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Microbiology 214 > Microbial Nutrition > Flashcards

Microbial Nutrition Flashcards

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1
Q

Why is metabolism crucial in bacterial cells?

A

The cells need to acquire and synthesize the necessary components for cell division.

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2
Q

What are organisms predominantly composed of?

A

Macroelements and macronutrients, which are required in relatively large quantities.

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3
Q

Name the nutrients that are only required in small amounts.

A

Microelements or trace elements.

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4
Q

Crucial elements required for life in microorganisms (macroelements/nutrients).

A

C>O>N>H>P>S>Se

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5
Q

Essential cations and anions in living organisms.

A

Na+;K+;Mg2+;Ca2+;Cl-

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6
Q

List some essential trace elements.

A

Mn; Fe; Co; Ni; Zn

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7
Q

Which elements compose 95% of the cell mass?

A

C; O; H; N; S; P; K; Ca; Fe; Mg

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8
Q

Which elements form part of lipids, carbohydrates, proteins and nucleic acids?

A

C, H, N, O, S, P

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9
Q

Potassium function.

A

Responsible for enzyme activity.

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10
Q

Calcium function.

A

Contributes to the resistance of bacterial endospores.

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11
Q

Magnesium function.

A

Acts as a cofactor for many enzymes.

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12
Q

Iron function.

A

Forms part of the cytochrome.

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13
Q

What function do microelements have?

A

Form part of enzymes or form part of various enzymatic reactions.

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14
Q

Why is nitrogen so NB in cells?

A

It forms parts of amino acids, purines and pyrimidines. Can be acquired directly from ammonia, or it can be fixated from atmospheric N2. Organisms cannot grow readily without N.

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15
Q

Importance of Phosphorous.

A

Present in phospholipids, ATP and nucleic acids. In low P environments (aquatic), growth can be limited. Primary source of P is via inorganic phosphate sources.

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16
Q

Importance of Sulphur.

A

Present in amino acids and biotin. Most often sourced from sulphates. Biotin = vitamin that is NB for growth in organisms.

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17
Q

Which elements provide electrons in cells?

A

C, H, O.
C = synthesizes the organic molecules from which organisms are built.
H and O = also NB elements found in organism molecules.

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18
Q

What are the electrons from C, H & O used for?

A

Electron movement = supplies energy.

Reduces molecules during biosynthesis.

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19
Q

Carbon requirements and energy sources for autotrophs.

A

Use CO2 as their main source of carbon.
Light can also be used as an energy source.
Mostly photosynthesizing organisms.
CO2 does not supply H or energy to the cell & N2 fixation = v energy demanding process, so bacteria get their CO2 from other complex molecules.

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20
Q

Carbon requirements and energy sources for heterotrophic organisms.

A

Make use of previously formed, reduced organic compounds as main carbon and energy sources. These reduced molecules are usually from other organisms.
Heterotrophs = flexibility wrt carbon sources.

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21
Q

Actinomycetes C sources.

A

Rubber, paraffin, alcohol.

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22
Q

Burkholderia cepacia C sources.

A

Almost every C source utilized = over 100 C sources.

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23
Q

Leptospira C sources.

A

Limited to long-chain fatty acids.

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24
Q

What is the name of the chemical PCB?

A

Polychlorobiphenyl.

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25
Q

What was PCB previously used for?

A

This toxic chemical was previously used in the production of plastics.

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26
Q

Why was PCB outlawed/banned?

A

When released into the atmosphere = killed birds and animals.

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27
Q

How is PCB being degraded in nature?

A

Selection pressure has forced bacteria to mutate, enabling them to break down PCB. These bacteria are becoming dominant in the environment.

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28
Q

Although elements can mutate in nature, they can also be altered in labs. Give an example of a scientist that has achieved this.

A

Chakrabarty developed a bacteria, in the lab, that breaks down oil.

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29
Q

Name the two sources of energy for organisms.

A

1) Light energy

2) Energy derived from the oxidizing of organic and inorganic molecules.

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30
Q

Phototroph.

A

Organism uses light as its energy source.

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31
Q

Chemotroph.

A

Organism obtains energy from the oxidation of organic and inorganic molecules.

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32
Q

Lithotroph.

A

When the electron for an organism is sourced from inorganic compounds. (rock eaters)

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33
Q

Organotroph.

A

When an organism obtains electrons/H from organic components.

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34
Q

Mixotroph.

A

Bacteria that make use of inorganic energy sources and organic carbon sources.

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35
Q

Give the energy, electron and carbon sources for a Photolithoautotroph.

