CHAPTER 1 SELF QUIZ
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Organisms without a membrane-bound nucleus and without compartmentalization are called what?
Organisms with a membrane-bound nucleus and membrane-bound organelles are called what?
What scientific advances influenced microbial classification?
The use of electron microscopy to study detailed structures of microbial cells, the determination of the biochemical and physiological characteristics of many microbes, and the sequencing of nucleic acids and proteins from a wide variety of microbes
Comparison of ribosomal RNA from a variety of organisms led to what classification schemes?
Two-domain classification scheme
How would you best describe bacteria?
Cell wall is composed of peptidoglycan
How would you best describe archaea?
Usually live in extreme environments, exhibit unusual metabolic characteristics, and plasma membrane composed of unique lipids
Name a microorganism that the domain Eukarya includes
Name a major type of protist
Algae, protozoa, and slime and water molds
What is a diverse group of microorganisms that are multicellular, form hyphae, and absorb nutrients from the environment called?
What do viruses require?
Host cells to replicate
What is the name for an infectious protein that causes spongiform encephalopathies?
In the scientific method, and educated guess used to explain observations is called what?
What would microbiologists consider to be an important attribute of life?
What was most likely the first self-replicating molecule on the primitive earth?
Why was RNA most likely the first self-replicating molecule?
It can catalyze chemical reactions, it can regulate gene expression, and ATP (the energy currency of the cell) is composed of a ribonucleotide
The universal phylogenetic tree was constructed from comparison of which molecule amongst diverse organisms?
According to the universal phylogenetic tree...?
The eukarya and the archaea are more closely related and evolved from a common ancestor after the bacteria
Describe the origin of the eukaryotic organelles?
The endosymbiotic hypothesis
The hydrogen hypothesis describe the evolution of which eukaryotic organelle?
A major source of genetic diversity in bacteria is what?
Horizontal gene transfer
Why is the traditional biological species concept applied to some eukaryotes not valid for bacteria?
Because bacteria reproduce asexually
What is the name for a collection of bacterial or archaeal strains that share many stable properties and differ significantly from other groups of strains?
What are important methods to microbiologists?
Microscopy, culture techniques, and genomic analysis
Who constructed simple microscopes, observed bacteria and protists, and reported his findings to the Royal Society of London?
Antony van Leeuwenhoek
What observation made by Francesco Redi refuted the idea of spontaneous generation?
He covered pieces of meat and they did not produce maggots spontaneously
Which scientists contributed to disproving spontaneous generation?
Francesco Redi, John Needham, and Lazzaro Spallanzani
Which scientist linked silkworm disease with a fungus?
What the processes of heating liquids to destroy undesirable microbes called?
Who first used phenol in surgery to prevent microorganisms from entering the wounds?
Make a statement to best illustrate Koch's postulates?
The suspected organisms are isolated and grown in pure culture
Why is agar an ideal solidifying agent for growing bacteria?
Because it is not broken down by most bacteria, it is in liquid form at 100 degrees celsius, it is in a solid form at 50 degrees celsius
Who was the first scientist to knowingly use attenuated bacteria in vaccination?
Pasteur and Roux
Name major discoveries in the field of immunology?
Injection with attenuated microorganisms that provided immunity, discovery of antibodies, and the discovery of immune system cells
Who made the discovery that soil bacteria could oxidize iron, sulfur, and ammonia to obtain energy?
What is the name for the genetic information that an organism contains?
What is the name for molecules made by combining two or more different DNA molecules together?
Recombinant DNA molecules
Which field of microbiology that studies the spread of communicable disease, detects outbreaks, and implements appropriate control measures called?
Which field of microbiology that studies the role of divers microorganisms in the environment?
Which field of microbiology researches new uses for microbes and and ways of culturing and isolating their products?
