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Lactic Acid Bacteria is a very general name for a class of bacteria that are gram-positive, non-sporing, non-respiring, round or rod in shape bacteria, which produce lactic acid as a major end product during the fermentation of carbohydrates.

Science Section What Is Gram +/-?


The phrase gram-positive is a term used by microbiologist to classify bacteria into two groups gram-positive or gram-negative. This positive and negative reference is based on the bacterium’s chemical and physical cell wall properties.

To determine if a bacteria is gram positive or gram negative a microbiologist will perform a special type of staining technique, called a Gram Stain.

Who Discovered Gram Positive And Negative Bacteria ?

The name Gram comes from its discoverer and inventor, the very modest Danish born Mr Han Christian Gram who devised the test in 1882 however did not publish his findings until 1884.

He discovered a technique that involved exposing bacteria to solution that created visible staining to the cell walls of some microorganisms but not others due to the thickness of their cell walls. This method made it possible to identify different types of microorganisms, giving them the name Gram positive and Gram negative.

This stain will either stain the cells purple (for positive) or pink (for negative).

What is Gram Positive Bacteria?

Gram-Positive bacteria have a very thick cell wall made of a protein called peptidoglycan. These bacteria retain the crystal violet dye (one of the 2 main chemicals used for gram staining). Whereas, gram negative bacteria have a very thin peptidoglycan layer that is sandwiched between an inner cell membrane and a bacterial outer membrane.

What is Gram Negative Bacteria?


Gram negative bacteria do not retain the crystal violet stain because of its physical makeup and will stain pink. This is why they are called gram-negative.

Can I see Gram bacteria with the naked eye?

No you need a microscope to see this stain colouring. The microbes are still very tiny and are usually placed on a slide prior to staining.

Are Gram Bacteria good or bad?

Usually, gram positive bacteria are the helpful, for example Probiotic bacteria we hear about in the news are gram positive bacteria that live in our gut and help us digests food absorb nutrients and help maintain the balance of good bacteria .

Gram negative bacteria by coincidence, are usually thought of as the nasty bugs the bully of the playground that can make us sick and can be harmful.

For example, several species of Escherichia coli (E. coli) are common causes of food-borne disease. Another example is Vibrio cholera, the bacteria responsible for cholera, is a waterborne pathogen.

Example of Bad Bacteria (Gram –Negative)

During the 19th century, cholera spread across the world from its original reservoir in the Ganges Delta in India.

Six subsequent pandemics killed millions of people across all continents. The current (seventh) pandemic started in South Asia in 1961, and reached Africa in 1971 and the Americas in 1991. Cholera is now endemic in many countries and to date still effects millions of people.

What Is Cholera?

Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Cholera remains a global threat to public health and an indicator of inequity and lack of social development. Researchers have estimated that every year, there are roughly 1.3 to 4.0 million cases, and 21,000 to 143,000 deaths worldwide due to cholera.

Are all Gram Positive Bacterium Good?

No this is just a generality and it cannot be assumed that all gram-negative bacteria are harmful. Gram-positive bacteria can also be pathogenic. For example Clostridium Botulinum is a gram-positive bacterium.

What Is Botulinum?

Botulinum also referred to as the "miracle poison" aka Botox is used to fight wrinkles and in the treatment of chronic conditions when in the hands of trained professionals. However the Bacteria has a far more sinister side left to its own devices and can be deadly,

As it is responsible for producing neurotoxins that can kill a human being in hours.

Thanks to the hard work and dynamic thinking from scientist like Han Christian Gram, discoveries are continually being made to win the war on pathogens.

His legacy lives on today as we have the tools for lighting up the way to a better understanding of microbiology and the Gram Staining method remains the most important reliable method for distinguishing between the two major classes of bacteria still in use today.

Big up to the scientific community who work feverishly to tackle pathogens of today help create cures for the future.

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