CH. 6: Microbial Growth Flashcards
1
Q
growth
A
increase in numbers of cells, not size
2
Q
colonies
A
hundreds of thousands of cells
3
Q
population
A
growth to billions of cells
4
Q
knowledge of microbial growth needed to
A
control growth of pathogenic microbes and increase growth of good microbes as well as those we want to study
5
Q
physical requirements for growth
A
temp
pH
osmotic pressure
6
Q
chemical requirements for growth
A
carbon N, S, P trace elements oxygen organic growth factor
7
Q
most bacteria will grow at (temp)
A
37C
8
Q
minimum growth temp
A
lowest temperature at which there will be some growth
9
Q
optimum growth temp
A
usually closer to the max end of the temp range; best growth conditions
10
Q
maximum growth temp
A
highest temp at which growth is possible
11
Q
growth temperature ranges span
A
30C
12
Q
3 primary groups of microbe classification based on preferred temp range
A
- psychrophiles
- mesophiles
- thermophiles
13
Q
psychrophiles grow at
A
0C and optimum 15C
usually no growth at 25C
14
Q
psychrophiles grow where?
A
ocean depths, and polar regions
15
Q
psychrotophs grow at
A
[classification not as strict]
0C (same as psychrophiles)
optimum between 20-30C (when psychrophiles will die)
not at temps above 40C
more common than psychrophiles & these cause food spoilage
16
Q
mesophiles
A
– most common type of microbe
optimum growth between 25-40C
– the mesophiles include most of the common spoilage and disease organisms
17
Q
thermophiles grow at
A
optimum 50-60C (T for hot water tap)
many do not grow below 40C
important in organic compost piles
18
Q
hyperthermophile archaea grow at
A
80C or higher
19
Q
hyperthermophiles found where
A
hydrothermal vents (ie. deep sea vents)
20
Q
hyperthermophiles useful bacteria in
A
biotechnology (e.g. deep vent DNA polymerase or PCR)
Tli has proofreading capability
Taq does NOT
21
Q
most bacteria grow b/w pH of
A
6.5-7.5 (near neurtrality)
22
Q
foods fermented preserved via acidity bc
A
very few bacteria like acidic conditions
23
Q
acidophiles
A
grow in acidic environments
24
Q
molds and yeasts grow between pH of
A
5-6 (acidic)
25
bacterial cultures produce ______ that inhibit their growth: ______ are included in media to counter this
acids
| buffers
26
hypertonic environments (or an increase in salt or sugar) cause
plasmolysis (shrinkage of cytoplasm)
27
most bacteria grow in media that is
mostly water
28
agar
a complex polysaccharide used to solidify media constitutes only 1/5%
(increasing agar concentration can cause plasmolysis and inhibit bacterial growth)
29
extreme or OBLIGATE halophiles (archaea)
require HIGH osmotic pressure (salty water)
30
facultative halophiles
do not require but can tolerate high osmotic pressure
31
carbon...
maintains structural organic molecules
is an energy source
important requirement for bacterial growth (besides water)
32
[carbon] chemoheterotrophs..
use organic carbon sources
--> organisms that derive energy by ingesting intermediates or building blocks that they are incapable of producing on their own
33
[carbon] autotrophs...
use CO2
34
half of dry weight of bacteria is
carbon
35
nitrogen...
for anabolic processes ie. synthesis of amino acids (for proteins), DNA and RNA
36
14% of dry weight of bacteria is
nitrogen
37
nitrogen obtained from
- - protein-containing matter - decomposition of proteins
- - NH4+ in organic matter or NO3-
- - a few (photosynthesizing) bacteria use N2 via NITROGEN FIXATION
38
example of bacteria that uses nitrogen fixation
Rhizobium
39
sulfur...
used to make amino acids and vitamins (thiamine and biotin)
40
sources of sulfur
decomposition of sulfur-containing proteins
| some bacteria use SO4(2-) or H2S
41
phosphorus...
in DNA, RNA, ATP, and membranes (phospholipids)
42
phosphorus source
PO4(3-)
43
4% of dry weight of bacteria is
P and S together
44
trace elements
inorganic elements required in small amounts
usually as enzyme cofactors
ie. iron, copper, molybdenum, zinc
* tap water is the source
45
microbes also use _____ as cofactors
potassium, magnesium, and calcium
46
oxygen...
required for aerobic respiration but can be toxic
47
obligate aerobes =
only aerobic growth, O2 required
48
obligate aerobes grow (test tube)
at the top, where high O2 concentrations have diffused into medium
49
facultative anaerobes =
both aerobic and anaerobic growth
| greater growth in presence of oxygen
50
facultative anaerobes (test tube)
most growth at top (where MOST O2 is present); but growth occurs throughout the tube as well
51
obligate anaerobes =
only anaerobic growth; growth stops in presence of O2
52
obligate anaerobes (test tube)
growth only occurs at the bottom of the tube where there is no oxygen.