CHAPTER 1 TRUE/FALSE
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Microorganisms are always one millimeter or less in diameter
Classification of microbes is difficult due to their vast diversity
The five-kingdom classification system is widely accepted and used in the field of microbiology
Viruses, viroids, and virusoids are examples of cellular entities studied by microbiologists
All bacteria are pathogens, or disease-causing organisms
The archaea are different than the bacteria in regards to cell wall composition and plasma membrane lipids
The domain eukarya includes some microbial members
Together, algae and cyanobacteria produce about 75% of planet's oxygen
Most fungi are unicellular
Viruses cannot live outside a host cell
Scientific theories are proven absolutely with many observations and experiments
Hypotheses that are refuted through experimentation are of no value to the scientific community
Unlike other fields of microbiology, the study of microbial evolution does not follow the scientific methods
The primitive earth was hospitable for the evolution of early life
Organisms alive today can assist scientists in understanding the origins of life
Microbial fossils indicate that microbial life began approximately 3.5 billion years ago
Due to its ability to do cellular work, DNA was likely the first self-replicating molecule on the planet
In the RNA world, RNA was capable of storing, copying, and expressing genetic information, as well as catalyzing other chemical reactions
The appearance of cyanobacteria-like cells released oxygen and altered the Earth's atmosphere allowing the evolution of aerobic respiration
The universal phylogenetic Tree is based on comparison of small subunit rRNA molecules
Evolutionary distance between organisms can indicate definitely when they diverged from one another
The last universal common ancestor (LUCA) is well known and characterized
Organisms with similar nucleotide sequences are more distantly related evolutionarily
The endosymbiotic hypothesis is generally accepted as the origin of eukaryotic organelles
In the hydrogen hypothesis, if an endosymbiont developed the capacity to perform aerobic respiration, it evolved into a mitochondrion
Sexual reproduction is the primary means of generating genetic diversity in the archaea
The bacteria and the archaea are easily classified using the biological species concept of eukaryotes
The linnaean binomial classification system is applied to the bacteria and the archaea
Microbiology is defined both by the organisms it studies and the tools used to study them
Culturing microorganisms outside of their natural environment provides valuable information about their ecology
Scientists have been observing organisms with microscopy since the 1600s
The theory of spontaneous generation advanced the field of microbiology
Many scientists throughout the 1700s to 1800s disproved the theory of spontaneous generation through repeated experimentation and observations
The belief in spontaneous generation was an obstacle to the development of microbiology as a scientific discipline
Pasteurization is widely used today to destroy undesirable microbes in food and beverages
The use of antiseptics in the 1800s transformed the field of surgery and provided strong indirect evidence for the role of microorganisms in disease
The first direct demonstration of the role of bacteria in causing disease came from the study of anthrax
Koch's postulates are applicable and feasible for all microbes
Injection of attenuated virus is usually lethal
CHAPTER 3 SELF QUIZ
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In what way are bacterial and archaeal cells similar?
In cellular organization
How are bacterial cells that grow in irregular groups and divide in random planes are characterized as what?
Which characteristics contribute to variation in bacterial and archaeal size and shape?
Surface area-to-volume ratio, presence of filamentous structures, and cytoskeletal elements
Describe the layers of bacterial cellular organization (starting internally and working outward)
Cytoplasm, plasma membrane, cell wall, and capsule
What is the purpose of the nucleoid in bacterial and archaeal cells?
Localization of genetic material
What is the function of the plasma membrane in bacterial cells?
To detect and respond to chemicals in the surrounding environment, to provide a selectively permeable barrier, and to facilitate important metabolic processes
How would you best describe the current understanding of the fluid mosaic model of membrane structure?
Phospholipid bilayer with peripheral and integral membrane proteins
Why are hopanoids important to bacterial cells?
Because they likely provide membrane stability
How would you best describe the bacterial cell wall?
It protects the cell from osmotic lysis, contributes to pathogenicity, and site of action of several antibiotics
Most gram-positive bacterial cells exhibit which characteristics?
Thick layer of peptidoglycan with teichoic acids and small periplasmic space
Most gram-negative bacterial cells exhibit which characteristics?
Thin layer of peptidoglycan without teichoic acids, large periplasmic space, and outer membrane
What is the function of lipopolysaccharides (LPSs) on gram-negative bacterial cells?
