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MICR221 Lectures 1-38 > MICR221 Lecture 1 - Physical and Chemical Requirements of Microbial Growth > Flashcards

MICR221 Lecture 1 - Physical and Chemical Requirements of Microbial Growth Flashcards

1
Q

what is microbial growth?

A

an increase in the number of cells that causes population growth

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2
Q

what is binary fission?

A

the division of a bacterial cell

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3
Q

what is the process of binary fission?

A

1 parent cell –> cell elongates –> chromosomal DNA replicates (2 copies of genetic material are in 1 cell for a short period of time) –> each chromosome moves to opposite ends of the elongated cell –> septum (special cross-wall) starts to form –> fully formed septum causes the elongated cell to divide into 2 identical daughter cells

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4
Q

what is the equation for cell growth?

A

2^n

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5
Q

what determines bacterial cell shape?

A

depends on the plane of division during binary fission

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6
Q

how is a diplococcus shape formed from a coccus shape?

A

coccus cell is divided into 1 plane to create a diplococcus cell (1–>2)

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7
Q

how is a streptococcus shape formed from a coccus shape?

A

coccus cell is divided into 1 plane to create a diplococcus cell and then the diplococcus cell is divided into 2 planes to create a streptococcus cell

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8
Q

how is a cluster shape formed from a coccus shape?

A

coccus cell is divided into many planes to create a cluster cell

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9
Q

why is a small bacterial cell shape more common among bacteria?

A

a small bacterial cell shape increases the surface area to volume ratio and this increases the uptake of nutrients in the cell supporting a rapid cell growth

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10
Q

how does a large bacterial cell shape increase surface area to volume ratio?

A

by having a convoluted plasma membrane

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11
Q

what are the 2 factors for the growth requirements of bacterial cells?

A

physical factors and chemical factors

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12
Q

what are the 4 physical factors of growth requirements?

A

gaseous atmosphere –> temperature –> pH –> osmotic pressure

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13
Q

what are aerobes?

A

cells that require oxygen for aerobic respiration

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14
Q

what are anaerobes?

A

cells that prefer the absence of oxygen for anaerobic respiration

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15
Q

what do aerobes use in terms of the electron transport chain?

A

use the electron transport chain with oxygen or another oxidant as the terminal electron acceptor

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16
Q

what do anaerobes use?

A

use the electron transport chain with an exogenous terminal electron acceptor such as nitrate and sulphate

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17
Q

what are facultative anaerobes?

A

cells that grow with or without the presence of oxygen

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18
Q

what is fermentation in terms of the electron transport chain?

A

generates no electron transport chain or proton motive force where ATP is synthesised from substrate-level phosphorylation

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19
Q

what is the electron acceptor in fermentation?

A

endogenous electron acceptor pyruvate

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20
Q

what are microaerophiles?

A

cells that require little oxygen

micro= little

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21
Q

what are capnophiles?

A

cells that require increased levels of carbon dioxide

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22
Q

what are the 5 oxygen concentrations (in terms of growth in test tubes)?

A 
obligate aerobes
facultative anaerobes
aerotolerant anaerobes
strict anaerobes
microaerophile
23
Q

what are obligate aerobes and what protective enzymes do they include?

A

cells that require oxygen

+ SOD and + Catalyse

24
Q

what are facilitative anaerobes and what protective enzymes do they include?

A

cells that prefer oxygen

+ SOD and + Catalyse

25
Q

what are aerotolerant anaerobes and what protective enzymes do they include?

A

cells that grow with or without the presence of oxygen

+ SOD and - Catalyse

26
Q

what are strict anaerobes and what protective enzymes do they include?

A

cells that oxygen is toxic for

- SOD and - Catalyse

27
Q

what are microaerophiles and what protective enzymes do they include?

A

cells that grow between 2-10% oxygen conc

28
Q

where does bacteria grow if it is an aerobe in a test tube?

A

at the top of the test tube

29
Q

where does bacteria grow if it is an anaerobe in a test tube?

A

at the bottom of the test tube

30
Q

how is oxygen toxic to anaerobes?

A

oxygen can be converted by metabolic enzymes into highly reactive derivatives such as O2- which is a superoxide free radical and this damages cells. Anaerobes do not possess the protective enzymes to break down O2-

31
Q

how to aerobes break down O2- (superoxide free radical)?

A

O2- is converted into hydrogen peroxide by the enzyme superoxide dismutase and then is further broken down by the protective enzymes catalase or peroxidase

32
Q

how many protective enzymes will aerobes contain?

A

2/3 protective enzymes

33
Q

what are the 5 types of bacteria based on their temperature preferences?

A 
psychrophiles
psychrotrophs
mesophiles
thermophiles
hyperthermophiles
34
Q

what temperature do psychrophiles grow?

A

below or around 10’C

35
Q

what temperature do psychrotrophs grow?

A

around 25’C

36
Q

what temperature do mesophiles grow?

A

around 35-40’C

37
Q

what temperature do thermophiles grow?

A

optimum temp is above 45’C

38
Q

what temperature do hyperthermophiles grow?

A

around 90’C

39
Q

what pH do most bacteria grow at?

A

between pH 6-9

40
Q

what is osmotic pressure?

A

determined by the number of molecules in solution

41
Q

what is the most favourable environment for bacterial growth?

A

isotonic, when the bacterial cell contents have the same concentration as the surrounding medium

42
Q

what are the 2 chemical factors for growth requirements?

A

water

energy and electron source

43
Q

what does temperature affect?

A

affects the availability of water

44
Q

what does water affect?

A

affects osmotic pressure

45
Q

what are phototrophs?

A

derive energy from sunlight

46
Q

what are chemotrophs?

A

derive energy from the oxidation of chemical compounds either organic or inorganic
e.g sugars or amino acids

47
Q

what are lithotrophs?

A

reduced inorganic substances

48
Q

what are organotrophs?

A

reduced organic compounds

49
Q

what are autotrophs?

A

use only inorganic carbon in the form of CO2

50
Q

what are heterotrophs?

A

utilise organic carbon - proteins, lipids and carbohydrates

51
Q

what is the combined term for energy, electron and carbon sources?

A

chemo organoheterotrophs

52
Q

what are chemo organoheterotrophs?

A

most non-photosynthetic microbes

53
Q

what are aerobes?

A

cells that require oxygen for aerobic respiration

54
Q

what do aerobes use?

A

use the electron transport chain with oxygen or another oxidant as the terminal electron acceptor

MICR221 Lectures 1-38 (10 decks)

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