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Microbiology 1 > Lecture #5 - The Effect of Physical & Chemical Conditions on Microbial Growth > Flashcards

Lecture #5 - The Effect of Physical & Chemical Conditions on Microbial Growth Flashcards

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1
Q

Temperature is a major environmental factor controlling…

A

microbial growth

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2
Q

Cardinal temperatures:

A

the minimum, optimum, and maximum temperatures at which an organism grows

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3
Q

Optimum

A
  • where organism grows FASTEST (according to temp)
  • you can give it the temp it likes most (optimal temp), but if nutrient [ ]’s are not on point, pH isn’t controlled, salt [ ] isn’t good etc. it doesn’t matter if you give optimal temp
  • but it’s just 1 variable - more needs to be considered for the reality
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4
Q

These cardinal temperatures are characteristic of…

A

each different organism

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5
Q

Minimum temp

A
  • mem. specifically solidified

- LESS mobile “sleeping” –> metabolically inactive

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6
Q

Maximum temp

A

mem. melted
- higher temp
- death
- breakage of VdW’s b/c of increased movement

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7
Q

Optimum temp

A

best growth rate possible (highest)

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8
Q

What would maximum outcomes do to the cell? If it’s melted, what has happened to structure of mem. & what does that mean about cell state?

A

falls apart - completely dismembers - no shape so cell dies b/c PM all about shape (butter in microwave)

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9
Q

What would minimum outcomes do to the cell? If its solidified, has the cell lost its mem. integrity or is it a lil less mobile?

A

less mobile –> “sleeping”

  • metabolically inactive (not gonna work but when taken out of fridge or freezer & put in optimal its metabolically active & vegetative)
  • won’t kill with exception of outlier
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10
Q

Min to optimum is characterized by a gradual slope - indicating that…

A

temp decreases don’t have as dramatic effect as temp increases

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11
Q

What will mem. state be at its optimum (necessary state for PM)?

A

semi-fluid

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12
Q

Optimum to max we see…

A

substantial drops in the growth rate that occur within that region

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13
Q

What will happen to the movement & therefore VdW’s interactions within the PL tails at excessively high temps?

A

breakage of VdW’s b/c of increase movement

- loses structural integrity

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14
Q

Reason growth rate changes in COLD is b/c:

A

membrane phospholipids move LESS in COLD allowing MORE van der waals to form –> “gelling” or solidification
- but mem’s need to be semifluid

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15
Q

Describe what happens to the protein (has to have certain shape) when HEAT is added

A

breaks H-bonds, VdW’s & ionic bonds

DENATURED = non-functional

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16
Q

Describe what happens to the protein (has to have certain shape) when COLD is added

A

move LESS & ionic, H-bonds & VdW’s form

DENATURED - COMPACT b/c increase # of bonds

  • lil easier to recover from
  • functional for cold loving organisms
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17
Q

@ Minimum

A

membrane gelling; transport processes so slow that growth cannot occur

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18
Q

@ Maximum

A

protein denaturation; collapse of the cytoplasmic membrane; thermal lysis

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19
Q

Microorganisms can be classified into groups by their growth temperature optima

A
  • Psychrophile
  • Mesophile
  • Thermophile
  • Hyperthermophile
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20
Q

Psychrophile:

A

low temperature

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21
Q

Mesophile:

A

midrange temperature

*include us & medically relevant bacteria & flora within the body

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22
Q

Thermophile:

A

high temperature

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23
Q

Hyperthermophile:

A

very high temperature

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24
Q

Mesophiles:

A

organisms that have midrange temperature optima (~38 degrees celsius)

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25
Q

Mesophiles found in:

A

• Warm-blooded animals (include us, cows, goats etc.)

• Terrestrial and aquatic environments
- diff bodies of water

• Temperate and tropical latitudes
- warm-temp within this range most of the time

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26
Q

Cold-Loving Microorganisms

A
  • Extremophiles
  • Psychrophiles
  • Psychrotolerant
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27
Q

Extremophiles

A

• Organisms that grow under very hot or very cold conditions

OR like LOW pH/HIGH pH/HIGH [salt] etc.

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28
Q

Psychrophiles

A

• Organisms with cold temperature optima (<20oC)

• Inhabit permanently cold environments
- Deep ocean, Arctic and Antarctic environments

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29
Q

Psychrotolerant

A
  • Organisms that can grow at 0oC but have optima of 20oC to 40oC
  • More widely distributed in nature than true psychrophiles

can tolerate - don’t have a desire in either temps (can tolerate either), but prefer temps that are warmer (mediocre like we like)

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30
Q

2 ways a mem. can offset freezing to maintain semi-fluid state & do characteristics of life even when its super cold?