To assist in evading the host immune response, to contribute to the negative charge on the cell surface, and to create a permeability barrier
Why do gram-positive cells stain purple?
Because ethanol shrinks the peptidoglycan pores and prevents loss of crystal violet
If bacterial cells treated with lysozyme are placed into a hypotonic solution, what would be the result?
The cells would likely swell and lyse
How do slime layers assist bacterial cells?
By facilitating motility
What is a unique feature of archaeal cell s-layers?
They are located just outside the plasma membrane
Why are archaeal membrane lipids unique?
Because they contain branched hydrocarbons derived from isoprene units, they are attached to glycerol by ether links, and they are often composed of C20 diethers and C40 tetraethers
What is the best way to describe the most common archaeal cell wall?
S-layer composed of glycoproteins or proteins
How would you best describe the function of the bacterial cytoskeleton?
It facilitates cell division, localizes proteins to certain sites in the cell, and determines cell shape
Ladderlane lipids compose which of the following bacterial organelles?
When aquatic bacteria are living under phosphorus-limited conditions with abundant carbon availability, which of the following structures may be visible via microscopy?
Which structures allow aquatic bacteria to orient themselves in the earth's magnetic field?
What is the function of ribosome in the bacterial cell?
To synthesize proteins
Give a true statement regarding plasmids
The replicate autonomously
What is the name of a bacterial cell with flagella spread evenly over the whole surface?
What is the primary function of bacterial flagella?
How do archaeal flagella differ from bacterial flagella?
They are thinner than bacterial flagella, they are composed of multiple subunit types, and their flagellum is solid instead of hollow
What is flagellar movement driven by?
Which bacterial movements are type IV pili associated with?
What allows for bacterial cells to sense a chemical gradient and respond appropriately?
What is a true statement regarding bacterial endospores?
Endospores survive in nutrient limited conditions
Which structure of the endospore contributes to its resistance to heat and other lethal agents?
The exporium and spore coat, the inner membrane, and the core
What has viviparity been observed in?
CHAPTER 3 TRUE/FALSE
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Bacteria and archaea are uniform in shape and size
Pleomorphic cells are variable in shape and lack a single, characteristic form
Larger cells have a greater surface area-to-volume ratio
Bacterial and arachaeal cells share a common cell organization
Peripheral proteins in the plasma membrane are easily removed and comprise up to 30% of membrane proteins
Scientists agree upon all aspects of the fluid mosaic model
At higher temperatures, bacterial phospholipids have more saturated fatty acids
Hopanoids in bacterial cell membranes contribute significantly to the world's petroleum formation
Peptidoglycan is common to both gram-positive and gram-negative bacterial cells
Periplasmic space comprises a larger portion (20-40%) of the gram-positive cell wall
The component of lipopolysaccharides (LPSs), lipid A, elicits an immune response by an infected host
In the gram staining preocedure, iodine is used to promote dye retention
Capsules are layers outside the cell wall that are well organize and not easily washed off
S-layers are currently being studies for their potential use in the field of nanotechnology
Archaeal membrane lipids are capable of forming pentacyclic rings
Archaeal cell walls have the same chemical composition as bacterial cell walls
Eukaryotic and bacterial cytoskeletons have analogous components
Polyphosphate granules store phosphate in bacterial cells living in nutrient-limited conditions
Archaeal and bacterial ribosomes have the same make up and size
All bacteria have one circular chromosome
Bacteria cells can lose plasmids spontaneously
Type IV pili are involved in bacterial motility and uptake of DNA during transformation
Chemotaxis is best described as random, aimless movement in bacteria and archaea
Endospore position in the sporangium is valuable for identification of some bacterial species
CHAPTER 5 SELF QUIZ
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The genetic material found in a virion is usually what?
Either DNA or RNA
Viral particles are composed of what?
DNA or RNA, a coat of protein, and layers of carbohydrates, lipids and additional proteins
What is the best microscopic methods for studying viruses?
What is the function of the viral capsid?
To the protect the viral genome
The Tobacco mosaic virus exhibits which type of capsid symmetry?
An example of a virus that exhibits binal symmetry is known as what?
