3. Microbial Growth and Nutrition Flashcards
1
Q
Macronutrients
A
- elements required in large amounts to build macromolecules
- CHONPS
- make up more than 90% of the dry weight cell
2
Q
Types of macromolecules
A
lipids, carbs, proteins and nucleic acid
3
Q
Proteins
A
- CHON and sometimes S
- polymer made of building blocks
- more than 50% of dry weight
4
Q
Lipids
A
- CHO and sometimes P
- building blocks of fatty acids and glycerol
5
Q
Carbohydrates
A
- CHO and sometimes N
- building blocks of sogars
6
Q
Nucleic acids
A
- CHONP
- building blocks of nucleotides
7
Q
If the macromolecular composition of a cell has a lipopolysaccaride what kind of gram is it
A
gram negative
8
Q
Other macronutrients - inorganic ions
A
K, Mg, Ca, Fe
9
Q
What are inorganic ions used for
A
metabolic cofactors
- used in addition to macronutrients
- its the non-protein component required for enzyme function
10
Q
K+, Fe2+, Mg2+, Ca2+
A
K+ - enzymes for protein synthesis
Fe2+ - cytochromes to carry
Mg2+ - stabilize membranes and nucleic acids
Ca2+ - stabilize cell walls and heat stability for endospores
11
Q
How can you remember all macronutrients?
A
C HOPKNS CaFe Mg - the c hopkins cafe is mighty good
12
Q
Micronutrients
A
- trace elements required in very small amounts
- cofactors for enzyme
13
Q
Growth factors
A
- small organic molecules required for growthh
14
Q
What happens if an organism cannot synthesize a growth factor?
A
it must be added to medium to grow that microbe in the lab
15
Q
Three classes of growth factors
A
- Amino acids
- Purines and pyrimidines
- Vitamins
16
Q
Amino acids
A
needed for protein synthesis
17
Q
Purines and pyrimidines
A
AG - 2 rings
TCU - 1 ring
needed for nucleotides, building blocks of RNA and DNA
18
Q
Vitamins
A
- small molecules used to make organic cofactors
- non-protein components required by some enzymes
19
Q
Growth factor requirements
A
- many have none (E.coli) some require alot (Leuconostoc mesenteroides)
-some may require a medium to promote growth
20
Q
Nutrient sources of O and H
A
- no specific nutrient
- Found in H2O and organic media components
21
Q
Nutrient sources of P
A
- usually a phosphate salt
22
Q
Limiting nutrient
A
In relatively low concentration compared to other nutrients
- when it runs out, growth stops despite other nutrients present
23
Q
Nutrient sources of N
A
- inorganic - salt - reduced to NH3 to make amino acids
- organic - rich organic molecules - doesn’t need to be reduced
- atmospheric N2 - N2 is reduced to NH3 - nitrogen fixation - energy expensive - only bacteria and archaea
24
Q
Nutrient sources of S
A
- inorganic - salt - reduced to S2- to make amino acids - assimilative sulfate reduction
- organic - pre-made amino acids - less energy to assimilate
25
Nutrient sources of C
- Depends on the type of organism
- If heterotrophs - organic carbon (C and H) - 1 or more C is reduced
- If autotrophs - inorganic carbon (CO2) as their sole source of carbon - needed energy to assimilate - photosynthesis
26
Metabolism
the sum total of all the chemical rxns in a cell
27
Catabolic reactions
energy releasing metabolism - break down
- fermentation, respiration
28
anabolic reactions
energy-requiring metabolism - build up
- biosynthesis
29
Microorganisms can be categorized by
1. energy source
2. electron source
3. carbon source
30
energy sources
chemo - chemical
photo - light
31
electron sources
organo - organic
litho - inorganic
32
carbon sources
hetero - pre-existing
auto - inorganic
33
Chemoorganotrophs
energy from chemical reactions involving organic material
34
chemolithotrophs
energy from inorganic chemical reactions
35
36
phototrophs
energy from light
37
heterotrophs vs autotrophs
h - use organic carbon for building cell carbon and biomass
a - use co2 to synthesize cell carbons
38
Basic medium
nitrogen fixing photolithoautotroph
39
medium 1
allows Non-nitrogen fixing photolithoautotrophs to grow
40
medium 2
reduced organic carbon source - energy and e- for chemoorganotrophs
- some chemoorganoheterotrophs
41
medium 3
allows growth of chemoorganoheterotrophs with a growth factor requirement
42
medium 4
vitamins! - N source, alternate source of carbon energy and e-
43
defined medium
exact chemical composition is known
- used to study metabolism
44
minimal medium
a type of defined medium that provides the minimum nutritional requirements for growth
45
complex medium
exact chemical composition is not known
- usually made from meat or yeast
- supply a variety of growth factors
46
differential medium
allows different bacteria to be distinguished
47
Example of differential medium
Blood agar - tsoy plate - 5% sheeps blood
48
Hemolytic bacteria (destroying red blood cell)
alpha - incomplete destruction of blood cells
beta - complete destruction
gamma - no destruction (not hemolytic)
49
Selective medium and example
contain ingredients that inhibit the growth of unwanted microbes - allow only specific microbes to grow
- Ex) mannitol salt agar - contains very high salt so only halotolerant bacteria can grow - isolate staphylococci from skin
50
Enriched medium
- supplemented with special nutrients to encourage the growth of fastidious bacteria
- complex nutrient requirements
- Ex) blood agar, chocolate agar
51
how is growth measured for microbio?
