in what type of environment would you be most likely to find anaerobes?

9.Eastward: Microbial Growth (Exercises)

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nine.1: How Microbes Grow

The bacterial cell cycle involves the germination of new cells through the replication of DNA and division of cellular components into 2 daughter cells. In prokaryotes, reproduction is ever asexual, although all-encompassing genetic recombination in the form of horizontal gene transfer takes place, equally will be explored in a dissimilar affiliate. Most bacteria have a single circular chromosome; all the same, some exceptions exist.

Multiple Choice

Which of the following methods would be used to measure the concentration of bacterial contamination in processed peanut butter?

1. turbidity measurement
2. total plate count
3. dry weight measurement
4. direct counting of bacteria on a calibrated slide under the microscope

Answer

B

In which phase would y'all look to detect the most endospores in a Bacillus jail cell civilisation?

1. death phase
2. lag phase
3. log phase
4. log, lag, and death phases would all have roughly the same number of endospores.

Answer

A

During which phase would penicillin, an antibiotic that inhibits cell-wall synthesis, exist most effective?

1. death phase
2. lag phase
3. log stage
4. stationary phase

Answer

C

Which of the post-obit is the best definition of generation time in a bacterium?

1. the length of time it takes to reach the log phase
2. the length of fourth dimension information technology takes for a population of cells to double
3. the time it takes to reach stationary phase
4. the length of time of the exponential phase

Answer

B

What is the part of the Z ring in binary fission?

1. Information technology controls the replication of Dna.
2. It forms a contractile ring at the septum.
3. It separates the newly synthesized Dna molecules.
4. It mediates the add-on of new peptidoglycan subunits.

Answer

B

If a civilisation starts with 50 cells, how many cells will exist present subsequently five generations with no prison cell decease?

1. 200
2. 400
3. 1600
4. 3200

Answer

C

Filamentous cyanobacteria often divide by which of the post-obit?

1. budding
2. mitosis
3. fragmentation
4. formation of endospores

Reply

C

Which is a reason for antimicrobial resistance beingness higher in a biofilm than in gratis-floating bacterial cells?

1. The EPS allows faster diffusion of chemicals in the biofilm.
2. Cells are more metabolically active at the base of operations of a biofilm.
3. Cells are metabolically inactive at the base of a biofilm.
4. The construction of a biofilm favors the survival of antibiotic resistant cells.

Answer

C

Quorum sensing is used by bacterial cells to determine which of the following?

1. the size of the population
2. the availability of nutrients
3. the speed of h2o flow
4. the density of the population

Answer

D

Which of the following statements virtually autoinducers is incorrect?

1. They bind direct to DNA to activate transcription.
2. They tin can activate the cell that secreted them.
3. N-acylated homoserine lactones are autoinducers in gram-negative cells.
4. Autoinducers may stimulate the product of virulence factors.

Answer

A

Fill in the Blank

Direct count of total cells can be performed using a ________ or a ________.

Answer

hemocytometer, Petroff-Hausser counting chamber

The ________ method allows direct count of total cells growing on solid medium.

Answer

plate count

A statistical estimate of the number of alive cells in a liquid is usually done by ________.

Answer

about probable number

For this indirect method of estimating the growth of a culture, you measure ________ using a spectrophotometer.

Answer

turbidity

Active growth of a culture may exist estimated indirectly past measuring the following products of cell metabolism: ________ or ________.

Answer

ATP, acrid from fermentation

Matching

Lucifer the definition with the proper noun of the growth stage in the growth curve.

___Number of dying cells is college than the number of cells dividing	A. Lag stage
___Number of new cells equal to number of dying cells	B. Log phase
___New enzymes to use bachelor nutrients are induced	C. Stationary phase
___Binary fission is occurring at maximum rate	D. Expiry stage

Answer

D, C, A, B

Short Answer

Why is it of import to measure the transmission of light through a control tube with only goop in it when making turbidity measures of bacterial cultures?

In terms of counting cells, what does a plating method accomplish that an electronic prison cell counting method does not?

Order the following stages of the development of a biofilm from the earliest to the terminal footstep.