Viral spikes or peplomers are involved in what?
Which structures are associated with the influenza virus?
Neuraminidase enzyme, hemagglutinin protein, and glycoproteins
The most common viral nucleic acid types are what?
dsDNA and ssRNA
What is the first step in the generalized viral life cycle?
Attachment of virus to host cell
What is viral host specificity most likely attributed to?
Interaction between receptors on the surface of the host cell and ligands on the surface of virions
Which mechanisms do eukaryotic viruses enter host cells through?
Through fusion of the viral envelope with the host cell membrane, entry by endocytosis, and injection of nucleic acid
Which types of viruses must carry their own replication enzymes in their nucleocapsid?
RNA viruses only
Where does the energy that is required for bacteriophage assembly come from?
Host metabolic activity
What is a common virion release method observed in enveloped viruses?
What is the name of the relationship with the host cell in which the virus remains within the host without destroying it called?
What does an advantage of lysogeny to the host include?
Resistance to superinfection
When more phage are present in the environment than there are host cells, which type of host relationship is most desirable?
What are microscopic and/or macroscopic damages to host cells caused by eukaryotic viruses called?
What is the name for a type of viral infection in which there is a low release of virions without cell death?
What cellular genes required for normal growth, but when mutated or overexposed, cause carcinogenesis?
Which of the following viruses is NOT definitely linked to causing cancer in humans?
Which methods can be used to cultivate plant viruses?
Grow in cultures of plant cells lacking cell walls, mechanically break leaves to expose cells to infection, or graft diseased part onto a healthy plant
What can be used to determine direct counts of viral particles?
What is an indirect method of counting animal viruses?
The number of plaque-forming units (PFUs) is calculated from a viral plaque assay by.....?
Multiplying the number of plaques per volume by the dilution
What is teh dilution taht contains the number of viral cells large enough to destroy 50% of the host cells or organisms called?
The lethal dose
What are infectious RNAs that primarily infect plants called?
What are infectious proteins responsible for bovine spongiform encephalopathy called?
CHAPTER 5 TRUE/FALSE
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Viruses are considered to be living organisms
Scientists classify viruses based on genome structure, life cycles, morphology, and genetic relatedness
Most viruses are approximately the same size as bacteria (0.2 to 2 micrometers)
Hos-independent growth has never been observed in either the bacterial or archaeal viruses
The size of a helical capsid is influenced by both its protomores and the nucleic acids enclosed within the capsid
The icosohedral capsid maximizes efficiency and requires few genes for its coding
An envelope is present in all viruses
Spikes can be used to identify many types of viruses
All virions lack enzymes
Most DNA viruses use dsDNA as their genetic material
Many RNA viruses have segmented genomes with each segment coding for a protein
Viral attachment to the host cell is a random process
Variation in receptors used by a virus for attachment is partly responsible for host specificity
All viruses inject their nucleic acid into the cytoplasm of their host, leaving the capsid outside and attached to the cell wall
Human immunodeficiency virus (HIV) enters the host cell by fusing directly with the host cell plasma membrane
DNA and RNA viruses replicate using the same processes
Bacteriophages are assembled in the host cytoplasm
All animal viruses are assembled in the cytoplasm
Many nonenveloped viruses lyse their host cells at the end of the intracellular phase
When viral cells are released via budding, the host cell may survive and continue releasing virions for some time
Actin filaments in the cytoskeleton can aid in the release of eukaryotic viruses
Temperate phages must release from the host cell via lysis
Temperate phages can integrate their genome with the host genome
Host cells that are infected with a temperate virus cannot be infected by other virions of the same type
temperate phages can alternate between lysogenic and lytic stages
Lysogeny enables survival of host cells in an environment with low multiplicity of infection (MOI)
A chronic infection is a situation in which a virus slowly releases virions without killing the cell
Most human viruses associated with cancer have dsDNA genomes
Some strains of human papillomavirus (HPV) can cause cervical caner
Tumor activator proteins promote formation of tumors in human dsDNA viruses
Viruses are easily cultivate in agars and broths, much like bacteria
Plaque assays determine viral numbers based on infectivity of the virus
The number of plaque-forming units (PFUs) is equal to the number of viruses because all virions are infective
The infectious dose (ID60) of a virus is the dose that, when given to a number of hosts, causes and infection of 50% of the hosts under particular conditions
Viroids, or infectious RNAs, cause many important plant diseases
CHAPTER 6 SELF QUIZ
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Name 3 macronutrients required in large amounts for microbial nutrition
Carbon, Iron, Phosphorous
What are nutrients required by microbes only in small amounts called?
