Week 3 (Microbial Growth, Metabolism)

NAD+ is ___________(reduced/oxidized) to NADH

REDUCED

In which of the following is chemical energy used for carbon fixation? A. Photosynthesis B. Krebs cycle C. Fermentation D. Glycolysis

A. Photosynthesis

Which of the following is not true about fermentation? A. The final electron acceptor is an inorganic molecule B. The energy yield is less than that of cellular respiration C. The final electron acceptor is an organic molecule D. Fermentation does not require oxygen

A. The final electron acceptor is an inorganic molecule

Aerobic respiration differs from anaerobic respiration in which of the following respects? A. The final electron acceptors are different B. Aerobic respiration requires the electron transport chain while anaerobic does not C. None of the above D. Both A and B

A. The final electron acceptors are different

A function of fermentation is A. The regeneration of NAD+ for use in glycolysis B. Production of large amounts of ATP C. Production of NADH for use in the electron transport chain D. all of the above

A. The regeneration of NAD+ for use in glycolysis

Twenty Staphylococcus aureus cells contaminated the macaroni salad you were making for a picnic. Given a generation time of 60 minutes, how many bacteria would you have after 2 hours? A. 160 B. 80 C. 40 D. 1200

B. 80 (starts with 20, each hour it doubles. So after 1 hour it's 40, then 2 hours it's 80.)

Botulism was first described as a clinical disease in the early 1800's, when it was known as the sausage disease. Blood sausage was made by filling a pig stomach with blood and ground meats, tying shut all the openings, boiling it for a short time, and smoking it over a wood fire. The sausage was then stored at room temperature." How did this attempt at food preservation include most of the requirements for an outbreak of botulism (describe what was occurring in each step)

Kill competing bacteria (by heating) -allow heat-resistant C. botulinum endospores to survive -provides anaerobic conditions and an incubation period for toxin production

Fermentation is used as a means of preserving foods. Why would it slow spoilage?

Lactic acid would inhibit or kill food-spoil bacteria.

The process of endospore formation is called

sporulation

True/False: Energy use within a cell is a closed system (energy does not need to be replenished)

FALSE

How do lactic acid bacteria exert their antilisterial effect?

"Mitigation of Listeria monocytogenes in Ready-to-Eat Meats Using Lactic Acid Bacteria" It is a common bacterium in natural environments, including vegetation, agricultural soils and livestock, so it may be brought into the plant in raw animal and plant materials, dust, water and even through plant employees. Secondly, it typically finds its niche in cold, humid environments, making it a potential nightmare to control in RTE meat processing facilities once it has established itself on the premises. Its ability to form biofilms and persist in this protective microbial community is one of the most common reasons for its difficult eradication, despite aggressive cleaning and sanitizing. Lastly, L. monocytogenes can survive and even grow in refrigerated, packaged RTE products, including those packed under low-oxygen conditions.

Facultative Anaerobes Test tube Example

(2nd test tube in picture) 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. 5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

Enzymes SOD and catalase Test tube Example

(4th tube in picture) 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. 5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

Under ideal conditions, the fermentation of one glucose molecule by a bacterium allows a net gain of how many ATP molecules? A. 2 B. 4 C. 38 D. 0

2

What is the end product of glycolysis?

2 Pyruvic Acid — which have 3 carbons each. Glucose got split in half. Two ATP and two NADH and 2H+ ions

In which temperature range would a mesophile not grow best? A. -50 C B. 12 C C. 40 C D. 37 C

A. -50 C

Cytochrome c oxidase (Complex IV) is a carrier molecule in bacterial and eukaryotic Electron Transport Chains. Cyanide inhibits Complex IV. A. Explain how cyanide is effective as a common poison. B. A shipping company employee notices that the inside of ships' hulls, where ballast water is stored, are deteriorating. The hull paint contained cyanide to prevent microbial growth. Bacteria, however, were still growing on the hulls. What could you conclude about the metabolic pathway of these bacteria?