1. secretion of EPS
2. reversible attachment
3. dispersal
4. germination of h2o channels
5. irreversible zipper

Infections among hospitalized patients are oft related to the presence of a medical device in the patient. Which conditions favor the formation of biofilms on in-dwelling catheters and prostheses?

Disquisitional Thinking

A patient in the hospital has an intravenous catheter inserted to allow for the delivery of medications, fluids, and electrolytes. Iv days after the catheter is inserted, the patient develops a fever and an infection in the peel around the catheter. Blood cultures reveal that the patient has a blood-borne infection. Tests in the clinical laboratory place the blood-borne pathogen as Staphylococcus epidermidis, and antibody susceptibility tests are performed to provide doctors with essential information for selecting the all-time drug for treatment of the infection. Antibacterial chemotherapy is initiated and delivered through the intravenous catheter that was originally inserted into the patient. Within seven days, the skin infection is gone, claret cultures are negative for S. epidermidis, and the antibacterial chemotherapy is discontinued. However, 2 days after discontinuing the antibacterial chemotherapy, the patient develops another fever and skin infection and the blood cultures are positive for the same strain of Southward. epidermidis that had been isolated the previous week. This time, doctors remove the intravenous catheter and administer oral antibiotics, which successfully treat both the skin and blood-borne infection caused by S. epidermidis. Furthermore, the infection does non render after discontinuing the oral antibacterial chemotherapy. What are some possible reasons why intravenous chemotherapy failed to completely cure the patient despite laboratory tests showing the bacterial strain was susceptible to the prescribed antibiotic? Why might the second round of antibiotic therapy accept been more successful? Justify your answers.

Why are autoinducers small molecules?

Refer to Figure B.1 in Appendix B. If the results from a pond water sample were recorded equally 3, ii, ane, what would be the MPN of leaner in 100 mL of pond water?

Refer to Figure 9.1.14. Why does turbidity lose reliability at high prison cell concentrations when the culture reaches the stationary stage?

ix.ii: Oxygen Requirements for Microbial Growth

Ask most people "What are the major requirements for life?" and the answers are likely to include water and oxygen. Few would argue about the need for h2o, but what about oxygen? Tin can there be life without oxygen? The answer is that molecular oxygen is non e'er needed. The earliest signs of life are dated to a period when weather condition on globe were highly reducing and gratis oxygen gas was essentially nonexistent.

Multiple Choice

An inoculated thioglycolate medium culture tube shows dense growth at the surface and turbidity throughout the residuum of the tube. What is your conclusion?

1. The organisms dice in the presence of oxygen
2. The organisms are facultative anaerobes.
3. The organisms should be grown in an anaerobic sleeping room.
4. The organisms are obligate aerobes.

Reply

B

An inoculated thioglycolate medium culture tube is clear throughout the tube except for dense growth at the bottom of the tube. What is your determination?

1. The organisms are obligate anaerobes.
2. The organisms are facultative anaerobes.
3. The organisms are aerotolerant.
4. The organisms are obligate aerobes.

Respond

A

Pseudomonas aeruginosa is a common pathogen that infects the airways of patients with cystic fibrosis. It does non grow in the absence of oxygen. The bacterium is probably which of the post-obit?

1. an aerotolerant anaerobe
2. an obligate aerobe
3. an obligate anaerobe
4. a facultative anaerobe

Answer

B

Streptococcus mutans is a major cause of cavities. It resides in the gum pockets, does not accept catalase action, and can be grown outside of an anaerobic chamber. The bacterium is probably which of the following?

1. a facultative anaerobe
2. an obligate aerobe
3. an obligate anaerobe
4. an aerotolerant anaerobe

Respond

D

Why do the instructions for the growth of Neisseria gonorrheae recommend a CO₂-enriched atmosphere?

1. It uses CO₂ as a final electron acceptor in respiration.
2. It is an obligate anaerobe.
3. It is a capnophile.
4. It fixes CO₂ through photosynthesis.

Answer

C

Matching

4 tubes are illustrated with cultures grown in a medium that slows oxygen diffusion. Match the culture tube with the correct type of bacteria from the following list: facultative anaerobe, obligate anaerobe, microaerophile, aerotolerant anaerobe, obligate aerobe.

