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Microbiology 265 > Week 4/5 Microbial Growth and Control > Flashcards

Week 4/5 Microbial Growth and Control Flashcards

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1
Q

Lag Phase

A

The nutrients are being internalized by the bacteria and enzymes are being made. The cellular components like DNA and ribosomes are also being replicated.

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2
Q

Exponential Phase

A

The bacterial population growth is doubling as fast as possible, the time is dependent on the organism.

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3
Q

Stationary Phase

A

The bacteria are running out of nutrients, the growth slows and some cells die. There is no net increase in cell number synthesis of endospores.

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4
Q

Death Phase

A

Rupture of plasma membrane and destruction of DNA.

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5
Q

Exponential Growth/ Generation Time

A

Generation time is the time needed for the population to double in size. This varies depending on the species of the microorganism. It ranges from 10mins to several days.

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6
Q

Growth outside the Lab

A

Growth in the natural environment happens at a slower rate

progression through these stages doesn’t always occur sequentially.

The organisms are usually part of a mixed culture, or a biofilm.

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7
Q

Asexual Reproduction

A

New cells from one set of chromosomes yields daughter cells which are genetic clones of parent.

* Binary fission 
* Budding 
* Fragmentation
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8
Q

Sexual Reproduction

A

Combination of genetic material from two organisms yield new organism.

* Conjugation
* Transformation
* Transduction
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9
Q

Binary Fission

A
  1. Cell elongates
    1. Septum forms
    2. Septum, and cell wall form completely. The cell separates.
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10
Q

DNA Replication

A

In binary fission DNA needs to replicate, replication starts at the Ori C. Chromosomes segregate and the ftsZ ring forms leading to cell division.

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11
Q

Cytokinesis**

A

The cytoplasmic contents are replicated and the daughter cells separate. Separation occurs in the middle of the cell where the ftsZ protein ring is.

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12
Q

Divisome

A

The divisome is the ftsZ ring, which is made from a bunch of fts proteins. The protein ZipA anchors the Z ring to the cytoplasmic membrane and ftsA recruits FtsZ, it also helps connect the ring to the cytoplasmic membrane.

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13
Q

Z ring Localization

A

The Z ring is localized to the center of the cell. The proteins MinCD form a spiral around the cell and repel ftsZ from polymerizing.

Min E forms in the center of the cell and pushes MinCD to the poles of the cell which allows ftsZ to form.

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14
Q

Peptidoglycan synthesis

A
  • occurs in the middle of the cell

- Pre-existing peptidoglycan is cut to allow new peptidoglycan to be added to the newly growing cell.

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15
Q

Peptidoglycan biosynthesis

A
  1. N- acetyl glucosamine is made by glycolysis
  2. N- acetyl muramic acid is made using UDP-NAG
  3. UDP-NAM gets amino acids/ peptide repeating units added to the COOH
  4. Bactoprenol binds to NAM using the phosphate, and NAM/NAG glycosidic bond is also formed
    (peptidoglycan pre-cursor)

*1-4 occur in the cytoplasm *

  1. Translocation of NAG/NAM to the periplasm (G-ve) or extra cellular space
    (G+ve)
  2. Trans glycosylation, occurs where more NAMs and NAGs get linked.
  3. Transpeptidation occurs where the peptides on NAM form peptide cross links with other peptidoglycan molecules
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16
Q

What Elements are found in a cell

A

C,N,P,O,S Ca+ Na+, K+ Mg+ Cl-

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17
Q

Macronutrients

A

Required in large amounts and play an important role in cell structure and metabolism.

C, N, O

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18
Q

Micronutrients

A

Present in smaller amounts and are sued in enzyme function and maintenance of protein structure.

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19
Q

Iron nutrients

A

Iron is present in low amounts so organisms try hard to acquire it. An important nutrient.

Found in cytochromes, catalases, peroxidases, iron-sulfur clusters proteins, oxygenase’s, all nitrogenases

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20
Q

Copper Nutrients

A

Used in respiration by Cytochrome C oxidase in photosynthesis.

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21
Q

Zinc Nutrients

A

found in Carbonic anyhydrases, nucleic acid polymerases, and DNA binding proteins.

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22
Q

Nicotinic acid

A

precursor of NAD+

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23
Q

Riboflavin

A

Precursor of FMN, FAD

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24
Q

Pantothenic acid

A

precursor of coenzyme A

25
Q

How does temperature affect growth rate ?

A

Low temperature means slow growth. Too low a temp would cause the cells processes to happen too slowly that no growth would occur. The membrane would freeze and become rigid.

high temperature means fast growth. Too high a temp would cause the cells proteins to denature and the cell would lyse.

26
Q

Optimal Temperature in different classes of bacteria.

A 
Psychrophile- 4 C
Mesophile ( E.coli)  - 39 C 
Thermophile - 60 C
Hyperthermophile - 88 C
Hyperthermophile - 106 C
27
Q

Can Bacteria adapt to high temps ?

A

Yes. They use Calcium to help keep their enzymes (pullulanase) efficient and working

28
Q

What is Osmolarity?

A

total concentration of solute

29
Q

What is Tonicity?

A

The concentration of permeable solutes

30
Q

Osmotolerant microorganisms can…?

A

grow well in media with high solute concentrations

31
Q

What is a halophile ? What are the 4 types of halophiles ?

A

An organism that can tolerate high salt. They can adjust their internal osmolarity to match the high external salt temperatures.

Nonhaloterant (E.coli) - don’t need salt

Halotolerant (S.aureus)- don’t need salt, but can grow in high salt

Halophile- can tolerate high salt

Extreme halophile- grow well at very high salt levels.

