Exam Two Microbiology Questions

Which of the following best describe the difference between a disinfectant and an antiseptic?

The first is an antimicrobial chemical used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. The second is an antimicrobial chemical that can be used on skin or tissues to achieve the same result.

Which of the following describes stationary phase of a growth curve?

The number of cells dividing equals the number dying

Why would an organism use fermentation to generate ATP?

The organism is only capable of generating ATP via oxidative phosphorylation.

Sugar or salt can be used for food preservation because

They dehydrate the cells, They create a hypertonic environment, unfavorable for growth

Which of the following statements accurately describe biochemical pathways?

They only function for a few times. They convert an initial substrate through a series of steps into an end product. They are well-organized and structured. They are carefully regulated. They always run at their maximum rate.

All germicides are somewhat harmful to humans and the environment. This parameter identifies HOW harmful the chemical is

Toxicity

Which of the following is a method of choice for achieving a sufficient level of microbial control in routine day to day situations

Treatment of any materials both before and after they come into contact with human tissues to avoid spread of infectious agents.

In a biochemical pathway, the product of the first reaction becomes the substrate in the second reaction.

True

Nitrogen-fixing cyanobacteria are critically important ecologically

True

Protons used to set up the proton motive force are generated as macromolecules like glucose are oxidized in the cell

True

Certain microbes are highly resistant to killing methods (e.g. endospores).

Type of Microorganisms

Microbes that grow readily on the benchtop or in a temperature-controlled incubator that is not sealed from the atmosphere in the room are

aerobes

Microorganisms that have complicated nutritional requirements are

fastidious

Streptococcus pneumoniae lacks an electron transport chain. Therefore, S. pneumoniae generates ATP via

fermentation

The rhizobia group of microbes

form a nodule that creates an endosymbiotic relationship between legume plants and the bacterial cells.

Production of extracellular polymeric substances (EPS) enables bacteria to

form biofilms

Table Enzyme (y-axis) Acidic & Basic (x-axis),

Below Optimal pH, Optimal pH, Above Optimal pH

Table Enzyme (y-axis) Temperature (x-axis),

Below Optimal temperature, Optimal temperature, Above optimal temperature

Dirt, grease, and bodily fluids in/on an area can interfere with control methods, as can temperature, pH, and even humidity levels.

Environmental conditions

Cells are actively growing, doubling the population with each generation

Exponential/Log Phase

An enzyme can only bind one substrate at a time

False

Biofilms are primarily important in growth of bacteria in nature, and as a result are mainly studied by environmental microbiologists.

False

Handwashing with regular soap removes all normal microbiota from the skin.

False

Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperature

False

Sterilization is the destruction of all living microbes from a surface by physical or chemical means.

False

The main difference between purple sulfur bacteria and purple non-sulfur bacteria is that purple sulfur bacteria prefer to use organic molecules rather than hydrogen sulfide to generate reducing power

False

The more bacteria present on or in something, the longer it takes to kill them all.

False

Used to treat semi-critical instruments such as gastrointestinal endoscopes.

High-level disinfectants

Gram-negative obligate chemolithotrophs, use H2 as an energy source with O2 as a terminal electron acceptor

Hydrogen-oxidizing bacteria

Used to treat non-critical instruments such as stethoscopes.

Intermediate-level disinfectants

Members of this group of microbes can break down glycogen deposited in the vaginal lining in response to estrogen. This helps to drop the pH in the area, preventing infections

Lactic acid bacteria

You have a culture of bacteria in which cells are actively expressing genes and synthesizing enzymes, but cells are not dividing. This culture is most likely in _________ phase

Lag

Cells are not dividing but are synthesizing enzymes required for growth

Lag Phase

Used to treat floors, furniture, walls and so on.

Low-level disinfectant

Slows or stops critical enzyme reactions in some (but not all) microorganisms.

