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Microbio > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

bacterial nutritional categories are based on

A

how cells get energy, electrons, and carbon

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2
Q

use reduced, pre-formed organic molecules as their carbon source

ex: us many bacteria

A

heterotrophs

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3
Q

use CO2 as their carbon source

A

autotrophs

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4
Q

most autotrophs are

A

photosynthetic organisms

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5
Q

what are typical problems with carbon dioxide as a carbon source

A
  • lacks hydrogen
  • most oxidized form of carbon
  • cannot be used as a source of protons, electrons, or energy
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6
Q

chemical energy
organic e- source
organic carbon source

A

chemoorganoheterotroph

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7
Q

chemical energy source
organic electron source
inorganic carbon source

A

chemoorganoautotroph

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8
Q

chemical energy source
inorganic electron source
organic carbon source

A

chemolithoheterotroph

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9
Q

chemical energy source
inorganic electron source
inorganic carbon source

A

chemolithoautotroph

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10
Q

light energy source
organic electron source
inorganic carbon source

A

photoorganoautotroph

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10
Q

light energy source
organic electron source
organic carbon source

A

photoorganoheterotroph

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11
Q

light energy source
inorganic electron source
organic carbon source

A

photolithoheterotroph

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12
Q

light energy source
inorganic electron source
inorganic carbon source

A

photolithoautotroph

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13
Q
  • required in relatively large amounts
  • C, O, H, N, S, and P (carbs, lipids, proteins, and nucleic acids)
  • ions such as sodium, potassium, calcium, magnesium, iron, and chloride ions
A

macronutrients / macroelements

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14
Q

roles of ionic macroelements

A

enzyme cofactors, osmotic balance, ATP synthesis, etc

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15
Q
  • required in very small amounts
  • act as enzyme cofactors
  • Mn2+, Zn2+ Co2+, Mo2+, Ni2+, Cu2+
A

micronutrients / trace elements

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16
Q

we need electrons for

A

biosynthesis and metabolic pathways

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17
Q

organotrophs get their electrons from

A

reduced organic molecules (e.g. glucose)

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18
Q

lithotrophs get their electrons from

A
  • water, reduced inorganic molecules (sulfur, iron, nitrogen-based molecules, ferrous iron, ammonia, hyddrogen sulfide)
  • “rock eaters”
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19
Q

capture energy from oxidation or organic or inorganic compounds/chemicals

A

chemotrophs

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20
Q

capture light energy to produce ATP

A

phototroph

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21
Q
  • occurs when pre-formed bacterial toxins are ingested
  • pathogen doesn’t grow in host, symptoms occur quickly
A

foodborne intoxication

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22
Q
  • natural reservoir in soil
  • home-canned foods, baked potatoes in foil
  • inhibits synaptic vesicle fusion in motor neurons by targeting SNARE proteins in motor neurons
  • paralysis and respiratory failure
A

Clostridium botulinum (botulism)

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23
Q
  • main reservoir is nasal cavities
  • high protein foods: meat and dairy
  • extracellular enterotoxins
  • nausea, vomiting, cramps
A

Staphylococcus aureus

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24
Q

how does C. botulinum impact SNARE proteins in motor neurons

A
  • if the SNARE protein is not synthesized or turned on, acetylcholine is not secreted, and therefore no muscle contraction occurs
  • can lead to flaccid paralysis –> death
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25
Q
  • found in raw oysters
  • 10^8 ingested cells for illness
  • marine organism
  • incubation time 6-96h
A

Vibrio parahaemolyticus

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26
Q
  • from under or uncooked poultry (half of sold poultry)
  • < 10 ingested cells can cause illness
  • symptoms arise in 2-5 days
A