A
  1. MORE UNsaturated PL’s tails - so VdW’s are less likely to form even though they want
  2. Produce ANTI-FREEZE compounds - prevent water from solidifying
    - mem. stay in fluid state that’s req & inside the cell as well
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31
Q

Molecular adaptations that support psychrophily

A

(present inside cell that allow for support)
- if they don’t have those molecular dets, there will def be problems with their ability to thrive

• Production of enzymes that function optimally in the cold
- if it can’t handle these cold conditions then its out of luck

• Modified cytoplasmic membranes
- High unsaturated fatty acid content

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32
Q

Unsaturation creates a kink in that fatty acid tail –>

A

makes packaging challenging
- positioning within the mem.

(could also be both tails)

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33
Q

As things move MORE & MORE, bonds…

A

BREAK

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34
Q

As things move LESS & LESS, bonds…

A

FORM

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35
Q

As things move less, bonds want to be forming but prob is that…

A

now as the bonds want to form & mem. wants to solidify, you incorporate unsaturation & so bond still doesn’t form

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36
Q

It’s positional change, that understanding that despite lesser movement & desire to form these bonds is gonna happen, you just…

A

move them further apart & the bonds won’t form

- idea is to maintain a mem. that’s semi-fluid consistency

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37
Q

Above ~65oC…

A

only prokaryotic life forms exist

NO EUK CAN
think: car that is complicated & has more that can go wrong & less you’ll be able to tolerate

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38
Q

Above ~65oC, only prokaryotic life forms exist

A

• Chemoorganotrophic (use organic molecules) and chemolithotrophic (use inorganic molecules) species are present
• No phototrophy above approx. 70oC - chemotrophy
- phototrophic organisms have a bunch of intracellular mem. content that allows for the absorption of light energy & conversion into chemical energy (therefore, that machinery can’t handle high temp, it loses its structural integrity & ability to function & that machinery to be able to convert light energy into chemical energy also has temp restrictions, even if we’re talking about a photosynthetic prok (cyanobacterium)
• High prokaryotic diversity
- even at excessively high temps - therefore high density translates into fact that living in these high temps, some organisms use nitrogen metabolism, others use sulfur metabolism, diverse in terms of where they live & enzymes & wastes they produce etc. that translate into what these organisms will look like when they’re growing
- Both Archaea and Bacteria are represented (proks, but at extreme temps its mostly archaea)

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39
Q

Thermophiles:

A

organisms with growth temperature optima between 45oC and 80oC (more mediocre than hyperthermophiles)
• Terrestrial hot springs, very active compost –> nutrient rich, therefore more metabolism, more to eat, means more diversity which means more metabolic activity, which produces heat as a waste product
- fact its so metabolically rich due to all the nutrients, that’ll produce a ton of heat selectively for organisms that like higher temp

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40
Q

Hyperthermophiles:

A

organisms with optima greater than 80oC
• Inhabit hot environments, including boiling hot springs and seafloor hydrothermal vents that can experience temperatures in excess of 100oC (breaking H-bonds holding molecules together & you get phase change to gaseous state - water remains liquid - imp. b/c water is a polar solvent & so it must be liquid for cell activity)
• Current temperature maximum record is held by an archaeon, Methanopyrus kandleri, which can grow at 122oC
- wouldn’t be destroyed by an autoclave

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41
Q

Excess of 100oC (hyperthermophiles):

A

breaking H-bonds holding molecules together & you get phase change to gaseous state - water remains liquid - imp. b/c water is a polar solvent & so it must be liquid for cell activity

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42
Q

Autoclave

A

used to sterilize material

combines temp & pressure so water remains as steam @ 121 degrees celsius (necessary to achieve sterilization)

destruction of all life, viruses & ENDOSPORES (can tolerate envir extremes)

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43
Q

Sterilize definition

A

destruction of all life, viruses & ENDOSPORES (can tolerate envir extremes)

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44
Q

Current temperature maximum record is held by an archaeon, Methanopyrus kandleri, which can grow at 122oC

Can it be destroyed by an autoclave?

A

NO - autoclave is 121 degrees celsius

- but it won’t grow in many places

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45
Q

Where should you check for antibiotics?