increase in the number of cells of apopulation not individual growth
- increase through binary fission - cell division following enlargement of a cell to twice its mini size
52
generation time (G)
time required for microbial cells to double in number
53
cell division - euk vs pro
pro: growth in cell size, chromosome replication and septum formation occur at the same time - no mitosis
euk: growth, replication, seperation are at differnt times
bacteria have shorter generation times than eukaryotes
54
what is generation time dependent on
growth medium and incubation conditions
55
exponential growth
growth of a microbial population in which cell numbers double at a constant and specific time interval
56
relationship between initial number vs final number
Nf = N0x2^n - final cell number is equal to inital cell number multiplied by 2 to the power of number of generations
57
exponential growth for this one
0.5 hour
58
What is this graph showing?
because cells increase exponentially the increase in cell number is initially slow but increases at an ever faster rate following an exponential curve - cells are doubling at a constant rate
59
Why is unlimited growth called exponential growth
it generates a curve whose slope increases conitnuously
60
Growth rate (k)
- rate of increase in population number or biomass
61
Why is pro growth rate expressed as the number of doublings per hour
they grow by binary fission - always doubling
62
N0 = 0.5 x 107 cells
NF = 1.00 x 107 cells
Dt = 4.2 - 3.5 = 0.7 hour
K? and G?
k = (log1x107 - log0.5x107)/(.301)(0.7)
k = 1.43 gen/hr
g=1/k
g= 1/1.43 = 0.7hr/gen
63
specific growth rate
for each organism, they have a growth rate that is the fastest in the best growth medium at optimal temperature
64
batch culture
a closed-system microbial culture of fixed volume - once inoculated - thats all you get - because theres a fixed number of resources
65
Growth curve for population of cells phases
1. lag phase
2. exponential phase
3. stationary phase
4. death phase
66
lag phase
interval between inoculation of a culture and beginning of growth
- adapting to new environment
- ex) when you add bacteria to a tsoy plate
- small increase in cells is due to transition - elongating cells but not division
67
exponential phase
- LOG phase - doubling happens here
- cells in this phase are typically in the healthiest state
which is why we use it for calculating growth rate
68
stationary phase
- cells metabollically active but growth rate of population is zero
- either an essential nutrient is used up or wast product of organism accumulates in medium
69
death phase
- if incubation continues after cells reach stationary phase, cells will eventually die
- not all bacteria die, some bacteria form spores of cysts or dormant stages that allow a significant proportion of cells to survive a long time
70
continuous culture
an open system microbial culture of fixed volume
- new nutrients and wastes are consistent
71
chemostat
most common type of continuous culture device
- growth rate and population density of culture can be controlled independently and at the same time
- dilution rate - rate at which fresh medium is pumped in and spent medium is pumped out
- concentration of a limiting nutrient controls the population size and the growth rate
72
microbial counts
direct microscopic observations using a counting chamber
- each square corresponds to a calibrated volume
-results can be unreliable
73
limitations of microscopic counts
- cannot distinguish between live and dead cells without special stain
- small cells can be overlooked
- precision is difficult
- needs a specific microscope
- low density cells are hard to count
- hard to count motile cells
- debris can be mistaken for cells
- cells may move and form clumps
74
flow cytometry
automaticlaly counts the total number of cells based on laser beams, dyes and electronics
75
viable cell counts and how?