Campylobacter jejuni

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27
Q
  • very common
  • disease lasts 1-2 days, includes vomiting, diarrhea, abdominal pain
  • infection rates highest under crowded conditions
  • incubation time: 12-48h
A

norovirus

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28
Q

occur via ingestion of pathogen followed by growth in intestines

A

food-borne infections

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29
Q
  • most pathogens
  • organic carbon source (C, O, H), energy source, and e-
A

chemoorganoheterotrophs

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30
Q
  • cyanobacteria, sulfur bacteria
  • more flexible in metabolism
  • CO2 as carbon, light energy source, inorganic e- source (H2O)
A

photolithoautotrophs

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31
Q
  • comprised of catabolism and anabolism
  • all of the chemical reactions in an organism
A

metabolism

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32
Q

breaking down large molecules into smaller molecules and releasing energy

A

catabolism

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33
Q

building biomolecules from precursors using energy

A

anabolism

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34
Q

aspects of metabolism are common to all organisms

A
  1. life obeys the laws of thermodynamics
  2. energy cells obtain from their environment is often conserved as ATP
  3. redox rxns play a critical role in energy conservation
  4. chemical rxns that occur in cells are organized into pathway
  5. each rxn of a pathway is catalyzed by an enzyme
  6. functioning of biochemical pathways is regulated
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35
Q

why is the catalysis of each reaction of a pathway by an enzyme so important

A

critical for survival because enzymes decrease activation energy

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36
Q

laws of thermodynamics

A

energy is only transformed not created or destroyed

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37
Q

living organisms need energy to build

A

biomass

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38
Q

bacterial growth biomass depends on

A

energy change of catabolic rxns

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39
Q

dG (Gibbs free energy) depends on

A

the enthalpy and entropy changes associated with the rxn

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40
Q
  • acquired thru meat, fruits, veggies
  • ~500 cells ingested can cause illness
  • 3-4 day incubation pd
  • vomiting, diarrhea, and/or fever
A

E. coli 0157:H7 (acquired Shiga toxin)

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41
Q

how does the Shiga toxin work?

A
  • cleaves rRNA, blocking protein synthesis
  • binds receptors on kidney and blood vessel cells causing bloody diarrhea and kidney failure
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42
Q
  • acquired thru meat, poultry, eggs
  • > 10^5 ingested cells for illness
  • incubation time as short as 8 hours, often longer (12-72h)
  • typhoidal or nontyphoidal
  • g- and bacillus shaped
A

Salmonella enterica

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43
Q

how do we prevent food spoilage

A
  • reduction of water activity
  • acidity
  • chemical preservatives
  • controling temp
  • irradiation
  • modified atmosphere packaging
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44
Q

removes oxygen or floods packaging w/ CO2

A

modified atmosphere packaging

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45
Q

UV, gamma, or X-rays used to kill microbes damaging DNA

A

irradiation

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46
Q

how do we control temperature to prevent food spoilage

A

pasteurization + refrigeration, freezing

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47
Q

intrinsic factors that impact the likelihood of food spoilage

A
  • water availability
  • osmolarity
  • nutrient content
  • pH and buffering capacity
  • antimicrobial constituents
  • biological structures such as rinds or shells
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48
Q

extrinsic factors that impact food spoilage

A
  • temperature
  • humidity
  • presence and concentration of gases
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49
Q

steps to milk spoilage

A
  1. acid production by Lactobacillus fermentation
  2. yeasts and molds degrade the lactic acid
  3. protein-digesting bacteria (cadaverine, putrescine putrefy the milk)
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50
Q

refers to microbial changes that render a product unpalatable for consumption

A

spoilage

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51
Q

acid fermentation products produce what taste

A

sour

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52
Q

alkaline fermentation products produce a what taste

A

bitter

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53
Q

oxidation of fats promotes

A

rancidity

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54
Q

decomposition of proteins promotes

A

putrefaction

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55
Q
  • pathogenic bacteria typically
  • you cannot tell if it will make you sick
A

contamination

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56
Q

consists of visible microbial growth, gross

A

spoilage

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57
Q
  • amino acids, certain ions that increase osmolarity inside cell to prevent water loss
  • help microbes survive high salt environments
A

compatible solutes

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58
Q
  • adapted to salty (3.5%), low water environments
  • ocean, skin surface
A

halophiles

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59
Q

more than 30% salt, use compatible solutes to survive

A

extreme halophiles

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60
Q

a measure of the number of solutes in a solution and is inversely related to water activity

