Micro Exam 2, chapter 4-7

Which of the following correctly describe facultative anaerobes?

- they can grow without O2- their growth is faster when O2 is available

Which of the following describe or relate to a Petri dish?

-It is a two-part covered container made of plastic or glass. -It excludes airborne contaminants. -A culture medium in a Petri dish can be referred to as a plate of that medium, e.g., an agar plate.

Microbial death rates may be affected by

-pH -temperature -the presence of organics

Typical conditions used for sterilization are

121°C at 15 psi for 15 minutes.

A urine sample with more than 100,000 organisms is considered indicative of infection. A urine sample containing 5,000 bacteria, with a generation time of 30 minutes, sits for 3 hours before finally being assayed. How many bacteria will then be present within the sample?

320,000

If a process kills 90% of the organisms per minute, how many minutes would it take to kill all organisms when starting with 100,000 organisms?

6 minutes

There are ______ codons to code for the 20 possible amino acids.

61

Which of the following is most likely to be a pure culture?

A single colony growing on a streak plate.

Which enzyme drives ATP synthesis in respiration?

ATP synthase

Which of the following organisms does not use O2 at all for growth?

Aerotolerant anaerobe

A halophilic, aerobic mesophile has a generation time of 20 minutes. You place 1x104 of these organisms on an appropriate solid medium, and incubate the plate for 100 minutes. Select the FALSE statement.

After incubation, a colony on the plate contains 5 x 104 cells.

The polysaccharide found in marine algae that is commonly used to solidify culture media is called ______.

Agar

A worker in a cheese-making facility argued that whey, a nutrient-rich by-product of the process, should be dumped into a nearby pond to serve as fish food. Is this a good idea or a bad one, and why?

Bad idea—bacteria would thrive on this rich nutrient source and multiply, using the oxygen in the water to harvest the energy from the whey. Without the oxygen, the fish will die.

Chemolithotrophs near hydrothermal vents support a variety of life forms. Why is this analogous to photosynthetic microbes supporting life forms closer to the surface of the planet?

Because all life forms need some energy source, electron source, and carbon source. Chemolithotrophs fix inorganic carbon and, if consumed by other microbes, could serve as sources for all three requirements for life. This is very similar to the role that photosynthetic microbes play in the top levels of the oceans/lakes.

Why are cells growing in a colony on solid media likely to be in many more different phases of growth than cells growing in liquid culture?

Cells in liquid culture experience a relatively uniform environment, so they are much more likely to be in the same phase of growth. Unlike cells on the edge of a colony, those in the center of a colony face depleted levels of nutrients and O2, yielding different phases of growth

Which pair is correctly matched, regarding electron transport carriers in eukaryotes?

Complex III - cytochrome bc1 complex

Which of the following does not describe interactions of mixed microbial communities?

Conditions in mixed microbial associations are readily reproduced in the laboratory.

Heart muscle is damaged after a heart attack (MI) because blood flow to the heart is stopped. A researcher injected cyanobacteria into the damaged hearts of test animals that has been given MIs. The animals' conditions improved after the procedure, but not significantly. The researcher repeated the experiment, this time illuminating the cyanobacteria with high intensity light after injecting the cells into the damaged hearts. Now the animals did much better, recovering well from their heart attacks. Which of the following explains this outcome?

Cyanobacteria produce oxygen by photosynthesis. Illuminating the cells increases amount of O2 released that is then used by heart cells for aerobic respiration.

Please select the INCORRECTLY matched pair.

D-value - time to destroy 10% of microbes present.

Consider interactions of mixed microbial communities. Match the descriptions in the left column with those that best correlate with them in the right column. Instructions

Difficult to reproduce in the laboratory matches Choice, Conditions in close microbial associations Conditions in close microbial associations Simpler to reproduce in the laboratory matches Choice, Pure cultures Pure cultures Inhibit competitors matches Choice, Synthesis of toxic compounds Synthesis of toxic compounds Nutrients for another microbe matches Choice, Production of metabolic wastes by one microbe Production of metabolic wastes by one microbe Creation of low O2 microenvironment matches Choice, Consumption of O2 by aerobic growth Consumption of O2 by aerobic growth

Which of the following is an example of phase variation?

E. coli producing pili for attachment to epithelial cells.

Which of the following is NOT common to aerobic respiration, anaerobic respiration, AND fermentation

Electron transport chain

What is the number of tRNA molecules that may be associated with translation?

