Important Notes on Shapes of Bacteria for NEET Biology

Shapes of Bacteria: Important Notes on Biology for NEET

Bacteria are the most abundantly existing microorganisms on Earth. As a part of the NEET curriculum, it is considered one of the most vital topics where various bacteria shapes cover the maximum part. Since you have just a few weeks left before the examination, revising the chapter top to bottom can be difficult.

So, you can refer to the below mentioned important notes of biology for NEET shapes of bacteria for fast and adequate revision.

What are Bacteria?

They are single-celled, prokaryotic organisms which are found everywhere. An essential characteristic of bacteria is that it can grow in extreme conditions such as snow, oceans, hot springs, etc. where other organisms cannot live.

To know more about this microscopic organism take a look at the following features of the same:

  • Bacteria cell does not have a nucleus.

  • There are different bacteria shapes, sizes and arrangements.

  • It also lacks membrane-bound cell organelles.

  • The DNA of bacteria is found in cytoplasm. Notably, it is not wrapped for the formation of chromatin, like in the case of eukaryotic cell.

  • In comparison to human cells, bacterial cells are ten times smaller.

  • The diameter of each bacteria cell is ~1µm (10^-6 m).

  • A bacteria cell is covered by a rigid cell wall which helps in providing constructional integrity.

  • The main component of the cell wall of a bacterium is peptidoglycan or murein.

  • Different shapes of bacteria form a characteristic feature of a particular bacteria species.

  • The cells of bacteria may consist of external attachments like flagella, cilia, etc.

  • This microorganism can be chemoautotrophs, photoautotrophs or parasites.

Bacteria Cell Morphology

Morphology not only indicates the shape of a bacterial cell but also determines its pathogenicity. The morphological attributes are an essential factor for the evolution and adaptability of a bacterial cell. Bacteria shape also affects a lot of other traits like mode of nutrition, motility, etc.

As mentioned earlier, the bacterial cell wall is constructed with peptidoglycan. This polymer is made up of sugars where alternating N – acetylglucosamine is joined with amino acids and N – acetylmuramic acid peptide chain. The variety in shape and morphology of bacteria cell is because of modification in its thickness and polymer configuration.

The various bacteria shapes help in classifying them. So, take a look at the different bacteria shapes:

  1. Spherical

Cocci bacteria shape is spherical. They can be one, or more than one in a group of two, four, eight, etc. Moreover, they can be oval, round, bean-shaped or elongated. Its cell wall can be gram-positive having a thick layer of peptidoglycan or gram-negative if the cell wall has a thin layer of peptidoglycan.

Depending on the Cell Arrangements of Cocci, These Bacteria can be Further Divided into Multiple Types like:

  • Monococcus

These exist as one spherical shaped cell.

  • Diplococcus

After Division of Cell, the Cells of Diplococcus are Ordered in Pairs. Some Examples are:

  1. Gram-Positive: Moraxella catarrhalis and Neisseria spp.

  2. Gram-Negative: Enterococcus spp, Streptococcus pneumonia, etc.

  • Streptococcus

These are connected at a consistent level and organised in the form of a chain. Streptococcus are gram-positive, aerobic, non-motile bacteria which are responsible for many diseases.

Streptococcus pyogenes, Streptococcus bovis, Streptococcus mutans, etc. are a few examples of streptococci.

  • Tetrads

These bacteria show four-cell arrangement and division of cell takes place in two planes. Two primary examples of tetrads are Micrococcus spp and Pediococcus.

  • Staphylococcus

Cells of this type of bacteria are organised in a cluster form like grapes. Staphylococcus aureus and Staphylococcus haemolyticus are few examples.

  • Sarcinae

These occur in the form of 8 cells group and usually exist in skin and large intestine. Some examples are Clostridium maximum, Sarcina auranatica, etc.

  1. Rod-shaped

Bacilli are rod-shaped, and after their cell division, they can occur in singular or multiple cells form. These organisms again can be divided into various kinds:

  • Bacillus

It has one unattached cell which has the shape of a rod. Salmonella enterica and Bacillus cereus are two examples.

  • Diplobacilli

This organism has two rods joined with each other and exists in pairs. One example is Moraxella bovis.

  • Streptobacilli

Here, the bacilli are ordered in the form of a chain. One example is Streptobacillus felis.

  • Coccobacilli

These bacilli are short in size as compared to other ones and of oval shape. Haemophilus influenzae is one example of this kind.

  • Palisades

After division of the cell, the bacilli bend and form a fence-like arrangement. An example of palisades is Corynebacterium diphtheria.

  1. Spiral 

Depending on flexibility, thickness and cell motility, spiral bacteria can be subdivided into two kinds:

  • Spirillum

They are rigid and gram-negative and have external flagella, and its examples include H.pylori, Campylobacter jejuni, etc.

  • Spirochete

Spirochetes have internal periplasmic flagella and are flexible. Examples are Treponema, Leptospira, etc.

  1. Comma Shaped

These bacteria are curved and have the shape of a comma. Also, they are responsible for causing foodborne diseases. Vibrio cholera and Vibrio parahaemolyticus are few examples.

Apart from the four primary bacteria shapes, it has multiple other morphologies like:

  1. Filamentous

  2. Star-shaped

  3. Rectangular

  4. Pleomorphic

  5. Appendaged

  6. Trichome

  7. Lobed

  8. Fusiform

  9. Stalked

  10. Sheathed

Revise Thoroughly for Desired Results

The most crucial examination for medical aspirants is NEET. If you want to crack this entrance exam at one go, you will have to prepare accordingly. With regards to different shapes of bacteria, do not miss out on any of its categorisation, whether cocci, vibrio, spirillum or bacillus bacteria shape; you must study all of them.

Furthermore, make sure to take care of your health as falling ill will hamper your preparation. You should enjoy short breaks and practise yoga to stay fit and energetic.

FAQ (Frequently Asked Questions)

1. How to Recognise Unknown Bacteria?

Ans. One can identify unknown bacteria by performing a gram stain, followed by observing its colony appearance and features.

2. How Many Types of Bacteria are There on the Basis of their Shape?

Ans. There are mainly four bacteria shapes,namely – spherical, spiral, comma-shaped and rod-shaped.

3. What are the Reasons that Lead to Bacterial Morphology Changes?

Ans. Morphology of bacteria is immensely diverse. Due to the pressure of adapting, bacterial fitness optimises and results in its different shapes. These various shapes further have an impact on the nutrient acquisition, dispersion, motility, etc.