Chapter 8

Question 1

3 types of nutrients + examples for each

Answer 1

1. macronutrients (carbon, nitrogen, sulfur, phosphorous, oxygen, hydrogen, potassium, magnesium, calcium, sodium)
2. micronutrients (iron, trace metals)
3. grown factors (vitamins, purines, pyrimidines, amino acids or other organic molecules that the organisms needs for growth but can not synthesize itself. Some growth factors are the by-product or waste of anoher microorganism)

Question 2

what is binary fission

Answer 2

the way most of the prokaryotes multiply: the cell grows in size until it forms a partition (septum) that constricts the cells into 2 daughter cells

Question 3

what does growth of the population + what is the generation time of E. Coli

Answer 3

it increases number of cells or biomass

Generation time of E.Coli= 20 min in lab

Question 4

what each daughter receive (5)

Answer 4

one copy of the chromosome
sufficiient ribosomes
macromolecules
monomers
other molecules to exist as an independent cells

Question 5

3 steps of growth of microorganisms

Answer 5

1. cell elongation
2. septum formation
3. completion of septum: formation of walls; cells separation

Question 6

cell division requires what (2) + role of bactoprenol

Answer 6

require synthesis of new cell wall material, but also it requires its destruction by autolysis
- bactoprenol allows peptidoglycan subunits to be exported across the cytoplasmic membrane

Question 7

what happens at the division ring (FtsZ) + what is wall bands

Answer 7

at the division ring, autolysins create some gap in the peptidoglycan. This allows rearrangment of the peptidoglycan and synthesis of a new cell wall.
- wall bands: scar between old and new peptidoglycan

*** similar mechanism in Archaea with a cell wall

Question 8

what happens with the MacConkey (selective medium)

Answer 8

• bile salts inhibit growth of Gram +, permissive for Gram - enteric pathogens. Selective medium.
• differentiate (differential media) between lactose fermenters (pink) and lactose non-fermenters (colorless)
• lactose = glucose + galactose
• glucose = glycolytic pathway= fermentation: lactate (lactic acid, reduce pH)

** E.Coli forms dark pink colonies with bile precipitate

Question 9

Mannitol-salt : used for what, differential media, selective medium..

Answer 9

• high NaCl concentration: inhibits most Gram - and many Gram -
• used for isolation or detection of Staphylococcus
• differential media: manitol fermenters = + and yellow
  non-fermenters= pink and -
• staphylococcus aureus is mannitol + (so turn out yellow)

Question 10

5 reasons to count bacteria/measure growth

Answer 10

1. evaluate contimation of food, water..
2. ensure enough microorganisms are inoculated during process requiring them: beer, wine, yogurt, cheese..
3. evaluate the efficiency of antimicrobial growth
4. study microbial populations from different ecosystems
5. measure effect of mutation of genes involved in methabolic pathway, survival, protection, virulence…

Question 11

spread-plate method vs pour-plate method

Answer 11

spread:

1. sample is pipetted onto surface of agar plate (0.1ml or less)
2. sample is spread evenly over surface of agar using sterile glass spreader

pour:

1. sample is pipetted into sterile plate
2. sterile medium is added and mixed well with inoculum
   * * colonies in the pour plate method will grow on the surfaces and inside whereas the spread-plate is only on surfaces

Question 12

how can we get a viable count of bacteria cultures that can reach high numbers of cells (billions)

Answer 12

serial dilutions have to be made

Question 13

how works microbial counts + pros and cons

Answer 13

count all cells: dead, alive, and cells that can not be grown in lab.

• • put it in counting chamber where there are little square: so count the number of bacteria in square (that perfectly know the volume) and make an average, don’t count the ones that touch the right line and the top
    pros: fast, no need o wait until bacteria are grown
    cons: small cells can be missed, motile cells are hard to count and must be immobilized

Question 14

what viability scanning can be used for

Answer 14

to differentiate red (dead cells) and live (green cells) when we count

Question 15

3 characteristics of flow cytometry

Answer 15

• better at counting big cells: protozoan, yeast, mammalian cells..
• detection of fluorescent dyes allow labeling of specific cell types or species
• can be used to sort cells according to size, shape, labeling..

Question 16

3 characteristics of turbidimetric method

Answer 16

• keep in mind: measure the contribution of both livind and dead cells to turbidity
• optical density is affected by properties of cells: size, clumping…
• a standard curve must be made and the relationship between optical densoty and cell number must be established empirically

Question 17

what is generation + depends on what + what is the formula when the conditions are right

Answer 17

• generation time: time needed for the population to double
• it depends on the growth medium and the conditions
• when the conditions are right, microorganisms can grow exponentially; the population doubles at a constant rate
  N= N02^n

Question 18

4 phases of the growth curve in batch culture

Answer 18

1. lag: time needed by the batceria to adjust the new condition, slow growth
2. exponential: doubling of the population at a constant rate
3. stationary: limiting nutrients are depleted or accumulation of a waste products that inhibits growth; growth is stopped. No net increase in cell number, cells are still metabolicaly active, induction of survival systems
4. death: cells start to die, metabolism has stopped, in some cases cell death occur with cell lysis. Death phase is also an exponential function.

