MM Ch 06 Quiz

In addition to physical requirements, bacterial growth and multiplication also entails chemical requirements. Which of the following statements would accurately describe chemical requirements and conditions associated with growth in the Lake of the Ozarks environment?

- Fecal coliforms will likely contain enzymes to counteract toxic oxygen forms. - Fecal coliforms will need to acquire trace elements for growth in the lake environment. - The lake environment will support the growth of facultative anaerobes.

A broth medium has been inoculated, and microbial numbers will be counted periodically to generate a bacterial growth curve. At 2 hours after inoculation, the culture has progressed through lag phase and is now in log phase. At this point, the population size is 1 million cells. The generation time is 30 minutes. Assuming the continuation of log growth, how many cells would there be at 2 hours of growth in log phase?

16 million

Starting with three cells, how many cells would result from three rounds of replication?

24

A microbe reproduces by binary fission every 20 minutes under favorable conditions. If you started with one cell, how long would 10 generations take and how many bacteria would be present if all the conditions were just right?

3 hours 20 minutes, producing 1024 bacteria

Put the following steps of bacterial replication in the correct order, starting from a parent cell. 1-Cell elongation 2-Septum formation 3-Chromosome replication 4-Separation of daughter cells

3, 1, 2, 4

If you begin with six cells, how many cells would you have after three rounds of division?

48

What factors that are important when formulating culture media?

All of these -pH -water availability -O2 levels

the figure shows a typical bacterial growth curve with the y-axis indicating the log of the number of bacteria and the x-axis indicating time in culture. In the figure, which sections of the graph illustrate a logarithmic change in cell numbers?

B & D

Which biosafety level (BSL) is appropriate for handling organisms that present a moderate risk of infection?

BSL-2

A chemostat is continuous culture system that is designed to promote and prolong exponential growth and prevent bacteria from entering stationary phase. How might this work?

Chemostats provide a continued source of fresh nutrients and remove wastes and dead bacterial cells.

Which of the following is NOT a step in bacterial cell division?

Disappearance of nuclear envelope

What would you expect to observe when a halophile that cannot ferment mannitol is cultured on mannitol salts agar?

Good growth accompanied by no change in color of the medium.

Each of the three graphs shown below includes data collected during exponential growth of a species of bacteria grown in three different growth conditions. Which growth condition resulted in the longest generation time?

Growth condition C

The reaction that is carried out by the enzyme catalase produces __________.

H20 and O2

After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity you will indicate the statements that correctly describe what is happening during stationary phase

Harmful waste products may be accumulating The cells are likely running out of nutrients The number of cells that are dying is balanced by the number of new cells that are being formed

Drag the following descriptions to the appropriate location on the bacterial growth curve

In order from left to right. 1st - Log of the number of bacteria 2nd(bottom) - Bacteria are metabolically active 3rd(top) - Period of most rapid growth 4th(bottom) - time 5th(right in the middle) - population growth has halted last box - Rate of cell death exceeds

How long does it take for the daughter cells to initiate or start the next round of replication?

No time is required -- they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right.

The Lake of the Ozarks is a human-made lake, so it collects runoff from coal strip-mining, fertilizers, resort wastewaters, and septic drainages. The average lake temperature is between 10∘∘C and 21∘∘C. Consider the physical requirements for growth and multiplication that would allow fecal coliforms to "blossom" in the Lake of the Ozarks. Which of the following would accurately describe these organisms?

Psychrophiles Facultative halophiles Mesophiles

Which of the following statements accurately describes the culture medium necessary for growing an obligate anaerobe, such as Clostridium tetani?

Reducing media are complex media containing chemicals, such as thioglycolate, that combine with oxygen, creating an anaerobic environment.

Which step of binary fission is the reason for genetically identical daughter cells?

Replication of the bacterial chromosome

How is pathogenic Staphylococcus aureus distinguished from other species of Staphylococcus?

Staphylococcus aureus is able to ferment mannitol, while other members of the genus are not.

When bacteria are inoculated into a new sterile nutrient broth, their numbers don't begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don't bacterial numbers increase immediately?

The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes.

What enables the copied chromosomes to separate during binary fission?

The chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes.

What would happen if the septum did not form during binary fission?

The parent cell would now have two copies of the chromosome.

Which of the following statements regarding infections involving biofilms is FALSE?

There is no way to prevent biofilms from developing on surfaces

What results when a single bacterium reproduces?

Two genetically identical daughter cells

Bacteria naturally prefer company instead of solitude for growth. Examples of this kind of communal growth pattern can be found everywhere, from surfaces of the teeth and the intestines, to the surface of a slimy rock in the lake, to the thick floc that clogs water pipes. These examples of communal bacterial growth are known by what name?

biofilm

Sampling lake water for microscopic organisms is not as easy as it sounds when you want to both count and identify species. In a given water sample, your bacteria of choice can be rare or difficult to culture, particularly given the mixture of bacteria in a biofilm. Which of the following culture media would be best for growing fecal coliforms when they are relatively less abundant than other bacteria in the lake?

enrichment culture medium

Bacteria that can grow in the presence or absence of oxygen (O2) are called

facultative anaerobes

Cultures of the Lake of the Ozarks water samples were grown on enrichment media for identification. However, these organisms are present to some degree in all samples. An important question from a clinical perspective is whether or not there is a significant increase in the fecal coliform populations that would put people's health at risk. If you were part of the team investigating this outbreak, how would you best enumerate the fecal coliform threat?

filtration count culture

Which of the following methods used to count microbes is correctly identified as direct or indirect?

filtration--direct method

Which of the following phases of the bacterial growth curve is matched with the correct definition?

log phase--the phase in which organisms are actively dividing and the generation time is constant

Microbes have very narrow optimum temperature ranges. Which of the following classifications of microbes are most likely to cause human disease, based on their temperature requirements?

mesophiles

For which of the following types of microbes would a microbiologist employ living host cells to support their growth?

obligate intracellular organisms, such as chlamydia and viruses

Which of the following methods would be most appropriate for gathering data to plot a bacterial growth curve throughout the four phases?

plate count

Which process is best for the short term storage of bacterial cultures?

refrigeration