- Is E coli Gram positive or negative?
- Which step is the most crucial or most likely to cause poor results in the Gram stain?
- What is the most crucial step in Gram staining?
- What happens if you forgot the safranin in a Gram stain?
- What color is gram negative bacteria?
- What happens if Decolorizer is not left on long enough?
- What does Decolorizer do in Gram staining?
- What happens if you Decolorize a Gram stain too long?
- What is the difference between a gram positive and gram negative bacteria?
- What stain does not require heat fixation?
- What is the most likely reason for the poor appearance of the bacteria on this slide?
- What would happen if you forgot to add crystal violet to a Gram stain?
- What factors can affect the results of a Gram stain and why?
- What happens if you forgot the decolorization step?
- What happens if you don’t add iodine to a Gram stain?
- What are 3 factors that affect a good Gram stain?
- Does heat fixing kill bacteria?
- What can go wrong in Gram staining?
Is E coli Gram positive or negative?
coli) The gram-negative bacterium Escherichia coli is the most numerous aerobic commensal inhabitant of the large intestine.
Certain strains cause diarrhea, and all can cause infection when they invade sterile sites (eg, the urinary tract)..
Which step is the most crucial or most likely to cause poor results in the Gram stain?
decolorization stepIt is clear that the decolorization step is the one most likely to cause problems in the Gram stain. The particular concerns in this step are listed below. Heat fixing the cells, when done to excess, alters the cell morphology and makes the cells more easily decolorized.
What is the most crucial step in Gram staining?
The critical step of the Gram staining procedure is the decolorization step. Hold the slide in a tilted downward position and allow the decolorizer to flow over the smear. Be careful not to miss any portion of the smear. Usually a few seconds will suffice.
What happens if you forgot the safranin in a Gram stain?
A safranin counterstain is used to stain these Gram-negative cells pink. However, if the safranin counterstain were forgotten, the Gram-negative bacteria would remain unstained, as the original crystal violet stain would have been removed during the ethanol wash, and no additional stain would have been applied.
What color is gram negative bacteria?
RedGram negative organisms are Red. Hint; Keep your P’s together; Purple is Positive. Gram stains are never pink they are red or purple so you don’t destroy the rule; keep your P’s together. In microbiology bacteria have been grouped based on their shape and Gram stain reaction.
What happens if Decolorizer is not left on long enough?
It is possible to leave the decolorizer on too long and strip the blue stain out of all the bacteria, even the Gram positive ones. … If the decolorizer is not left on long enough, the blue color will remain in the Gram negatives and they will appear Gram positive (purple) Page 4 c.
What does Decolorizer do in Gram staining?
A decolorizer such as ethyl alcohol or acetone is added to the sample, which dehydrates the peptidoglycan layer, shrinking and tightening it. The large crystal violet-iodine complex is not able to penetrate this tightened peptidoglycan layer, and is thus trapped in the cell in Gram positive bacteria.
What happens if you Decolorize a Gram stain too long?
Do NOT decolorize for a full minute! The decolorizer should stay on the slide for no more than 15 seconds! If the decolorizer is left on too long, even gram positive cells will lose the crystal violet and will stain red.
What is the difference between a gram positive and gram negative bacteria?
Gram positive bacteria have a thick peptidoglycan layer and no outer lipid membrane whilst Gram negative bacteria have a thin peptidoglycan layer and have an outer lipid membrane.
What stain does not require heat fixation?
bacteria are not heat fixed so they don’t shrink, and. some bacterial species resist basic stains (Mycobacterium) and one way they can be visualized is with the negative stain.
What is the most likely reason for the poor appearance of the bacteria on this slide?
What is the most likely reason for the poor appearance of the bacteria on this slide? The slide was heat fixed for too long.
What would happen if you forgot to add crystal violet to a Gram stain?
Steps for gram staining: … 95% ethanol, because it removes the primary stain (crystal violet) from Gram-negative cells. If missed, then the bacteria would remain purple and give a false positive result. Gram-negative releases CV-I complex and Gram-positive retains CV-I complex.
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. The most common reasons for false gram reactions?
What happens if you forgot the decolorization step?
If the decolorization step were omitted, both types of cell walls would retain the primary stain, which is crystal violet.
What happens if you don’t add iodine to a Gram stain?
Question: What Would Happen As A Result If You Forget To Use The Mordant (iodine) When Performing A Gram Stain? … It Wouldn’t Matter Because Iodine Doesn’t Color The Cells B. Both G+ And G- Cells Would Look Purple Because The Crystal Violet Dye Would Not Be Able To Leak Out Of The Cells During Decolorization C.
What are 3 factors that affect a good Gram stain?
microbio- lab 1QuestionAnswerWhat are some factors that can affect the accuracy of a gram stain?-timing of decolorization -too thick -freshness of reagents -improper fixing of smear -changes in organism itself -age of microorganisms/acidity of culture52 more rows
Does heat fixing kill bacteria?
Heat fixing kills the bacteria in the smear, firmly adheres the smear to the slide, and allows the sample to more readily take up stains.
What can go wrong in Gram staining?
Several factors may affect the results of Gram staining: If the smear is too thick, proper decolorizing will not be possible. If the smear is overheated during heat fixing, the cell walls will rupture. … Cells from old cultures may stain Gram negative even if the bacteria are Gram positive.