What is an organism that obtains carbon, hydrogen, oxygen, and electrons from organic molecules?
What are organisms that use carbon dioxide (CO2) as their sole or principal source of carbon?
What is an organism that uses light for energy and carbon dioxide as a carbon source?
What are microbes that are used industrially to make foods and beverages called?
Purple nonsulfur and green bacteria are classified as what?
Microbes use which processes to obtain nitrogen?
Metabolism of amino acids, incorporation of ammonia directly, and reduction of nitrate to ammonia
Phosphorous is required in microbial metabolism for what?
Organic compounds that cannot be synthesized by an organism but are essential for growth are called what?
What does a major class of growth factors include?
Amino acids, purines and pyrimidines, and vitamins
Movement of molecules from a region of high concentration to a region of low concentration without the expenditure of energy is known as what?
Diffusion involving carrier proteins that created channels through the plasma membrane is called what?
The rate of transport of molecules across the membrane via facilitated diffusion increases as....?
the concentration gradient of the molecule increases
Facilitated diffusion is most prominent in which of the following groups?
What is the transport of solute molecules against a concentration gradient with the input of metabolic energy?
What is lactose entering the E. coli cell along with a proton an example of?
What is the name for an energy-dependent form of transport that chemically modifies a molecule as it is brought into the cell?
The phosphoenolpyruvate, sugar phosphotransferase system (PTS), is an example of what?
Microbes in an iron-limited environment will secrete _______________ externally to bind ferric iron
Growth media that contains some unknown ingredient in which the exact chemical composition is not known in called what?
What is a type of media that distinguishes among different groups of microbes and can aid in tentative identification?
Blood agar distinguishes between hemolytic and nonhemolytic bacteria as well as growing fastidious microbes. For these reasons, blood agar is what?
Both enriched and differential
Mannitol salt agar's high concentration of salt grows only staphylococci. In addition, some staphylococci that use mannitol as a carbon source turn the medium yellow. For these reasons, mannitol sugar is what?
Both selective and differential
What is a population of microbial cells arising from a single cell, representing a single species called?
What is an appropriate qualitative method for isolating microbe into a pure culture?
The streak plate
A microbiology student would like to quantify the number of bacterial cells growing in her sample of nutrient agar. Which method will help her with this goal?
The most active bacterial cells on the colony would be found where?
Growing along the edge of the colony
CHAPTER 6 TRUE/FALSE
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Magnesium (Mg+) is an example of a macronutrient required by microbes
Calcium (Ca2+) is an example of a micronutrient required by microbes
Electrons provided by organic carbon sources are used in oxidation-reduction and in the electron transport chain
Heterotrophs can use organic molecules as a source of carbon, hydrogen, oxygen, and electrons
Most microbes are capable of metabolizing only a narrow range of organic compounds
Carbon dioxide (CO2) serves both as a source of carbon and a source of electrons for autotrophs
Lithographs use reduced inorganic substances as a source of electrons
All pathogens are chemoorganoheterotrophs
All microbes are classified into only one nutritional type
Nitrogen is required for the synthesis of amino acids, purines, and pyrimidines
Phosphorous is required for the synthesis of the amino acids cystein and methionine
Vitamins act as enzyme cofactors and are required only in very small amounts
Some microorganisms are able to synthesize large quantities of vitamins
Uptake of nutrients into microbial cells is random and non-specific
Transport of nutrients via group translocation has been observed in all three domains
A large concentration gradient is required to transport molecule across a membrane via passive diffusion
The microbial cell membrane is permeable to all substances
Facilitated diffusion reaches a maximum rate due to saturation of carrier proteins
Membrane permeases are specific for particular solutes
ATP-binding cassette transporters are involved in both import and export of substances across the cell membrane
Microorganisms rarely have more than one transport system for a nutrient
Phosphoenolpyruvate, sugar phosphotransferase systems (PTSs), are widely distributed in bacteria
Siderophores are released when iron is abundant in a microbe's environment
Examples of complex media include nutrient broth, trypic soy broth, and MacConkey agar
Agar is useful to solidify media because most microorganisms can degrade it
Selective media often contains dyes that suppress the growth of one type of bacteria
It is not possible to isolate microbes as a pure culture in the laboratory
A colony is composed of clones resulting from one bacterium
CHAPTER 7 SELF QUIZ
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Sexual reproduction is a characteristic of which domain?
