chapter 6

Question 1

physical requirements for microbial growth

Answer 1

• temperature
• pH
• osmotic pressure

Question 2

chemical requirements for microbial growth

Answer 2

• macronutrients (CHONPS)
• trace elements
• oxygen
• growth factors

Question 3

what does temperature affect?

Answer 3

protein function in a cell (properly folded)

Question 4

different classes for optimal growth in temperature

Answer 4

• psychrophiles: 0-25 degree celsius (food spoilage)
• mesophiles (normal): 25-40” (37)
• thermophiles: 40-80”
• hyperthermophiles: ober 80”

Question 5

temperature tolerance vs optimal growth
look at chart in lecture notes

Answer 5

• x: mesophile (sensitive to high temperature)
• y: mesophile (tolerates high temperature to a point and has widest range of thermotolerance)
• z: thermophile (requires higher temperature)

Question 6

are halophilic in a hypertonic or hypotonic environment and why?

Answer 6

hypertonic since salt is outside the cell (over 5% salt) and it must adapt to high osmotic pressure

*note: hypertonic=shrinkage, hypotonic=swelling

Question 7

optimal pH range for most microorganisms, acidophiles, alkaliphiles, and fungi

Answer 7

• 6.5-7.5
• acid: less than 6
• alk.: 8-11
• fungi: 5-6

Question 8

what causes internal pH to drop (acidic)?

Answer 8

weak acid diffuses into cell while partially giving up protons. it also leads to a growth inhibitory effect

Question 9

what do buffers do?

Answer 9

maintain pH

Question 10

what are the chemical requirements for growth?

Answer 10

essential nutrients, macronutrients, micronutrients, and growth factors

Question 11

define essential nutrients

Answer 11

cannot be synthesizes and must be supplied

Question 12

what are the required macronutrients?

Answer 12

CHONPS, K, Mg, Ca
- C: biggest influence on growth. it is an energy source that can be complex (heterotroph) or CO2 (autotroph)
-cations serve as cofactors or signaling molecules

Question 13

what are the required micronutrients?

Answer 13

Co, Cu, Mn, Fe, Mo, Ni, Zn

Question 14

what are the organic growth factors?

Answer 14

vitamins, amino acids, blood, serum

Question 15

Describe aerotolerance (oxygen tolerance)

Answer 15

• oxygen used by aerobes in cellular respiration to obtain energy (ATP) from the breakdown of nutrients; serves as terminal electron acceptor (used to differentiate between anaerobic and aerobic)
• enzymes react with O2 to for either reactive superoxide or hydroxyl radicals
  -damages DNA, RNA, proteins

Question 16

How are microbes that do not use O2 affected by aerotolerance?

Answer 16

microbes become susceptible to damage and require protection

Question 17

name and describe the protective enzymes against oxygen radicals

Answer 17

1.) superoxide dismutase (SOD): neutralizes the affect of O2 radicals
2.) catalase and peroxidase: neutralize peroxide anions (O2) in H2O2

Question 18

locate the growth zones on the tube

Answer 18

i cant put a fucking picture on here bruh. just imagine it i guess

Question 19

more energy (ATP) in anaerobes lead to…?

Answer 19

more growth

Question 20

where there are the most enzymes in test tubes represent what?

Answer 20

where growth is at optimal oxygen

Question 21

describe the tubes of O2 effect on growth (i cant put a picture so just look at lecture slide)

Question 22

describe obligate aerobe and microaerophile

Answer 22

• obligate: (atmospheric) oxygen at 21% (highest)
• microaerophile: oxygen is 5-10% (less)

Question 23

describe obligate anaerobe and aerotolerant

Answer 23

• both do not use O2 and either ferment or respire anaerobically
• obligate: O2 is TOXIC because it lacks protective enzymes
• aerotolerant: O2 is NOT toxic

Question 24

describe facultative anaerobe

Answer 24

• can use or not use O2, can ferment or respire aerobically/anaerobically (process taken depends on what’s available)
• O2 is NOT toxic

Question 25

growth medium is formed by a combination of what?

Answer 25

macro- and micro-nutrients

Question 26

complex vs defined media

Answer 26

- complex (rich): pre-formed, nutrients cells can readily assimilate (proteins, yeast extract, beef extract) - defined (minimal): chemical composition is known and cells must synthesize all required molecules (requirement for fastidious (longer list) bacteria) *prob should look at a pic

Question 27

liquid vs solid culture media

Answer 27

- liquid: growth studies, harvest DNA, protein isolation - solid: agar, formation of colonies, need for pure culture

Question 28

selective vs differential media

Answer 28

- selective: add inhibitory agents - differential: see metabolic differences between types

Question 29

define generation time of bacterial growth

Answer 29

- length of time for a cell to divide - Generation time (or doubling time) = minutes/generation

Question 30

growth formulas (represents population size):

Answer 30

N0 x 2n = NT ; n = # of generations; NT = # cells after n generations; N0 = # cells at start

Question 31

list and describe the phases of the bacterial growth curve

Answer 31

1.) lag phase: no growth, acclimation, syntehsis, turn on/off genes - factors affecting it: inoculum age and size, media composition, and physical factors 2.) log phase: most active, fastest growth, cell size increases -mid: most active and biggest -late: slow down of growth begins 3.) stationary phase: growth rate=death rate, stress response (nutrient limited) leads to cell size decreasing and conserving energy, *endospores start forming* 4.) death phase: lack of nutrients and pH changes lead to exponential death

Question 31

describe the fed-batch culture

Answer 31

it feeds additional nutrients (glucose) at mid-log phase leading to extra growth

Question 32

biofilm formation occurs in what? what part of the cell has biofilm?

Answer 32

- disease and the environment (ex: catheters) - fimbriae/pili

Question 33

describe the stages of biofilm development

Answer 33

- via chemical and environmental signals - originally planktonic cells or "swimmers" (motile form) 1.) attachment monolayer - seeks a favorable environment 2.) microcolonies - kinda lose its flagellum 3.) expopolysacc. (EPS) production - sugar covers cells - synthesis - "stickers" 4.) mature biofilm - biofilm towers - sustained with the flowing nutrients supply 5.) dissolution and dispersal - flow in and out to feed everyone, and dissolve if not enough food available - return to motile form and reseek favorable environment