53
aerotolerant anaerobes =
only anaerobic growth, but continues in presence of oxygen
54
aerotolerant anaerobes (test tube)
growth occurs evenly throughout, O2 has no effect
55
microaerophiles =
obly aerobic growth; O2 required in LOW CONCENTRATION
56
microaerophiles growth (test tube)
in the middle of the medium, not near bottom where no O2, not near top where lots of O2 diffused into medium.
57
toxic oxygen
singlet oxygen
superoxide free radicals
peroxide anion
hydroxyl radical
58
singlet oxygen
1O2-
| --> boosted to a higher energy state than O2 and is extremely reactive
59
superoxide free radicals
O2 w/ funny dot/line superscript
- -> are formed in small amounts during the normal respiration of organisms that use oxygen as a final electron acceptor, forming water.
- -> Their toxicity is caused by their great instability, which leads them to steal an electron from a neighboring molecule, which in turn becomes a radical and steals an electron, and so on.
60
peroxide anion
O2(2-) (from H2O2)
--> Because the hydrogen peroxide produced during
normal aerobic respiration is toxic, microbes have developed enzymes to neutralize it. The most familiar of these is catalase, which converts it into water and oxygen.
--> The other enzyme that breaks down hydrogen peroxide is peroxidase, which differs from catalase in that its reaction does not produce oxygen.
61
hydroxyl radical
OH with funny little dot
- - transient
- - The hydroxyl radical (OH·) is another intermediate form of oxygen and probably the most reactive. It is formed in the cellular cytoplasm by ionizing radiation. Most aerobic respiration produces traces of hydroxyl radicals, but they are transient.
62
macrophage phagolysosome
after ingestion of microbe by phagocyte, there is formation of a phagosome.
- -> then FUSION OF THE PHAGOSOME WITH A LYSOSOME to form a phagolysosome
- -> then digestion of ingested microbe by enzymes
63
organic growth factors
organic growth compounds obtained from the environment
| ie. vitamins, amino acids, purines, pyrimidines
64
biofilms
microbial communities in nature; share nutrients; sheltered from environmental harm (dessication, antibiotics, immune system)
65
another name for biofilm
hydrogel
66
biofilm matrix composed of
polysaccharide (glycocalyx), DNA and proteins sometimes called slime
67
quorum sensing
cell-to-cell communication that occurs in biofilms
68
conjugation in biofilms:
transfers genes like antibiotic resistance
69
structures in biofilms
pillar like (allows water flow to bring nutrients and remove waste)
70
biofilms formed when
a plantonic (free-living) cell adheres to a surface
- - can also form floc in sewage or streamers in running water
- - catheter example: pts with indwellings recieved contaminated heparin; bacterial numbers in heparin too low to cause infection; but 84-421 days after exposure, pts developed infections
71
medical relevance of biofilms
- microbes in films are very resistance to microbicides
- cause most (70%) of human bacterial infections
- cause most nosocomial infections (catheters, heart valves)
- infections from contact lenses, dental caries
72
prevention of biofilms
- treat surfaces with antimicrobials
- interrupt quorum sensing pathways
- inhibit surface mobility essential for biofilm formation (ie. lactoferrin binds iron and inhibits surface mobility reducing pseudomonad biofilm formation in cystic fibrosis)
73
culture medium:
nutrients prepared for microbial growth; must meet nutritional requirements, be at correct pH and moisture levels, be sterile, and incubated at correct temp
74
inoculum:
introduction of microbes into medium
75
culture:
microbes growing in/on culture medium
76
agar
complex polysaccharide from maine algae
- used as solidifying agent for culture media in petri plates/slants/deeps
- - generally NOT METABOLIZED by microbes (metabolites are added to it)
77
agar liquifies at
100C
78
agar solidifies at
40C
79
chemically defined media:
exact chemical composition is known
80
complex media:
extracts and digests of yeasts, meat, or plants
- - energy requirements primarily in form of protein
- - nutrient broth
- - nutrient agar
81
