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Micro > Microbial Growth > Flashcards

Microbial Growth Flashcards

1
Q

What are the major elements (macronutrients)?

A
  1. Carbon
  2. Oxygen
  3. Nitrogen
  4. Hydrogen
  5. Phosphorus
  6. Sulfur
  7. Potassium
  8. Magnesium
  9. Calcium
  10. Iron
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2
Q

What are carbon’s sources and functions in bacterial cells?

A

Source: carbon dioxide or organic compounds.
Function: It is the main component for the structure of the material of a cell. It is used to build nutrients for the cell (ex: carbohydrates, lipids).

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3
Q

What are oxygen’s sources and functions in bacterial cells?

A

Source: organic compounds, water (H2O), and carbon dioxide (CO2)
Function: In aerobic respiration, oxygen is the final electron acceptor. It is also used as a component of cell water and cellular material.

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4
Q

What are nitrogen’s sources and functions in bacterial cells?

A

Source: organic compounds, nitrogen gas (N2), ammonia (NH3), and nitrate (NO3).
Function: component of coenzymes, amino acids, and nucleic acids nucleotides.

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5
Q

What are hydrogen’s sources and functions in bacterial cells?

A

Source: organic compounds, hydrogen gas (H2), and water (H2O)
Function: the main component of cell water and organic compounds.

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6
Q

What are phorphorus’ sources and functions in bacterial cells?

A

Source: inorganic phosphates
Function: component of lipopolysaccharides, teichoic acids, nucleotides, phospholipids, and nucleic acids

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7
Q

What are sulfur’s sources and functions in bacterial cells?

A

Source: organic sulfur compounds, sulfate (SO4), and hydrogen sulfide (H2S).
Function: component of multiple coenzymes, cysteine, glutathione, and methionine.

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8
Q

What are potassium’s sources and functions in bacterial cells?

A

Source: potassium salts.
Function: cofactor for particular enzymes and it is the main cellular inorganic cation.

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9
Q

What are magnesium’s sources and functions?

A

Source: magnesium salts.
Function: cofactor for particular enzymatic reactions, and it is an inorganic cellular cation

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10
Q

What are calcium’s sources and functions in bacterial cells?

A

Source: calcium salts.
Function: cofactor for particular enzymes, it is an inorganic cellular cation, and it is a component of endospores

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11
Q

What are iron’s sources and functions in bacterial cells?

A

Source: iron salts.
Function: cofactor for some enzymatic reactions, and it is a component of nonheme iron proteins and cytochromes.

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12
Q

What is a trace element?

A

needed in very small amounts. Since they are needed in really small amounts, it can be hard to detect them
- function as cofactors for necessary enzymatic reactions.

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13
Q

What are a couple examples of trace elements?

A
  1. cobalt (Co)
  2. zinc (Zn)
  3. copper (Cu)
  4. molybdenum (Mo)
  5. manganese (Mn).
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14
Q

What is a defined (synthetic) media?

A

Know the exact concentration of all components

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15
Q

What are examples of defined (synthetic) media?

A
  1. minimal media (nutrients at its most basic; carbon source + salts)
  2. EZ medium
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16
Q

What is complex (undefined) media?

A

Do not know the exact concentration of all components

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17
Q

What are examples of complex (undefined) media?

A
  1. blood agar (5% sheep’s blood)
  2. TSA (tryptic soy agar; soybean extract)
  3. nutrient broth
  4. brain heart infusion.
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18
Q

What is minimal media?

A

A media that only provides the precise nutrients needed for the growth of the organism.

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19
Q

What are examples of minimal media?

A

M9 minimal medium

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20
Q

What is selective media?

A

A media that has components added to it that will prevent the growth of a certain type of bacteria. It promotes the growth of the desired species of bacteria. Only certain organisms will grow.

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21
Q

What are examples of selective media?

A
  1. TSA + ampicillin
  2. MSA: mannitol salt agar (6.5 NaCl makes it selective)
  3. EMB/MacConkey
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22
Q

What is differential media?

A

A media that helps distinguish between different types of bacteria based on the pattern of their growth on the medium. Organisms look different on the media.

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23
Q

What are examples of differential media?

A
  1. blood agar –> hemolysis
  2. MSA –> Mannitol fermentation
  3. EMB/Moc –> lactose fermentation
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24
Q

What is enrichment media?

A

This culture media has a component that allows the growth of specific types of bacteria. It encourages certain organisms to grow.

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25
Q

What are examples of enrichment media?

A

Leaving out a source of nitrogen in order to encourage organisms that can fix nitrogen to grow.

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26
Q

What are the oxygen [gaseous] requirements of (obligate) aerobes?

A

Requires oxygen to survive

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27
Q

What are the oxygen [gaseous] requirements of obligate anaerobes?

A

only grow in the absence of oxygen. If oxygen is present, they are killed.

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28
Q

What are the oxygen [gaseous] requirements of facultative anaerobes?

A

When there is oxygen present, it will use it. If there is no oxygen present, it can still grow but not as well.

29
Q

What are the oxygen [gaseous] requirements of aerotolerant anaerobes?

