Biology

Difference between Gram-positive and Gram-negative

Main difference

Bacteria are of different types depending on their location and the families to which they belong. There are also several ways to tell them apart, and one of those methods is called a Gram stain, which is a four-step method used to improve your microscopic image. With this, Christian Gram introduces a method to divide bacteria into two different types. The stain that is used mainly an alkaline solution and the base of it, together with the cell structure, bacteria are grouped into two different types. Obviously, these are different from each other and have several characteristics that are there to categorize them. Some of those differences are given here to help erase the confusion between them. The best way to know the difference is the basis of this test, Bacteria that can maintain their original color after the grain test are called gram-positive bacteria, while those that lose their color during the test are found as gram-negative bacteria. There are many other differences as well, for example, the cell wall of gram-positive bacteria is thicker and generally 20-25 nm, while the cell wall of gram-negative bacteria is less thick and is around 8-11 nm thick. . Another difference in the wall is that the former has a smooth surface while the latter has a curved surface. Other factors that help to separate the two include that there is no periplasmic space present in gram-positive bacteria while the outer membrane along with porins are missing. In the case of gram-negative bacteria, the periplasmic space and the outer layer are present, which also contain the porins. Even during the reaction, it is possible to tell the difference between them, as gram positive bacteria turn blue or purple in color, while gram negative bacteria turn reddish-brown. In general, resistance in gram-positive bacteria is higher since it is able to stop drying and different reactions while resistance is lower in gram-negative bacteria. Mesosomes are more prominent in the first type of bacteria because the flagellar structure consists of in dual rings, while mesosomes are less noticeable in the latter and therefore has a four-ring structure. Some of the other differences between them will be mentioned in the last section. resistance in gram-positive bacteria is higher since it is capable of stopping drying and different reactions, while resistance is lower in gram-negative bacteria. Mesosomes are more prominent in the former type of bacteria because the flagellar structure consists of dual rings, while mesosomes are less noticeable in the latter and thus has a four-ring structure. Some of the other differences among them will be mentioned in the last section. resistance in gram-positive bacteria is higher since it is capable of stopping drying and different reactions, while resistance is lower in gram-negative bacteria. Mesosomes are more prominent in the first type of bacteria because the flagellar structure consists of dual rings, while the mesosomes are less noticeable in the latter and therefore it has a four-ring structure. Some of the other differences between them will be mentioned in the last section.

Comparative chart
Gram positive Gram-negative
Definition Bacteria that can maintain their original color during the staining test. Those that cannot retain their color during this process.
Colour It turns into a blue or purple substance. It turns into a red or brownish-red substance.
Membrane Without outer membrane Distinct outer layer
Size cell wall is thick and around 20-25 nm cell wall is around 8-11 nm

Definition of gram-positive bacteria

During the gram test, if the bacteria can maintain their distinctive color, they are called gram positive bacteria, but that is not the only way they can be classified. There are many other properties for which they are named. For example, they do not have an outer membrane and during the gram reaction, they can maintain a bluish purple color that gives them distinction. They have a cell wall present that is down to a few nanometers and is smoother compared to other parts. They also have a flagellar structure in which there are two rings that form a body. It also produces toxins in the form of exotoxins while also having a higher resistance to drying. In the case of chemical reactions, they also show a good response and resist any change.

Definition of gram-negative bacteria

During the gram test, if the bacteria cannot maintain their distinctive color, they are called gram-negative bacteria, but that is not the only way they differ. Some of the other properties, such as the color they obtain during the staining process, give them the characteristics. They get a red color during the process and have a flagellar structure with four rings. They have an outer membrane that contains a considerable amount of porins, but teichoic acids are absent along with a small presence of murein that is only 20%. Its cell wall is also thin compared to the other type of bacteria and can vary between 7-11 nm. They have a higher amount of lipid content in the wall which is not smooth and gives it a rougher and more wavy look.

Differences in a nutshell
  1. Bacteria that can maintain their original color during the staining test are known as gram-positive bacteria, while those that cannot retain their color during this process are called gram-negative.
  2. During the staining reaction, gram-positive bacteria turn into a blue or purple substance, while gram-negative bacteria turn into a red or reddish-brown substance.
  3. Most pathogenic bacteria are known as gram-negative, while few are termed gram-positive.
  4. Teichoic acids are present in the wall of gram-positive bacteria, while it is absent in gram-negative bacteria.
  5. There are mesosomes in gram-positive bacteria, while they are less prominent in gram-negative bacteria.
  6. There is no outer membrane in gram-positive bacteria, whereas there is a distinct outer layer of gram-negative bacteria.
  7. The cell wall of gram positive bacteria is thick and measures around 20-25 nm, while the cell wall of gram negative bacteria is around 8-11 nm.
  8. The cell wall is smoother and contains up to 80% murein for gram-positive bacteria, while the cell wall is wavy and contains up to 20% murein for gram-negative bacteria.
Final Thought

All in all, this article will help develop a clear understanding of how things work when it comes to Gram-positives and Gram-negatives. The weights can be confusing at times as there are so many units and that can create problems for people who do not have a proper understanding of the topics and related activities.

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