Morphology And Physiology Of Bacteria Question And Answers

Morphology And Physiology Of Bacteria Important Notes

1. Bacteria and their arrangement

2. Contents of bacterial cell

• Cell
• Cytoplasmic membrane
• Cytoplasm
• Nucleus
• Capsule
• Flagella
• Fimbriae
• Spore

3. Organism and shape of its spores

Morphology And Physiology Of Bacteria Long Essays

Question 1. Classify bacteria depending on their shape. 
Answer:

Morphology And Physiology Of Bacteria

Depending upon the shape, bacteria are classified into:

Morphology And Physiology Of Bacteria Short Essays

Question 1. Bacterial Spore
Answer:

Bacterial Spore

• Spores are highly resistant resting stages of the bacteria formed in unfavorable environmental conditions.
• Sporulation is not a method of reproduction.

Morphology of Spore

Read And Learn More: Microbiology Question and Answers

Spores consist of the following structures Cell

• Some of the spores contain exosporium
• It is the loose outer covering

Morphology And Physiology Of Bacteria

Bacterial Spore Shape and Position:

• Bacterial Spore Position
  • Spores may be
    • Central
    • Subterminal (or)
    • Terminal
• Bacterial Spore Shape:
  • They may be
    • Spherical
    • Oval
      • Depending on the diameter, they may be
    • Bulging
    • Non-bulging.

Bacterial Spore Properties:

• Resistance
  • Spores are extremely resistant to ordinary boiling, disinfectants, and heating.
• Used for sterilization
  • Spores of some species of bacteria act as indicators for proper sterilization
• Gemination
  • Gemination is the process of spore conversion into vegetative cells under favorable conditions.

Bacterial Spore Demonstration:

Spore Forming Bacteria are:

Question 2. Gram staining/Gram stain?
Answer:

Gram staining/Gram stain

• Gram stain is the most widely used stain in bacteriology.
• Gram staining is the essential procedure used in the identification of bacteria and is frequently the only method required to study their morphology.

Gram staining Method:

• Gram staining involves four basic steps.
  • The primary staining with a pararosaniline dye such as crystal violet, methyl violet (or) gentian violet for one minute
  • Application of gram’s iodine [dilute solution of io¬dine) over the slide for one minute.
  • Decolorization with an organic solvent such as ethanol, acetone (or) aniline for 10-30 seconds
  • Counterstaining with a dye of contrasting color such as carbon fuchsin, safranin, or neutral red for 30 seconds

Differentiation on gram staining: It is called a differential stain because it differentiates between gram-positive and gram-negative bacteria

Gram staining Mechanism:

Morphology And Physiology Of Bacteria

1. The exact mechanism is not understood.

2. It may be attributed to the following:

• Permeability of bacterial cell wall and cytoplasmic membrane:
  • The protoplasm of the Gram-positive cells is more acidic than that of Gram-negative cell
  • Due to this, it retains the basic dyes strongly
  • Now when iodine is added to it, the acidic nature of the protoplasm increases
  • As a result, iodine combines with the dye and forms a dye-iodine complex and fixes the dye in the bacterial cell
  • The Cytoplasmic membrane of Gram-positive cells is less permeable to this complex
  • Thus the dye-iodine complex gets trapped within the cell
  • In contrast, the Gram-negative cell wall has increased permeability
  • This leads to the outflow of the complex during decolorization
• The integrity of the cell wall
  • If the cell wall is damaged, the Gram-positive bacteria becomes Gram-negative

Question 3. Acid fast stain/Ziehl Neelsan stain?
Answer:

Acid fast stain/Ziehl Neelsan stain

• The acid-fast stain was discovered by Ehrlich and subsequently modified by Ziehl and Neelsen.
• Some organism retains carbol fuchsin even when colorized with acid. Such organisms are called acid-fast organisms.
• Example: Mycobacteria

Acid-fast stain Method:

• Pour carbol fuchsin satin on a slide containing a fixed smear
• Gently heat the underside of the slide till it produces steam
• Leave carbol fuchsin over the slide for 5-10 minutes along with intermittent heating
• Don’t allow the slide to dry out for it adds stain to it and reheat
• Wash the slide in tap water
• Decolorize the smear with 20% sulphuric acid and wash it With water
• Repeat the procedure till the pink/ red color stops coming out
• Counter-stain the smear with 2% methylene blue for 1¬2 minute
• Wash it with water and air dry it
• Observe under microscope

