Lecture 7 - Growth PART 1

Question 1

Bacteria will go in nature and in the lab.
In nature, what two forms do bacteria exist?

Answer 1

1. Planktonic: individual, free-floating bacterial cells.
2. Biofilm: polymer-encased communities of one or more bacterial species, which are attached to a surface.

Question 2

what type of bacteria comprises 70% of human infections?

Answer 2

Biofilm

Question 3

how do biofilm end up stroking surfaces?

Answer 3

with the help of capsule and pili

Question 4

what benefits do bacteria receive when biofilm grows?

Answer 4

-There is a sharing of nutrients between bacteria.
-There is protection from harm (desiccation, antibiotics, immune system).
-There is an easier exchange of genetic material.

Question 5

what harmful effects does biofilm have on us, humans? what is an example?

Answer 5

-They are harder to clean and treat for us.
Example: Pseudomonas aeruginosa in lungs of cystic fibrosis patients.
So it is good for bacteria but bad for us.

Question 6

Biofilm has Quorum sensing - what is that?

Answer 6

It is a chemical language through which bacteria talk to each other

Question 7

in what bacteria was quorum sensing discovered?

Answer 7

in Vibrio fischeri (short curved rod)

Question 8

when does the quorum sensing produce light?

Answer 8

it produces light only at high cell density.

Question 9

at high cell density, the concentration of a particular signal called ____ reaches a threshold, that turns on the genes responsible for group-specific behaviors like light or toxin production.

Answer 9

autoinducer

Question 10

what does autoinducer do?

Answer 10

it turns on the genes that are responsible for group-specific behaviors like light or toxin production.

Question 11

at low cell density, what happens with the bacterial quorum sensing?

Answer 11

nothing happens

Question 12

quorum sensing allows bacteria to act in unison to do what?

Answer 12

to perform big tasks that are useful for the community

Question 13

what does V. fischeri produce in the light organs of Hawaiian bobtail squid? how does this help the squid?

Answer 13

it produces light which minimizes the squid’s shadow and allows it to hunt stealthily

Question 14

quorum sensing can be used to design ____ that attack ____?

Answer 14

can be used to design antimicrobials/antibiotics to attack the autoinducer.

Question 15

in the lab, microbial growth is often in pure cultures, which are what?

Answer 15

they are cultures with only one species of bacteria

Question 16

what are the two types of culture (growth) mediums?

Answer 16

-Nutrient broth (NB): liquid.
Turbidity = cloudiness.
-Nutrient agar (NA): solid.
Isolated colonies: a colony is a distinct mass of cells arising from a single cell by multiple rounds of cell division.

Question 17

have all known bacteria been cultured in the lab?

Answer 17

NO, 99% of bacteria haven’t been cultured in the lab.

Question 18

what is the great plate count anomaly?

Answer 18

it is the number of cells observed under the microscope are greater than the number of colonies on a plate.
this means that we aren’t able to grow 99% of bacteria in the culture.

Question 19

what % of bacteria is unculturable?

Answer 19

99%

Question 20

do we know the identity of bacteria though? how?

Answer 20

we do know the identity through DNA studies; we can find their DNA but don’t know how to grow them

Question 21

how do we measure the growth of bacteria?

Answer 21

by the number of them

Question 22

what is binary fission?

Answer 22

it is when the bacterial cell splits into two.
1. the cell gets longer and the DNA replicates.
2. the DNA is moved into each future daughter cell and the cross wall forms.
3. the cell divides into two cells
4. the cells separate
5. two daughter cells form

Question 23

does binary fission of bacteria have mitosis or meiosis?

Answer 23

NO

Question 24

bacteria has exponential growth, what is that?

Answer 24

it is the rapid and exponent growth of the bacteria

Question 25

what is the generation (doubling) time of the bacteria? what is an example?

Answer 25

it is the time it takes for 1 cell to divide into 2 daughter cells. example: E. coli on a salad at room temperature goes from 10 cells to 40,000 cells in 4 hours.

Question 26

how do we grow bacteria?

Answer 26

in a closed (batch) system. this is when we use either broth or agar where we do not replenish the nutrients OR remove wastes.

Question 27

what are the 4 phases of microbial growth and what do they consist of?

Answer 27

1. Lag: this is before the actual division of bacterial cells, it is just prepping for the next steps. 2. Log/exponential phase: this is when there is an exponential increase in cell number; this is the MAX growth rate. 3. Stationary: this is when there is no increase in cell number. when the growth rate = the death rate. the dead cells lyse and provide food for the growing cells. 4. Death: this is when there is a decrease in cell number; eventually all bacteria will die.

Question 28

what does the X and Y axis of the growth curve chart consist of? what type of growth is recorded?