A

Tolerate oxygen but they do not use it, always use some type of anaerobic metabolism

30
Q

What are the oxygen [gaseous] requirements of capnophile?

A

need high concentrations of carbon dioxide in order to grow.

31
Q

Why are some microbes not able to grow in the presence of oxygen and what allows microbes to grow in the presence of oxygen?

A

Any organism that is growing and surviving in the presence of oxygen must have enzymes to deal with reactive oxygen species (oxygen radicals). Obligate anaerobes are missing these enzymes. For this reason, some microbes are not able to grow in the presence of oxygen while others can.

32
Q

What would growth look like for (obligate) aerobes in thioglycolate media?

A

All the growth would be seen at the top of the tube.

33
Q

What would growth look like for obligate anaerobes in thioglycolate media?

A

All the growth would be seen at the bottom of the tube.

34
Q

What would growth look like for facultative anaerobes in thioglycolate media?

A

There would be growth throughout the tube, but growth would be heavier at the top.

35
Q

What would growth look like for aerotolerant anaerobes in thioglycolate media?

A

The growth would be seen as spread evenly throughout the tube.

36
Q

What is the temperature profile of a psychrophile?

A

They are microbes that can grow in cooler temperatures from 0°C and lower. Their optimum growth temperature is around 15°C.

37
Q

What is the temperature profile of a mesophile?

A

These microbes grow at moderate temperatures. Their optimal growth temperature is about 20°C to 45°C.

38
Q

What is the temperature profile of a thermophile?

A

Microbes with an optimal temperature of 50° C to a high of 80°C. They are heat-loving, they like hotter temperatures.

39
Q

What is the temperature profile of a hyperthermophile?

A

These microbes grow at temperatures ranging from 80°C to a maximum of 110°C. They like extremely hot temperatures.

40
Q

What is the pH requirement of an acidophile?

A

Microbes grow optimally at pH that is less than 6.

41
Q

What is the pH requirement of a neutrophile?

A

These microbes grow the best at a pH around the neutral pH (6-8)

42
Q

What is the pH requirement of an alkaliphile?

A

These microbes optimally grow at a pH above 8.

43
Q

What are the growth conditions (osmotic tolerance) for halophiles?

A

They are salt-loving microbes that grow in environments with high salt concentrations.

44
Q

Most microbes are not tolerant to osmotic pressure. How has this been used for controlling growth, especially by the food industry?

A

To prevent food from spoiling, foods are preserved by drying them or by adding high concentrations of either salt or sugar. Water activity is lowered in order to prevent the growth of bacteria on food.

45
Q

What are the growth conditions (pressure tolerance) for barophiles?

A

need a high atmospheric pressure (barometric pressure) in order to grow

46
Q

Describe a typical growth curve for a bacterial population.

A

The growth curve for a bacterial population is represented by the logarithm of living bacterial cells plotted against time. The graph is divided into four phases corresponding to the slope.

47
Q

What are the major stages of a bacterial growth curve and their characteristics?

A

The major stages are the lag phase, the log phase, the stationary phase, and the death or decline phase.
1) The lag phase is the beginning of the growth curve. In this stage, the bacteria are adjusting to their new conditions in order to start up and grow again. The number of bacterial cells does not change, so there is no increase.
2) In the log (exponential) phase, there is an exponential increase in the number of cells as they are actively dividing by binary fission.
3) In the stationary phase, a plateau is reached by the total number of live bacterial cells. Since there are limited resources, it slows and stalls the growth of the population. Death rate of the cells is the same as the rate of cell division.
4) In the death phase, cells die in greater numbers as there is a lack of nutrients. The number of cells that are dying is greater than the number of cells dividing. The death stage exhibits an exponential decrease in the number of living bacterial cells.

48
Q

What stage is best for Gram staining? Why?

A

The log phase because in order to gram stain, there needs to be healthy and growing cells with cell walls that are intact. This can be seen in the log phase. The stationary and death phase would not work as the cell walls of the dead cells would break down. This would make gram positive bacteria appear gram negative. For this reason, the best stage for gram staining would have to be the log phase.

49
Q

What stage is generally most susceptible to antibiotics?

A

The log phase because most antibiotics work best against cells that are exponentially growing. In the log phase, bacteria are the most susceptible to antibiotics that affect the synthesis of protein, DNA, or cell walls.

50
Q

How does direct cell count (Petroff-Hauser chamber) work?

A

In the Petroff-Hauser chamber, the concentration of cells in a sample can be estimated by counting individual cells in a number of squares. This determines the volume of the sample that is observed. A small sample is taken out of a broth and put into a special microscope slide that has a small grid. The grid allows one to know what the volume of the sample is. It also helps to count the cells. The counting is done by hand with a clicker. Cells in multiple small squares are counted and the average is taken to get a reliable measurement.

51
Q

What are the advantages and disadvantages of direct cell count?

A

Advantages: This method is relatively fast, inexpensive, and easy to use.
Disadvantages: This method does not work well with dilute cultures. The reason for this is because there may not be enough cells to count. Also, one cannot tell which cells are dead or living.