Low-temperature storage

Heat applied to beverages to prevent spoilage and kill pathogens. High-temperature-short-time protocols include holding liquids at 72°C for 15 sec. Does not sterilize.

Pasteurization

During a one hour time period in a population of approximately a billion cells, ten cells divide, and a hundred thousand cells die. This pattern suggests the population is experiencing which phase of a growth curve?

Phase of prolonged decline

Anabaena is a genus of filamentous cyanobacteria commonly found in aquatic environments, where it harvests energy from sunlight and fixes both carbon dioxide and nitrogen. Knowing this, how would you classify Anabaena?

Photautotroph

Rank the germicides from most to least potent

Sterilant, High-level disinfectants, Intermediate-level disinfectants, Low-level disinfectants

Some germicides may lose efficiency over time or may be required in very large amounts that would make them impractical for frequent applications.

Storage and stability

Which of the following binds to the active site of an enzyme

Substrate

Gram-negative rods/spirals, may form filaments, obtain energy by oxidizing hydrogen sulfide and thiosulfate with O2 as a terminal electron acceptor

Sulfur-oxidizing bacteria

A farmer would encourage the growth of Rhizobium species near certain plants because the rhizobia

produce a nitrogen source that can by used by the plant

Enzymes are usually

proteins

Agrobacterium species

stimulate tumor-like growths in plants to obtain nutrients.

In aerobic respiration, oxygen acts as

the terminal electron acceptor.

The generation time of Mycobacterium tuberculosis is

12 hours

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

8

From which of the following would you be most likely to obtain a pure culture?

A streak growing on an agar slant

Some germicides may become less efficient when used in/on areas with organic matter

Activity in the presence of organic matter

How common are food spoilage microorganisms?

Almost all of our foods contain them

Nutrients (source of nitrogen, sulfur, etc.) to Cell structures (cell wall, membrane, ribosomes, surface structures) is?

Anabolic processes use energy from ATP to drive synthesis of molecules used to make up cell structures

Extreme halophiles/extreme thermophiles are members of the domain

Archaea

Which of the statements about autoclaving is/are correct?

Autoclaving involves the use of both temperature and pressure, Biological indicators such as heat-resistant endospores are used to endure that an autoclave is working properly, Autoclaving is consistently effective in sterilizing most objects

Consider the biochemical pathway: A → B → C Enzyme 1 catalyzes A → B Enzyme 2 catalyzes B → C If enzyme 2 is inactive, which of the following compounds will accumulate?

B only

Energy source (glucose) to Waste products (acids, Carbon dioxide) is?

Catabolic processes harvest energy released from the breakdown of compounds to make ATP

Must be non-toxic. Weak organic acids such as benzoic or sorbic acids often used. Nitrate and nitrite can also be used to inhibit germination of endospores of C. botulinum.

Chemical preservatives

Botulism, a disease characterized by flaccid paralysis

Clostridium botulinum

Antibiotic-associated diarrheal disease

Clostridium difficile

Gas gangrene: a disease characterized by necrotic tissue and the production of gas

Clostridium perfringens

Tetanus: a disease characterized by painful muscle spasms

Clostridium tetani

Uses an autoclave called a retort to destroy the endospores of Clostridium botulinum. It will not destroy the endospores of some thermophiles.

Commercial canning

Some substances are negatively affected by treatment with some germicides (i.e. corrosives damaging metals/rubber).

Compatibility with the material being treated

Different materials respond differently to control measures. Some may even be destroyed by certain methods, preventing their use.

Composition of the item

Which of the following concerns would lead a user to wash an item after it had been treated with a germicide

Corrosive or toxic residue left behind following treatment.

Some germicides are highly effective but are rare and/or expensive.

Cost and availability

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

Cross septum

You have a culture of bacteria in which cells are dying off at a constant rate. This culture is most likely in _________ phase.

Death

Due to nutrient depletion and waste accumulation, cells begin to die at an exponential rate

Death Phase

Which of the following are examples of biofilms?

