Chapter 7

A 5% urea solution is hypotonic to a 10% urea solution.

True

Diffusion is one of the processes whereby materials are exchanged between a cell and its environment.

True

If a cell is placed in an isotonic medium, there will be no net movement of water.

True

Rod-shaped bacteria synthesize new cell walls over the entire surface of the cell.

True

With respect to oxygen requirements, an _________ can use gaseous oxygen and possesses enzymes to process toxic oxygen products.

aerobe

Bacteria that grow in oxygenated environments are referred to as ______.

aerobes

Death Phase

cells begin to die at an exponential rate and are unable to multiply

What is the effect of heat on a population of bacteria?

cells die at temperatures that exceed maximum

Stationary Phase

cells enter a survival mode, where they stop growing or greatly reduce their metabolic activity/ growth due to depleted nutrients and the buildup of waste products

Exponential Phase

cells reach their optimal doubling time, increasing the population by a factor of 2 with each new cycle, and this rate remains constant as long as the environment is favorable

What is the effect of cold on a population of bacteria?

cells survive but do not divide at temperatures below minimum

Still other organisms, called _________ __________, prefer oxygen but can grow in its absence.

facultative anaerobes

Most bacteria reproduce by ______.

fission

What food product is least likely to contain viable vegetative pathogens?

foods stored in the refrigerator

Because this bacterium requires a temperature above 16.5 degrees Celsius, it would be classified as a ______.

mesophile

Real time PCR

method that allows for the quantification of microorganisms in environmental or tissue samples without isolating them or culturing them

Simple diffusion is defined as the movement of

molecules from areas of higher concentration to areas of lower concentration.

Bacteria that thrive in environments with a pH of greater than 7 are classified as ______.

neutrophiles

Expanding on this classification, an _________ aerobe cannot grow without oxygen.

obligate

What term describes an organism that lacks superoxide dismutase and catalase enzymes?

obligate anaerobe

Which of the following will pass through a cell membrane most easily?

small nonpolar molecules

The rate of diffusion is affected by which of the following?

temperature, size of molecules and steepness of the concentration gradient

When sugar is mixed with water, equilibrium is reached when

the dissolved sugar molecules are evenly distributed throughout the solution.

Select characteristics of biofilms that differentiate them from planktonic bacteria.

-Microorganisms live singly, independently. -Microorganisms participate in quorum sensing. -Microorganisms secrete extracellular material, usually polysaccharide, that forms a matrix. -Microorganisms are readily eradicated using antibiotics. -Microorganisms exist as part of a diverse interdependent community.

The process of binary fission

1. A Young Cell (metabolically active) 2. Chromosome is Replicated (New and old chromosomes move to different sides of the cell) 3. Protein band forms in the center of the cell (this structure is comprised of substances that resemble actin and tubulin) 4. Septum Formation (Formed by the cell wall) 5. Septum is complete and cell is divided (Some species separate completely while others remain attached)

Place the steps of binary fission in the correct order to test your understanding of bacterial cell division.

1. Cell enlarges and the chromosome is replicated. 2. A transverse septum grows inward as the two chromosomes are pulled towards opposite ends of the elongating cell. 3. Septum is completed. 4. Daughter cells are separated or may remain attached.

Place the steps in the correct order to review the process of biofilm formation.

1. Pioneer bacteria attach to a surface 2. Bacteria secrete sugars and proteins for attachment. Quorum sensing begins. 3. Additional species join the biofilm secreting their own chemicals. 4. Quorum sensing is at a minimum in the mature biofilm. Some cells may revert to being planktonic

The generation time of Mycobacterium tuberculosis is

12 hours

After six generations, how many bacteria would have formed from the reproduction of one bacterium?

64

Consider the following hypothetical conditions: A population of 10,000 bacteria has a doubling time of 20 minutes, under a given set of growth conditions. The culture is allowed to grow for 2 hours. Select the number of bacteria that best predicts the population size at the end of the 2 hours incubation. Assume there is no lag phase.