A

Energy: light
Electron: Inorganic e- donor
Carbon: CO2

36
Q

Give the energy, electron and carbon sources for a Photoorganoheterotroph.

A

Energy: light
Electron: organic e- donor
Carbon: organic carbon

37
Q

Give the energy, electron and carbon sources for a Chemolithoautotroph.

A

Energy: inorganic chemicals
Electron: inorganic e- donor
Carbon: CO2

38
Q

Give the energy, electron and carbon sources for a Chemolithoheterotroph.

A

Energy: inorganic chemicals
Electron: inorganic e- donor
Carbon: organic carbon

39
Q

Give the energy, electron and carbon sources for a Chemoorganoheterotroph.

A

Energy: inorganic chemicals
Electron: organic e- donor
Carbon: organic carbon

40
Q

Name the three growth factors that bacteria have to obtain from their surroundings.

A

1) Vitamins
2) Amino acids (protein synthesis)
3) Purines and Pyrimidines (nucleic acid synthesis)

41
Q

Biotin functions (vitamin).

A
  • Carboxylation (CO2 fixation)

- One carbon metabolism

42
Q

Folic acid function/s (vitamin).

A
  • One carbon metabolism
43
Q

Pyridoxine function/s (vitamin).

A
  • Amino acid metabolism (e.g. transamination)
44
Q

Lipoic acid function/s (vitamin).

A
  • Transfer of acyl groups.
45
Q

What is the first step in the utilization of a nutrient?

A

The uptake of the nutrient across the cell membrane.

46
Q

Microbes are usually found in nutrient poor environments. They therefore need multiple ways of transporting nutrients into the cell to ensure that maximum nutrients can be absorbed. What are these different transportation mechanisms?

A

1) Passive diffusion
2) Facilitated diffusion
3) Active transport
4) Group translocation
5) Iron acquisition

47
Q

What is simple diffusion?

A

Simple diffusion is the movement of molecules across a semi-permeable membrane via a concentration gradient, where the molecules move from a high conc. (outside of the cell) to a low conc. (inside the cell). NO ENERGY REQUIRED.

48
Q

What is facilitated (passive) diffusion?

A

Facilitated diffusion is the movement of molecules, with the aid of transport proteins, across a semi-permeable membrane due to a concentration gradient, where the molecules move from a high conc. (outside of the cell) to a low conc. (inside the cell). NO ENERGY REQUIRED.

49
Q

What is active transport?

A

Transport where either ATP or the stored energy from the ion gradient (between the inside and the outside of the membrane) is used to move molecules into the cell. Often, a carrier protein is needed in this protein. This movement of molecules occurs AGAINST a concentration gradient, which is common for many microbes because of their nutrient poor environment.

50
Q

What are some common molecules transported via passive diffusion?

A

Smaller molecules such as H2O, O2 & CO2.

51
Q

Which factor affects the rate of diffusion?

A

The size of the concentration gradient:

  • high conc. gradient = more nutrients entering/exiting the cell –> essential for adequate nutrient uptake.
  • low conc. gradient = poor efficiency.
52
Q

When will the rate of diffusion begin to decrease?

A

When nutrients begin to accumulate within the cell, there will be a smaller concentration gradient between the conc. outside of the cell compared to the conc. within the cell (when inside and outside of membrane is near/ at equilibrium).

53
Q

How can the rate of diffusion be increased?

A

By using carrier proteins - permeases - which are embedded in the plasma membrane. They create passages within the membrane.

54
Q

What is diffusion called when carrier proteins are involved? What is special about these proteins?

A

Facilitated diffusion. These permeases are highly selective and only transport similar solutes. NO ENERGY IS REQUIRED.

55
Q

Which family of proteins are permeases related to, and where is this family of proteins found?

A

Major intrinsic proteins (MIP), which are found in almost all organisms.

56
Q

What are two major intrinsic protein (MIP) channels commonly found in bacteria?

A

1) Aquaporins, which transport water

2) Glycerol facilitators

57
Q

How do permeases accept and then release molecules?

A

The solute molecules will bind to the outside of the permease, forcing it to open and allow the molecules inside. The permease will then change conformation, closing the molecules off from the outside of the cell, but opening towards the inside of the cell to release these molecules. The carrier will then revert its shape and is ready to bind with new molecules.

58
Q

Why is facilitated diffusion not the predominant transport process in bacteria and archaea?

A

They live in environments where the nutrient concentration outside of the cell is low, so a poor concentration gradient in produced.

59
Q

Which carrier proteins are commonly used for active transport?

