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microbes to medicine > Lecture 1 - Physical and chemical requirements of microbial growth > Flashcards

Lecture 1 - Physical and chemical requirements of microbial growth Flashcards

1
Q

Bacterial growth is

A

exponential

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2
Q

Population =

A

2^n where n is the division number

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3
Q

The time it takes for one cell (and therefore the whole population) to divide is called the …

A

Mean generational time (doubling time)

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4
Q

Why is it better to put microbial growth as logarithmic compared to arithmetic?

A

On graphs usually plotted as a log10 number of cells to produce a straight line - also as exponential curve has its disadvantages such as it being difficult to separate plot points at the beginning of the population growth and as the population numbers get high it is hard to plot them

Logarithmic scale easier to read than the arithmetic (exponential) curve

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5
Q

Binary fission steps

A

Elongation - DNA replication - Cross wall forms (septum) - two cells separate

There are two copies of the genetic material in one cell just before the septum forms. The chromosome migrates, one to each end of the cell and when the septum completely forms the cells separate and this is the end of one cycle of binary fission

End up with two identical daughter cells

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6
Q

Surface area to volume ratio

A

Small cell increases SA:V ratio

As the SA:V ratio increases, the uptake of nutrients become more efficient which therefore supports a rapid growth rate

Larger bacteria do exist but often use different characteristics such as a convoluted surface to maximise the SA:V ratio

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7
Q

Cocci

A

Roughly spherical cells - can exist singly or can be in an arrangement

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8
Q

Diplococci

A

Diplococci arise when cocci divide and remain together to form pairs.

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9
Q

Chains: streptococcus

A

Long chains of cocci result when cells adhere after repeated divisions in one plane; this pattern is seen in the genera Streptococcus, enterococcus and lactococcus

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10
Q

Clusters

A

Members of the genus staphylococcus divide in random planes to generate irregular, grape-like clusters

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11
Q

Rods

A

sometimes called bacilli (singular = bacillus) differ in length to width ratio

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12
Q

Organisms can be divided into two categories according to their energy source …

A 
Phototrophs = derive energy from sunlight 
Chemotrophs = energy derived from oxidation of chemical compounds (organic or inorganic) e.g. sugars, amino acids
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13
Q

Phototrophs

A

derive energy from sunlight

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14
Q

Chemotrophs

A

energy derived from oxidation of chemical compounds (organic or inorganic) e.g. sugars, amino acids

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15
Q

Electron sources..

A

Reduced inorganic substances = lithotrophs

Reduced organic compounds = organotrophs

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16
Q

Carbon sources…

A 
Autotrophs = utilise only inorganic carbon in the form of carbon dioxide 
Heterotrophs = utilise organic carbon (proteins, carbohydrates and lipids)
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17
Q

Lithotrophs

A

Reduced inorganic substances

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18
Q

Organotrophs

A

Reduced organic substances

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19
Q

Autotrophs

A

Utilise inorganic carbon in the form of carbon dioxide

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20
Q

Heterotrophs

A

Utilise organic carbon (proteins, carbohydrates and lipids)

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21
Q

chemoorganoheterotrophs

A

= uses organic energy sources

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22
Q

List the physical requirements of microbial growth

A

Gaseous atomosphere (oxygen)
Temperature
pH
Osmotic pressure

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23
Q

List the chemical requirements of microbial growth

A

Water
energy and electron source
Carbon
Macronutrients and micronutrients

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24
Q

Cardinal temperatures

A

Minimus below which growth is not possible (~8 degrees), optimum where growth is most rapid (~37 degrees), and maximum above which growth is not possible (~65 degrees)

Minimum temperature may kill but is more likely to send the microbe into a protective dormancy phase (slows everything in the cell down), whereas maximum temperature kills

25
Q

pH

A

Bacteria usually like a neutral range (6-9) (fungi are a bit wider), each bacteria has an optimum pH for its extracellular environment
Always exceptions to the rule such as acidophiles and archaea
Buffers are often put in growth media to keep the pH near neutral because that is what most of the microbes like
Acidophiles = growth optimum between pH 0-5.5
Neutrophiles between pH 5.5 and 8.0
Alkaliphiles between pH 8.0 and 11.5

26
Q

Acidophiles

A

growth optimum between pH 0-5.5

27
Q

Neutrophiles

A

growth optimum between 5.5-8

28
Q

Alkaliphiles

A

Growth optimum between 8-11.5

29
Q

What is osmotic pressure determined by?

