What might cause a Gram positive cell to appear gram negative?
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What might cause a Gram positive cell to appear gram negative?
If the decolorizing agent is applied on the cell for too long time, the Gram-positive organisms to appear Gram-negative. Under-decolorization occurs when the alcohol is not left on long enough to wash out the CV-I complex from the Gram-negative cells, resulting in Gram-negative bacteria to appear Gram-positive.
Under what circumstances can Gram positive bacteria stain like Gram negative and why?
The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet. Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with.
Why do old cultures of Gram positive bacteria tend to appear gram negative?
Gram stain is reliable only on cells from cultures that are in the exponential phase of growth. Older cultures contain more ruptured and dead cells. Cells from old cultures may stain Gram negative even if the bacteria are Gram positive.
What is the major factor that determines if bacteria are Gram positive or gram negative?
The major difference between the two groups of bacteria is the thickness of the cell wall and the presence of an outer membrane in Gram negative bacteria only. The bacterial cell wall ranges from 20–80 nm thick for Gram positive and between 1.5–10 nm thick for Gram negative bacteria.
What factors can affect the results of a Gram stain and why?
The many variables that can affect this stain are age of the culture, amount of decolorizer used, the time of decolorization, the type of organism (acid-fast bacteria and spores do not stain well), thickness of the smear, and the general care of the stainer.
What is the best explanation for a Gram positive bacteria appears pink after performing a Gram stain?
The staining procedure differentiates organisms of the domain Bacteria according to cell wall structure. 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.
What are the characteristics of Gram positive bacteria?
Characteristics of gram-positive bacteria
- No outer membrane. Gram-positive bacteria don’t have an outer membrane, but gram-negative bacteria do.
- Complex cell wall.
- Thick peptidoglycan layer.
- Certain surface appendages.
What factors are important in achieving a good Gram stain?
Gram Staining Best Practices
- Don’t make your smear too heavy.
- Always test your incoming stains and reagents.
- Use a fresh culture.
- Air dry the slide completely before fixing it.
- Fix the specimen on the slide by using heat or methanol.
- Don’t over-decolorize.
- Keep reagents closed between use.
Why might a Gram-positive cell stain pink?
What antibiotics treat Gram positive?
Beta-Lactams. Beta-lactams are a wide range of antibiotics,the first of which to be discovered was penicillin,which Alexander Fleming identified in 1928.
What are the characteristics of Gram negative bacteria?
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.
What makes a Gram positive organism Gram positive?
Gram-positive bacteria are bacteria with thick cell walls. In a Gram stain test, these organisms yield a positive result. The test, which involves a chemical dye, stains the bacterium’s cell wall purple. Gram-negative bacteria, on the other hand, don’t hold the dye.
What are Gram positive organisms?
The bacteria can also form a bacillus or rod shaped. The rod shaped gram positive organisms are usually divided into spore forming or non spore forming. Members of the Bacillus bacteria will produce spores as a reproductive measure. Gram positive bacteria describes a group of microorganisms that is diverse in shape and function.