Microbial Nutrition and Growth

Question 1

Microbial growth

Answer 1

increase in a population of microbes

Question 2

Growth requirements

Answer 2

use variety of nutrients for the energy needs to build organic molecules and cellular structures

Question 3

Oxygen requirements

Answer 3

Oxygen is essential for obligate aerobes.
Oxygen is deadly for obligate anaerobes.

Question 4

Four toxic forms of oxygen

Answer 4

Singlet oxygen
Superoxide radical
Peroxide anion
Hydroxyl radical

Question 5

Facultative anaerobes

Answer 5

grow better with O2, but can live without it

Question 6

Aerotolerant anaerobes

Answer 6

are unaffected by O2 levels

Question 7

Nitrogen fixation

Answer 7

by certain bacteria is essential to life on Earth.
All cells recycle nitrogen for amino acids and nucleotides

Question 8

Trace elements

Answer 8

only required in small amounts

Question 9

Growth factors

Answer 9

Necessary organic chemicals that cannot be synthesized be certain organisms. For example, vitamins

Question 10

Physical requirements - Temperature

Answer 10

Temperature affects three-dimensional structure of proteins. If too low, membranes become rigid and fragile. If too high, membranes become too fluid. Bacteria love our temp.

Question 11

Mesophiles

Answer 11

microbes that are comfortable around our body temperatures

Question 12

Psychrophiles

Answer 12

comfortable around 15-degree Celsius

Question 13

Psychrotolerant

Answer 13

organisms can tolerate, but don’t grow best in the cold

Question 14

Thermophiles

Answer 14

grow at temp above 45-degree celsius such as compost piles and hot springs

Question 15

Hyperthermophiles

Answer 15

grow at temp above 80-degree celsius

Question 16

pH - Physical Requirements

Answer 16

organisms sensitive to changes in acidity

Question 17

Neutrophiles

Answer 17

grow best in a narrow range around neutral pH

Question 18

Acidophiles

Answer 18

grow best in acidic habitats

Question 19

Alkalinophiles

Answer 19

live in alkaline soils and water

Question 20

Water - Physical Requirements

Answer 20

microbes require water to dissolve enzymes and nutrients and water is also important in reactant in many metabolic reactions. Most cells will die in the absence of water, therefore, some cells retain water. Endospores and cysts will stop metabolic activity in dry environments and still survive.

Question 21

Osmotic pressure

Answer 21

solution is the pressure exerted on a membrane by a solution containing solutes that cannot cross freely the membrane

Question 22

Hydrostatic pressure

Answer 22

water exerts pressure in proportion to its depth

Question 23

Hypertonic solution

Answer 23

lower solute concetration

Question 24

Hypotonic solution

Answer 24

greater solute concetrations

Question 25

Obligate and facultative halophiles

Answer 25

restricts organisms to certain enviroments, like growing in high osmotic pressure/higher salt concetration

Question 26

Biofilms

Answer 26

complex, synergistic relationships

Question 27

Culture

Answer 27

the act of cultivating microorganisms or the microorganisms that are cultivated

Question 28

Inoculum

Answer 28

to cultivate microorganisms is introduced into a collection of nutrients called a medium

Question 29

Colony forming unit (CFU)

Answer 29

cultures composed of cells arising from a single progenitor; the progenitor is termed CFU

Question 30

Streak plate

Answer 30

spreading inoculum across the surface of a petri dish

Question 31

Pour plates

Answer 31

CFUs are separated from one another using a series of dilutions

Question 32

Culture media

Answer 32

variety of liquid and solid media used to culture, grow, microbes

Question 33

Nutrient broth

Answer 33

common liquid medium

Question 34

Agar

Answer 34

common addition to make media solid; commonly used to make petri plates and slant tubes

Question 35

Slant tubes

Answer 35

used for fungal identification; warm agar is poured into test tubes at an angle and left to cool until the agar solidifies

Question 36

Defined media

Answer 36

used for research; exact chemical composition is known

Question 37

Complex media

Answer 37

contains reasonably familiar material but varies slightly in chemical composition from batch to batch; exact chemical composition is unknown; nutrients commonly derived from breakdown of yeast, beef, soy, and proteins; supports growth of a wide variety of microorganisms; useful when nutritional needs of an organism are unknown

Question 38

Yeast extract - Complex Media

Answer 38

most routine lab cultures use mediaa containing peptone from meat or fish and such media are sometimes enriched w yeast extract, which contains a number of vitamins, conenzymes, and nucleotides

Question 39

Casein Hydrolysate

Answer 39

made from milk and contains many amino acids and used to enrich media.

Question 40

Blood Nutrients

Answer 40

blood also contains nutrients that is needed for some pathogens, including, serum, blood (agar), and heated blood (chocolate agar)

Question 41

Selective media

Answer 41

contain substances that favor or inhibit growth of particular microorganisms

Question 42

Differential media

Answer 42

has an ingredient in it that will cause a color change on the media or the colony; during this process, we are looking for metabolic pathways that have a series of chemical reactions that could be associated with the waste products that could be pH or bind with something that could cause the color change in the first place

Question 43

Nutrient agar

Answer 43

Gram positive and Gram negative will grow here

Question 44

MacConkey agar

Answer 44

selects Gram negative and inhibits Gram positive; however, lactose can also come into play if it can ferment. Those that could ferment lactose will stand out, those that can't won't be easily distinguishable. Fermentation of lactose will start to make acid and have the colony then turn red.

Question 45

Transport media - culture media

Answer 45

used by healthcare personnel to ensure clinical specimens are not contaminated and to protect people from infection; rapid transport of samples is important

Question 46

Preserving cultures

Answer 46

refrigeration-stores for short periods of time deep freezing-stores for years lyophilization-stores for decades; involves removing water from a frozen culture through an intense vacuum

Question 47

Binary fission

Answer 47

most unicellular microorganisms reproduce through this technique by having the cell grow twice its size and divide in two producing daughter cells

Question 48

Generation time

Answer 48

time required for a bacterial cell to grow and divide depending on chemical and physical conditions; ex tuberculosis is really slow to grow

Question 49

Lag phase - bacterial growth curve

Answer 49

cells are adjusting to their new environment

Question 50

Log phase - bacterial growth curve

Answer 50

population increases logarithmically, which is faster then arithmetically

Question 51

Stationary phase - bacterial growth curve

Answer 51

eventually the number of dying cells equals the number of cells being produced and the size of the population remains constant

Question 52

Death phase - bacterial growth curve

Answer 52

if nutrients are not added and wastes not removed, a population reaches a point at which cells die at a faster rate than they are produced

Question 53

Chemostat

Answer 53

Used to maintain a microbial population in a particular phase of growth, particularly in log phase by controlling the amount and type of fresh medium added while removing an equal amount of old culture.