- measure only living cells - cells that are capable of growingto form a population
- 2 main ways: spread plate or pour plate
76
issues with viable cell counts
- needs alot of preparation and incubation time for a culture
- plate counts are unreliable when used to assess total cell numbers of natural samples
- selective culture media and growth conditions target only particular species - a single medium cant grow every microbe - can only count the types of bacteria that can grow in the medium selected
77
great plate anomaly
- microscopic counts reveal more organisms than plate counts
- genome techniques suggest that only 1-10% of microbial diversity is culturable from most environment samples because
1. microscopic methods count dead cells and viable methods dont
2. differnt organisms may have vastly different requirements for growth
3. we dont know the specific requirements for all organisms
78
spectrophotometric counts
used for turbidity measurements
- optical density measurement
- bacteria are like small particle and absorb and scatter light
- only a portion of the incident light makes it to the photocell
- the larger the number of particles, the greater the absorbance, the lower the light transmission to the photocell
- can't distinguish dead cells from living cells
79
what does this graph say
standard curve: viable cell counts and weight of biomss produced
- optical density has a fixed linear range of measurement
- it only works if the cells are evenly distributed throughout the medium
80
dry weight measurement (total mass of cells)
a specific aliquot cells are concentrated, washed to remove media components, concentrated and dried
81
other spectrometric techniques are used for
to measure compoenets of the cell, protein, DNA
82
cardinal temps
the minimum, optimum and maximum temps at which an organism grows
83
psychrophile
low temp is optimum
84
mesophile
midrange temp is optimum
- warm blooded animals, trrestrial and aquatic, temperate and tropical latitudes
85
thermophile
high temp optimum
86
hyperthermophile
very high temp optimum
87
cold loving microorgnaism
extremophiles - organisms that grow under very hot or very cold conditions
psychrphiles - organisms with cold temperature optima - inhabit permanently cold environments
psychotolerant - organisms that can grow at 0 but have optimum of higher
88
adaptations that support cold loving microorganisms
- enzyme; function optimally in the cold
- modified cytoplasmic membranes - high unsaturated fatty acid content
89
heat loving microorganisms
- only prokaryotic life forms exists
including chemoorganotrophic and chemolithotrophic species - high diversity
- thermophiles: organisms with growth temperature optima between 45 and 80 - hot springs, compost
-hypothermophiles: organisms with optima greater than 80 - hot environments like boiling hot springs, seafloor hydrothermal vents
90
adaptations that support heat loving microorganisms
- cytoplasm membrane:
bacteria - lipids rich in saturated fatty acids
archaea - lipid monolayer rather than bilayer
- hyperthermophiles produce enzymes widely used in industrial microbiology - hydrolytic enzymes like proteases, cellulases and lipases
- enzymes of thermophiles are more stable and have higher activity than mesophilic counterparts
91
what is the dying temp for life?
140-150
92
_________ closest descendants of ancient microbes
hyperthermophiles - deepest and shortest branches of the phylogenetic tree
- oxidation of H2 is common
- maybe first energy-yielding metabolism
93
pH and microbial growth
some organisms grow best at high or low pH
- most organisms grow between 6-8 - neutrophiles
- less than 6 (low ph) - acidophiles
- higher than 9 (high ph) - alkaliphiles
94
bottom line of pH and adaptations
- cytoplasmic membrane maintains its integrity at the growth pH
- the internal ph must stay relatively close to neutral even though the external ph is highly acidic or basic
95
how do microbial culture media maintain ph
buffers!
- some bactera produce acids to decrease ph
some bacteria grow on amino acids to increase ph
96
water activity
water avaialbility is expressed in physical terms
- ratio of vp of air in equil w a substance/solution to vp of pure water
- reflects the amount of water thats interacting with ions and polar compounds in solution
97
cytoplasm has a ____ solute concentration than the surroundings
higher; water wants to move into the cell creating turgor pressure
98
halophiles
grow best at reduced water potential and have a specific requirement for NaCl
- many marine microbes
- high solute concentration
99
extreme halophils:
require high levels of nacl for growth
15-20%
- microbes in the dead sea
100
halotolerant
can tolerate some reduction in water activity of environment but generally grow best at lower solute concentrations
- staphy aureus
101
osmphiles
organisms that grow with high sugar as solute
102
xerophils
organisms able to grow in very dry environments
103
specialized and rare organisms
honey, jams and jellies, beef jerky and salted cod
104
high osmolarity created with nacl is used to _________
select for acid producing microorganisms
- fermentation
- high salt and low ph prevents growth of MOST pathogens in the finished product
105
mechanisms for combatting low water activity in surroundings:
- pumping inorgnic ions from environment into cell
- synthesizing or concentrating organic solutes
- compatible solutes: compounds used by cell to counteract low water activity in surrounding environment
106
obligate aerobes
require oxygen to live
107
strict anaerobes
don't require oxygen to live and may die from exposure to oxygen
108
facultative aerobes
can live with or without oxygen - they use it if its available
109
aerotolerant anaerobes:
can tolerate oxygen and grow in its presence even though they cannot use it
110
microaerophiles
can use oxygen only when it is present in a small amount
111
how can oxygen tolerance be distinguished?