A

check for antibiotics in a place you know that temp & envir is v. unique, microbial diversity will be characteristic of that place, so what might this organism be producing that might be of use to us

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46
Q

Describe the water column and vent

A

b/c of this pressurization of this water so far down the surface of earth, it makes a situation where even if water tends to boil under atmospheric pressure, under this high level of pressure the water molecules are forced into close proximity to 1 another
- even though heat will make them wanna move more, they’re so close to each other that they form a H-bond so it stays in a liq state as a result

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47
Q

Molecular adaptations to thermophily

A

• Specific modifications provide thermal stability to enzymes and proteins
• Modifications in cytoplasmic membranes to ensure heat stability
- Bacteria have lipids rich in saturated fatty acids
- Archaea have lipid monolayer rather than bilayer

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48
Q

Modifications in cytoplasmic membranes to ensure heat stability

What do bacteria have?

A

Bacteria have lipids rich in saturated fatty acids

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49
Q

Modifications in cytoplasmic membranes to ensure heat stability

What do archaea have?

A

Archaea have lipid monolayer rather than bilayer (space = no VdWs there)

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50
Q

Hyperthermophiles produce

A

enzymes widely used in industrial microbiology
• Example: Taq polymerase used to automate the repetitive steps in the polymerase chain reaction (PCR) technique
• Hydrolytic enzymes including proteases, cellulases and lipases

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51
Q

Taq polymerase

A

used to automate the repetitive steps in the polymerase chain reaction (PCR) technique
- b/c enzyme required to separate strands & applies heat for destruction
• Hydrolytic enzymes including proteases, cellulases and lipases
- needed for normal destruction of organic material

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52
Q

Enzymes of thermophiles are…

A 
more stable (b/c functioning under excessive characteristics) and tend to have higher activity than their mesophilic counterparts
*rxn rates can be increased by increased temperature
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53
Q

Rxn rates can be increased by…

A

increased temperature

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54
Q

Rxn rates can be increased by increased temperature

In our cell we could never do this b/c…

A

it would be disruptive & if you turn up the temp, you turn up all the rxns
- whereas an enzyme will more specifically be ablel to turn up some & not others

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55
Q

What are the upper temperature limits for life?

A
  • New species of thermophiles and hyperthermophiles are still being discovered
  • Laboratory experiments with biomolecules suggest 140–150°C (may be able to isolate an organism - imp. b/c you might run into lifeforms at high temps like hot springs, allows us to understand more about complexes that these organisms are able to generate & more about if theres antibiotics there that would’ve been ignored)
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56
Q

Describe the cap or limit where bacteria & archaea can grow

A

bacteria start at around 60 degrees celsius & cap at around 100 degrees celsius

archaea start at around 80 degrees celsius & cap at around 125 degrees celsius (therefore higher ceiling & floor –> higher temp limits)

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57
Q

Hyperthermophiles may be the closest descendants of…

A

ancient microbes

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58
Q

Hyperthermophiles may be the closest descendants of ancient microbes

Explain

A
  • Hyperthermophilic Archaea and Bacteria are found on the deepest, shortest branches of the phylogenetic tree
  • The oxidation of H2 is common to many hyperthermophiles
  • May have been the first energy-yielding metabolism
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59
Q

Evolution and Hyperthermophily

Describe

A

Thermophilic Phototrophy - until 73 degrees celsius

Thermophilic Chemoorganotrophy (use organic chemicals) - until 110 degrees celsius

Thermophilic Chemolithotrophy (use inorganic chemicals) - until 122 degrees celsius

all cross over until 73 degrees celsius

at 95 degrees celsius - elemental sulfur & reduced iron is used for nutrients

H2 - energy poor but abundant - used to support organisms like prok. that have v. low energy demands (considered on early earth as a potential nutrient source for the earliest of life forms)

60
Q

Elemental sulfur, Reduced Iron & H2 are restricted energy availability vs. organic chemicals (b/c heavily reduced) BUT

A
  1. Small - simple prok. organisms

2. Eat more (even though H2 is poor in terms of energy, but eat more)

61
Q

The pH of an environment greatly affects…

A

microbial growth

62
Q

Some organisms have evolved to grow best at…

A

low or high pH

63
Q

Most organisms grow best between pH 6 and 8 –>

A

neutrophiles

    • cause problems inside our body
  • have medical relevance
64
Q

Acidophiles

A

• Organisms that grow best at low pH (<6)

can vary pH - etc. 5.5, 5, 2 etc.