Fewer than 64

Why is it a good idea for a bacterial cell to be able to use glucose FIRST as an energy source (until it is depleted), THEN switch to lactose?

Glucose is an easier compound to break down and obtain energy from than lactose AND for conservation of energy: why use the energy to make the enzymes for breaking down lactose when glucose doesn't need any extra enzymes for breakdown?

In what ways is microbial growth in a colony the same as growth in a liquid?

In both cases, cells compete with one another for available nutrients. Both involve a lag phase followed by exponential growth.

What is the effect of poisons such as mercury in antimicrobial products? Recall that mercury oxidizes the S-H groups of the amino acid cysteine in proteins, converting it to cystine.

Irreversible non-competitive inhibition—the mercury binds to an allosteric site on the enzyme and permanently changes the shape of the active site, so that the enzyme becomes nonfunctional.

Which is not true of RNA?

It contains both uracil and thymine.

Which of the following describe or relate to a Petri dish?

It excludes airborne contaminants. It is a two-part covered container made of plastic or glass. A culture medium in a Petri dish can be referred to as a plate of that medium, e.g., an agar plate.

Select the FALSE statement regarding hydrogen peroxide.

It immediately kills all bacteria when applied to a wound.

Clostridium paradoxum grows optimally at 55°C, pH 9.3; it will not grow in the presence of O2. Please select the TRUE statement about this organism.

It is an obligate anaerobe.

Which of the following describes the optimum temperature of a psychrophile relative to a thermophile?

It is lower than a thermophile.

Which is FALSE about the RNA transcript?

It is made in short fragments that are then stitched together.

Which is true about DNA replication?

It is semiconservative. It starts at an origin of replication. It is bi-directional. It requires RNA primers.

Which is true of iodine?

It is usually found as tinctures or iodophors.

What would true about an organism called Bacillus fastidiosus?

It might be expected to be very strict in its growth requirements.

A batch culture has which of the following characteristics?

It typically involves growth of bacteria or archaea either on agar plates or in tubes or flasks of broths. Nutrients are not renewed. It is a closed system. Wastes are not removed.

Which of the following describes a microbe that must have O2 to survive?

Obligate aerobe

When E. coli is placed in a medium containing both glucose and lactose, why does cell growth stop temporarily when the glucose is used up?

Once glucose is depleted, the cell must use the lactose; before it can do this, it must express the lac operon and synthesize the enzymes needed to use lactose, which takes time.

a ______ culture contains ONE species of microorganisms descended from a single cell

PURE

Experiments designed by ______ suggested that living cells caused the fermentation of sugar to produce alcohol.

Pasteur

Which of the following is/are not (a) sterilization method(s)?

Pasteurization

A common environmental organism that may even grow in certain chemical disinfectants is

Pseudomonas aeruginosa.

Which term describes a microorganism that has an optimal temperature between 15∘C and 30∘C, but grows well on refrigerated foods?

Psychrotroph

RNA is characterized by which one of the following features?

Ribose

Hexachlorophene has been particularly effective against

Staphylococcus aureus.

A physician sends a stool sample to your lab, and wants to know if there are lactose fermenting microbes in the sample. How might you determine if these microbes are present or not from this mixed-microbe specimen?

Streak the sample for isolation on a MacConkey agar plate (which contains lactose and a pH indicator that turns pink when acid byproducts are present).

True or false: A colony is a distinct mass of microorganisms which develop from a single cell growing on a solid medium

TRUE

Cells are often ground up with abrasive to get to their internal enzymes/molecules, followed by removal of the abrasives. Here are two situations and two outcomes. What is the correct interpretation of the results? In situation #1, radioactive amino acids are mixed with ground-up cell material. Radioactive proteins are produced. In situation #2, radioactive amino acids AND the enzyme RNAse (an enzyme that degrades RNA) are mixed with ground-up cell material. No radioactive proteins are produced.

The mRNA from the cell can be used to make proteins with the radioactive amino acids in the first situation. In the second situation, the mRNA is destroyed by the RNAse before it can be translated into protein containing the radioactive amino acids.

Which answer best explains the events in the figure leading to plasmolysis?

The solute concentration of the medium is greater than that in the cell, causing water to diffuse out of the cell due to osmosis.

Please select the FALSE statement regarding the central metabolic pathways.

The transition step and TCA cycle are repeated four times to yield ATP, reducing power, and three different precursor metabolites.

Why would a cell ferment rather than respire?