Answer 28

X-axis: time per hour, day, month, or year. Y-axis: the logarithmic growth because of the exponential speed of growth.

Question 29

what is a continuous system?

Answer 29

when the cells are in constant log/exponential phase.

Question 30

how might you create a continuous system?

Answer 30

by taking out wastes and giving food for the bacteria to grow constantly

Question 31

in agar, the cells on the outside are in the dead phase? ask prof

Answer 31

In a colony, cells in the middle are in the death phase and the ones on the periphery are in the exponential phase.

Question 32

Penicillin attacks growing bacteria, so in which phase of the growth curve does penicillin work best?

Answer 32

during the log/exponential phase

Question 33

what are the 4 environmental factors that can affect the growth of microbes?

Answer 33

they are physical (environmental) conditions. 1. temperature 2. pH 3. osmotic pressure (hyper vs. hypo) 4. oxygens

Question 34

what are the chemical (nutrients) factors that can affect the growth of microbes?

Answer 34

1. macronutrients (CHONPS; carbon, hydrogen, oxygen, nitrogen, phosphurus, sulfur). 2. micronutrients: Fe, Zn, Me, Ni.

Question 35

what are psychrophiles and psychrotrophs?

Answer 35

they are cold-loving bacteria. (philes = loving; trophs = eating)

Question 36

what are mesophiles?

Answer 36

they are bacteria that grow the fastest in optimum 37 degrees celsius.

Question 37

can mesophiles grow in other temperatures?

Answer 37

yes they can still grow in other temperatures but just grow the fastest in optimum temp

Question 38

all pathogens that create diseases in humans are what type of organism?

Answer 38

mesophiles

Question 39

what are thermophiles?

Answer 39

heat-loving bacteria

Question 40

what are hyperthermophiles?

Answer 40

superheat-loving

Question 41

at minimum growth rate, what happens?

Answer 41

the membrane is gelling; the transport processes are so slow that growth cannot occur

Question 42

on the way from minimum to optimum growth rate, what happens?

Answer 42

the enzymes and reactions occur at an increasingly rapid rate

Question 43

what happens at optimum growth rate?

Answer 43

when the enzymes and reactions occur at the maximal possible rate

Question 44

what happens at maximum growth rate?

Answer 44

protein denaturation: there is a collapse of the cytoplasmic membrane; thermal lysis occurs

Question 45

how do bacteria survive in very hot environments?

Answer 45

through two things: 1. rigid thermostable proteins: tightly folded proteins to prevent denaturation. 2. rigid membranes: have tightly packing lipids

Question 46

high temperatures are usually _____?

Answer 46

bactericidal = bacteria killing

Question 47

low temperatures are usually ____?

Answer 47

bacteriostatic = bacterial growth stopped

Question 48

what temperatures are considered the "danger zone"?

Answer 48

Between: 15 and 50 degrees celsius. 60 and 130 degrees Fahrenheit.

Question 49

does the temperature in the fridge kill the bacteria?

Answer 49

no, but it stops its growth

Question 50

are there significant growth of bacteria below freezing?

Answer 50

no

Question 51

what is pH?

Answer 51

the concentration of H+

Question 52

what is the pH of the cytoplasm of most bacteria?

Answer 52

7

Question 53

what are neutrophiles?

Answer 53

pH of 6-8

Question 54

what pH do most bacteria love?

Answer 54

most bacteria love neutral pH

Question 55

what are acidophiles?

Answer 55

bacteria that live in a pH of less than 5.5

Question 56

why do acidophiles live in that environment? what does it give them?

Answer 56

it gives them a competitive edge; it has more food and water to grow since not many other bacteria can live in that acidic of an environment

Question 57

what are alkaliphiles?

Answer 57

bacteria that grow in a pH over 8.5

Question 58

how do bacteria survive in low or high pH environments?

Answer 58

1. Pumping protons in (which alkaliphiles do) or pumping protons out (which acidophiles do). 2. Having membranes that are less permeable to protons. 3. Having more buffers in the cytoplasm to maintain pH.

Question 59

what is osmotic pressure?

Answer 59

water availability

Question 60

what do bacteria undergo in hypertonic environments? what is it used for?

Answer 60

plasmolysis - it is used in food preservation

Question 61

what does the term facultative refer to?

Answer 61

refers to when the bacteria can survive with or without that certain thing

Question 62

what does the term obligate refer to?

Answer 62

when that bacteria NEEDS that certain thing and cannot live without it

Question 63

what are facultative halophiles? what is another name for them?

Answer 63

there are salt-loving organisms that can survive with or without salt. aka halotolerant

Question 64

what NaCl percentage do facultative halophiles live under?

Answer 64

NaCl up to 10% or higher

Question 65

what is an example of facultative halophiles?

