Gram Negative Bacteria

Gram negative bacteria are a type of bacteria that do not turn purple as part of the Gram staining process. Instead, they will turn a red or pink sort of color. The bacteria will be applied to a slide, which is examined under a microscope for identification purposes. Hans Christian Gram created this test in 1884.

Gram was working in the city hospital’s morgue in Berlin, Germany at the time. His first observation using this test was that the bacteria Typhus bacillus, or typhoid, didn’t stay purple after the test, so it was known as the first “Gram negative bacteria”. The purple comes from the crystal purple dye. Gram negative bacteria will turn this pinkish or red color after the slide is rinsed with a certain counterstain.

The purpose of Gram’s method or staining process is to find out if the bacteria are Gram negative or positive. This test detects the polymer peptigoglycan, which is part of the bacteria cell wall. The peptigoglycan forms a thick layer in Gram positive bacteria, which will result in a purple color after the test. Then, the Gram negative bacteria result will be the reddish color. The Gram staining method is typically the first step when identifying the type of bacteria. To complicate matters, there are even some bacteria that are Gram-variable and Gram-indeterminate as a result of the test. A Gram-variable pattern is a mix of purple and pink cells.

Ninety to ninety five percent of Gram negative bacteria are harmful, or pathogenic. Types of Gram negative bacteria include the following well known scary or dangerous types of bacteria: cyanobacteria, spirochaetes and proteobacteria. Proteobacteria is a well-known and frightening group, which includes bacteria like e. coli, moraxella, salmonella, helicobacter, pseudomonas, legionella and stenotrophomonas. These Gram negative bacteria all have thinner cell walls. The outer cell layer is comprised of proteins and lypopolysaccharide, which can react with the immune system, thereby causing inflammation and infection. Most Gram negative bacteria interesting in that they do not sporulate, or produce spores as part of their life cycle.

Finally, bacteria are a special type of microorganism. Usually, they can only be seen under a microscope. They come in readily defined shapes including spheres, rods and spirals. One can find bacteria all over the planet, including in the dirt, air and even in live plants and animals. In fact, there are five nonillion bacteria on Earth, and their combined weight is greater than all of the plants and animals added together.