Which reproductive method is common to bacteria?
Binary fission, budding, and formation of uninucleoid spores
Replication is the bacterial chromosome is........?
How would you best describe chromosomal partitioning of daughter cells in bacterial reproduction?
It is pushing of chromosomes to opposite sides by RNA polymerase, condensation of daughter chromosomes pull the DNA opposite sides, and a cytoskeletal protein MreB moves the DNA to opposite poles
What is the most critical step in cytokinesis?
Assembly of the z ring
Where does peptidoglycan synthesis start in?
What are autolysins involved in?
Degrading the glycosidic bonds between peptidoglycan molecules
What does the new cell wall in reproducing rods form?
Along the sides of the cell but not at the poles
Organisms incubated in a closed culture vessel with a set volume of media is known as a(n).....?
Cells begin synthesizing new component during which phase?
During which phase do microorganisms grow and divide at their maximum rate?
Balanced growth in which all cellular constituents are manufactured at a constant rate, occurs during which phase?
Why do microbial populations enter the stationary phase?
Because of nutrient limitation, accumulation of toxic waste products, and limited oxygen availability
What is the name of proteins that make the cell more resistant to damage by starvation and other stressful conditions?
The number of viable cells decreases exponentially in which phase?
In death phase.......?
The number of living cells declines exponentially, cell become viable but nonculturable (VBNC) and undergo programmed cell death
How would you define the number of generations per unit time?
The mean growth rate
Which variables are important to calculation the microbial mean growth rate?
Initial population number, the population number at time (t), and the number of generation in time (t)
Which method would be best for counting the number of protists in a water sample?
What is the best method for counting living bacterial and archaeal cells?
The Petroff-Hauser counting chamber
Give examples of viable counting methods
Streak plate, pour plate, and membrane filtration
What is the most rapid and accurate method for measuring cell mass?
What will a more turbid broth culture of bacterial cells result in?
A high absorbance reading with the spectrophotometer
Bacterial cells growing in a chemostat will grow more with which change?
Increasing the dilution rate
Turbidostats work by what?
Maintaining a desired cell density
If a bacterial cell is placed into a hypertonic solution, then what?
Water will move out of the cell and the cell will shrink
Microbial cell respond to osmotic stresses by.........?
Opening and closing mechanosensitive (MS) channels, storing compatible solutions inside the cell, and using a contractile vacuole to expel excess water
Organisms that do not require oxygen for growth but grow better in its presence are called what?
What are organisms that grow optimally at temperatures at 55 degrees celcious or higher?
What are organisms that grow optimally within a pH range of 0 and 5.5 called?
How do acidophiles survive in low pH environments?
The survive by pumping protons outside the cell if they get in
Why are microbes vulnerable to high temperatures?
Because high temperatures inactivate enzymes responsible for metabolism
Thermophiles have which adaptations for survival at high temperatures?
Adaptations are that they have heat-stable enzymes and proteins, they have lipids that span the membrane and form a rigid monolayer, and they have saturated membrane lipids
Photosynthetic protists are most likely.......?
Which enzymes protect microbes against toxic oxygen (O2) products?
How can microbes be grown in anaerobic conditions?
