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Microbiology > Chapter 4: Microbial growth and its control > Flashcards

Chapter 4: Microbial growth and its control Flashcards

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Biology 101 flashcards
1
Q

Nutrients

A

Supply of elements required by cells for growth

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2
Q

Macronutrients

A

Nutrients required in large amounts

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3
Q

Micronutrients

A

Nutrients required in small amounts

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4
Q

Hetrotrophs

A

Obtain carbon from breakdown of organic polymers or uptake of monomers

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5
Q

Autotrophs

A

Synthesise organics from CO2

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6
Q

Nitrogen

A

-mostlu proteins, ammonia, nitrate or nitrogen gas
-Nealry all microbs us NH3
-many use nitrate
-Some use organics like amino acids or N2 (nitrogen fixing)

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7
Q

Other macronutrients

A

Oxygen and hydrogen from water
-Phosphorous: nucleic acids and phospholipids (usually inorganic phosphate)
-sulfur: sulfur containing amino acids, vitamins like biotin and microbes assimilate sulfate, sulfide or organics
-Potassium
-Magnessium: stabilises ribisomes, membranes, nucliec acids and required by many enzymes
-Calcium and sodium

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8
Q

Trace metals

A

Many enzymes require metal ion or small organic as a cofactor for catalysis
-Iron is used in cellular respiration, related oxidation-reduction reactions
-required in small amounts

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9
Q

Growth factors

A

vitamins: most function as coenzymes
others: aa, purines, pyramidines

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10
Q

Cobalt

A

Vitamin B12, transcarboxylase

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11
Q

Culture

A

Nutrient solution used to grow microbes
sterilised in an autoclave

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12
Q

Aseptic

A

Something that is contamination free

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13
Q

Sterile

A

It is the use of physical/chemical procedure to destroy all micro-organisms including spores

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14
Q

types of media

A

defined
complex
selective
differential

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15
Q

Defined media

A

Exact chemical composition is known

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16
Q

Complex media

A

Composed of digests of microbial, animal, or plant products (you know whats in but not how much)

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17
Q

Selective media

A

Contains compounds that selectively inhibit growth of some microbes but not others

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18
Q

Differential medium

A

Contains an indicator, usually a dye that detects particular metabolic reactions during growth
MacConkey is a medium that discrimanates between lactose fermenting and non fermenting bacteria

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19
Q

solid media

A

prepared by addition of gelling agent agar to liquid media
cells form colonies on this media
Morphology can be used to identify micro organisms and to check for contamination

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20
Q

Aseptic technique

A
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21
Q

Microscopic cell count

A

Direct count
Observing and enumerating cells present
dried on slides or on liquid samples
counting chambers with squares etched on a slide used for liquid samples
limitation is that you dont know if cells are alive or dead

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22
Q

Trpan blue

A

Azo dye
it selectively colours dead cells
it allows for a viable direct cell count as bacteria arent fixed

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23
Q

Colony counting limits

A

25-250 colonies
reported in colony-forming units (cfu/ml)

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24
Q

spread-plate method

A
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25
Q

Pour-plate method

A
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26
Q

Applications of the Plate count

A

quick and easy
used in food, dairy, medical and aquatic microbiology
high sensitivity
can target particular species in mixed samples
common in wastewater and other water analyses

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27
Q

Great plate count anomaly

A

Can only culture 1% of microbes and so culture is not an actual representative

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28
Q

Microscope vs plate count

A

Plate counts are always better as can indicate all microbes present

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29
Q

Indirect counts

A

Give an estimate
1. turbidity
2. Metabolic activity
3. dry weight

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30
Q

Turbidity

A

Cell suspensions are turbid because cells scatter light
More cells=more scattered light and increased turbidity
Turbidity measurements are rapid and used for estimates

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31
Q

Optical density

A

used to relate turbidity to cell numbers
measuered with a spectrophotometer
Unit is OD at a specific wavelenght
for unicellular organisms, OD is proportional to cell number up to 2 units
To relate a direct cell count to a turbidity value, a standard curve must first be established

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32
Q

Ad of turbity measurements

A

Quick and easy
do not require destruction or significant disturbance of sample
sample can be checked repeatedely
sometimes problematic when clumps or biofilms are formed

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33
Q

Metabolic activity

A

Method assumes that the CO2 meausered is directly proprtional to cell numbers
higher CO2 = higher cell pop

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34
Q

Dry weight

A

Used to track growth of filamentous fungi
fungus is filtered out of medium, dried in an oven or dessicator and then weighed.
dried ensures moisture content does not affect results

