BIOS 280 Lab Quiz 3 - include the proper and humidity, and suitable ...

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BIOS 280 Lab Quiz 3

• bacteria, like humans, need the appropriate conditions to thrive and grow; the conditions

include the proper and humidity, and suitable –Answer tem- perature nutrients

• bacterial growth is encouraged by placing organisms in appropriate

–Answer - media

• bacteria can be grown either in , which is liquid media or on ,

which is solid media –Answer broth agar

• in broth, the bacterial cells are usually dispersed throughout the liquid; on

solid media, the bacterial cells form –Answer evenly colonies

• in media, the chemical composition of a simple or defined medium is known exactly

–Answer simple (defined)

• in media, we know exactly what goes into the medium; there are no unknown

factors; an example is glucose mineral salts agar –Answer 1 / 3

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simple (defined)

• in media, there is an unknown chemical composition and/or amounts of the

components in them –Answer rich or complex (undefined)

• an example of rich or complex (undefined) media is that trypticase soy broth or trypticase soy

agar has some soy proteins, amino acids, vitamins, and other nutrients present; the medium contains enzymes that digest or extract; this undefined soup of nutrients is referred to as factors –Answer growth

• in rich or complex (undefined) media, some bacteria require growth factors to ; other

bacteria do not need growth factors in the media; this difference can be helpful in identifying bacteria –Answer reproduce

• trypticase soy agar is an example of a medium

–Answer rich (undefined)

• most bacteria grow well on media

–Answer rich

• a medium is one that only allows the growth of certain kinds of bacteria

–Answer selective

• an example of selective media is that eosin methylene blue (EMB) agar con- tains chemicals

that are usually toxic to Gram-positive bacteria; this means that usually only Gram- bacteria can grow on EMB agar –Answer negative

• an example of selective media is that mannitol salt agar (MSA) contains a high 2 / 3

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concentration of salt that selects for the growth of halophiles; the media usually discourages the growth of Gram- bacterial cells and encourages the growth of Gram- bacteria, especially bacteria of the genus Staphylo- coccus –Answer negative positive

• there are even selective agars that discourage growth; Sabouraud's

agar is toxic to bacteria but supports the growth of fungi –Answer bacterial

• a medium is one that, in some way, shows a difference between the colonies of

organisms that grow on the medium –Answer differential

• an example of differential media is that on EMB agar, the colonies of organ- isms that

ferment lactose appear , while the colonies of non-fermenters will be white or pale –Answer purple pink

• on some differential agars, there is a change in the color of the colonies; on other

differential agars the color of the itself may change; differential media can be very helpful in identifying bacteria –Answer agar

• glucose mineral salt agar (GMS) is a , chemically defined medium; to survive,

organisms need to make all their cellular components from and the inorganic salts that are in the medium; no growth factors are present –Answer sim- ple glucose

• / 3