Question 19

batch cultures are continually been affected by what

Answer 19

by the metabolic activities og the growing microorganism: depletion of nutrients, generation of toxic waste

Question 20

4 characteristics of most natural environment which are open systems

Answer 20

• constant supply of nutrients and diffusion of waste
• competition with other microorganisms
• predation (protozoan, worms..)
• changing environmental conditions
• • over time, it reachs an equilibrium: division rate equals death rate and in some cases, the main factor is the concentration of a limiting growth factor

Question 21

chemostats is used for what

Answer 21

• used to keep the microorganisms in a constant growth rate over a long period of time
• • fresh medium: supply of limiting nutrients
• • overflow: death of microorganisms

Question 22

7 factos affecting microbial growth

Answer 22

1. temperature
2. nutrients
3. pH
4. osmolarity
5. oxygen
6. pressure
7. radiation (visible light, UV light)

Question 23

whar are extremophiles

Answer 23

microorganisms that grow preferentially under extreme conditions

Question 24

characteristics of psychrotolerant

Answer 24

organisms that can grow at 0degree but have optima around 20 to 40 degree

Question 25

what are the 4 cardinal temperature

Answer 25

- minimum: membrane gelling; transport processes so slow that growth cannot occur * * between minimum and optimum: enzymatic reactions occuring at increasingly rapid rates - optimum: enzymatic reactions occuring at maximal possible state - maximum: protein denaturation; collapse of the cytoplasmic membrane; thermal lysis

Question 26

coolest temperatue that bacteria can growth + which one

Answer 26

-15 degree, planococcus halocryophilus

Question 27

5 adaptation to cold temperature

Answer 27

1. change in protein structure and sequence so the enzymes are active at low temperature 2. transport accross the membrane functions optimally at low temperature 3. requires modification of the cytoplasmic membrane so it stays fluid at low temperature 4. cold-shock proteins which help keeps proteins active 5. cryoprotectants: antifreeze proteins, glycerol.

Question 28

what do cryoprotectants

Answer 28

they help prevent the formation of ice crystals that can puncture the cytoplasmic membrane ** cold temperature does not kill microorganisms, ice crystals do!!

Question 29

microbial culture are preserved in which liquid at which temperature

Answer 29

in liquid nitrogen at -80 or -196 degree celsius

Question 30

which organisms can live at the hottest temperature

Answer 30

archaea (max= 122 degree), it is hotter thn autoclave (what we use in lab to sterilize)

Question 31

5 adaptations to high temperature

Answer 31

1. changes in protein sequences so the enzymes are not denatured by the high temperature and can stay active. These enzymes are heat-stable 2. transport across the membrane functions optimally at high temperature 3. requires modification of the cytoplasmic membrane so it remains stable at high temperature, for example the lipid monolayer of Archaea 4. heat-shock proteins which help keep proteins in the active conformation 5. protection mechanism to ensure stability of DNA

Question 32

1 adaptation at low pH

Answer 32

** every microbe has a pH range (2-3 pH units) within which growth is possible 1. changes of the cytoplasmic membrane to require high concentration of protons for membrane stability. Bacteria lyse at higher pH, because the membrane become unstable

Question 33

4 adaptations at high pH

Answer 33

1. changes of the cytoplasmic membrane to withstand low concentration of protons 2. use of Na+ gradient for transport and motility (low concentration of protons outside, pmf is hard to maintain) 3. keep the elcron transport chain close to the ATPase, so protons that are pumped out do not diffuse away. 4. proteases and lipases from alkaliphiles are added to laundry detergent

Question 34

how are called microorganisms that can grow at high salt concentrations + % of salt in seawater

Answer 34

halophiles seawater: 3% * * usually required NaCl for growth

Question 35

5 types of oxygen relationships of microorganisms (aerobes and anaerobes)

Answer 35

aerobes: 1. obligate (required oxygen) 2. facultative (not required, but growth better with O2), ex: E.Coli 3. microaerophilic (requires but at level lower than atmospheric) anaerobes: 4. aerotolerant: not required, and growth no better with O2 present 5. obligate (harmful or lethal) ** obligate and facultative aerobes are usually grown in liquid with constant shaking of the culture to ensure sufficient O2 concentration in the medium

Question 36

technique to identify the relationship between oxygen and the microorganism

Answer 36

- thioglycolate is added to the medium. It reduces O2 to H2O, which create a gradient of oxygen concentration - redox indicator reazurin is used to differentiate oxic and anoxic zones (pink when it is oxidizes)

Question 37

what happened during aerobic respiration vs to oxygenic photosynthesis

Answer 37

aerobic: oxygen is reduced to water oxygenic: water is oxidized to oxygen

Question 38

3 proteins present in all virtually cells that can reduced O2 into O2-

Answer 38

flavoproteins, quinone, iron-sulfur proteins

Question 39

what do toxic forms of oxygen

Answer 39

oxidize cell components, stopping key metabolic pathways and destroying key cultures

Question 40

3 reactions in aerobes and facultative aerobic

Answer 40

1. catalase: H202 + H202= 2 H20 + O2 2. peroxidase: H2O2 : NADH = 2 H20 + NAD+ 3. superoxide dismutase: O2- + O2- = H2O2 + O2 .... it will resist to H202