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35
Q

Binary fission

A

Cell division following enlargement of a cell to twice original size
-Quicker than mitosis because it does not have to generate mitotic spindle or dissolve nuclear membrane

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36
Q

septum

A

partiton dividng cells, pinches off between daughter cells

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37
Q

generation time

A

Time required for microbial cells to double in number

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38
Q

Batch culture

A

A closed-system microbial culture of fixed volume

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39
Q

Phases of growth curve

A

Lag phase
exponential phase
stationary phase
death phase

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40
Q

lag phase

A

Interval between inoculation of a culture and beginning of growth
-new conditions require alternating metabolic state
-Time needed for biosynthesis of new enzymes and to produuce required metabolites before growth can begin

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41
Q

Exponential phase

A

Doubling at regular intervals
close to metabolically identical
rates vary greatly, influenced by media, conditions, organism itself
continues until conditions can no longer sustain growth

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42
Q

Stationary phase

A

growth limited by nutrient depletion or waste accumulation
growth rate is zero
metabolism continues at greatly reduced rate

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43
Q

Decline phase

A

Total number decreases due to cell death

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44
Q

Cryptic growth

A

subpopulations adapt

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45
Q

Diauxic growth

A

Growth characterised by cellular growth in 2 phases
caused by presence of 2 sugars in a culture growth media, one of which is easier to metabolise

46
Q

Doubling time formula

A

Td= 0.693/B
B is the number from equation on graph

47
Q

Planktonic growth

A

Growth in suspension of free-floating/free-swimming cells

48
Q

Sessile growth

A

Attached to surface
can develop into biofilms
NB in medical and industrial applications

49
Q

Biofilm

A

cells emmeshed polysaccharide matrix attached to surface

50
Q

stages of biofilm growth

A

Planktonic cells attach (fimbriae, flagella, pili)
-Colonisation: growth and extracellular polysaccharide (EPS) production
-Development: metabolic changes
-Dispersal: colonise new sites
Can study in flow chamber

51
Q

Microbial mats

A

Multilayered sheets with differnt organisms in each layer

52
Q

Humans and biofilms

A

Implicted in join infections, implanted medical devices
-Responsible for cavities and cause gum disease
-Foul, plug, corrode pipes
-Form in fuel tanks and on ship hulls

53
Q

Biofilm lethality

A

Resistant to antibiotics and infections

54
Q

Optimum temperature for most microbes

A

Less than 40 degrees

55
Q

psychrophile

A

low, found in cold environments
optimal groth temp is below 15 and max 20 and min 0
constantly cold environments
found in polar regions

56
Q

Mesophile

A

midrange, commonly studied

57
Q

thermophile

A

high, hot environments

58
Q

hyperthermophiles

A

Very high, found in extremely hot habitats such as hot springs and deep-sea hydrothermal vents

59
Q

Extremophiles

A

Organisms that grow under extreme conditions (hot and cold)

60
Q

psychotolerant

A

can gro at 0 but optimum is 20-40
more widely distributed in nature
isolated from soils and water in temperate climates and food at 4 degrees

61
Q

Molecular adaptions for cold

A

More alpha helixes than B sheets: greater flexibility for catalysis at cold temp
More polar and fewer hydrophobic aa
fewer weak bonds
Cytoplasmic membrane has higher unsaturated and shorter fatty acid content as wll as polyunsaturated fatty acids which remain flexible at very low temp
-cold shock proteins
-Cryoprotectants prevent formation of ice crystals
-Expolysaccharide cell surface slime

62
Q

Hyperthermophile diet

A

Chemoorganotrophic and chemolithotrophic

63
Q

Thermophile

A

Growth temperature beteen 45 and 80

64
Q

Hyperthermophile

A

Growth greater than 80
inhabit hot springs and hydrothermal vents with temps greater than 100
above 65 only pro survives

65
Q

Adaptions to survive heat

A

-amino acid substitiutions that resist denaturation
-increased ionic bonding and hydrophobic interiors
-production of solutes like dyglycerol phosphate to help stabilise proteins
-saturated fatty acids increased

66
Q

useful thermophile

A

Taq polymerase for PCR

67
Q

adaptions of hyperthermophile

A

-They have C40 hydrocarbons made of repeating isoprene units bonded by ethers to glycerol phosphate and they have a monolayer memebrane

67
Q

Neutrophile

A

pH> 5.5 and <8

68
Q

Acidophile

A

grow best at low pH <5.5
governed by stability of cytoplasmic membrane
at neutral pH, acidophiles lyse as the require protons for stability

