G: Environmental Factors Influencing Growth Flashcards

1
Q

What does -phile mean

A

means prefer and often means requires

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2
Q

What does -tolerant mean

A

will grow in a wider range of conditions than non-tolerant

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3
Q

What does -facultative mean

A

optional mode

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4
Q

What does -obligate mean

A

an absolute requirement

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5
Q

What does -hyper mean

A

above/greater than

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6
Q

What does -extreme mean

A

outside of normal range

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7
Q

How is water activity expressed as, and what does it reflect

A

aw, reflects how wet/dry an environment is and concentration of solutes dissolve in the water

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8
Q

Equation for aw

A

aw= Psoln/Pwater where =vapour pressure

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9
Q

Give the range of aw. What does this mean

A

0 to 1. The higher the [soulte] the lower the water activity. Water has an aw of 1

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10
Q

How does bacterial cells in an environment with high aw protect themselves

A

by their peptidoglycan

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11
Q

When will bacterial cells undergo plasmolysis

A

in an environment with low aw (<0.9)

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12
Q

What is the typical aw minimum for bacteria

A

0.95-0.98

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13
Q

What are osmotolerant bacteria called if solute is NaCl

A

halotolerant

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14
Q

give an example of halotolerant bacteria and aw limit

A

Staphyloccocus spp. lower limit is 0.85

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15
Q

What are halophiles

A

adapted to grow in presence of salts like NaCl, require high levels to grow

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16
Q

How do osmotolerant and halophilic bacteria prevent plasmolysis

A

must keep internal [solute] the same or higher than that of enivironment

17
Q

How is internal [solute] the same as the enivironment. Hint: uptake

A

by uptake of synthesis of a compatible solute

18
Q

What are compatible solutes

A

hydrophilic molecules/ions that do not affect cellular fn. eg aa, sugars or ionic compounds like KCl

19
Q

Would H+ work as a compatible solute

A

no too acidic, must select stg that is neutral to environment

20
Q

application of water availability

A

food preservation: dried or freeze dried (water is frozen and then sublime in a vacuum) and sugar/salt added

21
Q

How can bacteria be preserved

A

lyophilized (freeze dried)

22
Q

what is the optimal pH

A

it varies, bacterial growth is affected by environmental pH

23
Q

acidophiles optimum pH is

A

under 5.5

24
Q

most bacteria have a pH of? they are called

A

optimal pH of 7 called neutrophiles

25
Q

give an example of neutrophile

A

gram -ive Helicobacter pylori

26
Q

how does Helicobacter pylori protect itself from stomach acid

A

secretes urease. substrate for urease is urea. one product of this rxn is ammonia which can bind hydrogen ions and therefore increase the pH

27
Q

alkalophiles optimum pH is

A

over 8.0

28
Q

application of alkalophiles

A

some Bacillus spp. can secrete proteases and lipases that are stable at high pH. theses enzymes are produced industrially and added to laundry detergents

29
Q

what does the optimal pH refer to

A

extreme environment only. cytoplasmic pH must remain near neutral (in most bacteria) to prevent denaturation of proteins and nucleic acids

30
Q

Why are buffers added to batch culture media

A

some bacteria produce waste products that change pH of environment. buffers keep media at optimal pH for the species being grown

31
Q

name an acid tolerance bacteria

A

E. coli O157:H7 has adapted to lower pH, helps it survive acidic human stomach