A

osmolarity

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61
Q

more solute =

A

less water activity

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62
Q

more water activity =

A

less solute

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63
Q
  • requires high pressure to grow, though they die at still higher temperatures
  • pressure adapted internal structures, unsaturated membrane lipids
  • greater than 380 atm
A

barophiles

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64
Q

organisms die as pressure increases

A

barosensitive

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65
Q
  • organisms grow to a certain pressure, but die at higher pressure
  • 10-500 atm
A

barotolerant

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66
Q
  • cannot eliminate ROS
  • die in presence of oxygen, cannot use or be near
  • (-) SOD, - Catalase, - Peroxidase

ex: Clostridium

A

strict anaerobe

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67
Q
  • grow oxygen using anaerobic metabolism
  • can’t use oxygen but don’t care, aren’t harmed by oxygen but don’t use it
  • (+) SOD, + Catalase or Peroxidase

ex: Lactobacillus

A

aerotolerant aerobes

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68
Q
  • can live without oxygen
  • can use oxygen or not, grow best in oxygen but can grow anaerobically
  • (+) SOD, + Catalase, + Peroxidase

ex: E. coli

A

facultative anaerobe

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69
Q
  • grow only at low O2 concentrations
  • use oxygen, grow best when there is 2-10% oxygen
  • (+) SOD (low levels), + Catalase, - Peroxidase

ex: Streptococcus

A

microaerophiles

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70
Q
  • can only grow oxygen is available, absolute requirement
  • grow in atmospheric oxygen (20%)
  • (+) SOD, + Catalase, + Peroxidase

Ex: Pseudomonas

A

obligate aerobes

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71
Q

the production of reactive oxygen species (ROS) often begins w/

A

FAD moving an electron to oxygen

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72
Q

generate ROS

A
  • superoxide radical union
  • hydrogen peroxide
  • peroxide radical
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73
Q

enzymes reactions that destroy ROS

A
  • superoxide dismutase (H2O2 into hydroxide radical)
  • catalase (H2O2 into water and oxygen)
  • peroxidase (H2O2 into water and NAD+)
74
Q
  • much more efficient for ATP synthesis
  • uses oxygen as an FEA
A

aerobic respiration

75
Q

use non-oxygen molecules as a final electron acceptor

A

anaerobic respiration and fermentation

76
Q

out of which methods of respiration use ATP most efficiently (most to least)

A

aerobic > anaerobic > fermentation

77
Q
  • rely heavily on sodium ion gradients
  • growth above pH 9
A

alkaliphiles

78
Q
  1. respiratory chain pumps H+
  2. H+ import through F1F0 ATP synthase drives ATP synthesis
  3. Na+ driven ATPases export Na+
A

Na+ transport gradient

79
Q

sodium ion motive force powers

A
  • motility
  • symport of some substrates
  • pH homeostasis
80
Q
  • altered membrane lipids to prevent protons from leaking out of the cell
  • reliance on Na+ gradients
A

alkaliphiles

81
Q
  • altered membrane lipids that decrease proton permeability
  • contains ill-defined proton extrusion mechanisms
  • thrive in lower pHs
  • growth below pH 3
A

acidophiles

82
Q

what is a con of having a high proton concentrated environment

A

protons can leak into the cell and damage enzymes

83
Q

what is a con of having a low proton concentrated environment

A

really hard to build proton motive force

84
Q

most enzymes function best between pHs of

A

5-8.5

85
Q
  • live in fridges
  • optimum around 15 degrees Celsius (below 15 degrees C)
  • more flexible proteins (glycines) and unsaturated membrane lipids
A

