Lecture notes in Microbiology

Difference between the Cell Wall of Gram Positive and Gram Negative Bacteria


Compare Cell wall Gram Positive and negative

Difference between the Cell Wall of Gram Positive and Gram Negative Bacteria

Most of the bacterial cells are surrounded by a thick rigid cell wall. The cell wall provides shape to the cell and protects the bacteria from changes in the osmotic pressure. Peptidoglycan (murein) is the principal component of the bacterial cell wall and it is responsible for the shape and extreme tough nature of the cell wall.

Based on the characteristics of the cell wall, the bacterial cells are classified into Gram Positive and Gram Negative, primarily based on the classical staining reaction called Gram Staining. In the previous post we have discussed about the Similarities and Differences between Gram Positive and Gram Negative Bacteria. Both Gram positive and Gram negative bacterial possess cell wall, however, their structural organization, chemical and physical properties varies. In general, the cell wall of Gram positive bacteria has simpler chemical structures compared to the Gram negative bacteria. The present post discusses the Differences between the Cell Wall of Gram positive and Gram negative bacteria with a comparison table.

OSC Microbio 03 03 CellWalls

Comparison of the Cell Wall of Gram Positive and Gram Negative Bacteria


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Biotechnology Lecture Notes

Batch Fermentation vs Continuous Fermentation Process: Similarities and Differences – A Comparison Table


Difference continuous and batch fermentation

Batch Fermentation vs Continuous Fermentation Process
(Similarities and difference between Batch Fermentation and Continuous Fermentation Process)

Batch Fermentation and Continuous Fermentation are the two commonly adopted Industrial Fermentation methods for the scale production of microbial biomass or metabolites.

Batch Fermentation: Here the fermenter is first filled with the raw material (carbon source). Then the microbes are added and allowed to ferment the raw material under optimum pH and aeration. The products remain in the fermenter until the completion of fermentation. After fermentation, the products are extracted and the fermenter is cleaned and sterilized before next round. Thus here the fermentation is done as separate batches.

Continuous Fermentation: Here the exponential growth rate of the microbes is maintained in the fermenter for prolonged periods of time in by the addition of fresh media are regular intervals. The metabolite or the product of fermentation is extracted for the overflow from the fermenter. Thus unlike batch fermentation, in continuous fermentation, the fermentation process never stops in between and it continues to run for a long period of time with the addition of nutrients and harvesting the metabolites at regular intervals.

The present post describes the Similarities and Differences between Batch Fermentation and Continuous Fermentation Process as a Comparison Table.

Similarities between Batch Culture and Continuous Culture Fermentation Methods

Ø  Both are industrial fermentation methods for the large scale production.

Ø  Both methods can be used for the production of microbial biomass or products.

Ø  Both run under controlled environmental conditions

Ø  The mechanical components of fermenter is almost similar in both types




Difference between Batch Fermentation and Continuous Fermentation Process

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Lecture notes in Microbiology

Compare Archaebacteria, Bacteria and Eukaryotes: Similarities and Differences (Table)


comparison chart archaebacteria bacteria and eukaryotes

The Three Domain System of Classification by Carl Woese (1977) based on variations in 16S rRNA sequence, divided the entire living organism in the biosphere into three major groups called Domains namely (1). Archaea, (2). Eubacteria (Bacteria) and (3). Eukarya or Eukaryota. In the earlier systems of classifications, Archaea were treated as a unique type of bacteria called Archaebacteria and they were included in the Kingdom Monera along with true bacteria and Cyanobacteria (blue green algae).  Now we are certain that Archaea possess distinct difference from true bacteria in their cellular structures and metabolic activities, and also they have a unique and separate evolutionary ancestry. Archaea shows some characters similar to true bacteria where as some unique sets of characters they share between eukaryotes. Due to these peculiarities, the group Archaea is now recognized as a distinct domain of life. The present post article describe what all are the similarities and difference between Archaea, Bacteria (eubacteria) and Eukarya (eukaryote) with a comparison table for easy understanding.

Similarities and Differences Between Bacteria, Archaebacteria and Eukaryotes: Comparison Table

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Lecture notes in Microbiology

Difference Between Gram Positive and Gram Negative Bacteria


Gram positive and gram negative staining

Gram Positive Bacteria Vs Gram Negative Bacteria
(Similarities and Differences Between Gram Positive and Gram Negative Bacteria)

What is Grams staining?

Christian Gram, a Danish Physician in 1884 developed a staining technique to distinguish two types of bacteria. The two categories of bacteria based on gram staining are Gram positive bacteria and Gram negative bacteria. Bacteria are first stained with crystal violet or gentian violet. All bacterial cells will stain blue or purple colour with crystal violet solution. Then the bacterial cells are treated with iodine solution (Lugol’s iodine) solution and washed with alcohol (de-staining solution).  Those bacteria which retain the blue or purple colour of crystal violet are called Gram positive bacteria and those bacteria which loose the colour of crystal violet after washing with de-staining solution is called Gram Negative bacteria. Gram negative bacteria are later stained with safranin or fuchsin for observation under microscope. Gram negative bacteria after safranin or fuchsin staining will appear red or pink colour. Gram staining differentiates bacteria by the chemical and physical properties of their cell walls by detecting the properties of peptidoglycan. Gram staining method is useful in differentiating majority of bacterial species into two broad categories. Even though all bacterial species cannot be differentiated based on gram staining technique, this method has immense application in clinical diagnostics and biological researches.


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Similarities between Gram Positive and Gram Negative Bacteria

Ø  Both are bacterial cells

Ø  Both groups are prokaryotic

Ø  Both lack membrane bounded organelles

Ø  Both groups have covalently closed circular DNA as the genetic material

Ø  Both groups contain extra-chromosomal genetic materials (plasmids)

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