Exam 2: Microbial Nutrition & Growth Part 2

Question 1

How does temp affect biological molecules?

Answer 1

Afftect the three-dimensional structures of biological molecules. Hydrogen bonds defining protein structure are especially sensitive to temperature. Membrane lipids are temperature-sensitive.

Question 2

Psychrophiles

Answer 2

10-15 C ideal, but can grow below 0C. Algae, fungi, archaea, and bacteria living in snowfields,ice, and cold water. Do not cause disease in humans but can cause some food spoilage in refrigerators.

Question 3

Psychrotrophs

Answer 3

psychrotolerant organisms. Tolerate cold temps but grow better at slightly higher temps. Can grow in fridge.

Question 4

Mesophiles

Answer 4

20-40C is ideal, can survive below this range, some can even survive pasteurization and canning.

Question 5

Thermophiles

Answer 5

Above 45C is ideal, hot springs, compost piles, etc. Do not cause diseases in humans as humans are too cold. Heat-stable enzymes are useful in the laboratory.

Question 6

Hyperthermophiles

Answer 6

above 80C ideal, many can grow above 100C and some above 130C. Members of archaea.

Question 7

Which of the following are most likely to be human pathogens, and why? psychrophiles, mesophiles, thermophiles, or hyperthermophiles

Answer 7

Mesophiles, their optimal temperature is the same as the human body.

Question 8

Which of the following are most likely to be food spoilage microorganisms, and why: psychrophiles, mesophiles, thermophiles, or hyperthermophiles?

Answer 8

Psychrophiles and psychrotrophs, they can grow in the fridge.

Question 9

What do you think is the optimal temperature for the growth of the common intestinal bacterium Escherichia coli? Explain.

Answer 9

20-40C, essentially body temp since the human body is their main environment.

Question 10

What is the optimal temperature for the growth of the leprosy-causing bacterium Mycobacterium leprae? Explain.

Answer 10

Optimal growth temperature 27-30C, human body is around 37C. Prefers cooler regions of the human body. Thrives in the mucous membrane where it can be spread and best multiplies. Chronically infected nerve cells are damaged by attaching immune cells, the skin and cooler areas of the body like appendages, ears, and nose are first to go.

Question 11

Mycobacterium leprae

Answer 11

Causative agent of leprosy, aerobic, rod-shaped, gram +, acid-fast bacteria. Slow growing, 12 day generation time due to time needed to synthesize mycolic acid. Obligate intracellular parasites and lack many genes required for living independently.

Question 12

What is the optimal temperature for the growth of the sexually transmitted spirochete Treponema pallidum? Explain.

Answer 12

Causative agent of syphilis. Optimal temp is between 33-35C (just below human body temp).

Question 13

Explain why intentional infection with the malaria-causing parasite Plasmodium can successfully eliminate the syphilis-causing bacterium Treponema pallidum from an infected individual. Does this sound like fun? Does our current access to antibiotics guarantee that this approach will never again be deemed necessary? Explain.

Answer 13

Pre-antibiotics intentional infection of plasmodium vivax “malaria” which caused high fever was to go to treatment. The high fever kills syphilis. However, it was only a one time treatment because the body develops antibodies against malaria. Nope, we are inching our way to a point when syphilis might be antibiotic resistant and old approaches might need to come back.

Question 14

How does pH affect microbe growth? What is the internal pH of microbes?

Answer 14

Hydrogen bonds stabilize macromolecule structures. Flooding the environment with H+ or OH- interferes with this hydrogen bonding.

Microorganisms are divided into groups based on their pH optima but their internal pH is always constant and typically near neutral.

Question 15

Benefits of the varying pH ranges in the body.

Answer 15

Normal acidity of certain regions of the human body inhibits microbial growth, for example the stomach. Another example is lactic acid bacteria that are normal vaginal flora. This acidic pH helps prevent yeast proliferation.

Question 16

At what range of pH values does an acidophile display maximal growth? Under these conditions, what is its internal pH?

Answer 16

3-5, internal pH 7

Question 17

At what range of pH values does an alkalophile display maximal growth? Under these conditions, what is its internal pH?

Answer 17

10-12, internal pH 7

Question 18

At what range of pH values does a neutrophile display maximal growth? Under these conditions, what is its internal pH?

Answer 18

5-8, internal pH 7

Question 19

Describe the importance of ion pumps to organisms growing in environments with extreme pH values.

Answer 19

The ion pumps mediate active transport that maintains the internal neutral pH regardless of the environment.

Question 20

Explain how solute concentration affects water availability.

Answer 20

If the solute concentration is higher inside the cell then outside the cell that means the water concentration is higher outside the cell. As a result water will flow across its gradient into the cell causing the cell to swell and burst.