psychrophiles

86
Q
  • most like us
  • pathogens, human microbiota
  • have an optimum temperature of about 35 degrees Celsius (15-45 C)
A

mesophiles

87
Q
  • have an optimum temp of about 60 degrees Celsius (50-80 C)
A

thermophiles

88
Q
  • often archaea
  • saturated membrane lipids, archaeal monolayers
  • fewer glycines = more rigid proteins
  • more chaperones
  • optimum temp around 90 degrees Celsius (growth above 80 C)
A

extreme thermophiles

89
Q

help proteins fold

A

chaperone proteins

90
Q

fewer glycines in the membrane =

A

more rigid proteins

91
Q

an organism’s cardinal temperature is influenced mainly by

A
  • enzyme function
  • membrane integrity
92
Q

growth between pH 5 and pH 8

A

neutralophile

93
Q

species specific time for doubling a population (doubling time)

A

generation time

94
Q

bacterial growth phases

A
  1. lag phase
  2. log phase
  3. stationary phase
  4. death phase
95
Q

bacteria are preparing their cell machinery for their growth

A

lag phase

96
Q

growth approximates an exponential curve (straight line, on a logarithmic scale)

A

log phase

97
Q
  • cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability
  • not dying, just arresting growth
  • endospore formation commonly occurs during this phase
A

stationary phase

98
Q
  • cells die with a half-life similar to that of radioactive decay, a negative exponential curve
  • incredibly prolonged and unpredictable
A

death phase

99
Q
  • used to detect bacterial-induced lysis (hemolysis) of RBCs
  • complex and differential
A

blood agar

100
Q

gamma hemolysis

A

no hemolysis / clearing

101
Q
  • partial hemolysis
  • partial clearing
  • bacteria makes hydrogen peroxide that oxidizes hemoglobin
A

alpha hemolysis

102
Q
  • otherwise known as true hemolysis, complete clearing where bacteria was streaked
  • bacteria secrete toxins that lyse RBCs and degrade hemoglobin
A

beta hemolysis

103
Q

brilliant green dye inhibits growth of what bacteria

A

gram positive

104
Q

organisms that ferment are what color on Brilliant Green agar

A

yellow

104
Q
  • distinguishes Gram-negative fermenters form non-fermenters
  • complex, and selective and differential
A

Brilliant Green Agar

105
Q

isolates microbes with specific properties by only allowing certain species to grow

A

selective media

106
Q
  • exploits differences between two species that grow equally well
  • recognize certain microbes based on visual reactions in the medium
A

differential media

107
Q

adds fresh nutrients and removes waste

A

continuous culture

108
Q
  • a closed system for adding specific bacterial in liquid media
  • no nutrients replenished, no waste removed
A

batch culture

109
Q
  • important for studying a single bacterial species
  • a culture in which only one strain or clone is present
A

pure culture

110
Q

liquid growth media

A

broth

111
Q

solid growth media

A

agar

112
Q

considerations we need to have when deciding which type of growth media to use in the lab

A
  • sterilization
  • environmental conditions (i.e. incubation)
113
Q

nutrient rich, poorly defined

A

complex media

114
Q
  • minimal nutrients, known composition
  • useful when we are specifically studying microbial physiology
A

defined media

115
Q

growth media must contain

A
  • sources of energy, carbon, and electrons
  • sources of other macroelements for macromolecules (N, P, S)
  • salts
  • growth factors (amino acids, vitamins, purines, and pyrimidines, etc)
116
Q

acid fermentation of milk produces

A

yogurt and cheese

117
Q

classes of fermentation commonly used in food production

A
  • alkaline fermentation (pidan)
  • acid fermentation of vegetables (kimchi, miso)
  • acid fermentation of dairy products, meat, and fish
  • ethanolic (alcoholic) fermentation (beer, wine, tequila)
  • propionic acid fermentation (bread)
118
Q

fermented foods depend on

A
  • indigenous flora

OR

  • starter cultures
119
Q

purposes of food fermentation

A
  • preservation (by limiting microbial growth)
  • improving digestibility
  • adding nutrients and flavor molecules
120
Q

