Microbiology - Lab 8-9

What is the purpose of the streak plate technique?

• To observe individual colonies

• To dilute a bacterial sample

• To differentiate mixed vs pure cultures

• All of the above

Which agar is selective for Gram-positive halotolerant bacteria?

• Nutrient Agar (NA)

• Mannitol salt agar (MSA)

• Eosin methylene blue (EMB)

• None of the above

Which agar is differential based on color changes if mannitol sugar is fermented?

• Nutrient Agar (NA)

• Mannitol salt agar (MSA)

• Eosin methylene blue (EMB)

• None of the above

Which agar contains eosin and methylene blue and is selective for Gram-negative bacteria?

• Nutrient Agar (NA)

• Mannitol salt agar (MSA)

• Eosin methylene blue (EMB)

• None of the above

Which agar differentiates Gram-negative lactose fermenters from Gram-negative non-fermenters based on colony color?

• Nutrient Agar (NA)

• Mannitol salt agar (MSA)

• Eosin methylene blue (EMB)

• None of the above

Which agar is not selective or differential?

• Nutrient Agar (NA)

• Mannitol salt agar (MSA)

• Eosin methylene blue (EMB)

• None of the above

Look at the MSA plate result below and answer: is the bacteria growing on the plate a Gram-positive halotolerant? 

• No

• Yes

• Can't determine

By looking at the color of the MSA plate below you are certain that the bacteria growing on the plate are able to:

• Ferment mannitol 

• Ferment sucrose

• Can't determine

What is the definition of a colony?

• A single cell dividing many times

• A group of bacteria growing in a medium

• A mixture of different bacterial species

• A type of special media

How can colonial morphology be identified?

• By colony color, shape, size, edge/margin, texture, and elevation

• By cellular morphology and shape

• By the ability to metabolize specific components

• By the appearance of the media itself