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Microbiology Prelim > Bacterial Growth, Nutrition, metabolism and Genetics > Flashcards

Bacterial Growth, Nutrition, metabolism and Genetics Flashcards

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1
Q

List the environmental effects on bacterial growth

A

Temperature
pH
Osmotic Pressure
Oxygen tension

any changes can stop the development of bacteria

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2
Q

How does temperature affect bacterial growth?

A

temp inc, reaction fast, temp is ideal human temp

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3
Q

Minimum temperature

A

o Temperature below which growth ceases, or lowest temperature at which microbes will grow
o They allow growth on a very small scale

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4
Q

Optimum temperature

A

o Temperature at which its growth rate is the fastest
o The optimum temperature for bacterial
growth is the normal body temperature

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5
Q

Maximum temperature

A

o Temperature above which growth ceases, or highest temperature at which microbes will grow
o Anything higher than this will cause the
bacteria to die that is why if you have to
sterilize you have to heat it very well

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6
Q

Ideal temperatures for Psychrophiles

A

0-20
Thrive at 4 deg
Polaromonas vacuolata

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7
Q

Ideal Temperatures for Mesophiles

A

20-45
warm-blooded animals
Thrives at 39°C
Bacillus stearothermophilus

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8
Q

Hyperthermophiles

A

Optima greater than 80°C

These organisms inhabit hot environments including boiling hot springs, as well as undersea hydrothermal vents that can
have temperatures in excess of 100°C
o Thrives at 88°C, Ex. Thermococcus celer
o Thrives at 106°C, Ex. Pyrolobus fumarii
but higher than that the growth stops

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9
Q

pH AND MICROBIAL GROWTH

A

acidophiles – optimum in pH
range 1-4 H. pylori, T. oxidans
alkalophiles – optimum in pH
range 8.5-11. V. cholera

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10
Q

Lactic acid bac. ideal pH

A

4-7

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11
Q

Thiobacillus thiooxidans pH

A

2.2 to 2.8

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12
Q

Fungi pH

A

4-6

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13
Q

How is internal pH regulated?

A

Buffers

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14
Q

What is the best pH for most organisms?

A

6-8

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15
Q

Pathogenic bacterium are
acidophile
neutrophile
Alkalophile

A

Neutrophile

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16
Q

OSMOTIC EFFECTS ON MICROBIAL GROWTH

A

• Osmotic pressure depends on the surrounding solute concentration and water availability
• Water availability is generally expressed in physical terms such as water activity (aw)
• Water activity is the ratio of the vapor pressure of the air in equilibrium with a substance or solution
to the vapor pressure of pure water (aw 1.00)

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17
Q

Osmophiles

A

organisms that thrive in high solute

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18
Q

Osmotolerant

A

organisms that tolerate high

solute

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19
Q

Halophiles –

A

organisms that thrive in high salt

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20
Q

Halotolerant –

A

organisms that tolerate high salt

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21
Q

Barophiles –

A

organisms that thrive in high

pressure

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22
Q

Barotolerant –

A

organisms that tolerate high

pressure

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23
Q

HALOPHILES

A

have evolved to grow best at
reduced water potential, and some (extreme halophiles, e.g. Halobacterium salinarium, Dunaliella) even require high levels of salt for growth
V. fischeri

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24
Q

HALOTOLERANT

A

can tolerate some reduction in
the water activity of their environment but generally grow best in the absence of the added solute.
o Ex. Staphylococcus aureus

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25
Q

XEROPHILES

A

are able to grow in very dry
environments
• Nonhalophile – Ex. Escherichia coli

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26
Q

AEROBES Obligate

A

require O2

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27
Q

Facultative aerobes

A

with or without o2

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28
Q

Microaerophiles

A

low levels of O2

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29
Q

Aerotolerant anaerobes –

A

can tolerate

oxygen but grow better without oxygen

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30
Q

Obligate –

A

do not require oxygen; killed by

oxygen

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31
Q

When treating infections specially in immunocompromised
patients, always think of a polymicrobial infection. You
always think that that infection has aerobic and anaerobic.
They can tolerate oxygen but grow better without oxygen,
these are anaerobes. That is why you will see anaerobic
infections in the back, in the gluteus maxims (butt), WHY?

