BIOS242 Exam 2 Check-Ins/Online Lab/Lecture Review

What is the most likely outcome for a halophile when it is exposed to drinking water?

It will become swollen as water enters the cell

What is the most likely outcome for a barophile when it is brought from the bottom of the ocean to the surface?

It will experience cellular damage or death due to the decrease in hydrostatic pressure

What is the most likely outcome for a thermophile grown at 5 C?

It will not grow due to the temperature being too low.

What happens to an acidophile when it is transferred to a basic environment?

It will not grow due to the pH being too high

In a clinical laboratory, a technician inoculates a liquid medium with bacteria from a patient’s sample. Impatient for results, the technician checks the sample four hours after inoculation and does not see bacterial growth in the medium. What is the most likely reason for this observation based on the bacterial growth curve?

The bacteria are in the lag phase, adjusting to the new environment

What is the primary purpose of the viable count technique in microbiology?

To count the number of viable cells capable of forming colonies

Which of the following best describes the significance of colony-forming units (CFUs) in microbiology?

Derived from a single bacterial cell in the original culture and indicate the number of live bacteria capable of growing and forming colonies

Imagine you are working in a microbiology lab and conducting the viable count technique. At each time point, you sample 0.1 mL of bacterial culture and add it to a solid medium. After allowing the plates to incubate overnight, you observe that one of your plates has 14 colony-forming units. How many colonies per mL were present in the original culture?

The original culture has 140 CFUs/mL

You are growing three different species of bacteria in your microbiology laboratory class using a thioglycolate tube. When you remove Tube 1 from the incubator, you observe that your organism exhibits growth only at the bottom of the tube. How should you classify this bacterium based on its oxygen requirements?

Obligate anaerobe

You are growing three different species of bacteria in your microbiology laboratory class using a thioglycolate tube. When you remove Tube 3 from the incubator, you observe that your organism exhibits growth all throughout the tube. How should you classify this bacterium based on its oxygen requirements?

Facultative anaerobe

The bacterium, C. difficile, grows in the low-oxygen environment of the large intestine. How would you classify this organism according to its oxygen, carbon source, and energy requirements?

Obligate anaerobe, heterotroph, chemotroph

Which of the following metabolic processes includes glycolysis?

Aerobic respiration, anaerobic respiration, and fermentation

Which of the following metabolic pathways involves the Kreb’s cycle and the electron transport system?

Aerobic respiration and anaerobic respiration

Which correctly identifies the process that produce the most cofactors?

Kreb’s cycle

Which of the following identifies the process that produces the most ATP

Electron Transport System

Which of the following uses organic compounds as the final electron acceptor?

Fermentation

What does a bactericidal agent do?

Kills bacteria

What does a bacteriostatic agent do?

Inhibits bacterial growth

A patient is prescribed an antibiotic for a bacterial infection. The drug prevents the bacteria from multiplying but does not kill them. How would you classify this drug?

Bacteriostatic

In a microbiology lab, a technician measures the zone of inhibition around an antibiotic disk on an agar plate. What does the zone of inhibition represent?

The area where bacteria are susceptible to the antibiotic

During a Kirby-Bauer experiment, a nurse observes a large zone of inhibition around a bactericidal antibiotic disk. What does this indicate about the antibiotic’s effectiveness?

The antibiotic is highly effective at inhibiting the growth of the bacteria

Fluoroquinolones

Target DNA/RNA synthesis

Polymyxin

Targets the cell membrane

Cephalosporin

Targets cell wall synthesis

Tetracycline

Targets protein synthesis

Trimethoprim

Targets folic acid synthesis

How does penicillin specifically target bacterial cells?

Prevents cell wall synthesis by inhibiting transpeptidase enzyme.

Which microorganism has a cell wall?

Bacteria

Which microorganism has no cell wall?

Virus

A patient presents with a sore throat, runny nose, and cough and asks her provider for some medication. The nurse notes that the patient has a fever, and the patient indicates that symptoms started after exposure to a family member who has “a cold”. Which of the following scenarios would indicate to the provider that penicillin should be used?

The patient has a positive rapid strep test indicating the presence of the bacteria Streptococcus pyogenes

What is the definition of mutualism in the context of microbiology?

A relationship where both organisms benefit.

Which of the following best describes the mutualistic relationship between the human microbiota and the host?

The microbiota benefits the host by aiding in digestion and producing vitamins, while the host provides nutrition and a living environment.

A nurse is explaining the role of the gut microbiota to a patient. Which of the following is an example of how the microbiota benefits the human host?

The microbiota helps in the digestion of complex carbohydrates.

In a clinical scenario, a patient is prescribed antibiotics for a bacterial infection. The nurse explains that antibiotics can disrupt the mutualistic relationship between the microbiota and the host. What is a potential consequence of this disruption?

Overgrowth of harmful bacteria leading to infections due to the reduced microbiota population

What is the definition of a localized infection?