65
Q

Alkaliphiles

A

• Organisms that grow best at high pH (>9)

can vary pH - 10.5, 10, 9.5 etc.

66
Q

What is our pH?

A

pH = 7.35 ish (with exceptions)

67
Q

pH affects…

A

protein/lipid structure etc.

68
Q

Describe protein molecules inside body that can oscillate b/t…

A

pH ~ 2.2
COOH -> COO-
COOH cannot form ionic bonds
COO- can form ionic bonds (to hold a protein together)

pH ~9.6
NH3+ -> NH2
NH3+ can form ionic bonds (to hold a protein in a certain shape)
NH2 cannot form ionic bonds

69
Q

As you change the pH, it has dramatic effects on…

A

chemical structure, proteins & other molecules & those dramatic effects on chemical structure translate into ability/inability to form a bond
- if you needed to form a bond & lost an ability b/c of pH change, these are substantial effects

70
Q

As pH changes…

A

charge changes, & changes are critical in formation of ionic bonds, which will then be associated with shape & consequently the function of the protein (ex ability to recognize substrate if its an enzyme, ability to transport nutrient if its an integral mem. protein etc.)

71
Q

Can manipulate organisms by using pH extremes

Same in body:

A
  • stomach pH ~1-3 based on if food is present b/c it serves as a buffer gastric juice has hydrochloric acid which is a pH of 1
  • serves to protect you against incoming microbes present on food
  • vaginal pH ~4.5 - protects against sexually transmitted infection
72
Q

The bottom line in the different adaptations is that:

A
  • The cytoplasmic membrane MAINTAINS ITS INTEGRITY at the growth pH
  • The internal pH of a cell must stay relatively close to neutral even though the external pH is highly acidic or basic

(1. mem. with structural integrity, 2. mem. with functional capacity - mem. must still be able to bring nutrients in & out & stabilize at these pH conditions (no repulsion), integral mem. proteins still need to be able to insert into the mem.)

73
Q

Microbial culture media typically contain…

A

buffers to maintain constant pH

- neutralizes acid or base produced as metabolic waste!

74
Q

Each organism has an optimal pH for growth

A

Some bacteria produce acids
• Acetic, lactic, sulfuric acid –> decreases the pH

Some bacteria grow on amino acids
• Releases ammonia –> increases the pH

75
Q

Microbial culture media typically contain buffers to maintain constant pH
• Each organism has an optimal pH for growth

Some bacteria produce acids

A

Acetic, lactic, sulfuric acid –> decreases the pH

buffer & GM can offset this

76
Q

Microbial culture media typically contain buffers to maintain constant pH
• Each organism has an optimal pH for growth

Some bacteria grow on amino acids

A

Releases ammonia –> increases the pH

buffer & GM can offset this

77
Q

If its living in low pH envir., what does it mean is in high [ ] outside cell? & what will they want to do in terms of rules of diffusion?

A

protons - rush in & acidify cytoplasm (bad), so must have way to keep inside (cytoplasm) neutral regardless of outside!

78
Q

If organism is neutrophile pH is…

A

~6-8

79
Q

If organism is acidophile, what EC characteristic do you anticipate?

A

low - pH ~ acidic <6

80
Q

If organism is alkaliphiles pH is…

A

> 8 ~basic

81
Q

What is the point about external envir.? What does it mean?

A

Doesn’t matter what external envir. is gonna be, inside cytoplasm it has to stay neutral despite what they can tolerate outside
- means they have to have elaborate mech’s to be able to pump out acid if they’re acidophilic, b/c acidophilic organisms are gonna have a lot of H+ outside - it’ll have a tendency for the protons to move in & acidify the cytoplasm & that’s where they must have some mode in place to protect against that to make sure that it doesn’t happen

82
Q

Ex with carton of milk & how its similar to growth media:

A
  • lot of lactose naturally present
  • microbes can do lactic acid fermentation, as they ferment lactose in milk, they start to build up acid & that acid will start to restrict their own growth (AKA own poop is poisonous to them & serves to arrest their activity)

growth media can have similar situation take place
- our responsibility as experimenters to add a buffer that’ll mop up that acid being produced, so it doesn’t serve to inhibit the success or growth of organism

83
Q

Ex: Alaline

Also, if it’s come together with a protein, what has it done to surrounding medium?

