5. Microbial Growth In Artificial Media

Question 1

What is general scheme for microbial growth

Answer 1

-Clinical specimen,raw food,water
-microscopic examination
-culture
-isolation(pure culture)
-identification based on morphologic, biochemical,serological,molecular analyses)

Question 2

What’s cultivation

Answer 2

Propagation of mo by providing proper enviromental conditions in metabolically accessible form

Question 3

How do mo get energy?

Answer 3

From light, autotrophs(photo-trophic organisms) and organic chemical compounds(chemo-trophic organisms)

Question 4

How do mo get their sources of carbon

Answer 4

Some organisms are photo and chemo litotrophic(CO2, other inorganic compounds)
Other are eterotrophic(organic compounds)

Question 5

How do mo get their sources of nitrogen

Answer 5

Atmospheric nitrogen, inorganic compounds containing nitrogen and from nitrogen in proteins

Question 6

What’s growth factor

Answer 6

Essential organic compound that the cell is unable to synthesize. Specific for microbial species

Question 7

What are the 6 elements that make up covalent skeleton of biological macromolecules(95% dry weight of the cell)

Answer 7

H, O, C, N, P(phosphorous), S

Question 8

What’s artificial culture medium

Answer 8

Solid or liquid mixture of nutrients and other compounds used to grow, transport and store mo

Question 9

What’s classification of artificial media based on?

Answer 9

1)chemical cimposition: defined(synthetic) or complex
2)physical nature: liquid, semisolid, solid
3)functuon: supportive, selective, differential

Question 10

What’s agar

Answer 10

Polysaccharudic extract(D-glucose, L-galactose, D-glucuronic acid of marine red algae); can’t be digested by mo. It’s a liquid up to 45°C and can be sterilized by heat

Question 11

What’s defined and complex artificial media

Answer 11

Defined=chemical composition is precisely known(completly synthetic)
Complex=undefined chemical composituon( microbial, plant, animal cell extracts)

Question 12

What’s enriched artificial culture media

Answer 12

Enriched=added with specific component(s) to faciliate the growth of a specific mo (ex: chocolate agar(heated and lysed red blood cells) for festiduous mo)

Question 13

What are non selective, selective and differential ACM(artificial culture media)

Answer 13

Non selective=mixed population
Selective=added with specific compounds that selectively inhibit the growth of some mo, but not others
Differential=added with indicator(ex: a dye) for the detection of chemical and metabolic reactions that are associated with microbial growth of a species

Question 14

What are basic components of ACM

Answer 14

1)Peptons= obtained by hydrolysis of proteins(meat, casein, soy): source of aa(can also be a source of nitrogen)
2)Carbohydrates: glucose, lactose, mannitol, saccharose(source of carbon)
3)Salts= for osmolarity(NaCl) ; as buffers for the medium(phosphate buffer); Manganese, Magnesium, Calcium, Iron : needed for enzymatic activity
4) Yeast extract: source of vitamins
5)pH indicators: for the detection of formation of acids starting from carbohydrates and bases from peptons

Question 15

What is enterobacteria

Answer 15

Large family of Gram negative bacteria

Question 16

What’s sterilization?

Answer 16

Total remotion or destruction of all mo

Question 17

What’s pure culture

Answer 17

A population of microbial cells that all originated from a single cell alone

Question 18

What’s a colony

Answer 18

Microscopically visible cluster of mo in or on a solid medium. Each colony represents pure culture

Question 19

What’s meant by hemolytic activity when using blood agar to identify cell culture

Answer 19

Ability to lyse red blood cells
We have:
Alpha-partial hemolysis
Beta–total hemolysis
Gama hemolytic-no hemolysis

Question 20

What’s Kirby-Bauer Test

Answer 20

Antiobiotic sensitivity test. If mo doesn’t grow around the antibiotic, it means it’s working(susceptible). If it grows next to it its non susceptible