A. CyanidecytochromecOxidaseblocksaerobicrespiration. B. These are bacteria are using fermentation.

When is ATP produced during photosynthesis? A. Light-dependent reactions B. Light-independent reactions

A. Light-dependent reactions

A reduced molecule A. has gained electrons B. has become more positive in charge C. has lost electrons D. is an electron donor

A. has gained electrons

Which organism produces catalase and superoxide dismutase A. obligate aerobe B. obligate anaerobe C. both A and B D. none of the above

A. obligate aerobe

The typical end products of complete aerobic respiration are carbon dioxide, water, and: A. ATP B. glucose C. Lactic Acid D. pyruvate

ATP

To prevent excess phosphate from entering lakes and streams, certain laws govern the amount of phosphorus allowed in laundry and dishwasher detergents. What can happen if phosphorus levels in a lake increase?

Algae plants require phosphorous to grow. Too much phosphorous will lead to algae overgrowth in lakes.

Which of the following is the best (most SPECIFIC) definition of respiration? A. A sequence of carrier molecules with oxygen as the final electron acceptor B. A sequence of carrier molecules with an inorganic molecule as the final electron acceptor C. A method of generating ATP D. A series of reactions in which pyruvic acid is oxidized to CO2 and H2O

B. A sequence of carrier molecules with an inorganic molecule as the final electron acceptor

Which of the following is not true? A. The botulism toxin is produced under anaerobic conditions B. The botulism toxin is produced by Clostridium endospores C. The botulism toxin is produced by Clostridium vegetative cells D. none of the above

B. The botulism toxin is produced by Clostridium endospores

Which of the following is the best definition of generation time? A. The length of time it takes for lag phase to occur B. The length of time it takes a population of cells to double C. The length of time a culture stays in stationary phase D. none of the above

B. The length of time it takes a population of cells to double

Which of the following is the best definition of fermentation? A. The reduction of glucose to pyruvic acid B. The oxidation of glucose with organic molecules serving as electron acceptors C. The complete catabolism of glucose to CO2 and H2O D. The production of ethyl alcohol from glucose

B. The oxidation of glucose with organic molecules serving as electron acceptors

Enzymes are: A. free radicals B. catalysts C. ions D. carbohydrates

B. catalysts

What is the basic reasoning for each bacterium having a minimum, optimum, and maximum growth temperature? A. lipid requirements B. enzyme requirements C. nucleic acid requirements D. none of the above

B. enzyme requirements

The "food spoilage" microbes that can survive in a refrigerator are A. psychrophiles B. psychrotrophs C. mesophiles D. thermophiles

B. psychrotrophs

Under ideal conditions, the complete aerobic oxidation of one molecule of glucose (aerobic respiration) by a bacterium allows a net gain of how many ATP molecules? A. 2 B. 4 C. 38 D. 0

C. 38

Reactions involved in the light-independent reactions of photosynthesis constitute the A. Krebs cycle B. Entner-Duodoroff pathway C. Calvin-Benson cycle D. pentose phosphate pathway

C. Calvin-Benson cycle

Where does the Electron Transport Chain take place in prokaryotic cells? A. Ribosomes B. Mitochondria C. Plasma Membrane D. Cytoplasm

C. Plasma Membrane

Oxygen is poisonous for: A. halophiles B. obligate aerobes C. obligate anaerobes D. facultative anaerobes

C. obligate anaerobes

A facultative anaerobe: A. doesn't use oxygen, but tolerates it B. is killed by oxygen C. uses both aerobic and anaerobic metabolism D. requires oxygen for growth

C. uses both aerobic and anaerobic metabolism

What is false about this graph? A. (1) = the lag phase where cell division is slow but is about to speed up. B. (2) = is called the logarithmic growth phase C. (3) = the phase of logarithmic death D. both A and C are false

D. both A and C are false

Which phase of the bacterial growth curve has more dead/dying cells than living cells. A. lag B. log C. stationary D. death

D. death

Which of the following bacterial groups would you expect to be MOST likely associated with human infections? A. thermophiles B. lactophiles C. psychrophiles D. mesophiles

D. mesophiles (body temperature)

Which of the following is not true regarding the electron transport chain? A. The final electron acceptor in aerobic respiration is an inorganic molecule B. electrons pass through ATP synthase in order to generate ATP from ADP C. the phospholipid bilayer in the plasma membrane is impermeable to protons (i.e. they cannot pass through, freely) D. water is a byproduct of the ETC

D. none of the above (Final electron acceptor is inorganic for respiration, organic for fermentation.)

Disease-causing bacteria vary widely in their ability to synthesize amino acids. What kinds of pathogens (extracellular or intracellular) are likely to make their own amino acids, and what kinds are not?