640,000 This problem can be solved using the equation, Nf = Ni 2n in which Ni is the number of bacteria at the start (in this case, 10,000) and n represents the number of generations. We must solve for Nf, which is the number of bacteria at the end of 2 hours. To determine n (the number of generations), we divide the total time, 2 hours or 120 minutes, by the generation time, 20 minutes, which is 6. Nf = (10,000)26 = (10,000)(64) = 640,000. Please refer to section 7.3 in the textbook for additional information.

How many generations does it take for a single bacterial cell to become 256?

8

If there were 4 viable bacterial cells in an oyster, how many cells would be present after 4 hours if the bacterium exhibited a 20 minute generation time?

8192

Two organisms living together in which both partners benefit from the relationship.

Mutualism

Two organisms living together in which one organism is benefited and the other (the host) is harmed.

Parasitism

Like budding, binary fission produces two differently sized cells that contain an equal amount of genetic information.

False

The molecules in a solid lump of sugar do not move.

False

What is the usual route for infection with Vibrio parahaemolyticus?

Ingestion of raw or undercooked shellfish

A majority of medically important microbes are classified as:

Mesophiles

Flow cytometry

Method requiring labeling of cells with a fluorescent dye in order to detect bacteria in a natural shape

_________ are aerobes, but they can only tolerate very minute concentrations of oxygen in their environment.

Microaerophiles

A red blood cell placed in a hypertonic medium will

Shrink

Passive Transport

Simple and Facilitated Diffusion

A relationship in which free-living organisms cooperate and share nutrients.

Synergism

Select the physical factors below that can affect microbial growth.

Temperature and Radiation

Lag Phase

The population of cells is not increasing at this time, yet individuals cells are metabolically active and in most cases dividing via binary fission during this phase

Why was it unusual that the oysters from Prince William Sound were contaminated with this bacterium?

The temperature of the Sound is normally too low

_________ represent a group of organisms whose members lack the required enzymes needed for using oxygen in respiration and may not be able to tolerate any free oxygen in their environment (strict anaerobes).

Anaerobes

A competitive relationship between free-living organisms in which one organism secretes substances that are toxic to the other in order to acquire more space or nutrients for itself.

Antagonism

Choose the phase of the bacterial growth curve during which a bacterial population has the briefest doubling time.

Exponential growth phase

All of the active transport mechanisms used by cells to test your understanding of active vs. passive transport.

Facilitated and Simple diffusion

Diffusion is a general term referring to the net movement of atoms and molecules along a concentration gradient, from an area of low concentration to an area of high concentration, due to random thermal motion.

False

Escherichia and Salmonella are cocci that divide by binary fission.

False

Active Transport

Carrier-mediated transport Group Translocation Phagocytosis Pinocytosis

Two organisms living together in which one organism is benefited and the other is neither benefited nor harmed.

Commensalism

The structure that divides the bacterial cell in two is termed the

Cross septum.

Facultative anaerobe

Describes an organism that can grow in the presence of oxygen and can detoxify it, but can also grow in the absence of oxygen

Microaerophile

Describes an organism that can't grow at normal atmospheric oxygen concentrations, but does require a small amount of oxygen for growth

Aerotolerant anaerobe

Describes an organism that does not use oxygen, but can grow to a limited extent in the presence of oxygen

Psychrophile

Describes an organism that grows optimally at temperatures ranging from 0°C to 15°C

Mesophile

Describes an organism that grows optimally at temperatures ranging from 20°C to 40°C

Thermophile

Describes an organism that grows optimally at temperatures ranging from 45°C to 80°C

Hyperthermophile

Describes an organism that grows optimally at temperatures ranging from 80°C to 120°C

Psychrotroph

Describes an organism that has an optimum growth temperature >20°C, but is able to grow slowly at colder temperatures

Obligate anaerobe

Describes an organism that is unable to use oxygen and lacks the enzymes to detoxify oxygen, thus requiring the absence of oxygen for growth

Obligate aerobe

Describes an organism which requires oxygen for growth and has the enzymes to remove toxic byproducts of oxygen metabolism

Select those cell counting methods that enable only living cells to be counted.

Direct cell count Flow cytometry Turbidometry

The time required for one complete cycle of binary fission is known as the _____ or generation time.

Doubling