Rhizobium Leguminosarum

Adam Tarrant

Gram Stain

Rhizobium Leguminosarum (R. Leg) is a gram negative bacteria; therefore it will appear pink under the microscope due to the safranin stain and the two layer cell wall. The first layer of the cell wall is made up of carbohydrates and proteins, and the second layer is made of lipids and carbohydrates. On a gram positive bacteria, there is only one layer in the cell wall. Is composed of carbohydrates and proteins.

Shape and Colony Type

Rhizobium Leguminosarum is a rod shaped (bacillus) bacteria that forms random (staph) colonies.

Methyl-red Test

The methyl-red test came back positive for Rhizobium Leguminosarum. A methyl-red test is a procedure to find out what kind of waste the cell puts out, acidic, neutral, or base. Rhizobium Leguminosarum came back positive so we know it produces acidic waste.


Rhizobium Leguminosarum is a motile bacteria. This means that when you do the motility test, the agar turns yellowish instead of the original color, purple. A Motility test is where you take an innoculating loop and bend the loop until it's straight. Then you fill a test tube about a fourth of the way full with a purple agar. Next, you scrape up a little bit of bacteria on the bent innoculating loop and stab straight into the middle of the agar and take it back out through the same hole.

Oxygen use

Rhizobium Leguminosarum is an aerobic bacteria. This means the the bacteria has to have oxygen to grow. To perform this procedure, you have to take a glass jar, put your bacteria (on an agar culture dish) in the jar, light a candle inside the jar, and put the lid on. once the candle goes out, that means there is no more oxygen in the jar. If the bacteria is aerobic, for example Rhizobium Leguminosarum, it will not grow. If it's anaerobic (can't grow with oxygen) or facultative (can grow with or without oxygen), it will grow.


A hemolysis test is a test to determine whether or not the bacteria digests hemoglobin. To perform this procedure, you streak a sheep's blood agar plate with the bacteria and incubate it. After the incubation process is finished, you take the plate and see if there are any clear spots on the culture dish. There are three classifications for the amount of hemoglobin digested, and they are Alpha, Beta and Gamma. Alpha is when only one protein in the structure digests the hemoglobin, and the agar turns brown. Beta is when the bacteria completely digests the hemoglobin, so the area around the bacteria is clear. Gamma is when the bacteria grows, but doesn't digest hemoglobin. Rhizobium Leguminosarum is beta so it digests all of the hemoglobin.


Rhizobium Leguminosarum grows at most temperatures, but it grows the best at 25 degrees Celsius or 77 degrees Fahrenheit.