Why are old 48 hour culture required for endospores stain?
Why is a 48 hour culture required for an endospore stain? Endospores form under environemental stress. If you wait 48 hours the bacteria will be lacking nutrients.
What color is Bacillus subtilis Endospore stain?
A typical staining of endospores of Bacillus subtilis. The vegetative cells (denoted with the white arrows) are stained red, while the endospores (denoted with the black arrows) are stained green.
Why do we stain two ages of Bacillus cultures 24 and 72 hours to inspect for spores?
Old cultures because spores are not produced until starvation, about 72 hrs. Thus older cultures are more likely to contain endospores.
Can Bacillus subtilis form endospores?
The Gram-positive bacterium Bacillus subtilis is able to form endospores which have a variety of biotechnological applications.
Why was a 48 hour culture of B subtilis used rather than a fresh culture for the endospore stain?
Why is a 48 hour culture required for an endospore stain? Endospores form under environemental stress. If you wait 48 hours, the bacteria will be lacking nutrients.
Why is using cultures older than 24 hours not advisable in Gram staining method?
Old cultures tend to lose the peptidoglycan cell walls, which predisposes gram-positive cells to be gram-negative or gram variable.
Is Bacillus subtilis endospore positive or negative?
From this lesson, it has been gathered that: Bacillus subtilis is a gram-positive bacterium that produces heat-resistant spores known as the endospore, under harsh environmental conditions.
Why would differences be observed in spore stains of overnight cultures of Bacillus subtilis and 72 hour cultures of Bacillus subtilis?
The 72 hour Bacillus culture had many free endospores and the chains were very long. Time would account for this difference because the Bacillus had longer to grow.
How long do endospores take to form?
approximately 6 to 8 hours
Spores are resistant to heat, dessication, chemicals, and radiation. Bacteria can form endospores in approximately 6 to 8 hours after being exposed to adverse conditions. The normally-growing cell that forms the endospore is called a vegetative cell. Spores are metabolically inactive and dehydrated.
Why is an 18 24 hour culture necessary for a Gram stain?
Old cultures or smears could give atypical results. That is why cultures of 18-24 hours or recent smears are recommended. It is very important to control the heat-fixation (few seconds), any excess heating could produce erroneous results. Highly chlorinated tap water could weak the counter staining.
Why is time an important factor in simple staining?
Why is time an important factor in simple staining? Time is important because it creates a contrast between the bacteria and the stain. If you over or under stain you won’t be able to see bacteria.
How long does it take for Bacillus subtilis to grow?
B. subtilis growth best at 37 °C and has a doubling time of 30 min. Always use flasks that comprise at least 5x times the volume of media used, and always use lids that are able to allow air passage.
How did the 24 hours and the 72 hour Bacillus cultures differ in appearance?
The 24 hour Bacillus culture had only a few central endospores and some free endospores. The chains also were not very long. The 72 hour Bacillus culture had many free endospores and the chains were very long. Time would account for this difference because the Bacillus had longer to grow.
How long can an endospore last?
Endospores enable bacteria to lie dormant for extended periods, even centuries. There are many reports of spores remaining viable over 10,000 years, and revival of spores millions of years old has been claimed.
Is Bacillus subtilis acid fast?
Therefore, it was noted that B. subtilis was acid-fast negative, whereas M. smegmatis was acid-fast positive. The acid-fast stain is classified under differential staining procedures that are used to pick out acid-fast organisms, including bacteria of the genus Mycobacterium.
Why Will old more than 48 hours cultures of Gram-positive bacteria stain as Gram-negative?
Old cultures tend to lose the peptidoglycan cell walls, which predisposes gram-positive cells to be gram-negative or gram variable. Gram stain is not useful for organisms without a cell wall like Mycoplasma species, and for smaller bacteria like Chlamydia and Rickettsia species.
Why will gram-positive cells more than 24 hours old stain gram-negative?
Why do gram-positive cells more than 24 hours old stain gram-negative? Because the cell wall begins to deteriorate and change.