69
Q

Akaliphiles

A

pH>8
found in soda lakes and high carbonante soil
used commercially in detergents
have sodium motive force

70
Q

water activity

A

ratio of water vapor pressure of air equilibrium with a substance or solution to vapor pressure of pure water

71
Q

positive water balance

A

cytoplasm has higher solute concentration than outside otherwise water flows out

72
Q

Halophiles

A

grow best at aw=0.98 which is sea water
have requirement for NaCl

73
Q

Halotolerant

A

Tolerate some dissolved solutes but grow best in absence

74
Q

Extreme halophiles

A

Need 15-30% NaCl and cant grow at lower concentrations

74
Q

Compatible solutes

A

Microbes pump these solutes into cell to maintain positive water balance
they do not inhibit biochemical processes

75
Q

Osmophile

A

Live in high sugar

76
Q

Xerophile

A

live in dry environment

77
Q

Why add reducing agents to culture?

A

To reduce oxygen to water

77
Q

resazurin

A

dye that indicates Oxygen concentration

77
Q

singlet oxygen

A

molecular O2 that has been boosted into higher energy state- extremely reactive

78
Q

Superoxide radical

A

formed in normal amounts due to respiration
toxic

79
Q

Peroxide anion

A

Byproduct of conversion of superoxide radicals
extremely toxic

79
Q

Hyrdoxyl radical

A

Formed by IONIZING RADIATION in cytoplasm
most reactive

80
Q

Superoxide dismutase (SOD)

A

Converts superoxide to H peroxide and O2

80
Q

Catalase and peroxidase

A

Convert H peroxide to O2 and H2O

81
Q

Facultative anaerobes

A

Both aerobic and anaerobic growth, greater with O2
-Growth is best where most O2 is but occurs everywhere
-Presence of SOD and catalase allows toxic forms of O2 to be neutralised

82
Q

Obligate aerobes

A

-Oxygen required
-growth occurs in high O2 concentrations
-Presence of SOD and catalase allows toxic forms of O2 to be neutralised

82
Q

Superoxide reductase

A

Converts superoxide to H peroxide without producing O2

83
Q

Obligate anaerobes

A

-Only grows without O2
-growth occurs where little O2
-lacks enzymes to neutralise O2

84
Q

Micro-aerophiles

A

-Only aerobic growth with low O2 concentration
-Growth occurs in low concentration
-produces lethal amounts of byproducts if exposed to atmospheric O2

85
Q

Aerotolerant anaerobes

A

-only anaerobic growth
-growth occurs evenly, O2 has no effect
-Presence of SOD partially neutralises O2

86
Q

Decontamination

A

Treatment of object to make safe to handle

87
Q

Disinfection

A

-directly targets pathogens
-kills or inhibts growth

88
Q

Heat sterilisation

A

most used
higher heat kills faster
moist heat penetrates better than dry heat

89
Q

Decimal reduction time

A

Amount of time reuired at a given temp to reduce viability 10-fold

90
Q

Thermal death time

A

time to kill all cells at a given temp and is affected by pop size

90
Q

Autoclave

A

Steam under pressure gets to temp of 121
kill endospores

91
Q

Ionising radiation

A

EM radiatipn that produces ions and reactive molecules
used for surgical supplies, labwear, etc

91
Q

Pasterurisation

A

uses heat to only kill pathogenic bacteria but not all organisms

92
Q

UV

A

-affects DNA leading to death
-Used for decontaminating surfaces
-poor penetration

93
Q

Filter sterilisation

A

used for heat sensitive liquid and gas
pores too small for organisms but does not trap viruses

94
Q

Depth filters

A

fibrous sheet made of overlapping paper or glass
-HEPA filters

95
Q

Bacteriostatic agent

A

Inhibit biochemical properties and bind weakly

96
Q

Bactericidal agents

A

bind tightly and kill without lysis

97
Q

Bacteriolytic agent

A

kills by lysis

98
Q

sterilants

A

destroys all micro including endospores

99
Q

Minimum inhibitory concentration

A

smallest amount of agent needed to inhibt growth
-can be determined via Kirby-Bauer assay

100
Q

Kirby-Bauer assay

A

-Antimicrobe agent added to filter paper
-diffuses into agar
-MIC is reached at some distance

101
Q

sanitizers

A

reduce M number but dont sterilise

102
Q

antiseptics

A

kill or inhibt growth but are non toxic enough to apply to living tissues

Microbiology (6 decks)

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