If the bacteria stays purple, they are Gram-positive. If the bacteria turns pink or red, they are Gram-negative.
Many experts agree that the bacteria that causes these pink stains is most likely Serratia marcescens, a bacteria which is found naturally in soil, food, and in animals. Serratia, which produce a characteristic red pigment, thrive on moisture, dust, and phosphates and need almost nothing to survive.
Gram positive bacteria have a distinctive purple appearance when observed under a light microscope following Gram staining. This is due to retention of the purple crystal violet stain in the thick peptidoglycan layer of the cell wall.
Gram-negative cells have a thinner peptidoglycan layer that allows the crystal violet to wash out on addition of ethanol. They are stained pink or red by the counterstain, commonly safranin or fuchsine.
Gram-positive organisms are seen as blue/purple (see image below). Gram-positive cocci. Gram-negative organisms are seen as pink/red (see image below). Gram-negative bacilli.
After gram staining, gram-positive Staphylococcus aureus turn purple and gram-negative Escherichia coli turn pink.
Gram-negative organisms
Gram-negative bacteria have cell walls with thin layers of peptidoglycan (10% of the cell wall) and high lipid (fatty acid) content. This causes them to appear red to pink under a Gram stain.
The pink colour is due to a pigment secreted by a species of bacteria known as Serratia marcescens, found naturally in soil, air and water. They can cause infections, but that generally happens in hospitals and affects people with compromised immune systems.
If the bacteria is Gram positive, it will retain the primary stain (crystal violet) and not take the secondary stain (safranin), causing it to look violet/purple under a microscope.
Gram positive bacteria: Stain dark purple due to retaining the primary dye called Crystal Violet in the cell wall. Gram negative bacteria: Stain red or pink due to retaining the counter staining dye called Safranin.
Gram-negative Pseudomonas aeruginosa bacteria (pink-red rods). Gram-positive and -negative bacteria are chiefly differentiated by their cell wall structure.
The Gram Stain is a differential staining technique that allows us to differentiate gram negative cells from gram positive cells based upon the chemistry and structure of their cell walls. After completing the staining protocol, gram positive cells appear purple while gram negative cells appear pink.
Some bacteria have had a gene called "Lac-Z" put into their genomes, so that when they're fed a certain substance, they pull the substance into their cells and cause it to turn blue. Colonies of bacteria that have the gene thus turn blue. Other similar genes can cause bacteria to turn red or other colors.
The organisms are identified based on color and shape. Gram-positive organisms are either purple or blue in color, while gram-negative organisms are either pink or red in color. Bacilli are rod-shaped, while cocci are spherical.
Lac positive. By utilizing the lactose available in the medium, Lac+ bacteria such as Escherichia coli, Enterobacter and Klebsiella will produce acid, which lowers the pH of the agar below 6.8 and results in the appearance of pink colonies.
agalactiae (Group B), enterococci (Group D), Strep viridans, and Strep pneumonia. Gram-positive bacilli (rods) subdivide according to their ability to produce spores.
Escherichia coli cultures grown on Tergitol-7 medium, with 2,3,5-triphenyltetrazolium chloride added, produced three main types of colonies: rough, intermediate, and mucoid. These colonies were yellow to amber in color and produced slight yellow zones in the medium.
A red or pink pigmented bacteria known as Serratia marcescens is thought to be the cause of the pink "stuff". Serratia bacteria are common inhabitants of our environment and can be found in many places, including human and animal feces, dust, soil, and in surface waters.
In contract Gram negative bacteria have two thin cell membranes with a thin peptidoglycan layer between them. To carry out a Gram stain, the bacteria are first washed in a purple stain called crystal violet followed by iodine. The iodine and crystal violet form large complexes which bind to the cell and turn it purple.
If you see green or yellow phlegm, it's usually a sign that your body is fighting an infection. The color comes from white blood cells. At first, you may notice yellow phlegm that then progresses into green phlegm.
Serratia marcescens is an opportunistic, gram negative, nosocomial pathogen which belongs to family, Enterobacteriaceae.
Nonpathogenic E. coli is a Gram-negative, rod-shaped bacterium (appears as red/pink colored rods upon Gram staining), known for its ability to extensively colonize the gastrointestinal tract of warm-blooded mammals and serve the useful task of keeping other bacterial organisms in check (Figure 1).
Gram-negative infections include those caused by Klebsiella, Acinetobacter, Pseudomonas aeruginosa, and E. coli., as well as many other less common bacteria.
Gram-positive cells have a thick peptidoglycan layer and stain blue to purple. Gram-negative cells have a thin peptidoglycan layer and stain red to pink.
Gram-negative bacteria are classified by the color they turn after a chemical process called Gram staining is used on them. Gram-negative bacteria stain red when this process is used. Gram-positive bacteria. Gram-positive bacteria stain blue when this stain is applied to them.