Difference Between Gram Positive and Negative Bacteria

In 1884, Cristiam Gram created a way to differentiate the type of bacteria by developing a specific series of pigments that, when in contact with the sample, adopted a certain color, which made it possible to differentiate one from another, for which it was possible from this to know the structure, membrane and cell wall of the bacterium in addition to its composition. This technique is still used and is known as Gram staining, and allows to differentiate between two types of bacteria according to the color they are stained, Gram-positive bacteria take on a dark blue or violet color, while Gram-negative bacteria take on a darker hue. light red or pink.

What are Gram Positive Bacteria?

Gram-positive bacteria are those that are painted dark blue or violet against the Gram stain, which indicates that we are dealing with a bacterium that has a thick layer of peptidoglycan that covers the membrane and that covers 90% of the membrane. In addition, teichoic acids are found in a smaller proportion in the cell. This composition in the walls of the bacterium makes it resistant and is what retains the dye, giving it that characteristic color.

There are different types of Gram-positive bacteria, the mobile ones like flagella, and the immobile ones that are divided into two: cocci, whose shape is rounded, and bacilli, which have an elongated body.

Peptidoglycan, although thick, has a mesh-like appearance so its surface is porous, during an infection it acts by stimulating the immune system, and usually produces a fever. Inside it contains a cytoplasmic membrane, which is formed by an aqueous solution called cytosol, which is the one that contains the ribosomes and in a less dense area is its nucleoid.

In general, Gram-positive bacteria are responsible for causing some of the skin diseases such as abscesses, cellulitis and skin wound infections. On the other hand, cocci cause lung or respiratory tract infections, while those caused by bacilli are usually diphtheria, infections of the heart valves, urinary tract or prostate, likewise Gram-positive bacteria are activated by eating food. contaminated, such as meat, milk, vegetables, among others.

What are Gram Negative Bacteria?

Gram negative bacteria are those that acquire a red or pink pigmentation when Gram’s stain is applied. The reason for the change in its color when applying the chemical compound used to differentiate them from other bacteria, is related to the conformation of the cell walls, since it is covered by two lipid membranes and a thin layer of peptodoglycan, which, being so thin, does not retains coloration.

It is formed inside by cytoplasmic membranes called periplasm, which house enzymes necessary for the nutrition of the bacteria. Likewise, lipopolysaccharides are found in its structure which, when broken, release a sterilization-resistant toxin. In the same way, near the nucleus we find lipoproteins.

Gram negative bacteria produce many common diseases according to the type of bacteria that contains them: if they are cocci, conditions such as gonorrhea, meningitis and respiratory system can develop. If they are bacilli depending on the species, some of the diseases that can be caused from them are urinary and gastrointestinal diseases, respiratory and nosocomial infections, the latter are infections contracted in hospital centers.

This type of bacteria usually shows resistance to antiseptics and antibiotics, such as penicillin, and this may be due to the fact that they acquire genes from other bacteria that have developed resistance to these treatments, so it can be considered that one of their characteristics is that their Genes have the ability to mutate.