A

the number of molecules in solution

30
Q

Isotonic

A

bacterial cell contents have the same concentration as the surround medium (most favourable)

31
Q

Hypertonic

A

high concentration outside the cell which draws water out of the cell, causes shrinkage of the membrane and plasmolysis which kills the cell

32
Q

Hypotonic

A

low concentration outside the cell which draws water into the cell, cell expands however the cell does not burst due to the rigid cell wall

33
Q

Some microbes are adapted to extreme hypertonic environments and can be called

A

oenophiles

34
Q

______ require the presence of NaCl at a concentration above about 0.2M

A

halophiles

35
Q

Water

A

Affects osmotic pressure and temperature affects the availability of water

Essential for bacterial growth, accounts for 80-90% of the bacterial cell

36
Q

Energy and electron source

A

important for essential cell functions

37
Q

Carbon

A

Half the dry weight of a bacterial cell is carbon

38
Q

Aerobes

A

Require molecular oxygen (aerobic respiration) (required for their growth and metabolism)

Completely dependent on atmospheric oxygen for growth

Electron transport chain, then final electron acceptor is oxygen (or some other oxidant)

39
Q

Anaerobes

A

Prefer the absence of oxygen (anaerobic respiration or fermentation)

Anaerobic respiration uses the electron transport chain, the final electron acceptor is exogenous e.g. nitrate, sulphate

Use glove box when you want to investigate microorganisms in an anaerobic environment

Obligate anaerobes do not tolerate oxygen and die in its presence

40
Q

In fermentation there is no…

A

ETC (or generation of proton motive force), ATP is synthesised by substrate level phosphorylation, electron is endogenous e.g. pyruvate

41
Q

Facultative anaerobes

A

grow with or without oxygen - better with oxygen, they use oxygen when it is present but are able to continue growing by using either anaerobic respiration or fermentation when no oxygen however the efficiency of producing energy decreases in the absence of oxygen

42
Q

Microaerophiles

A

require a little oxygen but not too much (ideal conc is between 2-10%, there is 20% oxygen conc in the atomsphere)

43
Q

Capnophiles

A

require increased levels of carbon dioxide (atmosphere is at 0.4%, they like 5% therefore 100 times more CO2 than in the environment)

44
Q

Aerotolerant anaerobe

A

grows equally well with or without oxygen

45
Q

Toxic oxygen

A

Oxygen can be converted by metabolic enzymes into highly reactive derivative such as the superoxide free radical (O2-), which is very damaging to cells (damage proteins, lipids and nucleic acids). Aerobes and most facultative organisms convert superoxide free radical to hydrogen peroxide by means of the enzyme superoxide dimutase. This is further broken down by catalase or peroxidase. Anaerobes do not possess these enzymes and therefore cannot tolerate oxygen

Superoxide and hydrogen peroxide are often referred to as “reactive oxygen species (ROS)”

46
Q

Toxic products of oxygen reactions

A

O2 + e- -> O2- (superoxide radical)
O2- + e- + 2H+ -> H2O2 (hydrogen peroxide)
H2O2 + e- + H+ -> H2O + OH- (hydroxyl radical)

aerobes and faculatative organisms produce protective enzymes:
superoxidedimutase (2O2- + 2H+ -> O2 + H2O2)
catalase (2H2O2 -> 2 H2O + O2)
peroxidase (H2O2 + NADH -> 2H20)

47
Q

Psychrophiles

A

like low temperatures, grows at 0 degrees and has an optimum growth temperature of 15 degrees or lower (e.g. arctic, antarctic, deep ocean water)

48
Q

Psychotrophs/psychotolerants

A

low temps, optimum is 20 degrees, may be responsible for food in the fridge spoiling (can grow around 0-7 degrees, max at around 35 degrees)

49
Q

Mesophiles

A

optimum temp around 37 degrees (between 20 and 45 degrees), lots of study done because it includes human pathogens

50
Q

thermophiles

A

optimum 60 degrees, compost sites or spas or hot water cylinders for example

51
Q

Hyperthermophiles

A

optimum approx 90 degrees, e.g. volcanoes, very hard to replicate these conditions in the laboratory

52
Q

Macronutrients

A

Macronutrients are necessary in large amounts; micronutrients tend to be needed in smaller amounts and are often trace elements.
Macroelements/nutrients = carbon, hydrogen, nitrogen, oxygen, phosphorus, sulphur (CHONSP - these elements make up 96% of all living organisms)
Found in organic molecules such as lipids, proteins etc

Other macro elements listed below. They exist as cations and anions and generally are associated with and contribute to the activity and stability of molecules and cell structures such as enzymes and ribosomes. Thus they are important in many cellular processes including protein synthesis and energy conservation.
Cations = potassium, sodium, magnesium, calcium, iron
Anion = chlorine

53
Q

Micronutrients

A

Micronutrients = zinc, cobalt, molybdenum, copper, manganese
Aid in catalysis of reactions and maintenance of protein structure

54
Q

Oxidation

A

Loss of electrons = oxidised
OIL = Oxidation is loss
The thing that is oxidised is the reducing agent/provides reducing power

55
Q

Reducing agent

A

The thing that is oxidised is the reducing agent/provides reducing power

56
Q

Reduction

A

Gains electrons = reduced
RIG = Reduction is gain
The thing that is reduced is an oxidising agent/provides oxidising power

57
Q

Oxidising agent

A

The thing that is reduced is an oxidising agent/provides oxidising power

58
Q

Oxidant

A

the oxidant or oxidizing agent gains electrons and is reduced.

59
Q

Reductant

A

the reductant or reducing agent loses electrons and is oxidized

microbes to medicine (12 decks)

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