Answer 65

S. epidermidis - it can grow on clean or sweaty skin (salty or non salty skin)

Question 66

when there are more solutes outside of the cell than inside, where does water flow?

Answer 66

towards the outside of the cell

Question 67

what are obligate halophiles?

Answer 67

these organisms NEED salt and cannot live without it.

Question 68

what percentage of salt do obligate halophiles need to live under?

Answer 68

NaCl of at least 9%. They can live in saturated salt (32%)

Question 69

what is an example of obligate halophiles?

Answer 69

Halobacterium salinarium

Question 70

how do bacteria prevent plasmolysis in high-salt environments?

Answer 70

they accumulate solutes in the cytoplasm so that they are isotonic with the salty environments around them. the salt in the environment = the salt in the cytoplasm

Question 71

what are obligate aerobes? what is an example?

Answer 71

bacteria that need O2 to grow. example: Pseudomonas

Question 72

what are obligate anaerobes? what is an example?

Answer 72

bacteria that die in the presence of O2. example: Clostridium

Question 73

how do obligate anaerobes grow without O2?

Answer 73

they grow via an anaerobic chamber/jar

Question 74

what are facultative anaerobes? what is an example?

Answer 74

bacteria that prefer O2 but can survive without it. example: E. coli

Question 75

what are microaerophiles? what is an example?

Answer 75

these bacteria need a little bit of O2. example: Helicobacter

Question 76

what are aerotolerant anaerobes? what is an example?

Answer 76

anaerobes that can tolerate the presence of O2. example: Streptococcus pyogenes

Question 77

how do bacteria deal with the toxic byproducts of O2 metabolism (like H2O2)?

Answer 77

O2 often makes toxic byproducts. We deal with these toxins by our enzymes like catalase and superoxide dismutase to detoxify the toxins.

Question 78

In which phase of the bacterial growth curve does the number of dividing bacteria equal the number of dying bacteria? 1. Lag phase 2. Log phase 3. Stationary phase 4. Death phase 5. Exponential phase

Answer 78

3. Stationary Phase

Question 79

The lag phase of the bacterial growth curve is marked by: 1. A decrease in cell mass 2. Dormant, metabolically inactive cells 3. Vigorously dividing cells 4. Metabolically active cells 5. A decrease in enzyme activity

Answer 79

4. Metabolically active cells

Question 80

Microorganisms that die in the presence of O2 are referred to as: 1. Facultative anaerobes 2. Obligate anaerobes 3. Microaerophiles 4. Aerotolerant anaerobes 5. Obligate aerobes

Answer 80

2. Obligate anaerobes

Question 81

In figure 1, which line represents the exponential growth phase of a mesophile with an optimum temperature of 350C incubated at 400C? (Hint: Distinguish optimum temperature vs. temperature range.) 1. a 2. b 3. c

Answer 81

2. b (not the fastest, but still grows)

Question 82

Case study: Of the following, what would be the LEAST important thing for the investigator to determine when studying the outbreak? 1. A description of the symptoms, including symptoms that are NOT present 2. If anyone else had been ill before or had gotten ill around the same time 3. A detailed food history over the last 72 hours 4. Contact information for the caller (phone numbers, address, etc.) 5. Where the caller suspects he got sick

Answer 82

5. Where the caller suspects he got sick. Explanation: Regardless of the source of digestive illness (whether it be food, water, or another person), complainants will often associate their illness with the last food or meal they consumed. While knowing about the restaurant as part of food history is good, one should not assume anything at this point. The investigator should keep an open mind and solicit information about the following: 1) Foods and beverages that may have been eaten at least 72 hours ago--since incubation periods of certain diseases can be 3 days or more 2) If anyone else had been ill before or had gotten ill around the same time--find out which foods and beverages that affected individuals had in common 3) A description of the symptoms, including symptoms NOT present e.g. fever--since this may help narrow down the list of possible diseases 4) Contact information is important in order to follow-up on the case, especially if the situation turns into an outbreak

Question 83

As the investigator, what would you advise the student to do? 1. Stay home and not go to school. 2. See a doctor. 3. Eat a bland diet until the symptoms stop. 4. Its okay to go to school if he feels better.

Answer 83

2. See a doctor. Explanation: A public health investigator is not a doctor and should not be giving medical advice, especially over the phone. This could lead to great liability if the case takes a turn for the worse. The other answers may be things that a doctor will advise the student to do.

Question 84

Do you think these cases of gastroenteritis represent an outbreak at the college? 1. Yes they do. 2. No, they do not. 3. They represent a student's attempt to get out of his Microbiology test

Answer 84

1. Yes they do. Explanation: YES. An outbreak is defined as the occurrence of more cases of a disease than expected for a particular place and time. Of course, the student's thinking may still be to get out of the Microbiology test!