A

Because you always lie in your back, that’s why there is low

oxygen tension there.

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32
Q

How to test for O2 requirements of Microorganisms?

A

Contains a reducing agent and provides aerobic and anaerobic conditions

a) Aerobic
b) Anaerobic
c) Facultative
d) Microaerophile
e) Aerotolerant

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33
Q

Carbon, Nitrogen weight per 100g of dry weight

A

50%, 12%

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34
Q

Most bacteria can use

A

Ammonia -NH3 and many

can also use NO3

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35
Q

Nitrogen fixers

A

can utilize atmospheric nitrogen

N2

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36
Q

NITROGEN REQUIREMENTS

A

• Although many biological components within living organisms contain N, and N2 is the most abundant component of air, very few organisms can “fix” or
utilize N2 by converting it to NH3
• N is often growth-limiting as organisms must find the source as NH4
+ for biosynthesis
• Photosynthetic organisms and many microbes can reduce NO3
to NH4

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37
Q

SIDEROPHORES

A

– iron-binding agents that cells

produce to obtain iron from various insoluble minerals

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38
Q

Anaerobes lack

A

superoxide dismutase and/or catalase

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39
Q

Anaerobes need high Chemica

A

Thioglycollate; pyrogallol + NaOH, H2

generator + catalyst

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40
Q

The candle jar

A

the technique used for anaerobic cultures

because if you do the candle jar you will consume all oxygen so you will have an anaerobic environment.

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41
Q

Culture media

A

supply the nutritional needs of
microorganisms (C, N, Phosphorus, trace elements,
etc.). The media that are used in microbiology
laboratories to culture bacteria are referred to as
synthetic or artificial media, because they do not
occur naturally; rather they are prepared in the
laboratory; is used when we grow bacteria

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42
Q

Defined medium:

A

precise amounts of
highly purified chemicals; is one in which
all the ingredients are known

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43
Q

Complex medium or (undefined):

A

highly

nutritious substances.

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44
Q

Complex medium or (undefined):

A

highly nutritious substances.

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45
Q

Selective:

A

contains compounds that
selectively inhibit; is used to discourage the growth of certain organisms without
inhibiting the growth of the microorganism being sought

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46
Q

Differential

A

contains indicator; allows one to

readily differentiate among the various types of organisms that are growing in the medium.

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47
Q

Media can be classified on three primary levels:

A
  1. Physical State
  2. Chemical Composition
  3. Functional Type
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48
Q

LIQUID MEDIA

A
  • Water-based solutions
  • Do not solidify at temperatures above freezing or tend to be free flowing
  • Includes broths, milks, and infusions
  • Measure turbidity
  • Example: Nutrient Broth, Methylene Blue Milk, Thioglycollate Broth
49
Q

SEMI-SOLID MEDIA

A
  • Exhibits a clot-like consistency at ordinary room temperature
  • Determines motility
  • Used to localize a reaction at a specific site.
  • Example: Sulfide Indole Motility (SIM) for hydrogen sulfide production and indole reaction and motility test.
50
Q

SOLID MEDIA

A

• Firm surface for discrete colony growth; for
morphology
• Advantageous for isolating and culturing
• Two Types
o Liquefiable (Reversible) - Reversible to liquid phase, contains a solidifying agent that
changes its physical properties in response
to change in temperature.
o Non-liquefiable - Non-reversible, less
versatile applications than agar as they do
not melt.
• Examples: Gelatin and Agar (Liquefiable)
Cooked Meat Media,
Potato Slices (Non-liquefiable)

51
Q

SYNTHETIC MEDIA

A
  • Chemically defined
  • Contain pure organic and inorganic compounds
  • Exact formula (little variation)
52
Q

COMPLEX OR NON-SYNTHETIC MEDIA

A
  • Contains at least one ingredient that is not chemically definable (extracts from plants and animals)
  • No exact formula; tend to be general and grow a wide variety of organisms
53
Q

