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Kingdom Monera: Eubacteria, Habitat, Shape, Structure, Motility, Practice Problems and FAQs

Did you know that one of the most primitive forms of life to inhabit planet earth are the bacteria? We are aware that bacteria are omnipresent and are found pretty much everywhere around us but did you ever stop to think how different a bacteria is from us? Well, you will be surprised to know that the cell structure of bacteria is extremely unique. Being one of the earliest organisms to have evolved on earth, they have a simple cellular organisation with no defined nucleus or membrane-bound organelles. Even then the bacteria is capable of performing all the necessary functions of life. Amazing right? Come, let’s learn more about this fascinating organism.

Table of Contents

Habitat

Eubacteria are found everywhere such as the ocean, hot springs, dry desert, soil. 

habitat of eubacteria

Shape

Bacteria exist in a variety of different shapes such as:

Coccus/Cocci

Bacillus/Bacilli

Spirillum/ Spirilla

Vibrio 

Spherical shaped

 

Examples - Diplococcus (in pairs), Streptococcus (arranged in a chain), Staphylococcus (arranged in clusters)

 

1

Rod shaped

 

Examples - E.coli, Bacillus anthracis




 

1

Spiral shaped

 

Examples- Spirillum voluntas, Treponema

 

1

Comma shaped

 

Examples - Vibrio cholerae

 

1

Structure of Eubacteria

Bacteria cells have a chemically complex cell envelope. The cell envelope consists of a tightly bound three layered structure.

  1. Outermost glycocalyx (Thick and tough - capsule or loose sheath - slime layer)
  2. Cell wall
  3. Cell membrane

Each layer of the envelope performs a distinct function and they together act as a single protective unit.

structure of eubacteria

On the basis of thickness of cell wall, there are two categories of bacteria:

Gram positive bacteria

Gram negative bacteria

Cell wall is single layered and contains lipids but in less quantity.

Cell wall has two layers - 

  • inner layer composed of peptidoglycan 
  • thick outer layer composed of lipopolysaccharides. 

Cells appear blue/purple under the microscope after the Gram staining process.

Cells appear red under the microscope after the Gram staining process.

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1

Gram Staining Process

Gram staining process helps to distinguish between bacteria based on their cell wall structure. The process involves staining the mounted bacterial culture with a purple/blue primary stain such as crystal violet or methylene blue. After letting the stain sit for a minute, it is washed with alcohol and then stained again with a red secondary stain such as safranin. The mounted culture is then viewed under a microscope.

Gram positive bacteria have very less lipids in their cell wall, hence the cell wall structure is not disturbed by the alcohol wash. Thus they retain the primary stain and appear blue under the microscope.

Gram negative bacteria have a thick outer layer composed of lipopolysaccharides which is washed off during the alcohol wash. Thus, they are unable to retain the primary stain and get stained with the secondary stain and appear red.

Motility in Bacteria

Bacteria are motile as well as non-motile. Movement in bacteria takes place with the help of flagella.

On the basis of flagella, bacteria are of following types:

  • Atrichous - Flagella absent.
  • Monotrichous - Only one flagellum is present on one end of the bacterium.
  • Amphitrichous - Single flagellum is present on both the ends of bacterium
  • Lophotrichous - A bunch of flagella is present on one end of bacterium.
  • Peritrichous - Flagella are found on the whole body of bacteria.
  • Amphilophotrichous - A bunch of flagella is present on both ends of bacterium.

classification of bacteria based on flagella

Pili

Bacteria cell walls are covered with hair-like structures called pili. They are smaller than flagella and help in sexual reproduction in bacteria, such as conjugation.
 

Practice Problems of Kingdom Monera

Question 1. Bacteria have two X and Y structures found on their cell surface. X helps in movement while Y is smaller than X and helps in sexual reproduction. Can you name X and Y.

a. X - Flagella, Y - Pili
b. X - Pili, Y - Pseudopodia
c. X - Tentacle, Y - Flagella
d. X - Pili, Y - Flagella

Solution:  Bacteria have flagella and pili on their cell surface. Flagella helps in movement while Pili is a hair-like structure smaller than flagella that helps in sexual reproduction. Thus, X is flagella and Y is Pili. 
Hence, the correct option is a.