An infection confined to a specific area of the body

What is the definition of a secondary infection?

An infection that occurs after a primary infection

A patient presents with a sore throat that developed into a sinus infection, and later, they developed pneumonia. How would you classify the pattern of infection in this scenario?

Focal infection

What is the name of the peptone that supports bacterial growth in the Durham tube carbohydrate fermentation test?

Trypticase

During the breakdown of trypticase in the Durham tube carbohydrate fermentation test, what compound is produced that raises the pH of the medium?

Ammonia

What is the purpose of phenol red in a Durham Tube carbohydrate fermentation test?

To indicate pH changes by changing color in response to acid or base production

What is the purpose of the Durham tube in a carbohydrate fermentation test?

To trap and indicate gas produced during fermentation

What component in a medium provides the basic nutrients that all bacteria need to grow?

An agar or broth base

Which component in a medium is a peptone and how would it support many species?

Amino acids and peptides that support growth by providing essential nutrients for many bacterial species.

When proteins in trypticase are broken down, do they produce acidic or alkaline by-products?

Acidic by-products that lower the pH of the medium, indicating fermentation.

During the breakdown of trypticase in the Durham tube carbohydrate fermentation test which compound would cause the pH to rise rather than fall?

Alkaline by-products such as ammonia are produced, causing the pH to rise.

What does phenol red measure in a medium?

Measures the pH, changing color in response to the acidity or alkalinity of the environment.

How would the color change if acid were produced versus if no fermentation occurs, and how would it help in interpreting the results?

The phenol red turns yellow, indicating a decrease in pH. If no fermentation occurs, the color remains red, suggesting no acid production.

What evidence in a carbohydrate fermentation test tells you that gas was produced?

The presence of bubbles or a gas pocket in the Durham tube indicates that gas was produced during fermentation.

What is the role of a small inverted tube (Durham tube) in a carbohydrate fermentation test?

It’s used to capture any gases produced during fermentation, allowing for the detection of gas production.

What would you expect to see inside the Durham tube if fermentation released gas?

Bubbles or a gas pocket inside the Durham tube indicating gas production during fermentation.

How would you know if bacteria were able to ferment dextrose?

You would observe a color change in the medium, typically from red to yellow, and the presence of bubbles in the Durham tube indicating gas production.

What is the indicator used to tell if fermentation happened?

Phenol red

How would a medium look if a bacterium could not ferment surcrose?

The medium would remain red, indicating no acid production from fermentation.

How can you determine that bacteria ferment a specific sugar?

Observing a color change in the medium and gas production in the Durham tube. A color change typically occurs from red to yellow, indicating acid production.

How can you recognize that bacteria produce gas?

By observing a gas bubble in the Durham tube, indicating gas production during fermentation.

During a Durham dextrose fermentation test, the broth remains red, but you also notice no bacterial growth in the tube. What is the most likely explanation?

The organism does not ferment dextrose

After incubation, a sucrose broth is yellow, but there is no bubble in the Durham tube. What is the best interpretation?

The bacteria fermented sucrose but did not produce gas

If there is no visible growth in a tube, can you rely on the color result?

No, because other factors may affect color change, such as pH fluctuations or testing errors.

What does the absence of turbidity suggest about whether the bacteria were transferred?

The bacteria were not transferred or did not grow in the medium.

After incubation, the sucrose broth is yellow, but there is no bubble in the Durham tube. What is the best interpretation?

The bacteria fermented sucrose but did not produce gas

If acid is produced what should happen to the pH indicator?

It should change color, indicating a decrease in pH.

Does acid production mean gas must be produced?

No, acid production does not necessarily indicate gas production. Some bacteria produce acid without gas.

Which fermentation pathways release gas and which do not?

Alcoholic fermentation and some types of lactic acid fermentation typically produce gas. Other pathways, like certain types of fermentation by propionic acid bacteria, may not.

During incubation, the broth turns orange, not clearly red or yellow. What is the most likely explanation?

The bacteria produced a small amount of acid

If only a small amount of acid is produced, would the color shift be strong or weak?

The color shift would be weak, indicating minimal acid production.

What does an orange color suggest about the amount of fermentation occurring?

A minimal amount of fermentation is occurring, likely due to low acid production.

After 48 hours, the dextrose broth is yellow, but after 72 hours it turns red again. What caused this reversion?

The bacteria used up the sugar and began breaking down proteins

What happens when bacteria run out of their preferred carbohydrate?

They start metabolizing proteins for energy, leading to an increase in pH.

Would switching to protein metabolism raise or lower the pH?

It would raise the pH due to the production of alkaline byproducts during protein catabolism.

How would switching to protein metabolism affect phenol red?

It would cause phenol red to shift to a more alkaline color, typically turning red as the pH rises.

A student notices tiny bubbles clinging to the sides of the Durham tube but no large bubble at the top. What is the best interpretation?