SELECTIVE MEDIA

A
  • Contains one or more agents that inhibit the growth of a certain microbe and thereby encourages, or selects, a specific microbe.
  • Example: Mannitol Salt Agar [MSA] encourages the growth of S. aureus. MSA contain 7.5% NaCl which inhibits the growth of other Gram + bacteria
54
Q

DIFFERENTIAL MEDIA

A

• Differential shows up as visible changes or variations in colony size or color, in media color changes, or in the formation of gas bubbles and
precipitates.
• Example: Spirit Blue Agar to detect the digestion of fats by lipase enzyme. Positive digestion (hydrolysis) is indicated by the dark blue color that
develops in the colonies. Blood agar for hemolysis
(α, β, and γ hemolysis), EMB, MacConkey Agar, etc.

55
Q

ENRICHMENT MEDIA

A
  • Is used to encourage the growth of a particular micro-organism in a mixed culture; adding extra nutrients to a medium called nutrient agar.
  • Examples: Manitol Salt Agar for S. aureus, blood agar , chocolate agar, Slenite F broth
56
Q

Generation time

A

is the time it takes for a single

cell to grow and divide

57
Q

Number of total bacteria

A

2n x number of initial bacteria
2 stands for the doubling of the number of the bacteria
n stands for the number of generations ( to get this, convert 3 hours to minutes divided by 30 minutes or how long the bacteria divides)
26 x 100 =6, 400 cells

58
Q

the lag phase

A

cells are recovering from a period
of no growth and are making macromolecules in
preparation for growth; The lag phase represents a
period during which cells, depleted of metabolites and
enzymes as the result of the unfavorable conditions
that existed at the end of their previous culture history

59
Q

log phase

A

cultures are growing maximally;
the bacteria multiply so rapidly that the number of
organisms doubles with each generation time (i.e.,
the number of bacteria increases exponentially).

60
Q

Stationary phase

A

occurs when nutrients are
depleted and wastes accumulate (Growth rate = death rate); eventually, the exhaustion of nutrients or the accumulation of toxic products causes growth to
cease completely

61
Q

death phase

A

death phase, the death rate is greater than
the growth rate; As overcrowding occurs, the
concentration of toxic waste products continues to increase and the nutrient supply decreases. The microorganisms then die at a rapid rate

62
Q

METHODS USED TO MEASURE MICROBIAL

GROWTH

A
  • Count colonies on plate or filter (counts live cells)
  • Microscopic counts
  • Flow cytometry (FACS)
  • Turbidity
63
Q

Viable Counts

A

o Each colony on plate or filter arises from
single live cell
o Only counting live cells); is typically
considered the measure of cell concentration.
For this, a 1-mL volume is removed from a
bacterial suspension and serially diluted 10- fold followed by plating 0.1-mL aliquots
(portions) on an agar medium. Each single
invisible bacterium (or clump of bacteria) will grow into a visible colony that can be counted

64
Q

DIRECT COUNT:

A

POUR PLATE, SPREAD OR STREAK PLATE

65
Q

MICROSCOPIC COUNT

A
  • Need a microscope, special slides, high power objective lens
  • Typically only counting total microbe numbers, but differential counts can also be done
66
Q

streak plate vs spread plate

A

www.differencebetween.com

67
Q

purpose of streak plate

A

isolate or purify specific species

68
Q

Streak plate inoculating tool

A

inoculation loop or cotton swab

69
Q

is a micropippete necessary for Streak plate?