52
Q

How does coulter counter work?

A

It is an electronic cell counting device that is used in a saline solution to detect and count the changes in electrical resistance. Each change in resistance represents a cell.

53
Q

What are the advantages and disadvantages of coulter counter?

A

Advantages: This method is fast and accurate except when the culture is too concentrated.
Disadvantages: If a culture is too concentrated results could be skewed since more than one cell could pass through the aperture. It also cannot differentiate between cells that are viable and those that are dead.

54
Q

How does viable plate count work?

A

It is a count of live (viable) cells.

55
Q

What is a CFU?

A

Colony forming units are used to express the results of the viable plate count. A calculated CFU is closer to the true number of live bacteria in the population.

56
Q

What are the advantages and disadvantages of viable plate count?

A

Advantages: provides estimates of viable bacterial numbers
Disadvantages: Some cells can be viable but nonculturable, other samples of bacteria can grow in clusters or chains that are hard to disperse, one colony could represent several cells. Statistically reliable numbers cannot be given if a sample has too few colonies or if a sample is overcrowded.

57
Q

How does a spread plate work?

A

The sample is mixed in with warm liquid agar. This is then poured into a sterile Petri dish and is mixed by swirling. The colonies that result after incubation are counted. This provides an estimate of the number of cells in the original volume that is sampled.

58
Q

How does a pour plate work?

A

The sample is poured onto solid agar and a sterile spreader is used to spread it evenly. The colonies that are formed after incubating are counted. This provides an estimate of the number of cells in the original volume samples.

59
Q

How does MPN work?

A

it is a statistical test that is used to estimate the number of viable microbes in a sample. It is often used for food samples and water samples. In samples of lake or pond water, it tells one likely how many coliforms there are in 100 milliliters. Sets of five lactose broth tubes are used in this process. The first set is inoculated with 10 mL of the sample of pond or lake water. In the next set, 1 mL of the sample is put in each tube. The last set is inoculated with 0.1 mL of the sample. The tubes are then taken and incubated. Each tube contains a pH indicator and a little tube in the middle. If the pH indicator goes from red to yellow, there was acid produced. If there is a big bubble in the little tube, it tells you that gas was produced. If a tube is yellow and contains a bubble, there is acid and gas resulting in a positive tube.

60
Q

How does turbidity work?

A

It measures the amount of light scattered and uses it to relate to the number of bacteria. A spectrophotometer is used to measure turbidity. A sample is taken and dropped into the spectrophotometer. A light source gets shot through a prism and hits the sample. If there are not many cells in the sample, light makes it through and hits the detector. If there are a lot of cells (cloudy), then a lot more light gets scattered and less light makes it to the detector.

61
Q

How does measurement of metabolites work?

A

It measures the activity of cells by looking at the production of metabolic products or the disappearance of reactants. To estimate the number of cells, ATP formation, consumption of oxygen, and biosynthesis of nucleic acids and proteins can be monitored.

62
Q

How does PCR/sequencing work?

A

This can help measure bacterial contamination of samples of DNA. PCR amplifies a contaminated DNA sample which can be compared against bacterial DNA to identify the bacteria present in the DNA.

63
Q

How does a chemostat work and what types of experiment does it allow for?

A

It is used to maintain a continuous culture. The feed is an opening that is used to add nutrients and the effluent is an outlet to remove contents. This dilutes toxic waste and dead cells. A chemostat adds and removes fluids to maintain the culture in the exponential phase of bacterial growth. It is used in industries that harvest microbial products.

64
Q

What is a biofilm?

A

A biofilm is a highly structured and complex ecosystem that provides a selective advantage to microbes. They form on a variety of surfaces.

65
Q

How do biofilms form?

A

There are multiple stages in biofilm formation.
1) First, planktonic cells attach and stick to a surface. This attachment is reversible.
2) Next, they become irreversibly attached as they build an extracellular matrix that makes them strongly physically attached. They transition into a sessile lifestyle.
3) Over time, the biofilm goes through growth and cell division (binary fission).
4) As it continues to grow, the production of EPS (extracellular polymeric substances) and the formation of water channels occurs. This makes the biofilm incredibly tough.
5) The final step is the dispersal of cells on the borders of the biofilm. They become planktonic once again to go to new sites.

66
Q

What is planktonic?

A

Planktonic cells are microbes that live in aquatic environments and are free-floating.

67
Q

What is sessile?

A

Sessile means attached to a surface. Planktonic cells attach to a substrate and become sessile.

68
Q

What role does quorum sensing play in biofilms?

A

allows the microbes to detect their cell density. This is done through the binding and release of autoinducers. In response to environmental stimuli, quorum sensing is used to coordinate their activities.

69
Q

How do biofilms impact human health?

A

Some biofilms can be helpful to human health while others can be harmful. Some in the lining of the intestinal and respiratory mucosa defend against infections by pathogens. Plaque that forms on teeth can contribute to dental disease. The biofilms that form in wounds can cause serious infections. Infections can also occur when biofilms form on medical devices that are used on the human body.

Micro (21 decks)

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