A

organism can use this as nutrient source b/c it has C as part of its backbone

  • BUT in order to feed this AA into something like cellular respiration, you have to do a deamination rxn (cleave off NH3 group), C framework is left behind & can be catabolized to make ATP
  • amino group (NH3) can come together with a H+ & form NH4+
  • if it’s come together with a protein, what has it done to surrounding medium?
  • less acidic (more basic) - b/c buffered protons that’s been around
84
Q

Water activity (aw):

A

water availability; expressed in physical terms (HOW MUCH WATER IS AVAIL. FOR CELL TO USE)
• Defined as the ratio of vapor pressure of air in equilibrium with a substance or solution to the vapor pressure of pure water
• Reflects the amount of water that is interacting with ions and polar compounds in solution

cell is 60-80% water

85
Q

Water is a polar solvent, explain

A

indicates it has partial + & partial - that exist throughout molecule to provide favourable int. with things like ions & polar monomeric molecules like AA, fructose, galatose, lactose
- so this molecule can provide solubility to that, keep it in solution so you don’t have chunks, but instead have flow

86
Q

Typically, the cytoplasm has a ____ solute concentration than the surrounding environment

A

HIGHER

• Water will want to move into the cell creating turgor pressure (from [low] –> [high])

SWELLS

  • if its a bacterium, they have a cell wall that can provide protection against rupture, but when it swells you have opp. to burst depending on how much water rushes in
87
Q

When a cell is in an ENVIRONMENT with a higher external solute concentration water will flow ___

A

OUT

  • cell SHRIVELS/DEHYDRATES as a conseq. of water loss

• Cells can sometimes have mechanisms in place to prevent this
- more adaption they have, more likely they’ll be to survive a partic. set of circumstances which will be beneficial to the cell

88
Q

Typically, the cytoplasm has a higher solute concentration than the surrounding environment

Reason this is a fair assumption for living cells (prok. especially b/c they are small compared to Euk cells):

A
  • volume is a characteristic of [ ] & since the cell will have a lot of solutes in such a small amount of volume, the [ ] in inevitably high
  • whereby, the ECF is gonna have solutes, but volume will be low by comparison
89
Q

Our blood/ECF/cytoplasm/most cytoplasm has a ___% NaCl =

A

0.9

ISOTONIC

90
Q

Halophiles:

A

grow best at reduced water potential; have a specific requirement for NaCl
• Many marine microbes - live in salt H20

LOVING OF SALT
- loss a lot of water b/c of high concentrated envir. & that’s how they thrive best

91
Q

Halophiles:

A

grow best at reduced water potential; have a specific requirement for NaCl
• Many marine microbes - live in salt H20

LOVING OF SALT
- loss of water b/c of high concentrated envir & that’s how they thrive best

92
Q

Extreme halophiles:

A

Require high levels of NaCl for growth
- has compacity to hold its water under these conditions
- has to have mech. in place to prevent dehydration
• 15–30% (can handle 3x NaCl compared to us (0.9%)
• Ex) Microbes from Great Salt lake or the Dead Sea

93
Q

Halotolerant:

A

can tolerate some reduction in water activity of environment but generally grow best at lower solute concentrations
• Ex) Staphylococcus aureus
• Lives on human skin
• Grows best at low NaCl (optimum is low)
• But can tolerate up to 17.5% (what a normal organism would consider isotonic)

94
Q

Are these optimal conditions according to the growth rate with respect to NaCl the only condition that you need to consider when you discuss the organism & its ability to reach its max growth?

A

NO - have to be cognizant of temp, pH, nutrition have to be met in order to achieve this

95
Q

Osmophiles:

A

• Organisms that grow with high sugar as solute

96
Q

Xerophiles:

A

• Organisms able to grow in very dry environments (v. lil water avail)

97
Q

Specialized and rare organisms

A

• Honey, jams and jellies do not have many organisms growing in them
- don’t need to be refrigerated - v. hypertonic envir., water lost from those organisms to the surroundings & won’t be able to continue
• Beef jerky and salted cod
- not refrigerated b/c its so concentrated, that any contaminants that made their way in are not gonna be able to cause spoilage b/c its so salty that they’ll immediately dehydrate

98
Q

High osmolarity created with NaCl (EC) is used to select for…

A

acid producing microorganisms

99
Q

High osmolarity created with NaCl is used to select for acid producing microorganisms

A
  • Used for sauerkraut and pickle fermentation
  • Combination of high salt and low pH prevents the growth of most pathogens in the completed product

AKA organisms tha can handle really concentrated EC envir. are often also associated with acid production (i.e. tolerate high salts & also metabolically produce acid as a waste product)
- then these organisms will decrease pH of surroundings

*- outcome: organism is gonna be collectively controlling for growth & pathogen (decrease pH will occur & pathogens that cause disease don’t grow)

100
Q

What is the outcome of “High osmolarity created with NaCl is used to select for acid producing microorganisms”?

