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

Chapter 4: Microbial growth and its control 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
Pour-plate method
26
Applications of the Plate count
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
27
Great plate count anomaly
Can only culture 1% of microbes and so culture is not an actual representative
28
Microscope vs plate count
Plate counts are always better as can indicate all microbes present
29
Indirect counts
Give an estimate 1. turbidity 2. Metabolic activity 3. dry weight
30
Turbidity
Cell suspensions are turbid because cells scatter light More cells=more scattered light and increased turbidity Turbidity measurements are rapid and used for estimates
31
Optical density
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
32
Ad of turbity measurements
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
33
Metabolic activity
Method assumes that the CO2 meausered is directly proprtional to cell numbers higher CO2 = higher cell pop
34
Dry weight
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
35
Binary fission
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
36
septum
partiton dividng cells, pinches off between daughter cells
37
generation time
Time required for microbial cells to double in number
38
Batch culture
A closed-system microbial culture of fixed volume
39
Phases of growth curve
Lag phase exponential phase stationary phase death phase
40
lag phase
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
41
Exponential phase
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
42
Stationary phase
growth limited by nutrient depletion or waste accumulation growth rate is zero metabolism continues at greatly reduced rate
43
Decline phase
Total number decreases due to cell death
44
Cryptic growth
subpopulations adapt
45
Diauxic growth
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
Doubling time formula
Td= 0.693/B B is the number from equation on graph
47
Planktonic growth
Growth in suspension of free-floating/free-swimming cells
48
Sessile growth
Attached to surface can develop into biofilms NB in medical and industrial applications
49
Biofilm
cells emmeshed polysaccharide matrix attached to surface
50
stages of biofilm growth
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
Microbial mats
Multilayered sheets with differnt organisms in each layer
52
Humans and biofilms
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
Biofilm lethality
Resistant to antibiotics and infections
54
Optimum temperature for most microbes
Less than 40 degrees
55
psychrophile
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
Mesophile
midrange, commonly studied
57
thermophile
high, hot environments
58
hyperthermophiles
Very high, found in extremely hot habitats such as hot springs and deep-sea hydrothermal vents
59
Extremophiles
Organisms that grow under extreme conditions (hot and cold)
60
psychotolerant
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
Molecular adaptions for cold
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
Hyperthermophile diet
Chemoorganotrophic and chemolithotrophic
63
Thermophile
Growth temperature beteen 45 and 80
64
Hyperthermophile
Growth greater than 80 inhabit hot springs and hydrothermal vents with temps greater than 100 above 65 only pro survives
65
Adaptions to survive heat
-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
useful thermophile
Taq polymerase for PCR
67
adaptions of hyperthermophile
-They have C40 hydrocarbons made of repeating isoprene units bonded by ethers to glycerol phosphate and they have a monolayer memebrane
67
Neutrophile
pH> 5.5 and <8
68
Acidophile
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
Akaliphiles
pH>8 found in soda lakes and high carbonante soil used commercially in detergents have sodium motive force
70
water activity
ratio of water vapor pressure of air equilibrium with a substance or solution to vapor pressure of pure water
71
positive water balance
cytoplasm has higher solute concentration than outside otherwise water flows out
72
Halophiles
grow best at aw=0.98 which is sea water have requirement for NaCl
73
Halotolerant
Tolerate some dissolved solutes but grow best in absence
74
Extreme halophiles
Need 15-30% NaCl and cant grow at lower concentrations
74
Compatible solutes
Microbes pump these solutes into cell to maintain positive water balance they do not inhibit biochemical processes
75
Osmophile
Live in high sugar
76
Xerophile
live in dry environment
77
Why add reducing agents to culture?
To reduce oxygen to water
77
resazurin
dye that indicates Oxygen concentration
77
singlet oxygen
molecular O2 that has been boosted into higher energy state- extremely reactive
78
Superoxide radical
formed in normal amounts due to respiration toxic
79
Peroxide anion
Byproduct of conversion of superoxide radicals extremely toxic
79
Hyrdoxyl radical
Formed by IONIZING RADIATION in cytoplasm most reactive
80
Superoxide dismutase (SOD)
Converts superoxide to H peroxide and O2
80
Catalase and peroxidase
Convert H peroxide to O2 and H2O
81
Facultative anaerobes
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
Obligate aerobes
-Oxygen required -growth occurs in high O2 concentrations -Presence of SOD and catalase allows toxic forms of O2 to be neutralised
82
Superoxide reductase
Converts superoxide to H peroxide without producing O2
83
Obligate anaerobes
-Only grows without O2 -growth occurs where little O2 -lacks enzymes to neutralise O2
84
Micro-aerophiles
-Only aerobic growth with low O2 concentration -Growth occurs in low concentration -produces lethal amounts of byproducts if exposed to atmospheric O2
85
Aerotolerant anaerobes
-only anaerobic growth -growth occurs evenly, O2 has no effect -Presence of SOD partially neutralises O2
86
Decontamination
Treatment of object to make safe to handle
87
Disinfection
-directly targets pathogens -kills or inhibts growth
88
Heat sterilisation
most used higher heat kills faster moist heat penetrates better than dry heat
89
Decimal reduction time
Amount of time reuired at a given temp to reduce viability 10-fold
90
Thermal death time
time to kill all cells at a given temp and is affected by pop size
90
Autoclave
Steam under pressure gets to temp of 121 kill endospores
91
Ionising radiation
EM radiatipn that produces ions and reactive molecules used for surgical supplies, labwear, etc
91
Pasterurisation
uses heat to only kill pathogenic bacteria but not all organisms
92
UV
-affects DNA leading to death -Used for decontaminating surfaces -poor penetration
93
Filter sterilisation
used for heat sensitive liquid and gas pores too small for organisms but does not trap viruses
94
Depth filters
fibrous sheet made of overlapping paper or glass -HEPA filters
95
Bacteriostatic agent
Inhibit biochemical properties and bind weakly
96
Bactericidal agents
bind tightly and kill without lysis
97
Bacteriolytic agent
kills by lysis
98
sterilants
destroys all micro including endospores
99
Minimum inhibitory concentration
smallest amount of agent needed to inhibt growth -can be determined via Kirby-Bauer assay
100
Kirby-Bauer assay
-Antimicrobe agent added to filter paper -diffuses into agar -MIC is reached at some distance
101
sanitizers
reduce M number but dont sterilise
102
antiseptics
kill or inhibt growth but are non toxic enough to apply to living tissues

Microbiology (6 decks)

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