The bubbles were formed during inoculation or handling

Where should gas collect if it is produced by fermentation?

Gas should collect at the top of the Durham tube.

Do small bubbles stuck to the glass always represent metabolic gas?

No, they may result from air being trapped during inoculation.

During a carbohydrate fermentation test, you notice that the Durham tube is cracked after incubation. How does this affect your interpretation of the results?

It may allow gas to escape, making gas results unreliable

If the tube is cracked, can it still trap gas the way it normally would?

No, it cannot trap gas effectively, leading to unreliable gas results.

What would happen to gas inside a cracked tube?

It would most likely leak out, compromising the reliability of the fermentation test results.

Why might a microbiologist choose to test multiple different carbohydrates (such as lactose, mannitol, or maltose) in separate Durham tube carbohydrate fermentation tests?

Different bacteria ferment different sugars, helping distinguish species

How could testing several carbohydrates help compare metabolic capabilities and tell species apart?

Allows microbiologists to determine which sugars bacteria can ferment, highlighting metabolic differences and aiding in species identification.

An unknown bacterium was tested in a Durham tube lactose fermentation tube. After inoculation, the broth turned yellow, but no gas bubble was visible in the Durham tube. How should you interpret this result?

The bacterium ferments lactose and produces acid but no gas

Does lactose fermentation always produce gas?

No, some bacteria ferment lactose producing only acid without gas.

What are ways healthcare professionals transfer microorganisms from fomites to their patients?

Using non-sterile medical instruments during a procedure and touching a contaminated surface and then a patient without washing their hands.

Dr. Rivera finished examining a patient and immediately moves to the next room to see another patient. She uses the same stethoscope without disinfecting it and does not wash her hands between visits. Later, the second patient develops a skin infection. What is the most likely way microorganisms were transferred in this scenario?

The stethoscope acted as a fomite, transferring microorganisms

What role might a stethoscope play in transferring microorganisms between patients?

It could be serving as a fomite, allowing pathogens to be passed from one patient to another.

Why is it important to disinfect medical equipment between uses, even if it does not appear visibly dirty?

Disinfecting medical equipment is crucial because invisible pathogens can remain on surfaces, posing a risk of infection transmission to patients. Proper disinfection helps prevent the spread of healthcare-associated infections.

Is hand hygiene alone enough to prevent transmission or is it also necessary to clean the equipment?

It’s essential, but it is not sufficient alone; cleaning and disinfecting equipment is equally necessary to prevent transmission of pathogens.

What determines how quickly bleach can kill E. Coli?

The concentration, exposure time, and temperature affect its efficacy.

Why would scientists want to observe bacteria before introducing disinfectants and what baseline information would it provide?

It allows scientists to understand the baseline characteristics of the microbial population, such as their growth patterns, resistance levels, and overall viability. This information is critical for evaluating the effectiveness of the disinfectants against specific bacterial strains.

Two types of bacteria, E. coli and S. aureus, are exposed to the same disinfectant for 5 minutes and 15 minutes. After 5 minutes, E. coli shows no growth, while S. aureus shows growth until 15 minutes. What do these results suggest?

S. aureus is more resistant to the disinfectant than E. coli

What does it mean when E. coli stops growing after just 5 minutes, but S. aureus continues to grow until 15 minutes and what might that say about it’s relative resistance?

It indicates that E. coli is more susceptible to the disinfectant than S. aureus, suggesting that S. aureus has a higher level of resistance.

What does the zone inhibition in a Kirby-Bauer test indicate?

The area where there is no bacterial growth

When you see a clear zone around an antibiotic disk, what does that suggest about the bacteria’s ability to grow in that area?

It suggests that the bacteria are susceptible to the antibiotic, indicating effective inhibition of growth in that region.

What does the size of the zone of inhibition suggest?

The effectiveness of the antibiotic; a larger zone indicates greater susceptibility of the bacteria to the antibiotic.

A student forgot to label the antibiotic disks on the plate. What is the best course of action?

Repeat the test with properly labeled disks

What is the importance of labelling the antibiotic disks in a Kirby-Bauer test? What kind of information would be lost without it, and would interpretation of the zones of inhibition be effective?

It’s crucial for identifying which antibiotic is being tested. Without labels, accurate interpretation of the zones of inhibition is impossible, as the specific antibiotic associated with each zone would be unknown, leading to incorrect conclusions about bacterial susceptibility.

What might be the cause of overlapping zones of inhibition on a Kirby-Bauer plate?

Placing the disks too close to one another

How do you measure the zone of inhibition, and what determines the edges?

The zone of inhibition is measured in millimeters from the center of the antibiotic disk to the edge of the clear zone surrounding it. The edges are determined by the point at which bacterial growth resumes in the presence of the antibiotic.

In a Kirby-Bauer test, what determines the effectiveness of an antibiotic?

Measuring the zone of inhibition around the antibiotic disk, which indicates the area where bacterial growth has been inhibited.