There is no oxygen present and it cannot use anaerobic respiration OR it lacks the ability to respire (i.e., no electron transport chain).

Imagine you are a microbiologist trying to isolate new species of prokaryotes. You collect numerous samples and return to your lab, where you proceed to encourage any prokaryotes present to grow. Disappointingly, you are not successful. Which is the LEAST likely explanation for this outcome?

There were no prokaryotes present where you sampled.

Which is true of nosocomial infections?

They are acquired by susceptible people in the hospital.

If a DNA triplet is AGT, the mRNA codon would be ______ and the tRNA anticodon would be ______.

UCA; AGU

You are in charge of water quality for your city's water treatment plant. Of the methods at your disposal, which will be the most efficient and cheapest method of determining the number of viable bacteria in the water coming out of your plant?

Using membrane filtration followed by placing the membrane in a growth medium for colony counts after incubation.

A regulatory protein binds to the operator in a strand of DNA, blocking transcription. The protein is

a repressor.

MacConkey agar is

a selective and differential agar.

If O2 is present in an environment, it is said to be _______.

aerobic

Oxygen serves as the terminal electron acceptor in

aerobic respiration

A microbe that doesn't use O2 but can grow in environments containing O2 is described as a(n) ______ anaerobe.

aerotolerant

which of the following does not use O2 at all for growth

aerotolerant anaerobe

Organisms that are indifferent to the presence of oxygen and do not use it are

aerotolerant anaerobes.

Culture media are usually solidified by the addition of a polysaccharide extracted from seaweed. This polysaccharide is known as

agar

Biosynthetic reactions that require energy for the conversion of molecular subunits into larger molecules are called

anabolic reactions.

An environment with little or no O2 present is called a(n) _____environment.

anaerobic

The five groups used to categorize microorganisms with respect to growth temperature (psychrophile, psychrotroph, mesophile, thermophile, and hyperthermophile) ______.

are based on optimum growth temperatures.

Ribozymes

are self-catalytic RNA AND suggest that nucleic acids evolved before proteins.

The term "precursor metabolite" refers to molecules that

are used in biosynthesis.

High concentrations of salt and sugar in foods

are useful in preserving the food AND tend to draw water out of a cell.

The sugar component of RNA and DNA nucleotides is synthesized

as ribose and then changed to deoxyribose.

an ______ requires only carbon dioxide as a sole carbon source

autotroph

Organisms that use CO2 as their source of carbon are called

autotrophs.

When bacteria or archaea are grown on agar plates or in tubes or flasks of broth, these closed systems are a ____culture. By contrast, cells can also be grown in an open system, or a continuous culture.

batch

Bacteria and archaea typically divide by a process known as

binary fision

Prokaryotic cells divide by a process known as

binary fission

What term is used to describe a group of microbes co-existing in polymer-encased communities?

biofilm

Many bacterial communities secrete polysaccharides and other hydrophilic polymers. This mesh-like accumulation can help protect the bacteria growing within from antibiotics or disinfectants. These communities are called

biofilms

Mercury in mercurochrome inhibits growth

by oxidizing the sulfhydryl groups in cysteine AND by changing the shape of proteins.

GCCCAAAG is a molecule of

cannot tell as written

Which of the following characterizes the lag phase of a normal bacterial growth curve?

cells are synthesizing enzymes needed for growth nut not increasing in number

A continuous culture system that adds nutrients and removes waste in order to maintain a constant growth rate and cell density is called a

chemostat

Which device is used to keep cells in a state of constant growth?

chemostat

An isolated ____ is a distinct mass of microorganisms appearing on a solid medium, arising from the multiplication of a single cell.

colony

In which phase of the growth curve is the number of viable cells decreasing?

death

Which are essentially equivalent treatments?

dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes

Bacteria growing in a natural environment experience ______.

dynamic and complex conditions

Generally, membrane filters are not used to remove

enzymes from liquids.

The log (logarithmic) phase of a normal growth curve is also referred to as the _______phase.

exponential

In the growth curve of a bacteria population, the bacteria are rapidly increasing in number in the

exponential (log) phase.

Some microorganisms live in harsh environments that kill most other organisms. The term used to describe an organism with this characteristic is

extremophile

Agar replaced gelatin as the gelling (solidifying) agent for media because

fewer bacteria can break down agar compared with gelatin.