A

No

70
Q

inoculum quantity streak plate

A

one loopful

71
Q

Sterilization of inoculum in streak plate

A

flamed until red hot

72
Q

Method of inoculation streak plate

A

Zig-zag spread

73
Q

purpose of spread plate

A

enumerate bacteria colonies in a sample

74
Q

inoculating tool spread plate

A

Sterile spreader

75
Q

is a micropipette necessary for spread plate

A

yes

76
Q

Sterilization of inoculum spread plate

A

95% alc and flamed

77
Q

Method of inoculation spread plate

A

spread evenly in fresh medium

78
Q

MICROSCOPIC COUNT

A

Need a microscope, special slides, high power objective lens

Typically only counting total microbe numbers, but differential counts can also be done

79
Q

FLOW CYTOMETRY

A

Flow cytometry is a laser-based method used for the
analysis of cells and selected cell components. One of the
most popular applications of flow cytometry is
immunophenotyping of cell populations. In this method,
single-cell suspensions are stream through a flow cell in
which the cells pass through a laser beam for sensing. As
the cells pass through the laser, they scatter light

80
Q

TURBIDITY

A

• Cells act like large particles that scatter visible light
• A spectrophotometer sends a beam of visible light
through a culture and measures how much light is scattered
Scales read in either absorbance or % transmission
• Measures both live and dead cells

81
Q

Linear pathways –

A

glycolysis,

82
Q

Spiral or cyclic

A

Krebs cycle

83
Q

ENZYME ACTIVITY

A 
• Enzyme activity may change
due to inhibitor or activator
molecules called effectors.
• Inhibitors can be competitive
(bind at substrate active site)
• Non-competitive inhibitors and activators bind to allosteric (regulatory) sites; separate from the active site;
• These effectors change the shape of the protein
and its activity as a catalyst.
84
Q

Feedback Inhibition:

A

o Rate limiting enzyme is first in pathway
and is allosteric
o End-product is a negative effector
(inhibitor) of first enzyme

85
Q

Feed Forward Activation

A

o Rate limiting enzyme of a branch point is allosteric
o Earlier-substrate is a positive effector
(activator) of a forward reaction enzyme

86
Q

REVERSE METABOLIC PATHWAYS

A

Amphibolic pathways:
o Catabolic direction
o Anabolic direction

87
Q

LUCOSE CATABOLISM

A

• ATP as the cellular energy storage unit can be
formed during respiration (R) or fermentation (F)
• Both contain the Glycolysis pathway; which produces ATP, the electron carrier molecule NADH, and pyruvate from glucose
• Aerobic Respiration will proceed via Krebs cycle and an ETC if there is oxygen to react as a terminal electron acceptor
• Oxygen is not the only possible terminal electron
acceptor in some bacteria (e.g. NO3 or SO4 can be used); called Anaerobic Respiration

88
Q

products of Pyruvate from Clostridium

A

Butyrate and Acetoacetate

89
Q

Pyruvate of Gluconobacter

A

Acetate,

90
Q

Pyruvate of Streptococcus and lactobacillus

A

lactic acid

91
Q

pyruvate of acetobacterium

A

Acetyl CoA

92
Q

HYDROLYSIS OF MAJOR BIOMOLECULES

A

Enzymes of Hydrolysis:
• Proteins by proteases
• Polysaccharide and other carbohydrates by glycosidase
• Nucleic acids (DNA or RNA) by nucleases
• Lipids by lipases

93
Q

AMPHIBOLIC NATURE OF METABOLISM

A

Most catabolic pathways have anabolic counterparts, so not
all compounds are used to generate ATP, but rather shunted
to make new cell biomass.

94
Q

Genetics is the study of heredity which is concerned with how

A 
○ information in nucleic acids is expressed
○ nucleic acids are duplicated and
transmitted to progeny
○ these processes account for the
characteristics of progeny
○ structure & function of genetic material
○ transmission of biological traits from
parent to offspring.
95
Q

Genome

A

– sum total of genetic material of an
organism (chromosomes +
mitochondria/chloroplasts and/or plasmids)

96
Q

GENOMES VARY IN SIZES

A

● smallest virus –4-5 genes
● E. coli–single chromosome containing 4,288 genes; 1 mm; 1,000X longer than cell
● Human cell –46 chromosomes containing 31,000 genes; 6 feet; 180,000X longer than cell

97
Q

Read DNA and RNA functions

A

page 16 of trans

98
Q

CENTRAL DOGMA THEORY

A

The central dogma theory of molecular biology is
represented by a simple pathway: DNA ® RNA ®
protein, which demonstrates the flow of genetic
information in a living cell

99
Q

Major processes of CDT theory

A

replication, transcription, and translation

100
Q

DNA polymerase enzyme

A

replicates all the DNA in the nuclear genome in a semi-conservative manner, meaning that the double stranded DNA is separated into two and a
template is made by DNA polymerase.