Question 2. Identify the bacteria based on the number and position of its flagella.

1

a. Peritrichous
b. Amphilophotrichous
c. Amphitrichous
d. Lophotrichous

Solution: In amphilophotrichous bacteria, a bunch of flagella is present on both ends of bacterium. Thus, the correct option is b.

Question 3. A teacher gave students two bacterial cultures ‘A’ and ‘B’ and asked them to perform gram staining on it. At the end, bacteria from culture A were purple coloured when observed under microscope while bacteria from culture showed red colour. Which of the following statements hold true for this observation?

a. Cells in culture A took up the secondary stain as they were Gram negative.
b. Cells in culture A took up the primary stain as they were Gram positive.
c. Cells in culture B up the secondary stain as they were Gram positive.
d. Cells in culture B up the primary stain as they were Gram positive.

Solution: Gram positive bacteria have a thick peptidoglycan layer with very less lipid concentration. Thus, they retain the violet colour of crystal violet and appear violet or purple after performing gram staining. Hence, cells in culture A are gram positive bacteria which have taken up the primary stain. 
Gram negative bacteria have a thin peptidoglycan layer and thick lipid layer. Thus, they do not retain crystal violet colour during the alcohol wash and take the secondary stain. Therefore, they appear red. Hence, bacterial culture B has gram negative bacteria.
Thus, the correct option is b.

Question 4. Find the incorrect match.

Column I (Bacteria shape)

Column II (Figure)

A

Coccus

1

B

Spirillum

1

C

Bacillus

1

a. A - iii, B - i, C - ii
b. A - i, B - iii, C - ii
c. A - ii, B - i, C - iii
d. A - ii, B - iii, C - i

Solution: Coccus bacteria have spherical shape.

1
Spirillum bacteria have spiral shape.

1
Bacillus bacteria have rod shape.

1
Thus, the correct option is a.

FAQs of Kingdom Monera

Question 1. Name the hair-like structure found in bacteria involved in conjugation.

Solution: Pilli is a hair-like structure found in bacteria which helps in sexual reproduction like conjugation.

Question 2. What is Gram staining?

Solution: Gram staining process helps to distinguish between bacteria based on their cell wall structure. The process involves staining the mounted bacterial culture with a purple/blue primary stain such as crystal violet or methylene blue. After letting the stain sit for a minute, it is washed with alcohol and then stained again with a red secondary stain such as safranin. The mounted culture is then viewed under a microscope.
Gram positive bacteria have very less lipids in their cell wall, hence the cell wall structure is not disturbed by the alcohol wash. Thus they retain the primary stain and appear blue under the microscope.
Gram negative bacteria have a thick outer layer composed of lipopolysaccharides which is washed off during the alcohol wash. Thus, they are unable to retain the primary stain and get stained with the secondary stain and appear red.

Question 3. Name the bacteria which has a comma shape?

Solution: Comma shaped bacteria are called vibrio. 

Question 4. What is the term used to describe a bacteria having a single flagella on both ends?

Solution: Bacterium possessing one flagellum on both ends are called amphitrichous. 

Other Related Topics

The Living World Biological Classification Plant Kingdom
Animal Kingdom Morphology of Flowering Plants Anatomy of Flowering Plants
Structural Organization in Animals Cells: The Unit of Life Biomolecules
Cell Cycle and Division Transport in Plants Mineral Nutrition
Photosynthesis in Higher Plants Respiration in Plants Plant Growth and Development
Digestion and Absorption Breathing and Exchange of Gases Body Fluids and Circulation
Excretory Products and their Elimination Locomotion and Movement Neural Control and Coordination
Chemical Coordination and Integration

Other Related Topic Of Biology

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