Autotrophs play a crucial role in the cycling of carbon in the environment by converting inorganic carbon to an organic form. This process is called carbon____

fixation

Post-translational modification may include

folding of the protein, often with the aid of chaperones AND removal of the signal sequence.

The simultaneous regulation of many bacterial genes is

global control.

The most common starting pathway for the breakdown of sugars is

glycolysis.

A graphical representation of a changing population size over time is called which of the following?

growth curve

The characteristic pattern that shows the changes in size of a bacterial population over time in a broth culture is called a bacterial

growth curve

Small organic molecules that must be provided to bacteria in order for them to grow are called

growth factors.

agar

has chemical and physical properties that make it almost ideal for solidifying media.

An organism that must consume organic matter is called a(n)

heterotroph

Which type of organism requires organic compounds for its carbon and energy needs?

heterotroph

The electron transport chain is a group of membrane-embedded carriers that pass electrons from one to the next, while simultaneously pumping ______ across the membrane, generating a(n) ______.

hydrogen ions; proton motive force

If you wanted to study psychrophilic microorganisms, you would most likely find them ______.

in lakes fed by glaciers

Trace elements

include zinc, copper, and manganese AND may be needed for enzyme function.

The molecules that bind to a repressor and cause it to no longer bind to the operator are called

inducers.

The most important function of nitrites in processed foods is to

inhibit the germination of Clostridium botulinum endospores.

From which body site could a facultative anaerobe be isolated?

intestine, deep wound, surface of skin

Some segments of the precursor mRNA in eukaryotes are non-coding and are called

introns.

Moist heat kills microorganisms by

irreversible denaturation of proteins

Feedback inhibition

is a way of regulating the amount of product produced.

Late log phase of the bacterial growth curve

is characterized by the production of secondary metabolites.

Chlorhexidine

is extensively used in antiseptics

Free energy

is the amount of energy gained by breaking bonds of a chemical.

Signal transduction

is the relay of information about conditions outside a cell to inside the cell.

When doing experiments with bacteria,

it is best to use bacteria from the same stage of growth

Hand washing with plain soap is very effective in controlling spread of microorganisms because

it is very effective at the mechanical removal of microorganisms.

______phase describes the initial phase after bacterial cells are placed into a new environment and are gearing up for cell division, but their numbers have not yet increased.

lag

The transition step

links glycolysis to the TCA cycle.

In which phase of the growth curve is the generation time measured?

log

Enzymes speed up reactions by

lowering the activation energy

What term is used to describe chemical substances such as carbon or phosphorous, which are found in large quantities in cells?

major element

Carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus, are examples of chemical substances called_______ , which are the essential components of the cell's macromolecules.

major elements

In nature, bacteria

may adhere to surfaces by means of pili and slime layers.

Anoxygenic photosynthetic bacteria

may obtain electrons from H2S.

Chemical germicides

may react irreversibly with proteins/enzymes. may react with cytoplasmic membranes or viral envelopes. may be disinfecting or even sterilizing. are sensitive to dilution factor, time of contact, and temperature of use.

E. coli and most other common bacteria are ______.

mesophiles

Human pathogens, adapted to growth in the human body, are ______.

mesophiles

The general term used to describe the anabolic and catabolic reactions in a cell is

metabolism

A microbe that requires small amounts of O2 (2-10%) for aerobic respiration but is inhibited by higher concentrations is called a(n) ______.

microaerophile

A(n)______ is an aerobe that requires O2 at a concentration less than that in the atmosphere.

microaerophile

A sterile item is free of

microbes, endospores, and viruses

An atom that has a lower affinity for electrons than another is ______ than the other.

more electronegative

DNA polymerases

move in a 3' to 5' direction on the template DNA.

Mycobacterium leprae is typically found infecting the ears, toes, and fingers of its host due to its

need for cooler temperatures.

Unlike sugar, proteins provide which of the following elements?

nitrogen

Alcohols are not reliably effective at destroying

non-enveloped viruses AND endospores

A(n)______ aerobe, or strictly aerobic organism, requires O2 for survival.

obligate

Bacteria that cannot multiply if O2 is present, and are often killed by even brief exposure to air, are termed

obligate anaerobes

If you inoculated a test tube of cooled liquid agar with an obligate anaerobe and incubated it, where would you expect to find growth?

only the bottom of the tube

The DNA site to which the repressor protein binds is the

operator.

