MICR221 Lecture 1 - Physical and Chemical Requirements of Microbial Growth

Question 1

what is microbial growth?

Answer 1

an increase in the number of cells that causes population growth

Question 2

what is binary fission?

Answer 2

the division of a bacterial cell

Question 3

what is the process of binary fission?

Answer 3

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

Question 4

what is the equation for cell growth?

Answer 4

2^n

Question 5

what determines bacterial cell shape?

Answer 5

depends on the plane of division during binary fission

Question 6

how is a diplococcus shape formed from a coccus shape?

Answer 6

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

Question 7

how is a streptococcus shape formed from a coccus shape?

Answer 7

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

Question 8

how is a cluster shape formed from a coccus shape?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

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

Answer 10

by having a convoluted plasma membrane

Question 11

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

Answer 11

physical factors and chemical factors

Question 12

what are the 4 physical factors of growth requirements?

Answer 12

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

Question 13

what are aerobes?

Answer 13

cells that require oxygen for aerobic respiration

Question 14

what are anaerobes?

Answer 14

cells that prefer the absence of oxygen for anaerobic respiration

Question 15

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

Answer 15

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

Question 16

what do anaerobes use?

Answer 16

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

Question 17

what are facultative anaerobes?

Answer 17

cells that grow with or without the presence of oxygen

Question 18

what is fermentation in terms of the electron transport chain?

Answer 18

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

Question 19

what is the electron acceptor in fermentation?

Answer 19

endogenous electron acceptor pyruvate

Question 20

what are microaerophiles?

Answer 20

cells that require little oxygen

micro= little

Question 21

what are capnophiles?

Answer 21

cells that require increased levels of carbon dioxide

Question 22

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

Answer 22

obligate aerobes
facultative anaerobes
aerotolerant anaerobes
strict anaerobes
microaerophile

Question 23

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

Answer 23

cells that require oxygen

+ SOD and + Catalyse

Question 24

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

Answer 24

cells that prefer oxygen

+ SOD and + Catalyse

Question 25

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

Answer 25

cells that grow with or without the presence of oxygen | + SOD and - Catalyse

Question 26

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

Answer 26

cells that oxygen is toxic for | - SOD and - Catalyse

Question 27

what are microaerophiles and what protective enzymes do they include?

Answer 27

cells that grow between 2-10% oxygen conc

Question 28

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

Answer 28

at the top of the test tube

Question 29

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

Answer 29

at the bottom of the test tube

Question 30

how is oxygen toxic to anaerobes?

Answer 30

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-

Question 31

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

Answer 31

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

Question 32

how many protective enzymes will aerobes contain?

Answer 32

2/3 protective enzymes

Question 33

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

Answer 33

``` psychrophiles psychrotrophs mesophiles thermophiles hyperthermophiles ```

Question 34

what temperature do psychrophiles grow?

Answer 34

below or around 10'C

Question 35

what temperature do psychrotrophs grow?

Answer 35

around 25'C

Question 36

what temperature do mesophiles grow?

Answer 36

around 35-40'C

Question 37

what temperature do thermophiles grow?

Answer 37

optimum temp is above 45'C

Question 38

what temperature do hyperthermophiles grow?

Answer 38

around 90'C

Question 39

what pH do most bacteria grow at?

Answer 39

between pH 6-9

Question 40

what is osmotic pressure?

Answer 40

determined by the number of molecules in solution

Question 41

what is the most favourable environment for bacterial growth?

Answer 41

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

Question 42

what are the 2 chemical factors for growth requirements?

Answer 42

water | energy and electron source

Question 43

what does temperature affect?

Answer 43

affects the availability of water

Question 44

what does water affect?

Answer 44

affects osmotic pressure

Question 45

what are phototrophs?

Answer 45

derive energy from sunlight

Question 46

what are chemotrophs?

Answer 46

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

Question 47

what are lithotrophs?

Answer 47

reduced inorganic substances

Question 48

what are organotrophs?

Answer 48

reduced organic compounds

Question 49

what are autotrophs?

Answer 49

use only inorganic carbon in the form of CO2

Question 50

what are heterotrophs?

Answer 50

utilise organic carbon - proteins, lipids and carbohydrates

Question 51

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

Answer 51

chemo organoheterotrophs

Question 52

what are chemo organoheterotrophs?

Answer 52

most non-photosynthetic microbes

Question 53

what are aerobes?

Answer 53

cells that require oxygen for aerobic respiration

Question 54

what do aerobes use?

Answer 54

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