Question 21

Hypertonic

Answer 21

Higher solute concentration outside of cell
Water displays a net flow out of the cell
Cell will shrink as it loses water

Question 22

Is water always present?

Answer 22

Water might be present but osmotically unavailable.

Question 23

Describe two methods by which certain microbes can deal with high osmolarity environments.

Answer 23

Actively pump ions into the cell to increase intracellular osmolarity.
Produce small solute molecules to increase internal osmolarity.

Question 24

Halophiles

Answer 24

organisms that require very high concentrations of salt to grow. Can require a minimum of 3-9% Nacl. Can spoil high salt or high-sugar foods.

Question 25

Osmotolerant

Answer 25

organisms that can tolerate salt. Often tolerate concentrations up to 10%. Do not require high salt concentrations.

Question 26

Mutualism

Answer 26

symbiotic relationship in which both partners benefit from the interaction.

Question 27

Examples of mutualism

Answer 27

Eukaryotic cells and their mitochondria; mitochondria get food and hospitable habitat and eukaryotic host cells receive ATP released by the mitochondria.

Termites and their gut microbes; termites themselves cannot
hydrolyse cellulose. Protozoa and bacteria microbes are fed by the wood and get a hospitable habitat. The termite receives nutrients following the microbes hydrolysis of the wood.

Question 27

Commensalism

Answer 27

one partner benefits and the other is not significantly affected.

Question 28

Commensalism exampl

Answer 28

Satellite colonies: central bacterial colonies have enzymes against ampicillin allowing them to grow in its presence. Satellite colonies are sensitive to ampicillin so they grow near the central bacterial colonies where the localized environment is devoid of ampicillin due to degradation by the central colony. The satellite colonies benefit but the central colonies are not affected.

Question 29

Parasitism definition and example

Answer 29

One partner benefits and the other is harmed. Parasite benefits and host is harmed. Treponema pallidum causes syphilis in humans.

Question 30

How do symbiotic relationships resemble non-symbiotic relationships? How do they differ?

Answer 30

Symbiosis involves a long-term close relationship between two or more species. Organisms are interdependent. At least one of the species often has lost the ability to live on their own. At least one partner benefits the other can benefit/be harmed/be unaffected.

Non-symbiotic relationships are no necessary for survival. Members can live independently though one or both my gain a benefit from the relationship.

Question 31

Synergism definition and example

Answer 31

relationship between two or more free-living organisms. Beneficial to both members but not necessary for survival. Difference between mutualism is that it’s not necessary for survival.

• Intestinal bacteria in the human colon. Bacteria receive food and hospitable habitat and humans receive nutrients released by bacteria.
• Biofilms

Question 32

Antagonism definition and example

Answer 32

association between free-living species arising from competition. one organisms secretes a substance that inhibits or kills another.

• lactic acid bacterium in the human vagina produces lactic acid which inhibits the growth of the yeast.

Question 33

What is a biofilm? Does it represent a pure culture of a microorganism? Explain.

Answer 33

Complex synergistic relationship between numerous microorganisms. Normally a mixed culture in which the species interact for mutual benefits. Attached to surfaces and is the primary organization of bacteria in nature. Biofilms function similar to a multicellular organisms.

Question 34

Give at least three example of biofilms that you have encountered in your life.

Answer 34

Bacterial slime in teeth, rocks in a stream,

Question 35

Dentl plaque

Answer 35

leads to cavities. Beginning with colonization by streptococcus mutans that break down sugars into glucose and fructose. Polymerizes glucose into glucan molecules of extracellular matrix (long strings of glucose). Traps bacteria to teeth and traps food. FErmentation leads to lactic acid which attacks tooth enamel.

Question 36

Are biofilms important in disease causation? Explain.

Answer 36

Yes, up to 70% of bacterial diseases in industrialized countries.

Question 37

In very basic terms, how are biofilms formed?

Answer 37

Free-living cells settle on a surface, an extracellular matrix develops, cells stick to each other and substrate, communication and coordination between the various biofilm members of the species. Lastly, cells secrete quorum-sensing molecules.

Question 38

Describe the process of quorum sensing.

Answer 38

Hormone-like molecules that bind to receptors on other cells. Increased density of cells and quorum-sensing molecules leads to increased number of bound receptors. Communicate number and types of cells in biofilm. Activate specific genes upon reach a certain threshold, microbes now have new characteristics.

As more microbes arrive the community continues to organize. The individual members of the biofilm have traits different from those cells living individually. Members assume different roles in different areas, functions like tissue of multicellular organism. Cells may leave the biofilm.

Question 39

Describe three areas of active research into combatting biofilms.

Answer 39

1) drug blocking microbial receptors that can disrupt communication and prevent biofilm formation.

