Why does petroleum have a rainbow-like reflection in the sunlight?
When the light strikes a thin film of a fluid(such as petrol)
in which light moves slower than air, there is an initial reflection off
of the surface. Some of the light is transmitted into the fluid and it reflects off the
bottom and then finally travels back out.
These waves take slightly longer
to reflect due to the travel of a very short distance through the
oil, they are now slightly out of phase with the initial reflection, creating a rainbow of interference
What's the difference between an enzyme and a hormone? - Joke
What's the difference between an enzyme and a hormone?
You can't hear an enzyme.
You can't hear an enzyme.
All cats with 3 or more colors are females, why?
Cats may have 3 colors at times, they are also known as Calico cats. Cats who have 3 or more colors are female, in other words male cats cant have more than 2 colors(with an exception, discussed later). So why is that? What is the biological reason for this phenomenon?
Like most of the mammals, cats have a XY sex determination system. So the female cats have two X chromosomes and the male cat has a X and a Y chromosome. The X chromosome is the chromosome which determines the color of the cat. So in females there are two chromosomes, so they can have an orange and a non-orange gene on each of the X chromosome.
But this is not possible in male cats as they have only one X chromosome which will either have a orange and a non-orange gene. However, there is one exception to this case where if a male cat has a genetic disease such as Klinefelter syndrome in which the male cat as an extra X chromosome. Klinefelter syndrome cats have XXY chromosome and can have 3 colors.
Staphylococcus aureus - Microbes Made Easy
Microbes Made Easy
Morphology:
Staphylococcus - therefore they are cocci (spherical cocci)
Gram nature: Gram positive
Sporing: No
Motile: No
Pigment: Golden yellow, only in aerobic conditions.
Culture medias and growth:
Nutrient agar - Golden yellow colonies
MacConkeys agar - If bile tolerant then they will produce small pink colonies
Morphology:
Staphylococcus - therefore they are cocci (spherical cocci)
Gram nature: Gram positive
Sporing: No
Motile: No
Pigment: Golden yellow, only in aerobic conditions.
Culture medias and growth:
Nutrient agar - Golden yellow colonies
MacConkeys agar - If bile tolerant then they will produce small pink colonies
SS Agar - Salmonella Shigella Agar (Medium)
Salmonella Shigella Agar made easy.
Primary Purpose
Isolation of organisms like Salmonella and Shigella species
Type of medium
Selective (for Gram negative bacteria)
Differential (differentiates between a few organisms such as Salmonella, Shigella, Escherichia and Enterococcus etc)
Nutrients for growth
Peptones and Beef extract
What inhibits the Gram negative organisms?
Bile salts
Brilliant Green
Sodium citrate
How are lactose fermentors recognized?
The organisms which breakdown lactose produce acid. The acid production is identified by pink color because of the presence of the indicator Neutral red in the medium.
How are Salmonella and Shigella differentiated from other organisms?
As both are Lactose non-fermenting organisms they grow as colorless colonies with or without black centers.
How to differentiate between Salmonella and Shigella?
Salmonella produces H2S and therefore produces black centered colonies, while Shigella doesn't produce black centers.
Why are black centered colonies produced?
The medium contains Sodium thiosulphate and ferric citrate. Sodium thiosulphate is reduced to sulphite and H2S gas (due to enzyme thiosulphate reductase). Black precipitate of ferrous sulphide is formed when H2S reacts with ferric citrate.
pH of medium
7.0 +/- 0.2
Some facts about Salmonella Shigella Agar
-It is used to isolate Salmonella and Shigella from pathological specimens and suspected foodstuff.
-It is also known as SS agar or SS Medium
Primary Purpose
Isolation of organisms like Salmonella and Shigella species
Type of medium
Selective (for Gram negative bacteria)
Differential (differentiates between a few organisms such as Salmonella, Shigella, Escherichia and Enterococcus etc)
Nutrients for growth
Peptones and Beef extract
What inhibits the Gram negative organisms?
Bile salts
Brilliant Green
Sodium citrate
How are lactose fermentors recognized?
The organisms which breakdown lactose produce acid. The acid production is identified by pink color because of the presence of the indicator Neutral red in the medium.
How are Salmonella and Shigella differentiated from other organisms?
As both are Lactose non-fermenting organisms they grow as colorless colonies with or without black centers.
How to differentiate between Salmonella and Shigella?
Salmonella produces H2S and therefore produces black centered colonies, while Shigella doesn't produce black centers.
Why are black centered colonies produced?
The medium contains Sodium thiosulphate and ferric citrate. Sodium thiosulphate is reduced to sulphite and H2S gas (due to enzyme thiosulphate reductase). Black precipitate of ferrous sulphide is formed when H2S reacts with ferric citrate.
pH of medium
7.0 +/- 0.2
Some facts about Salmonella Shigella Agar
-It is used to isolate Salmonella and Shigella from pathological specimens and suspected foodstuff.
-It is also known as SS agar or SS Medium
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