd those that stain pink or red are called gram negative bacteria.

As per the terms and conditons of HomeworkLib we are advised to answer only first four questions if you post a questionnaire.

But let me explain one more question to you for you.?

Bacterial cell wall is important because its helps us to distinguish between gram positive and gram negative bacteria with ease.

Having known the difference between them we can come up with different antibiotics against the gram positive ones because as early mentioned they are susceptible to antibiotics.

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