Extracellular pathogens are likely to make their own amino acid because they don't have it readily available. E.coli for example have the amino acids to synthesize their own. Bacteria that produce their own amino acids are pathogens.

Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt? Would you be susceptible to foodborne infection if you were to eat this spoiled fish?

Faculative halophiles, yes you could be susceptible to foodborne infection. Halophiles love salt. Osmophiles love sugar. Acidophile— An organism with optimal growth at pH levels of 3 or below. Alkaliphile —An organism with optimal growth at pH levels of 9 or above

True/False: Alcohol is a product of all fermentation pathways.

False

True/False: Only carbohydrates can be broken down within a cell and used for energy.

False

True/False: PABA is a competitive inhibitor which inhibits the catalysis of sulfanilamide to folic acid.

False

True/False; Extreme or obligate halophiles require high temperatures for growth.

False

True/False: Pyruvic acid can enter the Kreb's cycle

False (t cannot, so it has to go through decarboxylation, carbon will remove and it will leave CO2. NAD+ is an electron acceptor. NADH is potential energy. Acetyl Co-A can enter the Kreb's cycle. 2 Acetyl Co-A enters, twice, because there's 2.)

You are an emergency medical technician and are called to the home of Kevin, a 13-week-old boy who has become listless and is having trouble breathing. The parents report that Kevin used to smile, but lately he has not smiled, nor has he had other noticeable facial expressions in the last two days. Kevin's eyes are open when you arrive, but he does not seem to be focusing. You place your outstretched finger under his fingers and he fails to grasp it. You lift his foot and it drops back to the mattress. The parents report that he has not had a bowel movement in three to four days. What is your suspicion, based on what seem to be nervous system symptoms? What should be administered to Kevin at the earliest opportunity? How do babies acquire this condition? Although the diagnosis should be confirmed with laboratory tests, the tests should probably not be performed in the hospital lab. Why not?

Infant botulism—Clostridium botulinum is a spore-forming organism that is common in nature. The spores may be found in soil and certain foods (such as honey and some corn syrups). Infant botulism occurs mostly in young infants between 6 weeks and 6 months of age. It may occur as early as early as 6 days and as late as 1 year. Risk factors include swallowing honey as a baby, being around contaminated soil, and having less than one stool per day for a period greater than 2 months. Highly contagious.

You are a microbiologist working for a pharmaceutical company and discover a new metabolite that can serve as a medication. You now must oversee its production. Which phase of the bacterial growth curve do you need to maintain the bacteria in, in order to make sufficient amounts of this primary metabolite?

Late log phase is when they produce metabolites, so keep them at stationary phase. Antibiotics form response to nutrient depletion. Protects resources.

Which pathogen, associated with gastrointestinal infections, is prevalent in retail delis?

Listeria

What molecule enters the Electron Transport Chain? A. NAD+ B. Pyruvic acid C. NADH D. ATP

NADH

You have two flasks with broth media. One contains a species of cyanobacteria, which is a photosynthetic bacteria. The other flask contains Escherichia. coli (nonphotosynthetic bacteria). Both flasks are sealed and incubated under optimal growth conditions for two days. Assuming the cell volume and metabolic rate of the bacterial cells is identical in each flask, why would the carbon dioxide concentration be higher in the E. coli flask than in the cyanobacteria flask after the two-day incubation?

Photosynthesis uses CO2 and produces O2. E.Coli Fermentation produces CO2

You look in the refrigerator and find some orange, sugary drink you had forgotten was there. The drink now has an off taste and bubbles. What is the most likely explanation for the changes in the drink? (what specific metabolic pathway is occurring?)

Sugars have fermented to alcohol and the bubbles are CO2 from pyruvate.