A

outcome: organism is gonna be collectively controlling for growth & pathogen (decrease pH will occur & pathogens that cause disease don’t grow)

101
Q

Osmophiles, Xerophiles, Specialized and rare organisms & High osmolarity created with NaCl is used to select for acid producing microorganisms are…

A

Extracellular conditions (AKA environment)

102
Q

Mechanisms for combating low water activity in surrounding environment involves increasing the internal solute concentration by:

A

anything that creates an internal envir. that’s more isotonic - but don’t wanna introduce another prob. for yourself

• PUMPING INORGANIC IONS from environment into cell
- which is making cytoplasm more isotonic relative to surroundings - making an effort to hold water inside the cell as a result of this beh.

OR

• SYNTHESIZING OR CONCENTRATING ORGANIC SOLUTES

  • COMPATIBLE SOLUTE: compounds used by cell to counteract low water activity in surrounding environment
  • which will not upset or affect function of the cell - will not screw up concentration gradient that might be critical for something else
  • imp. that whatever is being brought in to offset loss of water, will not upset something else
103
Q

Compatible solutes:

A

compounds used by cell to counteract low water activity in surrounding environment

104
Q

Describe the sections of the test tube/the zones & thioglycolate broth

A

oxic zone - coloured production in medium indicates the presence of O2

thioglycolate broth - reducing medium that converts O2 into a reduced end product

anoxic zone - coloured production indicates the absence of O2

105
Q

Oxic zone

A

coloured production in medium indicates the presence of O2

106
Q

Thioglycolate broth

A

reducing medium that converts O2 into a reduced end product

107
Q

Anoxic zone

A

coloured production indicates the absence of O2

108
Q

Inoculate with bacterium of interest

Obligate anaerobe

A
  • poisoned by O2 (all at bottom)

- fermentation or anaerobic respiration to produce ATP

109
Q

Inoculate with bacterium of interest

Obligate aerobe

A
  • not poisoned by O2 (all at top)

- aerobic respiration to produce ATP

110
Q

Inoculate with bacterium of interest

Aerotolerant

A
  • not poisoned by O2 (no desire to go where O2 is or isn’t –> equally distributed)
  • they do not have ETC (meaning they cannot use O2, therefore any respiration is impossible)
  • so they can only use fermentation to produce ATP
111
Q

Inoculate with bacterium of interest

Microaerophile

A
  • poisoned by O2 BUT needs O2 for cell respiration (right below oxic zone)

use O2 for cell respiration, but O2 is NOT in high enough [ ] that it’ll ever accumulate to create the poisonous affects that the cell would otherwise experience so that’s why its there
- as soon as O2 comes in through ETC (located in PM of prok cells), it’s used & converted to H20

112
Q

What would happen if Microaerophile organisms (right below oxic zone) localize itself a lil bit higher in the test tube?

A

they’d die b/c O2 [ ] inside the cell would accumulate higher & cause poisonous affect & cell wouldn’t be capable of survival under those conditions

113
Q

Inoculate with bacterium of interest

Facultative aerobe

A

prefers oxic zone
- CAN SWITCH

  • not poisoned by O2
  • use cell respiration or fermentation to produce ATP
  • prefer O2 b/c ATP yield is way higher
114
Q

Obligate aerobes:

A

require oxygen to live

115
Q

Strict anaerobes:

A

do not require oxygen and may even be killed by
exposure
- poisoned by O2 presence, therefore stay far away from it

116
Q

Facultative aerobes:

A

can live with or without oxygen, they use oxygen when it is available
- not killed by O2, but prefer to use O2 if present b/c it allows for maximization of energy production for each substrate used (more energy yield) within the catabolic pathway

117
Q

Aerotolerant anaerobes:

A

can tolerate oxygen and grow in its presence even though they cannot use it (b/c they lack an ETC)

  • therefore, solely restricted to fermentation as a means of satisfying their energy requirement
  • no poisonous effects with O2
118
Q

Microaerophiles:

A

can use oxygen only when it is present at levels reduced from that in air

  • but poisoned by it as well (need it, but can’t handle it so they satisfy themselves in low concentration)
  • live at a part of the tube where O2 is avail., but O2 is minimized, therefore satisfies just their needs without creating a toxic effect
119
Q

Differences in oxygen use/tolerance can be distinguished using thioglycolate broth:

A
  • Complex medium (not defined) that separates microbes based on oxygen requirements
  • Thioglycolate reacts with oxygen creating an anaerobic environment
120
Q

Thioglycolate reacts with oxygen creating an anaerobic environment…

A
  • Oxygen can penetrate only the top of the tube
  • Contains an oxygen responsive dye that turns pink in the presence of oxygen and colorless when the oxygen is low or absent

thioglycolate - chemical that’ll eliminate O2 & force the tube to become anaerobic, especially within certain regions

121
Q

Describe oxic & anoxic zone in water column

A

oxic zone - at top area of water b/c non-polar attribute of O2 gas only allows it to reach in equil. here

anoxic zone - as you start to go lower down within water column - its anoxic b/c O2 polarity makes it not interact favourably with the polarity of the water
- b/c its anoxic, any organism that’ll be in this region will be microaerophilic (gets best of both worlds to be able to cater to its own needs)

122
Q

Obligate aerobe

Where does it grow?

A

grows only in the oxic zone at the top of the tube

123
Q

Strict anaerobe

Where does it grow?

A

grows only in the anoxic zone at the bottom of the tube

124
Q

Facultative anaerobe

Where does it grow?

A

grows throughout the tube
• Better growth occurs in the oxic zone, where it can generate energy by aerobic
respiration

125
Q

Microaerophile

Where does it grow?

A

grows in a narrow band between the oxic and anoxic zones
• Needs O2 for aerobic respiration
• Killed by atmospheric O2 levels

126
Q

Aerotolerant anaerobe

Where does it grow?

A

grows well throughout the tube
• Doesn’t use O2
• Not harmed by O2

127
Q

What is needed to grow ANAEROBIC microbes? Why?

A

Special techniques are needed to grow anaerobic microbes

  • b/c if an infection is anaerobic it’s understood that collectively that sample & exposing it to O2 is gonna kill your organism
  • when you get it to a lab later, you anticipate the organism isn’t gonna grow b/c its been killed off by the O2 concentration
  • therefore, have to be aware of this & collect sample properly or else it won’t make it to lab for further study, diagnosis etc.
128
Q

What special techniques are needed to grow ANAEROBIC microbes?

A

Reducing agents may be added to culture media to reduce oxygen
- take O2 & add e-‘s (e- donor, therefore reducing agent) to it & form H20 for ex which is benign - gets rid of poisonous O2 this way & water is no problem –> method of O2 removal to support anaerobes
• Ex’s: Thioglycolate (create anaerobic envir. in test tube of broth), cysteine (AA that can donate e’s from its R group), H2S and other sulfur containing compounds

Removal of air, and replacement with an inert gas
- remove ordinary atmospheric components from the top of this container & replace with inert gas to occupy space but not create unfav. activity)
• Ex) nitrogen or argon
OR anaerobic chamber - hands go in to allow you to work
- envir. present within chamber has been created such that theirs no O2 so it’ll continually support an organism that can’t handle O2 well

129
Q

Reason O2 is so toxic is b/c it has…

A

an oxidizing capacity

130
Q

Several toxic forms of oxygen can be formed spontaneously in the cell:

A
  • Superoxide anion - HIGHLEY REACTIVE
  • Hydrogen peroxide - FORMS HIGHLY REACTIVE MOLECULES (indirect)
  • Hydroxyl radical - HIGHLEY REACTIVE

worried about these

called ROS - reactive oxygen species

131
Q

ROS

A

reactive oxygen species

132
Q

Superoxide

A

O2 + e- –> O2-

  • O2 present in atmosphere has capacity to come together with a free e-
  • O2- unpaired e-
  • tendency to form this reactive O2 species is problematic b/c it has an unpaired e- - therefore, desperate to pair it off (think: desperate to find relationship - nothing good will happen)
  • will interact with DNA, protein, mem., & causes mutation (changes to chemical structure that can lead to changes in the function)
  • dangerous b/c of high reactivity - desperation to pair off the e-
133
Q

Hydrogen peroxide

A

O2- + e- + 2H+ –> H2O2

  • superoxide radical chooses to pair its e- with another e- avail. in a form of H atom & forms H202
    think: satisfying 1 alarm, but fix with another alarm inducing molecule
134
Q