A species grows most rapidly at its growth_____ temperature

optimum

Animals could not survive without autotrophs because without them the world would run out of ______.

organic carbon

Consider the following environmental factors. Which have the most impact on microbial growth?

pH water availability oxygen availability temperature

A flat covered container made from plastic or glass in which a solid culture medium can be added is called a

petri plate

If the solute concentration is higher outside the cell than inside the cell, water will diffuse out due to osmosis. This will result in

plasmolysis

Gamma rays cause biological damage in living systems by

producing reactive molecules such as superoxide and hydroxyl-free radicals.

Transcription begins at the ______ and ends at the ______, while translation begins at the ______ and ends at the ______.

promoter; terminator; start codon; stop codon

Regardless of the pH of the external environment, microbial cells maintain a constant internal pH, typically near neutral. For example, prokaryotes that grow in alkaline conditions bring_____ into the cell.

protons, H+, H

Candle jars are usually used to

provide an atmosphere with CO2.

Which term describes a microorganism that has an optimum temperature between -50C and 150C?

psychrophile

Match the term on the left with the description of the optimum temperature environment

psychrophile = cold Arctic regionspsychrotoph = refrigerationmesophile = human bodythermophile = compost heap

A ______ is most likely to be implicated in spoilage of refrigerated foods.

psychrotroph

Microbial cells must maintain a near-neutral internal pH. Because of this, bacteria that grow in acidic environments have mechanisms to ______.

pump out H+ that enter the cell

Which would be most effective against Pseudomonas?

radiation

The name given to the reaction involving addition of electrons or hydrogen atoms to a compound is

reduction

The transcription terminator

results in a hairpin loop structure in RNA, AND results in the polymerase falling off the DNA template.

Bacteria use ______ attached to the polymerase to direct RNA polymerase to promoters; eukaryotic cells use ______ that attach directly to the DNA first instead.

sigma factors; transcription factors

Which environment is more dynamic and complex?

soil and surroundings

During which phase of growth does the number of new cells balance the number of declining cells?

stationary

The _____ phase of the bacterial growth curve is when there are an equal number of cells dividing as there are dying.

stationary

the _____ phase of the bacterial growth curve is when there are an equal number of cells dividing as there are dying

stationary

The process of killing or removing all of the microorganisms in or on a material is called

sterilization

A common application of dry heat in the microbiology laboratory is to

sterilize the inoculating loop.

The simplest technique for isolating bacteria in growth media is referred to as the

streak plate method

The enzymes that deal with toxic oxygen-containing molecules is/are

superoxide dismutase AND catalase.

Environmental factors that may affect enzyme activity include

temperature, pH, AND salt.

All of the following are true about DNA sequence analysis EXCEPT

the (−) strand of DNA is used.

Energy is defined as

the capacity to do work

Microwaves do not kill organisms directly but kill by

the heat they generate in a product.

Eosin methylene blue agar (EMB) is a selective and differential medium. The dyes in the medium inhibit most Gram-positive organisms. Gram-negative organisms such as the coliforms grow on this medium. Coliforms that are fecal in origin produce colonies with a metallic green color on EMB, while those that are non-fecal produce colorless colonies. You plate a urine sample onto an EMB plate and incubate it. Metallic green colonies develop. From this, you can conclude that

the sample contains bacteria that are Gram-negative AND are fecal in origin.

Compounds of tin, mercury, arsenic, and copper are no longer used to prevent microbial growth in cooling water primarily because

their use contributes to serious pollution of natural waters.

How many nucleotides are in a codon?

three

Degradation of fats as an energy source involves all of the following except

transamination.

In a growth curve, cell numbers increase exponentially during the log phase and decrease exponentially during the death phase

true

In a growth curve, cell numbers increase exponentially during the log phase and decrease exponentially during the death phase.

true

Some species of microorganisms can be found in environments where no unprotected human could survive

true

Some species of microorganisms can be found in environments where no unprotected human could survive.

true

True or false: A colony is a distinct mass of microorganisms which develop from a single cell growing on a solid medium.

true

Chemoheterotrophs

use preformed organic molecules as a carbon source AND as an energy source.

Fermentation

uses an organic molecule as the final electron acceptor.

RNAi

uses short pieces of single-stranded RNA to direct the degradation of specific RNA transcripts

Coenzymes are derivatives of

vitamins

A drug that inhibits the activity of bacterial DNA gyrase ______ be a good antibiotic because ______.

would; it would selectively inhibit bacterial DNA synthesis due to differences between bacterial/human gyrase