Acid-fast stain Microscopic Examination: Acid-fast bacilli appear red in the blue background of pushing cells and epithelial cells

Acid-fast stain Principle:

• Acid fastness depends on
• The high content of lipids, fatty acids, and higher alcohols found in the cell wall of Mycobacterium
• The integrity of the cell wall

Question 4. Name four staining techniques in microbiology.
Answer:

Commonly used staining techniques in microbiology are as follows.

Question 5. Bacterial cell wall
Answer:

Bacterial cell wall

• The cell wall is a tough and rigid structure
• It surrounds the bacteria like a shell

Bacterial cell wall Functions:

• Accounts for the shape of the cell
• It takes part in cell division
• Protects the cell against osmotic damage
• Provide rigidity
• It possesses a target site for antibiotics, lysosomes, and bacteriophages

Morphology And Physiology Of Bacteria

Bacterial cell wall Structure:

• The rigid part of the cell wall is peptidoglycan
• It has the following components

1. Lipoprotein layer It connects the peptidoglycan to the outer membrane

2. Outer membrane

• It contains certain proteins named outer merm brane proteins
• These are target sites for bacteriocins

3. Lipo-polysacharride .

• This layer consists of lipid A to which polysaccha¬ride is attached
• The toxicity is associated with lipid A
• The polysaccharide determines a major surface an¬tigen to 0 antigen
• It contains endotoxin in gram-negative bacteria
• It is composed of 3 regions as follows
  • Region 1 – polysaccharide portion (0 antigen specificity)
  • Region 2 – core polysaccharide
  • Region 3 – Lipid A portion (responsible for tox¬icity)

4. Periplasmic space

• It is the space between the inner and outer membrane
• It contains various binding proteins

5. Peptidoglycan

Morphology And Physiology Of Bacteria Short Question And Answers

Question 1. Name capsulated bacteria
Answer:

Name capsulated bacteria

• Streptococcus pneumonia
• Klebsiella sp.
• Bacillus antacids
• Cryptococcus neoformans. (a fungus)

Question 2. Fimbriae
Answer:

Fimbriae

• Fimbriae is also called pili
• These are hair-like appendages projecting from the cell surface as straight filaments.

Fimbriae Types:

• Common pili
• Sex of F (fertility) pili
• Col 1 (colicin) pili

Fimbriae Functions:

• Adhesion
• Transfer of genetic material

Morphology And Physiology Of Bacteria

Fimbriae Demonstration:

• Fimbriae are demonstrated by
  • Electron microscopy
  • Haemagglutination test

Question 3. Flagella
Answer:

Flagella

Flagella are cytoplasmic appendages protruding through a cell wall.

Flagella Structure:

• They are thread-like structures
• Size:
  • Length – 5-20 micrometers
  • Diameter- 0.01-0.02 micrometer

Flagella Parts:

• It is composed of three parts
  • Filament
    • It lies external to the cell
    • It is connected to the hook at the cell surface ‘250
  • Hook
    • The hook-basal body is embedded in the cell envelope
  • Basal body.
    • It contains outer and inner rings

Flagella Composition:

• The flagella is made up of flagellin, a protein
• Specific flagellar antibodies are produced in high titers

Flagella Functions:

• These are organs of locomotion.
• Flagellar antibodies are used for serodiagnosis

Flagella Types:

Question 4. Differences between Gram-positive and Gram-negative cell walls:
Answer:

Differences between Gram-positive and Gram-negative cell walls

Morphology And Physiology Of Bacteria Viva Voce

1. Gram-positive bacteria appear violet and Gram-negative bacteria appear red on staining
2. In acid-fast staining, a positive reaction gives a red color while a negative reaction gives a blue color
3. All cocci except Neisseria are Gram-positive
4. Flagella is a locomotory organ
5. The nucleus of bacteria consists of plasmids or episomes
6. Bacteria without cell walls are called Mycoplasma