101
Q

transcription.

A

The process in which DNA is copied into RNA by RNA Polymerase

102
Q

REVERSE TRANSCRIPTASE

A

● Another process in this pathway is reverse transcription, which involves copying RNA information into DNA using reverse transcriptase
● Recently, this process has been defined and may expand the central dogma
● For example, retroviruses use the enzyme “reverse transcriptase” to transcribe DNA from an RNA
template
● The viral DNA then integrates into the nucleus of the
host cell. Then it is transcribed, and further translated into proteins
● This biological process effectively adds another pathway to the central dogma of molecular biology

103
Q

DNA REPLICATION IN BACTERIA

A

● Bacteria contain 1 chromosome
● Many contain plasmids
● When bacterial chromosomes replicate both strands are duplicated. Each strand functions as a template

104
Q

STEPS OF DNA REPLICATION

A
  1. DNA unwound with enzyme (replication fork)
  2. Complementary bases added to template
    (parent strand) using enzyme
  3. Replication fork moves down strand
  4. Newly replicated DNA rewinds
  5. Process called Semiconservative Replication
105
Q

Replication speed

A

1000 nucleo/sec

106
Q

Direction of copying in Replication

A

5’ to 3’

107
Q

RNA SYNTHESIS IN BACTERIA

A

1) RNA polymerase binds to DNA at a
promoter site near the gene to be
transcribed.
2) RNA polymerase travels the length of the DNA using it as a template to duplicate.
3) The RNA polymerase continues until it
reaches a termination site at which time the transcription is complete.

108
Q

STAGES OF PROTEIN SYNTHESIS IN BACTERIA

A

Protein synthesis is continuous and takes place in three stages:

  1. Initiation
  2. Elongation
  3. Termination
109
Q

CHAIN INITIATION

A 
● The beginning of protein synthesis
starts methionine which is the start
codon.
● Start codon is known as formyl
methionine (fmet).
● It is coded as AUG.
110
Q

CHAIN ELONGATION

A 
By a complex that
begins with f-met,
amino acids attach to
form a chain
(amino acids joined
repeatedly to form
proteins)
111
Q

CHAIN TERMINATION

A 
● Ends when the synthesis comes
to a termination codon
● Termination
codons are codes as UAA,
UAG, and UGA
112
Q

Rifamycin

A

binds to RNA polymerase

113
Q

Actinomycin D

A

○ binds to DNA & halts mRNA chain

elongation

114
Q

Erythromycin & Spectinomycin

A

○ interfere with attachment of mRNA to

ribosomes

115
Q

Chloramphenicol, lincomycin & tetracycline

A

○ bind to ribosome and block elongation

116
Q

Streptomycin

A

○ inhibits peptide initiation & elongation

117
Q

DIFFERENCE BETWEEN
EUKARYOTIC TRANSCRIPTION AND TRANSLATION
FROM PROKARYOTIC

A

● Do not occur simultaneously. Transcription occurs
in the nucleus and translation occurs in the cytoplasm
● Eukaryotic start codon is AUG, but it does not use formyl-methionine
● Eukaryotic mRNA encodes a single protein, unlike bacterial mRNA which encodes many
● Eukaryotic DNA contains introns - intervening sequences of noncoding DNA-which have to be
spliced out of the final mRNA transcript

118
Q

Codons

A 
A codon is a group of three
nucleotides in DNA which
acts as a code in the placing
of an amino acid in a protein
molecule
● AUG begins protein
synthesis
● UAA, UAG, UGA are
termination codons
○ When this codon is
reached, the ribosome
falls off and the last
tRNA is removed from
the polypeptide.

Microbiology Prelim (7 decks)

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