Dental plaque, scum accumulating in toilet bowls, capsule formation around Streptococcus pneumoniae

Sterilization

Destruction of all microbial life

Decontamination

Mechanical removal of most microbes from living or inanimate surfaces

Consider common human pathogens. Most of their enzymes likely function best under which of the following environmental conditions?

Moderate pH around 7, High alkalinity, High salt, Temperature around 37 degrees C, No oxygen availability, High acidity

Which of the following are examples of coenzymes?

NAD+, NADP+, FAD

Gram-negative bacteria that obtain energy by oxidizing inorganic compounds like ammonia

Nitrifying bacteria

It takes longer to kill many microbes than a small number.

Number of microorganisms

the observed pattern of growth based upon oxygen requirements

Obligate aerobe, Facultative anaerobe, obligate anaerobe, microaerophile, aerotolerant anaerobe

An enclosed compartment filled with an inert gas such as nitrogen would be most appropriate for growing

Obligate anaerobes

You observe bacteria growing on the surface of a Petri dish of nutrient agar you left on the counter in your lab. You can be confident that your bacteria are NOT which of the following?

Obligate anaerobes

Cells obtain energy by ________ food molecules such as glucose

Oxidizing

Used to treat heat-sensitive critical instruments such as scalpels.

Sterilant

Greenlake is a small lake in Seattle, WA that sometimes experiences blooms of cyanobacteria, photosynthetic nitrogen-fixing bacteria that typically grow as filaments. These blooms are especially likely to occur during warm summer weather and result in the production of large quantities of biomass that then dies off and decomposes, leading to unpleasant odors. In addition to the aesthetic problems, some strains make toxins that can be dangerous to ingest, leading to the closing of the lake. Treatment of the water with alum (aluminum sulfate) to remove phosphorus from the water has helped to limit growth of cyanobacteria. How would you classify the cyanobacteria from Greenlake in terms of their carbon and energy sources?

Photoautotroph

Identify the types of microorganisms based on their optimal growth temperatures. (by lowest temp to high temp)

Psychrophile, Psychophile, Mesophile, Thermophile, Hyperthermophile

Additions of sugar or salt or subjecting the food to a high vacuum environment.

Reducing the available water

Disinfection

Reduction of most microbial life on inanimate surfaces

Items that may come into direct contact with body tissues are more likely to cause serious infections if contaminated.

Risk for infection

Preservation

Slows microbial growth but does not reduce the number of existing microbes.

When studying microbes, why is it important to separate mixed communities into individual pure cultures of the different species?

So we can understand the biochemical characteristics of one species without confusing it with another species.

Which of the following are examples of growth factors?

Starch, Amino Acids, Phospholipids, Cholesterol, Vitamins, Nucleotides, Polysaccharides, Water

With nutrients depleted, total number of viable cells remains constant, with some dying while others multiply

Stationary Phase

During which stage of growth does cell division equal the rate of cell death?

Stationary phase

Requires use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes.

Steam under pressure

In bacteria, protons received from NADH

are transported (or pumped) through the membrane to the outside of the cell.

The most common organisms causing food spoilage are:

bacteria, yeast, and molds

A culture of bacteria is breaking down sugars to yield energy. This is best described as

catabolism

The synthesis of ATP via ATP synthase, driven by a proton motive force, is called

chemiosmosis

Some enzymes require a cofactor or a coeznyme in order to be active. What is the difference between cofactors and coenzymes?

cofactors are non-protein components that assist enzymes and are typically trace elements; coenzymes are organic cofactors that loosely carry molecules or electrons.

In prokaryotic cells, the electron transport chain (ETC) is located in the ___________, whereas in eukaryotic cells, the ETC is located in the ____________.

cytoplasmic membrane; inner membrane of mitochondria

By keeping food cold, the growth rate of food spoilage microorganisms is

decreased

Moist heat destroys microbes by

denaturing their proteins