[anaerobic culture methods]
| reducing media:
contain chemicals (thioglycolate or oxyrase) that combine with O2
- placed in tightly capped tubes
- heated to drive off O2 before use
82
capnophiles
microbes that require high CO2 concentrations
- prefer conditions similar to our intestines, resp tract, and other internal body tissues
- special culturing techniques
(CO2 packet, candle jar, CO2 incubators)
83
biosafety level 1
no special precautions
84
biosafety level 2
lab coat, gloves, eye/face protection
85
biosafety level 3
biosafety cabinets to prevent airborne transmission
86
biosafety level 4
sealed, negative pressure- air goes in (exhaust air HEPA filtered twice, separate air supply and suits for personnel)
87
differential media:
make it easy to distinguish colonies of different microbes (ie. blood agar)
88
selective media:
suppress unwanted microbes and encourage desired microbes (ie. mannitol-salt agar)
89
enrichment culture:
encourages growth of desired microbe
90
a pure culture:
contains only one species or strain
91
a colony:
is a population of cells arising from a single cell or spore or grom a group of attached cells
92
the streak plate method:
is used to isolate pure cultures
93
only _% of bacteria in ecosystem can be cultured
1%
94
3 examples of obligate intracellular pathogens:
- Mycobacterium leprae
- Treponema pallidum
- Chlamydia spp
95
preserving bacterial cultures short-term
refrigeration
96
deep-freezing
preserving bacterial cultures
| -50 to -95C
97
lyophilization
freeze-drying
| frozen (-54 to -72C) and dehydrated in a vacuum
98
reproduction in prokaryotes (4)
- - binary fission
- - budding
- - conidiospores (actinomycetes) [filamentous bacteria - at tips of filaments)
- - fragmentation of filaments
99
generation time
the time required for the population to double (log formula/0.301)
100
generation time formula
60 min x hours / number of generations = ____ mins/generation
101
[bacterial growth curve]
| LAG phase
intense activity preparing for population growth but no increase in population.
102
[bacterial growth curve]
| LOG phase
logarithmic, or exponential, increase in population (is due to reproduction by binary fission in bacteria or mitosis in yeast)
103
[bacterial growth curve]
| STATIONARY phase
period of equilibrium: microbial deaths balance production of new cells
104
[bacterial growth curve]
| DEATH phase
population is decreasing at a logarithmic rate
105
plate counts
- - measures number of viable cells
- - done by pour plate or spread plate method
- - takes time (>24h)
- - after incubation, count colonies on plates that have 25-250 colonies (CFUs)
106
numbers in plate counts reported as
CFUs (in a given volume or mass)
107
what helps ensure accuracy in plate counts?
performing serial dilutions
108
most probably number
multiple tube MPN test
- - count positive tubes
- - useful for organisms that do not grow on a solid medium
- - 95% statistical probability that the number falls within a given range
- - compare with statistical table
109
direct microscopic count
- - sample injected onto slide and stained
- - sample is viewed under high magnefication
- - DIFFICULT TO USE w/ MOTILE BACTERIA
- - DEAD CELLS will be included
- - HIGH SAMPLE CONCENTRATION required
- - VERY FAST
110
direct microscopic count formula
number of bacteria/ml =
| number of cells counted / volume of area counted
111
turbidity
using light, a bacterial suspension (test tube), and a spectophotometer with a light-sensitive detector
- - HIGH CONCENTRATION OF BACTERIA required
- - 10-100 million cells/ml
112
metabolic activity
measures a microbial product (ie. if they secrete a certain product/chemical etc).
- used in assays (e.g. studying effects of pressure on microbial activity)
113
metabolic activity assumes
amount of product is proportional to number of bacteria
114
dry weight
useful for filamentous bacteria or molds
| filamentous bacteria and spread plates do not work
115
[measuring microbial growth]
| DIRECT methods
1. plate counts
2. filtration
3. MPN
4. direct microscopic count
116
[measuring microbial growth]
| INDIRECT methods
1. turbidity
2. metabolic activity
3. dry weight