Answer

(a) obligate anaerobe, (b) obligate aerobe, (c) microaerophile, (d) facultative anaerobe

Short Answer

Why are some obligate anaerobes able to grow in tissues (e.grand., gum pockets) that are not completely complimentary of oxygen?

Why should Haemophilus influenzae be grown in a candle jar?

In terms of oxygen requirements, what type of organism would most likely be responsible for a foodborne affliction associated with canned foods?

Disquisitional Thinking

A microbiology teacher prepares cultures for a gram-staining practical laboratory by inoculating growth medium with a gram-positive coccus (nonmotile) and a gram-negative rod (motile). The goal is to demonstrate staining of a mixed culture. The flask is incubated at 35 °C for 24 hours without aeration. A sample is stained and reveals only gram-negative rods. Both cultures are known facultative anaerobes. Give a probable reason for success of the gram-negative rod. Presume that the cultures have comparable intrinsic growth rates.

9.iii: The Effects of pH on Microbial Growth

Leaner are generally neutrophiles. They abound all-time at neutral pH shut to 7.0. Acidophiles abound optimally at a pH nigh 3.0. Alkaliphiles are organisms that grow optimally betwixt a pH of 8 and ten.5. Extreme acidophiles and alkaliphiles grow slowly or not at all well-nigh neutral pH. Microorganisms abound best at their optimum growth pH. Growth occurs slowly or not at all beneath the minimum growth pH and above the maximum growth pH.

Multiple Selection

Bacteria that grow in mine drainage at pH ane–2 are probably which of the post-obit?

1. alkaliphiles
2. acidophiles
3. neutrophiles
4. obligate anaerobes

Answer

B

Bacteria isolated from Lake Natron, where the water pH is close to ten, are which of the following?

1. alkaliphiles
2. facultative anaerobes
3. neutrophiles
4. obligate anaerobes

Answer

A

In which environment are you near likely to see an acidophile?

1. human blood at pH 7.2
2. a hot vent at pH 1.5
3. homo intestine at pH 8.5
4. milk at pH 6.5

Reply

B

Fill in the Blank

A bacterium that thrives in a soda lake where the average pH is x.v can be classified equally a(n) ________.

Reply

alkaliphile

Lactobacillus acidophilus grows all-time at pH four.5. It is considered a(n) ________.

Answer

acidophile

Short Answer

Which macromolecule in the cell is nearly sensitive to changes in pH?

Which metabolic process in the bacterial cell is peculiarly challenging at loftier pH?

Critical Thinking

People who apply proton pumps inhibitors or antacids are more than prone to infections of the alimentary canal. Tin you explain the observation in light of what you lot accept learned?

9.4: Temperature and Microbial Growth

Microorganisms thrive at a wide range of temperatures; they take colonized different natural environments and take adapted to extreme temperatures. Both extreme cold and hot temperatures require evolutionary adjustments to macromolecules and biological processes. Psychrophiles abound best in the temperature range of 0–15 °C whereas psychrotrophs thrive between 4 °C and 25 °C. Mesophiles grow all-time at moderate temperatures in the range of 20 °C to about 45 °C. Pathogens are commonly mesophiles.

Multiple Choice

A soup container was forgotten in the refrigerator and shows contagion. The contaminants are probably which of the following?

1. thermophiles
2. acidophiles
3. mesophiles
4. psychrotrophs

Answer

D

Bacteria isolated from a hot tub at 39 °C are probably which of the following?

1. thermophiles
2. psychrotrophs
3. mesophiles
4. hyperthermophiles

Answer

C

In which surround are you well-nigh likely to encounter a hyperthermophile?

1. hot tub
2. warm sea water in Florida
3. hydrothermal vent at the bottom of the bounding main
4. human body

Answer

C

Which of the following environments would harbor psychrophiles?

1. mountain lake with a h2o temperature of 12 °C
2. contaminated plates left in a 35 °C incubator
3. yogurt cultured at room temperature
4. salt pond in the desert with a daytime temperature of 34 °C

Answer

A

Matching

Match the blazon of bacterium with its environs. Each selection may exist used once, more than once, or not at all. Put the appropriate letter of the alphabet beside the environment.