thioglycolate broth
112
name the type in each
a) obligate
b) strict
c) facultative
d) microaerophile
e) aerotolerant
113
how to grow anaerobic techniques
reducing agents to reduce oxygen
- removal of air and replacement with an inert gas
114
toxic forms of oxygen formed in cell
1. superoxide anion
2. hydrogen peroxide
3. hydroxyl radical
115
enzymes that neutralize toxic oxygen and who lacks some/all of these
catalase, peroxidase, superoxide dismutase, superoxide reductase
obligate anaerobes
116
sterilization
killing of all viable organisms within a growth medium
117
inhbiition
effectively limitng microbial growth
- no killing taking place
118
decontamination
the treatmeent of an object to make it safe to handle
119
disinfection
directly targets the removal of all pathogens
not necessarily all microorganisms
120
heat sterilization
- controlling microbial growth
- high temperatures denature macromolecules
121
What cells are resistant to sterilization and what would D be for this
- endospores because they have lipids, sugars, nucleic acids that decrease penetration
- D would be linear
122
What happens to time when temp decreases for sterilization
increase in temp decreases D or time
123
pasteurization
using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
- this does not kill all organisms - like endospores
-
124
milk and pasteurization and disease
can use diff temps
- LTLT - low temp but for a long time - 63 degrees for 30 mins
- HTST - high temp for a short time - 72 degrees for 15 seconds
- both processes kill Coxiella bernetii - the causative agent of Q fever
125
autoclave
a sealed device that uses steam under pressure
- allows temp of water to get 100 degrees
- 121 degrees for 15 minutes at 15 pounds per square inch of pressure is typically used
- the point it takes the longest to heat must stay at 121 for 15 minutes
126
what can kill better and faster? dry or moist
moist
127
ionizing radiation
- electromagnetic radiation that produces ions and other reactive molecules generates electrons, hydroxyl radicals, hydride radicals
128
sources of radiation and what its used for in the medical and food industry
- cathode ray tubes, xrays, radioactive nuclides
- approved by who and is used in the usa to decontaminate foods
129
filtration
- avoids the use of heat on sensitive liquids and gases
- pores of filters are too small for organisms to pass through - only liquids and gases
130
3 membrane filter types
1. syringe - small volume
2. pump - large - pushing out
3. vacuum - large - sucking in
131
nucleapore filtration
pore size 5 micrometer - bacteria can pass through
pore size 0.2 micrometer - prevents bacteria from passing through
132
antibacterial agents
1. bacteriostatic
2. bacteriocidal
3. bacteriolytic
133
bacteriostatic
- prevents cell growth as long as the antimicrobial agent is present
134
bacteriocidal
kills the cell but doesn’t lyse them
135
bacteriolytic
- kills and lyses them
136
why is the cell count still high in bacteriocidal
because the defining cell count is the cytoplasmic membrane - so if its not lysed its still there
137
MIC
minimum inhibitory concentration
- the smallest amount of an agent needed to inhibit growth of a mircoorganism
- because its expensive to use alot and it could also be toxic
- varies with the organism, inoculum, temp and ph
- lowest concentration with no growth
- it may still have living organisms that arent growing (bacteriostatic)
138
MLC
minimal lethal concentration
- when plating the broth from MIC and tubes with higher concentrations, do colonies form?
- the one where colonies stop forming is the MLC
139
whats higher, MLC or MIC
MLC
140
141
disc diffusion assay
- solid media
- antimicrobial agent is added to filter
- MIC is reached
- forms a zone of inhibition
- area of no growth around disc
142
antimicrobial agents 2 categories
1. products used to control microorganisms in commercial and industrial applications
2. products desgined to prevent grwoth of human pathogens in animate environments and on external body surfaces
143
ex of products used to control microorganisms in commercial and industrial applications
chemicals in foods, air conditioning cooling towers, textile and peper products, fuel tanks
144
ex of products designed to prevent growth of human pathogens in inaminate environments and on external body surfaces
1. sterilants - destroys all microorganisms including endospores
2. disinfectant; kills microorganisms but not all endospores
3. sanitizer - reduced the numbers of microorganisms on surfaces
4. antiseptic - kills or inhibits the growth of microorganisms but non toxic enough to be applied on living tissue like mouthwash
