Question

Give the classification of Bacteria based on the arrangement and number of flagella.

Answer 1

Bacteria are microscopic, single-celled organisms that grow in a lot of different environments. These microorganisms can grow in soil, the ocean and even inside the human gut. The relationship between humans and bacteria is complex. Sometimes bacteria are useful for us and act as a helping hand, as by curdling milk into yogurt or helping with our digestion. In other cases, bacteria are dangerous, causing diseases like pneumonia and methicillin-resistant Staphylococcus aureus (MRSA).

Complete answer:
Bacteria or monerans can be classified under many different criteria. Some of them are:
(A) Classification of bacteria based on nutrition: -
On the basis of nutrition bacteria are categorized as:

1. Autotrophic bacteria: - these types of bacteria are nonpathogenic, free living, self-developing in nature, which produce their own food with the help of utilization of sunlight and inorganic substances like carbon dioxide, nitrogen, etc. They are further classified into two types:
   (i) Photoautotrophs: - these types of bacteria have bacterio-chlorophyll and bacterioviridin and can produce their own food by fixing carbon dioxide in nature with the help of utilization of light energy.
   (ii) Chemoautotrophs: -these are the type of bacteria which produce their own food by utilizing the energy from oxidation of inorganic molecules like nitrogen dioxide, carbon dioxide etc. and they can also fix carbon dioxide and water for their food.
2. Heterotrophic bacteria: – this type of bacteria is not able to fix inorganic carbon but it depends on external organic carbon for their nutrition. They also can be categorized on the basis of presence and absence of light and on the basis of the culture media on which the bacteria are growing.
   (B) Classification of bacteria on the basis of number of flagella: -
   On the basis of flagella, the bacteria can be categorized into: -
   i) Atrichos: - These bacteria have no or zero flagella. Example: -Corynebacterium diphtheriae.
   ii) Monotrichous: - One flagellum is linked to one end of the bacteria cell. Example: - Vibrio cholerae.
   iii) Lophotrichous: - A group of flagella is attached to one end of the bacteria cell. Example: - Pseudomonas.
   iv) Amphitrichous: - A group of flagella appears from both ends of the bacteria cell. Example: - Rhodospirillum rubrum.
   v) Peritrichous: - The flagella are equally spread around the complete bacterial cell. Example: -Bacillus

Note:
Depending upon the staining given by Gram stain, bacteria can be categorized into two types: – (i) Gram positive bacteria: this type of bacteria preserve the gram stain which appears violet. For example: – Streptococcus.
(ii) Gram negative bacteria: they do not retain the Gram stain, but they take up the red color of the counter stain i.e. Safranin. For example: – Escherichia coli.