Hydroxyl radical

A

H202 + e- + H+ –> H20 + OH

H2O2 is effective of healing wound b/c it pairs with e-‘s in form of H atoms & forms hydroxyl radicals (like superoxides b/c desperate to engage or beh. with other species present)

135
Q

OH + e- + H+ –> H20

A

water

take unpaired e- of hydroxyl & combine with H atom which contains an e- & form water (benign)

136
Q

Enzymes are present to neutralize most of these toxic oxygen species:

A
  • Catalase
  • Peroxidase
  • Superoxide dismutase
  • Superoxide reductase

enzymes that have opp. to provide protection to organisms that can tolerate O2 (should have some combo to ensure survival is possible)

137
Q

Most obligate anaerobes lack some or all of these enzymes…

A

They don’t have a mechanism to combat OXIDATIVE STRESS - so they stay away from O2 to survive & molecules don’t suffer mutation & destructive effects from these species & able to produce less amounts of energy then if they could use O2 but at least they’ll be alive

think: someone putting book in front of fist so you’re not able to get punched & have damage to organs b/c something else bore the brunt of the punch

What we can do inside our cell when we have the potential to suffer damage from O2:

  • we can grab NADH (reduced) (book)
  • now instead of O2 causing damage to DNA through its radical formation to proteins etc.
  • you form H20 & NAD+
  • protect abdominal organs by consuming NADH that took punch instead - protected DNA & other critical cell structures by using an NADH equivalent in order to be able to undergo oxidation in expense of O2 reactivity

O2 + NADH –> NAD+ + H20

138
Q

What does NADH turn into inside your cell? It’s a reduced e- carrier, but what do we dedicate NADH to when we consider cellular activity?

A
  • NADH turns into ATP in ETC by giving off its high energy e-‘s
  • therefore, in this case you’re using what would’ve been ATP & instead using it to eliminate O2 that would’ve been causing problems inside cell, consuming it but protecting vital components in cell - imp. to us
139
Q

Catalase

A

H202 + H202 –> 2H20 + 02

- consumes 2 equivalents of H202 & produces benign things (well tolerated)

140
Q

Peroxidase

A

H202 + NADH + H+ –> 2H20 + NAD+

  • takes same H202 as catalase
  • put book in front of molecule (NADH equivalent together with H202)
  • H202 is aggressively oxidizing & NADH donates its e-‘s –> form H202 (benign) & NAD+ (empty e- carrier, which is now recyclable & able to be used in glycolysis, krebs & intermediate step to collect more e-‘s again)
  • but in doing so you: THEORETICALLY CONSUME 2.5 ATP = NADH’s worth in the ETC
  • b/c NADH can’t go to ETC anymore
141
Q

What is the same for Catalase & Peroxidase & what is diff.?

A

SAME - deadly reactant (H202)

DIFF - put book in front of molecule (NADH equivalent together with H202)

142
Q

Superoxide dismutase

A

O2- + 02- + 2H+ –> H202 + 02

  • consumes 2 “deadly” O2 equivalents (reactants we’re trying to eliminate from cell) & produces another alarm (H202)
  • you got rid of O2 equivalents which is good, but then you have to deal with H202…
143
Q

Superoxide dismutase/catalase in combination

A

402- + 4H+ –> 2H20 + 302

  • take 2 equivalents of superoxide & form H202
  • then you have catalase (another enzyme in combo)
  • takes 2 equiv. of H202 & finally are relieved (nothing bad from that rxn)
144
Q

Superoxide reductase

A

02- + 2H+ + rubredoxin(reduced) –> H202 + rubredoxin(oxidized)

  • O2 works with rubredoxin (reduced)

rubredoxin (reduced) is analogous to: NADH (book) - reduced form & has opp. to donate its e-‘s to O2 radical

H202 - another alarm b/c it poses problem inside cell again

rubredoxin (oxidized) is oxidized with its e-‘s
- e’s are on O2

145
Q

These are enzymes. Where do we get enzymes from? How do we have the opp. to make an enzyme or have it present in cell in the 1st place? Ex: catalase & peroxidase

A
  • encoded within the genome or present on a plasmid, chromosome, mobile element (somewhere within genetic makeup)
  • allows cell to tolerate O2 b/c it has the recipe to make the enzyme
    • if you don’t have recipe to make enzyme is when you have a problem

Microbiology 1 (15 decks)

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