They can be grown by removing oxygen chemically with a palladium catalyst, by removing air from the growth chamber with a vacuum, and by adding carbon dioxide (CO2) to the growth chamber to drive out oxygen
How are organisms that grow in the deepest trench of the Pacific Ocean classified as?
Which form of radiation is most harmful to microbes?
Why can ultraviolet (UV) radiation kill microorganisms?
Because it damages DNA by forming thymine dimers
Why is visible light damaging to microbial cells?
Because it generates singlet oxygen and oxidizes cells
What is the purpose of the extracellular polymeric substance (EPS) matrix created by biofilms?
To stick more stably to a surface
What is a density-dependent chemical communication between microbes known as?
When for Vibrio fischeri populations inside warm-water squids bioluminesce?
When N-acylhomoserine lactone (AHL) reached threshold levels
CHAPTER 7 TRUE/FALSE
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Sexual reproduction is a characteristic of all domains in life
In E. coli cytokinesis, Z-ring formation can only occur in the middle of the cell that lacks MinCDE
Chromosome and plasmid segregation utilizes the same types of proteins
Microbial shapes are fixed and unchanging
Penicillin binding proteins (PBPs) link strands of peptidoglycan together in cellular growth
Spherical cells build new peptidoglycan only at the septum during division
The cytoskeleton protein MreB plays an essential role in determining cell diameter during elongation of rod cells
Microbial cells experience the greatest increase in numbers during lag phase
Microbial cells begin to replicate their DNA in lag phase
During exponential (log) phase, microbes grow and divide at the maximum rate possible
The rate of growth is constant during exponential (log) phase
Unbalanced growth results when nutrient levels or other environmental conditions change
The rate of growth increases as the concentration of a limiting nutrient increases
Starvation proteins are made in response to stressful conditions during death phase
viable but nonculturable cells (VBNCs) are easy to grow under laboratory conditions
In programmed cell death, it is hypothesized that some cells within a population die to make their nutrients available for other cells
If a population of two bacterial cells doubles every two minutes, 16 cells will be present after six minutes
The mean generation time is the reciprocal of the mean growth rate
Direct microscopic counts and culture counts of environmental samples are approximately the same
Flow cytometry can count cells of different sizes
The number of colony forming units in a sample is the same as the number of organisms in the sample
Plate counts are an accurate way to estimate bacterial cell numbers in environmental samples
Because of the small size of bacterial cells, determining dry weight provides an accurate measure of cell mass
A continuous culture system maintains bacterial cells in a state of exponential growth
In a chemostat, the dilution rate is dependent upon both the flow rate and the volume of the vessel
In a chemostat, the cell density of a microbial population increases with a high dilution
A turbidostat operates best at high dilution rates
A bacterial cell placed in hypotonic solution will swell and lyse
Hyperthermophilic organisms live optimally between 80 and 113 degrees celcius
Alkalophiles grow optimally between pH 0 and 5.5
Many microbes keep the osmotic concentration of their cytoplasm somewhat above that of the habitat so that the plasma membrane is always pressed firmly against their cell wall
Halophilic organisms are capable accumulating large quantities of potassium and chloride in order to remain hypertonic to their environment
Water activity (aw) is a measure of the degree of water availability to microbes
Xerophilic organisms grow best at low water activity
A pH of 2 is twice a great as a pH of 1
Acid-shock proteins prevent denaturation of proteins under acidic conditions
At high temperatures, microbial membranes solidify
Bacteria and archaea are capable of growing at much higher temperatures than eukaryotes
Almost all human pathogens are mesophiles
Psychrophilic bacteria and fungi are major causes of refrigerated food spoilage
Obligate anaerobes are usually killed in the presence of oxygen
Strict anaerobes contain the enzymes superoxide dismutase (SOD) and catalase
It is not possible to culture microbes under anaerobic conditions in the laboratory
As the wavelength of electromagnetic radiation increases, the energy of the radiation increases
Carotenoid pigments protect cell against photo-oxidation
Biofilms are resistant to antibiotic treatments
AHLs regulate quorum sensing and bioluminescence amongst Vibrio fischeri, endosymbionts of the warm-water squid