2) Enzymes that degrade the biofilms extracellular matrix. Prevents organization.

3) Artificial amplification of quorum sensing when cells are not very numerous. Enhances elimination by the hosts immune system because it recognises them as foreign faster.

Question 40

Why are biofims difficult to teat?

Answer 40

Biofilms are difficult to treat with antibiotics because they fail to reach the biofilms core.

Question 41

Microorganisms are found throughout the entire biosphere. How does this compare to the range of environments in which any particular species of microorganism is found? Explain.

Question 42

Are microorganisms found in trout streams? How about in the Great Salt Lake? Are there any species that exist in both trout streams and in the Great Salt Lake? Why or why not?

Question 43

List the four main means of quantifying cell numbers.

Answer 43

Turbidity, Metabolic activity, dry weight, and genetic methods.

Question 44

turbidity

Answer 44

can be measured using a spectrophotometer which measures the amount of light passing through a sample. Take measurement of light that passes through sterile media, that’s zero absorbance. Take measurement of light that passes through light cell suspension and then through heavy cell suspension. This creates a mathematical relationship between the amount of bacteria in the tube and light that passes through. Requires > 10^7 cells/ml

Question 45

measuring metabolic activity

Answer 45

is proportional to cell number. Cell numbers can be inferred from measurements of nutrient utilization, waste products, or pH.

Question 46

Dry weight

Answer 46

filtered, dried, and weighed cultures. Use known bacteria weight to calculate. Works well for filamentous organisms.

Question 47

Genetic methods of counting microbes.

Answer 47

use techniques to isolate and identify unique DNA sequences. Thenus PCR and hybridization of DNA encoding to amplify the sequence and count them in a sample. This method works well for species that are too few in number to study directly and cannot be successfully cultured in the lab. Works well for uncultured microorganisms.

Question 48

List and describe three different means of direct cell counts.

Answer 48

Microscope counts, electronic counters, serial dilutions and plate counts, membrane filtration, most probable number test.

Question 49

Microscope counts

Answer 49

Take representative samples of known volume and place them in a cell counter. Do a grid count then use math to figure out the total population.

Question 50

Electronic counters

Answer 50

A coulter counter and a flow cytometer can count cells as they pass a single file through a small hole. Cells interrupt an electrical current in the culture counter and in a flow counter they interrupt light transmission.

Question 51

Serial dilutions and plate counds.

Answer 51

serial dilutions and plate counts: requires >100 cells/ml, bacterial sample is repeatedly diluted in series. Set volume of each dilution is spread on agar surface and incubated overnight. Colonies are counted at a convenient dilution typically 40-400 colonies. Multiply by dilution factor.

Question 52

membrane filtration

Answer 52

take known volume of liquid is passed through a filter, bacteria retained by the filter, wash filter with water, take bateria water mixture and incubate on solid media overnight. Count colonies and initial concentration is calculated.

Question 53

most probable number test

Answer 53

prepare and incubate serial dilutions in test tubes the note growth. Each tube is more diluted from the original sample. Count number of tubes that have gas and compare them to MPN table.

Question 54

In what way are direct cell counts inferior to viable cell counts?

Question 55

List and describe three different means of determining the number of viable cells in a sample.

Answer 55

Serial dilutions, membrane filtration, and most probable number test.

Question 56

MPN (most probable number) tests are commonly used to quantify viable cells following different stages of sewage treatment. Why do you think this method is used instead of plate counts or membrane filtration?

Answer 56

More cost efficient and less work involved. More realistic for regular and frequent testing that needs to be done.

Question 57

Have you ever quantified, to any degree, bacterial numbers based on turbidity? What do you think is a major strength of this procedure? Can you think of any limitations?

Question 58

Give three examples of cell products that can be measured as a means of determining cell numbers.

Answer 58

Turbidity, metabolic activity, dry weight, genetic methods.

Question 59

An organism whose metabolism uses O2 but can also survive in the absence of O2 is termed a(n) __________.

1. aerotolerant anaerobe
2. obligate anaerobe
3. obligate aerobe
4. acultative aerobe
5. faultative anaerobe
6. microaeropile

Answer 59

5. faultative anaerobe

Question 60

The relationship between a parasite and its host is an example of __________.

1. commensalism
2. agnosticism
3. hedonism
4. parasitism
5. mutualism
6. pluralism

Answer 60

4. parasitism

Question 61

When using a(n) _________, bacteria are detected (and counted) as they interrupt an electrical current while passing through a thin tube in single file.

1. membrane filter
2. counting chamber
3. plate count following serial diution
4. flow cytometer
5. MPN test
6. Coulter counter

Answer 61

6.Coulter counter