every fermentation pathway has what happening

A

NADH being reoxidized into NAD+

121
Q
  • an organic molecules is FEA (pyruvate, acetaldehyde)
  • no electron transport chain, allows oxidation of NAD+ thru generation of NADH
  • catabolic
A

fermentation

122
Q
  • used typically in photoorganoheterotrophs
  • a single-protein, light driven protein pump
A

bacteriorhodopsin

123
Q

mechanism of action (in order) of bacteriorhodopsin

A
  1. Retinal, in the all trans form, is covalently attached to the lysine of bacteriorhodopsin; nitrogen to which it is attached is protonated
  2. light absorption causes one double bond to isomerize to the cis form
  3. isomerization of the retinal causes the proton to be lost to the outside
  4. when the retinal spontaneously isomerizes back to the ground state, the lysine is re-protonated from the cytoplasm
124
Q

types of phototrophy

A

chlorophyll-based and rhodopsin-based

125
Q

what types of phototrophs use chlorophyll-based phototrophy

A

photolithoautotrophs

ex: cyanobacteria, green sulfur bacteria, purple sulfur bacteria

126
Q
A
127
Q

capture energy from the sun to create PMF and synthesize ATP

A

phototrophs

128
Q
  • electrons from Fe2+ must be passed up to NADP+ by this
  • the transfer of electrons through the electron transport chain through the reverse redox reactions, requires a lot of energy
A

reverse electron flow

129
Q

use reduced inorganic compounds for energy and electrons

A

chemolithotrophs

130
Q

more energy captured =

A

more ATP synthesized

131
Q

aerobic ETCs pump how many protons across the membrane

A

10

132
Q

anaerobic ETCs pump how many protons across the membrane

A

4

due to nitrate being reduced to nitrite

133
Q

build a proton gradient that is used to make ATP

A

electron transport systems

134
Q

why does anaerobic respiration yield less energy

A

because it uses an FEA with a lower reduction potential than O2

135
Q

a redox reaction is favored by … values of dE, which yields negative values of dG

A

positive

136
Q

ETC components are arranged in order of

A

increasing reduction potential

137
Q

larger E =

A

better electron acceptor

holds e- more tightly, at a lower energy state

138
Q

the amount of energy captured from an ETC depends on

A

the FEA used

139
Q

what does a negative dG value mean

A

bond energy decreases and/or disorder increases, and the reaction will go forward spontaneously

140
Q

a change in enthalpy (bond energy) is favorable if

A

negative

reaction forms molecules with more favorable/more stable/lower bond energy bonds than reactants

141
Q
A
142
Q

what happens when a change in entropy is positive

A

rxn increases disorder

143
Q

which law of thermodynamics states that thermodynamically favorable processes increase disorder

A

2nd law

144
Q

how do we make dG negative?

A
  • change temperature
  • increase concentration of reactants
  • product concentration kept low by removal
145
Q

couples metabolic species across species by removing product by another species

A

syntrophic relationship

146
Q

heterotrophs catabolize carbohydrates through which three main metabolic strategies

A
  • aerobic respiration
  • anaerobic respiration
  • fermentation
147
Q

which pathway of glycolysis is:
* highly conserved
* involves glucose undergoing a 10-step breakdown to pyruvate
* gains energy from the rxn

A

EMP pathway of glycolysis

148
Q
  • unique to bacteria and archaea
  • catabolizes sugar acids (not necessarily glucose, produces NADPH for biosynthesis
  • source of energy and electrons simultaneously
A