A

1) Primary active transporters:
- they use the energy provided by ATP to move substances against the concentration gradient.
2) Secondary active transporters:
- use the potential energy from ion gradients to transport substances against the conc. grad.

60
Q

What do metabolic inhibitors (that inhibit energy production) do?

A

They block the active transport sites, but not the sites where facilitated diffusion occurs.

61
Q

Which stored energy causes the ion gradient?

A

The proton motive force.

62
Q

Where are ABC transporters found? What does ABC stand for?

A

In bacteria, archaea and eukaryotes. ABC stands for ATP binding cassette transporters.

63
Q

What is the structure and function of ABC proteins and why are they important?

A

They are used for the import and export of substances. They consist of two membrane domains which cover span the membrane, forming a pore.
These proteins bind and hydrolyze ATP to facilitate the uptake of nutrients.
The solutes are binded to solute-binding proteins, which transport the solutes to the ABC transporters, binding the solute to these ABC transporters.

64
Q

What kind of transport system do ABC proteins exhibit?

A

Uniport system (one molecule transported at a time).

65
Q

Where does the ATP bind on the ABC transporter?

A

The nucleotide-binding domain.

66
Q

What do bacteria use to drive active transport?

A

They use a proton gradient.

67
Q

What is symport?

A

Active transport whereby a substrate and protons move TOGETHER.

68
Q

What is antiport?

A

Active transport whereby the protons and sodium move in opposite directions.

69
Q

What is group translocation?

A

The transport of a substance across a membrane that occurs together with the chemical modification of the substance. METABOLIC ENERGY IS USED.

70
Q

In which system can group translocation commonly be seen?

A

In the PTS ( sugar phosphotransferase system) AKA phosphoenolpyruvate system. This system transports a variety of sugars while simultaneously phosphorylating them. PEP is the energy source.

71
Q

Briefly describe the PTS (sugar phosphotransferase system) system.

A

1) Phosphoenolpyruvate (PEP) binds to enzyme I which removes the phosphate from PEP, leaving pyruvate.
2) The phosphate group then moves from enzyme I to a heat stable protein (HPr)
3) The phosphate group then moves to Enzyme IIa.
4) The phosphate group moves to enzyme IIb.
5) Phosphate group moves to enzyme IIc (inside the membrane) and stops.
6) The movement of the phosphate group allows the glucose molecule to move into the cell, but it binds to the phosphate group, chemically modifying it.

72
Q

What is iron acquisition and why is it NB?

A

Iron is needed for enzymatic and cytochromatic functions. Iron availability can be problematic due to its solubility.

73
Q

When is iron soluble in its Ferrous form?

A

In anaerobic conditions, Fe2+ is available.

74
Q

Under what conditions is iron insoluble?

A

Under aerobic, neutral conditions iron is only available in its insoluble, Ferric (Fe3+) form.

75
Q

How do bacteria and fungi overcome the insolubility of iron?

A

They secrete siderophores e.g. enterobactin (E. coli), ferrichrome (fungi) and aerobactin (plasmids). These molecular compounds are light and are able to complex with ferric iron to supply it to the cell.

76
Q

When are siderophores created by bacteria and fungi?

A

When iron is limiting.

77
Q

How is the iron-siderophore complex released into the cell?

A

Either by direct release after the complex binds to the cell, or the complex can be taken up by ABC transporters. The ferric iron is then reduced inside of the cell.

78
Q

How does iron unavailability affect the cell?

A

It limits the cells rate of growth.

79
Q

Defined/synthetic media definition.

A

A medium where the precise composition of all of the components is known.

80
Q

Complex media definition.

A

A medium containing components of unknown composition.

81
Q

What is agar?

A

It is a sulphide polymer consisting predominantly of D-galactose, 3,6-anhydro-L-galactose and D-glucuronic. Agar melts in the autoclave and solidifies around 48 degrees Celsius.

82
Q

What is the difference between solid and semi-solid media?

A

Solid media contains a higher concentration of agar, whereas semi-solid media has more freedom of movement because it contains a lower concentration of agar.

83
Q

Selective medium definition.

A

A medium that promotes the growth of certain/particular microorganisms.

84
Q

Differential medium definition.

A

A medium that can distinguish between bacterial groups. Allows the tentative identification of organisms based on their biological character properties. E.g. MacConkey agar.

85
Q

Enrichment media definition.

A

This media is used to isolate a species of interest in the lab. Intermediate from poor culture growth media and rich culture growth media, allowing the culture to adapt.

Microbiology 214 (4 decks)

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