Why do our pea plates contain 5% sheep blood?

Why do our pea plates contain 5% sheep blood?

PEA agar with 5% sheep blood is used in microbiology laboratories to inhibit gram-negative bacteria, specificallyProteus species, in specimens containing a mixed bacterial flora (1). Five percent sheep blood is added to the base medium to enhance the growth of anaerobic bacteria.

Why is pea not considered a differential media?

PEA is not considered a differential media because a differential media contains chemical indicators that allow microbiologists to distinguish two or more species of bacteria. PEA is selective because it inhibits gram negative bacteria while encouraging growth of gram positive bacteria.

Is chocolate agar selective or differential?

Chocolate agar also contains red blood cells, but with chocolate agar, the blood is autoclaved, thus changing the red blood cells to a brown color. This medium can be made selective by the addition of antibiotics.

Is a TSA plate selective or differential?

TSA (Trypticase Soy Agar) and NA (Nutrient Agar) are General Purpose Media that are not selective or differential, their purpose is simply to grow many types of bacteria cheaply.

Is Mac selective or differential?

MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms.

What does a TSA plate test for?

Tryptic Soy Agar (TSA) is mainly used as an initial growth medium for the purposes of observing colony morphology, developing a pure culture and achieving sufficient growth for further biochemical testing and culture storage. TSA slants are being used to store and ship bacterial cultures.

Why can a spread plate be used quantitatively and a streak plate Cannot?

We can estimate the number of cells in the original culture by counting the colonies and calculating the dilutions used in the process. The streak plates can not be used for quantitative purposes because the original volumes are not known and they are not evenly distributed to create separate, countable cultures.

Can bacteria grow on a streak plate?

After incubation, bacterial growth is visible as colonies in and on the agar of a pour plate. Can some bacteria grow on the streak plate and not be seen if the pour plate technique is used? Yes, the pour plate is O2 limited. Thus, some bacteria will only grow on the streak plate as it provides ample O2.

What is the difference between streak plate and pour plate?

Streak plate refers to a rapid qualitative isolation method for obtaining discrete colonies from a mixed population while pour plate refers to the method of choice for counting the number of colony-forming bacteria present in a liquid specimen.

Why is streak plate better than pour plate?

The pour plate method of counting bacteria is more precise than the streak plate method, but, on the average, it will give a lower count as heat sensitive microorganisms may die when they come contact with hot, molten agar medium.

What advantage does the streak plate method have over the pour plate method?

What advantage does the streak plate method have over the pour-plate method? The streak plate method does not require any additional media for dilution and only requires one plate for inoculation.

What would happen if you forgot to sterilize your loop in between each quadrant streak?

What is a bacterial colony? What would happen if you forgot to sterilize your loop in between each quadrant streak? You would spread a lot of bacteria back into quadrant one and probably not see isolated colonies.

What is being done to the inoculum as you streak from one quadrant to the next?

This is done by having the loop pick up only a small amount of bacteria from the previous quadrant’s streaks. Flaming the loop between streaks ensures that the loop starts clean and that only this small amount of bacteria is used to inoculate the next quadrant.

How can you tell if a plate is contaminated in agar?

If the plate has not been inoculated, the presence of any bacterial colonies indicates contamination. On an inoculated plate, look for colonies that display morphology different than what you would expect from the type of bacteria used to inoculate the plate.

Why are agar plates incubated upside down?

Petri dishes need to be incubated upside-down to lessen contamination risks from airborne particles landing on them and to prevent the accumulation of water condensation that could disturb or compromise a culture.

Why do you label the bottom of the agar plate?

Petri dishes are labelled on the bottom rather than on the lid. Write close to the edge of the bottom of the plate to preserve area to observe the plate after it has incubated. Labels usually include the organism name, type of agar, date, and the plater’s name or initials.

Why is it important to label the bottom of the agar plate the side with the agar and not the lid of the plate?

After the culture medium is set, and streaked with the required microbe/stock, the lid is put on and the petri dish is incubated upside down to minimize contamination. So, it is easier to read the label on the bottom. agar plates must be kept with lid on to avoid contamination when not being used.