___psychotroph	A. h2o heater fix at 50 °C
___mesophile	B. hydrothermal vent
___thermophile	C. deep sea waters
___hyperthermophile	D. human pathogen
___psychrophile	E. soil leaner in temperate forest

Answer

C, D, E, B, A

Short Answer

How are hyperthermophile'south proteins adapted to the high temperatures of their environment?

Why would NASA be funding microbiology inquiry in Antarctica?

Critical Thinking

The bacterium that causes Hansen's disease (leprosy), Mycobacterium leprae, infects by and large the extremities of the body: hands, anxiety, and nose. Can you make an educated guess as to its optimum temperature of growth?

Refer to Figure 9.4.2. Some hyperthermophiles tin survive autoclaving temperatures. Are they a business organization in health care?

nine.5: Other Environmental Conditions that Touch Growth

Microorganisms interact with their environment forth more dimensions than pH, temperature, and free oxygen levels, although these factors crave pregnant adaptations. We also observe microorganisms adapted to varying levels of salinity, barometric pressure, humidity, and light.

Multiple Selection

Which of the following is the reason jams and dried meats oft practice non require refrigeration to prevent spoilage?

1. low pH
2. toxic alkaline metal chemicals
3. naturally occurring antibiotics
4. low water activity

Answer

D

Bacteria living in common salt marshes are most likely which of the following?

1. acidophiles
2. barophiles
3. halotolerant
4. thermophiles

Answer

C

Fill in the Blank

A bacterium that thrives in the Smashing Salt Lake but not in fresh water is probably a ________.

Answer

halophile

Leaner isolated from the bottom of the ocean demand high atmospheric pressures to survive. They are ________.

Reply

barophiles

Staphylococcus aureus tin can be grown on multipurpose growth medium or on mannitol salt agar that contains vii.5% NaCl. The bacterium is ________.

Answer

halotolerant

Short Respond

Fish sauce is a salty condiment produced using fermentation. What blazon of organism is likely responsible for the fermentation of the fish sauce?

nine.6: Media Used for Bacterial Growth

The study of microorganisms is greatly facilitated if we are able to civilization them, that is, to keep reproducing populations alive under laboratory conditions. Culturing many microorganisms is challenging because of highly specific nutritional and environmental requirements and the diversity of these requirements amid dissimilar species.

Multiple Choice

EMB agar is a medium used in the identification and isolation of pathogenic bacteria. It contains digested meat proteins as a source of organic nutrients. Two indicator dyes, eosin and methylene blue, inhibit the growth of gram-positive leaner and distinguish between lactose fermenting and nonlactose fermenting organisms. Lactose fermenters form metallic dark-green or deep regal colonies, whereas the nonlactose fermenters course completely colorless colonies. EMB agar is an example of which of the post-obit?

1. a selective medium only
2. a differential medium only
3. a selective medium and a chemically divers medium
4. a selective medium, a differential medium, and a circuitous medium

Answer

D

Haemophilus influenzae must exist grown on chocolate agar, which is blood agar treated with rut to release growth factors in the medium. H. influenzae is described as ________.

1. an acidophile
2. a thermophile
3. an obligate anaerobe
4. fastidious

Answer

D

Make full in the Blank

Blood agar contains many unspecified nutrients, supports the growth of a big number of bacteria, and allows differentiation of leaner according to hemolysis (breakup of blood). The medium is ________ and ________.

Answer

complex, differential

Rogosa agar contains yeast extract. The pH is adjusted to five.2 and discourages the growth of many microorganisms; even so, all the colonies look like. The medium is ________ and ________.

Answer

complex, selective

Short Respond

What is the major difference between an enrichment culture and a selective civilisation?

Critical Thinking

Haemophilus, influenzae grows all-time at 35–37 °C with ~five% CO₂ (or in a candle-jar) and requires hemin (X factor) and nicotinamide-adenine-dinucleotide (NAD, besides known equally V factor) for growth.¹ Using the vocabulary learned in this chapter, draw H. influenzae.

Footnotes

1. 1 Centers for Disease Control and Prevention, World Health Organisation. "CDC Laboratory Methods for the Diagnosis of Meningitis Caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenza. WHO Manual, 2d edition." 2011. http://www.cdc.gov/meningitis/lab-ma...ull-transmission.pdf

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