ED pathway of glycolysis

149
Q
  • shunts carbon from glucose into biosynthesis
  • a source of carbon and electrons
A

PPP pathway of glycolysis

150
Q

what is the net yield of the EMP pathway of glycolysis

A
  • 2 three carbon pyruvate
  • 2 ATP
  • 2 NADH
151
Q

what is the net yield of the ED pathway of glycolysis

A
  • 2 three carbon pyruvate
  • ATP
  • NADH, NADPH
152
Q

what is the net yield of the PPP pathway of glycolysis

A
  • biosynthesis
  • ATP
  • 2 NADPH
153
Q

if a final electron acceptor is available post-glycolysis, pyruvate is oxidized to

A

Acetyl CoA and enters the citric acid cycle

154
Q

the bacterial glyoxylate shunt requires

A

two additional CAC enzymes

isocitrate lyase and malate synthase

155
Q

benefits of using a glyoxylate shunt

A
  • prevents loss of carbon via carbonn dioxide
  • creates more starting material for biosynthesis
156
Q

In the pentose phosphate pathway, glucose 6-phosphate is oxidized to 6-phosphogluconate, which is then decarboxylated to ribulose 5-phosphate. What is the main metabolic role of this pathway?

A

production of carbohydrates with three to seven carbon atoms, which can be utilized in biosynthesis

157
Q

Identify the oxidant in the following coupled redox reaction: Malate + NAD+ –> Oxaloacetate + NADH + H+

A

NAD+

158
Q

Because the reduction potential of the CO2/glucose redox pair is more negative than the Fe3+/Fe2+ redox pair, energy is released as electrons flow

A

from glucose (the donor) to Fe3+ (the acceptor)

159
Q

For a given electron donor, the most energy will be released when oxygen serves as the final electron acceptor because

A

oxygen is a stronger oxidizing agent than most other electron acceptors.

160
Q

The relationship between the reduction potential, E, and the change in free energy, ΔG is such that if E is ___…______, then ΔG is ____…_____ and the reaction is __…_______

A

positive; negative; unfavorable

161
Q

how is ATP primarily produced in chemolithotrophs

A

Electrons moving through an electron transport system to generate a proton motive force

162
Q

which type of metabolism does not use a membrane-associated ETS

A

fermentation

163
Q

lactic acid is a common fermentation product and is produced when … is reduced by electrons received from NADH

A

pyruvate

164
Q

bacteria that express bacteriorhodopsin protein are typically classified as

A

photoorganoheterotrophs

165
Q

a complex medium is one that

A

is nutrient rich, but the amounts and identity of specific nutrients are unknown

166
Q

which ingredient makes Mannitol Salt Agar a selective medium

A

NaCl

167
Q

which ingredients make Mannitol Salt Agar a differential media

A

mannitol and phenol red

168
Q

How would the growth curve change relative to the curve shown above if you used a medium that was 1 pH unit more acidic than optimal?

A

the slope of the log phase would decrease

169
Q

How would the growth curve change relative to the curve shown above if you diluted the growth medium so that the carbon source is half strength.

A

The cell yield would decrease by half

170
Q

How would the growth curve change relative to the curve shown above if you used an inoculum of exponentially growing cells instead of old cells from the refrigerator?

A

There would be a shorter lag phase

171
Q

How would the growth curve change relative to the curve shown if you omit all nitrogen from the medium?

A

There would be no growth at all.

172
Q

inactivates hydrogen peroxide

A

catalase

173
Q

inactivates superoxide

A

superoxide dismutase

174
Q

utilizes NADH to reduce peroxide

A

peroxidase

175
Q

an organism living under high pressure

A

barophile

176
Q

optimal growth at a pH below 5.5 describes

A

acidophile

177
Q

optimal growth at a pH above 8 describes

A

alkaliphile

178
Q

an organism able to grow over a wide range of solute concentrations is

A

halotolerant

179
Q

an organism that requires high levels of salt

A

halophile

180
Q

mechanisms halophiles typically employ to grow in habitats with high concentrations of salt

A
  • increase internal concentration of organic molecules such as chlorine
  • maintain high intracellular levels of potassium chloride and other inorganic solutes
181
Q

MAP helps to preserve food by

A

removing oxygen from the atmosphere

Microbio (3 decks)

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