Explain why sulfa drugs prevent bacterial growth without harming the human host.

Sulfa drugs act as a competitive inhibitor to PABA (binding its active site), which is required for bacteria to create folic acid. Humans don't create folic acid.

True/False: Endospores require higher temperatures to be destroyed as compared to vegetative cells

TRUE

True/False: At high temperatures, enzymes undergo denaturation and lose their catalytic properties; at low temperatures, the reaction rate decreases.

TRue

True/False: Oxygen is required during fermentation.

TRue

True/False: Pyruvic acid can only be broken down (during fermentation) by yeasts.

TRue

If Pasteur's swan-necked flask had contained endospores, what results would have been observed? (What was Pasteur's original experiment attempting to prove? What are endospores? How would the presence of endospores have altered the experiment?)

Temperature would not have killed the endospores. They would've multiplied and made the water cloudy. It would not have disproven spontaneous generation.

What is a major function of the Krebs cycle?

The major function of the Krebs cycle is to transfer most of the chemical energy from the breakdown of pyruvate (through acetyl CoA) to NAD+ and FAD during redox reactions.

Consumers are advised to avoid stuffing a turkey the night before cooking (where the stuffing would be made on the stove and then placed in the turkey), even though the turkey is refrigerated. A homemaker questions this advice and points out that the bacteria of human disease grow mainly at warm temperatures, not in the refrigerator. What explanation might you offer to counter this argument?

The stuffing would be hot, allowing bacteria that are psychrotrophs to potentially grow. These bacteria can also grow at refrigeration temperature.

Assume that you are working for a chemical company and you are responsible for growing a yeast culture that produces ethyl alcohol (ethanol). The yeasts are growing well on the maltose medium but are not producing alcohol. What is the most likely explanation? What could you do to fix the situation?

There is a presence of oxygen. — You can fix the situatuion by preventing oxygen from being in there

Why do most Americans refrigerate raw shell eggs while most Europeans don't?

They can safely do that because of the way eggs are produced in Europe, but it can't be safely done in the U.S. because of Salmonella.Salmonella bacteria, discovered in 1885 and named for the man who headed the U.S. Department of Agriculture (USDA) back then, can be transmitted via the outside of an egg if there is chicken manure present, or from inside the egg via the hen.

How can anaerobes grow in the human mouth when so much oxygen is there?

They could be protected in a biofilm. In addition, facultative anaerobes could consume O2 and obligate anaerobes could grow beneath them.

True/False: Carbon dioxide (CO2) is used to synthesize sugars in the Calvin-Benson cycle.

True

True/False: Endospores are resting structures formed by some bacteria for survival during adverse environmental conditions.

True

True/False: The phospholipid bilayer of the plasma membrane is permeable to protons (i.e. protons can easily pass through).

True

What is biocontrol ?

Use of one type of microbe to control others

If two cultures of a facultative anaerobe were grown under identical conditions except that one was exposed to oxygen and the other was completely deprived of oxygen, what differences would you expect to see between the two cultures? (What metabolic pathway would be occurring in each? Why?)

We would expect that the facultative anaerobe grown under oxygen would have better growth, more of the culture, because facultative anaerobes grow faster with oxygen but do not require it. It would take anaerobic respiration or fermentation.

What is decarboxlyation?

Where carbon is removed from pyruvic acid and releasing CO2. Ultimately turns it into Acetyl Co-A

A population of Bacillus species is growing in a soil sample. Suppose glycolysis came to a halt in these bacterial cells. Would this mean that the TCA (Krebs) cycle would also stop? Why /Why not?

Yes, TCA would stop, without glycolysis to create pyruvate, and without pyruvate there is no acetyl co-a.

The opportunistic pathogen, Pseudomonas aeruginosa colonizes wounds and the lungs of cystic fibrosis patients. P. aeruginosa also grows in soil. It can respire aerobically or else anaerobically by using nitrate. In which habitat (the lung or the soil) would P. aeruginosa respire aerobically or with nitrate?

aerobically in lungs ( because the lung has air), soil would use nitrate, because there's no oxygen.