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Yes, the age of the culture may influence the results of the stain.
With the current theory behind gram staining, it is thought that in gram-positive bacteria, the crystal violet and iodine combine to form a larger molecule that precipitates out within the cell. The alcohol/acetone mixture then causes dehydration of the multilayered peptidoglycan in the gram-positive call wall, thus decreasing the space between the molecules and causing the cell wall to trap the crystal violet-iodine complex within the cell. In the case of gram-negative bacteria, the alcohol/acetone mixture, being a lipid solvent, dissolves the outer membrane of the gram-negative cell wall (and may also damage the cytoplasmic membrane to which the peptidoglycan is attached). The thin layer of peptidoglycan is unable to retain the crystal violet-iodine complex and the cell is decolorized.
It is important to note that gram-positivity (the ability to retain the purple crystal violet-iodine complex) is not an all-or-nothing phenomenon but a matter of degree. There are several factors that could result in a gram-positive organism staining gram-negatively:
1. The method and techniques used. Overheating during heat fixation, over decolorization with alcohol, and even too much washing with water between steps may result in gram-positive bacteria losing the crystal violet-iodine complex.
2. The age of the culture. Cultures more than 24 hours old may lose their ability to retain the crystal violet-iodine complex.
3. The organism itself. Some gram-positive bacteria are more able to retain the crystal violet-iodine complex than others.
What else can I help you with?
What might cause a Gram variable reaction?
A Gram-variable reaction may occur when the bacteria have an atypical cell wall structure, making it difficult to predict whether they will appear as Gram-positive or Gram-negative under a microscope. This variability in staining can be caused by factors such as age of the culture, cell wall composition, or bacterial species.
Why is it necessary to use a young culture 24-hr old culture in gram staining?
less than 24 hours old. Older cultures tend to lose the ability to retain stains.
Is gram staining related to flagella?
No, gram staining and flagella are not directly related. Gram staining is a technique used to classify bacteria based on cell wall characteristics, while flagella are thread-like appendages that help bacteria move. Flagella presence or absence does not affect the results of a gram stain.
What are the gram reaction of mycobacterium?
Mycobacteria are typically Gram-positive, but their cell wall structure is unique and contains high lipid content, making them resistant to Gram staining. They are best visualized using acid-fast staining methods, such as the Ziehl-Neelsen or Kinyoun stains.
What is the name of the paper used to dry slides after gram staining?
Gram staining is used to identify whether a bacterium is gram positive or gram negative. Slides can be dried using filter paper or tissues. The technique is based on the reaction of stain that happens with the membrane of bacteria.
When bacteria culture age does it appear gram negative or gram positive?
Typically, a negative result can be doubted, but a positive staining cannot be. This is because the vast majority of bacteria that do revert (not to say that the majority of bacteria DO revert) will go from positive to negative. This is due to a decreased average level of peptidoglycan synthesis in Agar culture, as opposed to natural function in vivo. The decreased level of peptidoglycan allows the ethanol/acetone decolorizer to more quickly flush the Crystal Violet from Gram+ cells, making them appear either weakly positive, or fully negative.
Would it be useful to perform a gram stain on a mixed culture?
The purity of a culture of bacteria is important so it can test on that one type of bacteria. Gram staining can be good so you make sure everything in the streak plate is one color showing that it is gram positive and gram negative.
What is the primary stain used in Gram staining?
The primary stain used in Gram staining is crystal violet.
Who developed Gram staining?
Gram staining was devised by Hans Christian Gram of Denmark in the 1800s. (1853-1938)
What mordant is used in the process of gram staining?
The mordant used in the process of gram staining is called crystal violet.
What is the gram reaction of s epidermidis?
Staphylococcus epidermidis is a Gram-positive bacterium, meaning it retains the crystal violet stain in the Gram staining procedure. This results in a purple color under the microscope.
What are the factors that can result in variable gram reaction?
Genetics, Age of culture, type of growth medium, and technique used could result in a gram-variable reaction
