Morphology And Physiology Of Bacteria Question And Answers

Morphology And Physiology Of Bacteria Important Notes

1. Bacteria and their arrangement

Morphology And Physiology Of Bacteria- 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 Organism And Shape Of Its Spores

Morphology And Physiology Of Bacteria Long Essays

Question 1. Classify bacteria depending on their shape. 

Depending upon the shape, bacteria are classified into:

Morphology And Physiology Of Bacteria Bacteria Classified

Morphology And Physiology Of Bacteria Shapes and different arrangements of bacteria

Morphology And Physiology Of Bacteria Short Essays

Question 1. Bacterial Spore

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

Morphology And Physiology Of Bacteria Structure of bacterial spore

Read And Learn More: Microbiology Question and Answers

Spores consist of the following structures Cell

Morphology And Physiology Of Bacteria Spores Consists

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

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.

Morphology And Physiology Of Bacteria Types of bacterial spores

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:

Morphology And Physiology Of Bacteria Demonstration

Spore Forming Bacteria are:

Morphology And Physiology Of Bacteria Spore Forming Bacteria

Question 2. Gram staining/Gram stain?

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

Morphology And Physiology Of Bacteria Differentiation on gram staining

Gram staining Mechanism:

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?

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.

Commonly used staining techniques in microbiology are as follows.

Morphology And Physiology Of Bacteria Four staining techniques in microbiology

Question 5. Bacterial cell wall

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

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 Clinical Microbiology

Morphology And Physiology Of Bacteria Short Question And Answers

Question 1. Name capsulated bacteria

Name capsulated bacteria

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

Question 2. 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

Fimbriae Demonstration:

  • Fimbriae are demonstrated by
    • Electron microscopy
    • Haemagglutination test

Question 3. 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:

Morphology And Physiology Of Bacteria Flagella Types

Morphology And Physiology Of Bacteria Arrangement of flagella

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

Differences between Gram-positive and Gram-negative cell walls

Morphology And Physiology Of Bacteria Differences between Gram positive and Gram negative cell wall

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

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