32
Q

Aerobic organism require what type of oxygen ?

A

Obligate - need oxygen

facultative -don’t need oxygen but they grow better with it

microaerophilic - need very low levels of oxygen

33
Q

Anaerobic organisms need what type of oxygen ?

A

Obligate- oxygen is not needed, and it is harmful to them

Facultative - dont need oxygen and they dont grow better even if they have oxygen

34
Q

What are oxygen levels like in a test tube

A

the top is the oxic zone with high oxygen

the bottom is the anoxic zone with little to no oxygen.

35
Q

How do aeroboes protect themselves from ROS?

A

Aerobes make enzymes to break down the ROS’s that are created.

Catalase, breaks down H2O2 to oxygen
Peroxidase breaks down H2O2 to water and NAD+
Superoxide dismutase breaks down superoxide

36
Q

What are Reactive oxygen species ?

A

Created from the electron transport chain
ROS- reactive oxygen species, these are toxic.
- Superoxide (O2 + e = O2-)
- hydrogen peroxide (O2- + e + 2H+ = H2O2)
- hydroxyl radicals (H2O2 + e- + H+ = H2O + OH)
- water (OH + e- + H+ = H2O)

37
Q

Microbes that have a pressure requirement are called ?

A

Barotelerant- they don’t need high pressure but they can tolerate it

Barophilic - they need high pressure, they have changed their membrane to adapt.

38
Q

How can you measure cell density ?

A

With a spectrophotometer or with a membrane filter which is used for aquatic samples.

39
Q

What are the different types of media used to grow bacteria ?

A

Defined Media : The exact chemical composition of the media is known
Complex Media : The exact chemical composition of the media is unknown
Selective Media : Selects for the growth of some organisms by promoting their growth or inhibit the growth of other organisms.
Differential Media: Differentiates between organisms growing on one plate.

40
Q

Why is the type of bacteria media important ?

A

Bacteria need certain nutrients to grow, so the media used has to have the specific nutrients for the right bacteria to grow.

41
Q

Control of Bacterial populations- Bacteriostatic

A

The bacterial growth is stopped by a microbial killing agent, but the cells are not dying. If the agent is removed the bacteria can grow again.

42
Q

Control of Bacterial populations- Bactericidal

A

The bacterial cells are killed, but they are not lysed. exponential death is seen ( rapid decline). This is irreversible.

43
Q

Control of Bacterial populations- Bacteriolytic

A

The bacterial cells are killed and lysed. This is irreversible.

44
Q

Method for killing microbial cells: Sterilization

A

Destruction or removal of all viable organisms

45
Q

Method for killing microbial cells:

Disinfection

A

Killing, removing, or inhibiting the disease causing organism. Doesn’t remove endospores.

46
Q

Method for killing microbial cells: Sanitization

A

Reduction of microbial population to levels deemed safe.

47
Q

Method for killing microbial cells: Antisepsis

A

Prevention of infection of living tissues by microorganisms. Use chemical agents that kill or stop the growth of microorganisms, when added to a surface.

48
Q

Method for killing microbial cells: Chemotherapy

A

Kill or inhibit internal microorganisms

49
Q

How to kill microbes: Physical Methods (Heat)

A

High moist heat: autoclave. Destroys viruses, fungi, bacteria and endospores.

Low moist heat: pasteurization. Controlled heating. Used mainly for beverages. Kills pathogens and slows rate of spoiling by reducing the number of organisms present.

High temp means bacteria are killed faster.

50
Q

How to kill microbes: Physical Methods (Radiation)

A

UV Radiation: 260nm is used since its absorbed by DNA. Used for surface sterilization, causes thymine dimers.

Gamma radiation: Penetrates deep into objects. IT causes double strand DNA breaks, ROSs, and membrane damage. Kills bacteria and endospores, not as effective with viruses. Used for sterilization and pasteurization.

51
Q

How to kill microbes: Mechanical Methods (Filtration)

A

Membrane filtration: Physically remove bacteria, from the liquid sample by a filter.

52
Q

How to kill microbes: Mechanical Methods (HEPA)

A

HEPA filter to get clean air for gaseous samples as not to contamination them in the fume hood.

HEPA: High-efficiency particulate air

53
Q

How to kill microbes: Chemical Methods ( Phenolics)

A

Phenolics are used in labs and hospitals.
They denature proteins and disrupt the cell membrane. They kill bacteria, fungi and enveloped viruses.
They smell bad and can irritate the skin.

54
Q

How to kill microbes: Chemical Methods ( Alcohols)

A

Kill bacteria and fungi and enveloped viruses. They denature proteins and dissolve membrane lipids.

55
Q

How to kill microbes: Chemical Methods ( Halogens)

A

Oxidizes cell constituents and iodinates proteins. Kills bacteria, fungi, and viruses.

56
Q

How to kill microbes: Chemical Methods ( Aldehydes)

A

Crosslink proteins and stop metabolic activity. Kills most bacteria and fungi, including spores.

57
Q

How to kill microbes: Chemical Methods (Quaternary ammonium compounds)

A

Detergents that disinfect and have antimicrobial properties.
Kill bacteria, enveloped viruses, and some fungi
Have Nitrogen with 4 bonds to make them positively charged.

58
Q

How to kill microbes: Chemical Methods (Hydrogen Peroxide)

A

Kills most viruses, bacteria, and fungi. Oxidizes proteins, lipids, and sugars.

Microbiology 265 (7 decks)

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