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