What do microbes do in hypertonic solutions to adapt?
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They increase internal solute concentration with compatible solutes to raise their internal osmotic concentration.
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What do microbes do in hypertonic solutions to adapt?
They increase internal solute concentration with compatible solutes to raise their internal osmotic concentration.
What is a mature biofilm?
A complex, dynamic community of microorganisms.
What can limit growth during the log phase?
Nutrient concentrations may be limiting.
What does heterogeneity in biofilms refer to?
Differences in metabolic activity and locations of microbes.
What are compatible solutes?
Solutes that are compatible with metabolism and growth, used by microbes to adapt in hypertonic solutions.
What is septation in the context of cytokinesis?
Formation of cross walls between daughter cells.
What is the challenge in determining cell viability in microbiology?
Cells can exist in a variety of states between 'fully viable' and 'actually dead'.
What is the primary growth form of most microbes?
Attached to surfaces (sessile) rather than free-floating (planktonic).
What is the primary focus of Chapter 7?
Microbial Growth.
What is growth rate in microbial terms?
The rate at which a microbial population increases in number.
What is the replisome?
The protein complex that unwinds and copies DNA at the forks.
How must strict anaerobic microbes be grown?
Without O2.
What occurs when there is an abundance of nutrients during the log phase?
Transport mechanisms can become saturated, leading to minimal growth increase despite adding more nutrients.
What is the purpose of using dilution series in microbial counting?
To obtain accurate counts of microorganisms.
What is the typical method for measuring growth rate?
By plotting the number of cells over time on a growth curve.
What reproductive strategies do eukaryotic microbes use?
Asexual and sexual reproduction, with haploid or diploid forms.
What does VBNC stand for?
Viable But Non Culturable.
How is the generation time calculated?
By dividing the time interval by the number of generations that occurred.
How is the membrane of thermophiles stabilized?
By having more saturated, branched, and higher molecular weight lipids, as well as ether linkages in archaeal membranes.
What types of cells can counting chambers be used to count?
Both eukaryotes and prokaryotes.
What do strict anaerobic microbes lack or have very low quantities of?
Superoxide dismutase and catalase.
How do microbes adapt to hypotonic solutions?
They reduce osmotic concentration of cytoplasm by using mechanosensitive (MS) channels in the plasma membrane to allow solutes to leave.
What is the tolerance level of strict anaerobic microbes towards oxygen (O2)?
They cannot tolerate O2.
What happens during the log phase of microbial growth?
Cells grow as quickly as they can for the conditions available.
What does viable counting assess in microbiology?
Whether a cell is alive or dead.
What role does the replisome play in bacterial chromosome replication?
It unwinds and copies DNA.
What types of interactions occur among organisms in a biofilm?
Metabolic exchanges, DNA uptake, and communication.
What are Spread Plates and Pour Plates used for?
Quantitative methods for counting microorganisms.
What is the terminus in the context of bacterial chromosome replication?
The point where replication ends.
How is generation time defined?
The time it takes for a microbial population to double in number.
What is the purpose of the streak plate method?
To isolate individual cells on an agar surface.
What are the attached microbes in a community called?
Biofilm.
What factors can influence growth rate?
Nutrient availability, environmental conditions, and genetic factors.
Where are biofilms commonly found?
Ubiquitous in nature in water.
What is observed when microorganisms are cultivated in batch culture?
The Growth Curve.
What tool is commonly used in the streak plate method?
A bacteriological loop.
How does EPS and changes in physiology protect microbes?
It protects them from harmful agents.
What is the tolerance level of strict anaerobic microbes to oxygen (O2)?
They cannot tolerate O2.
What is the growth optimum pH range for acidophiles?
Between pH 0 - 5.5.
What does 'growth' refer to in the context of microorganisms?
The increase in the number of cells in the population.
What is the first step in the septation process?
Selection of site for septum formation.
What does each individual cell on a streak plate form?
A separate colony.
How must strict anaerobes be grown?
Without O2.
What is the primary process by which E. coli bacteria reproduce?
Binary fission.
How is the growth of microorganisms usually plotted?
As logarithm of cell number vs. time.
What are the two alternative hypotheses for the Death Phase in bacteria?
What is a potential consequence of organism sloughing from biofilms?
Contamination of the water phase above the biofilm.
What protein is involved in the assembly of the Z ring during septation?
FtsZ.
What does EPS stand for in the context of biofilms?
Extracellular Polymeric Substances.
What is the primary focus of research on D. radiodurans?
DNA repair mechanisms.
What type of conditions do most organisms prefer for growth?
Fairly moderate environmental conditions.
What type of environment can D. radiodurans survive?
Highly radioactive environments.
What is the optimal condition for enzyme functioning?
Enzymes have an optimal temperature at which they function best.
What role do histone-like proteins play in thermophiles?
They stabilize DNA.
What characterizes the Prolonged Decline in Growth of bacterial populations?
The population continually evolves with successive waves of genetically distinct variants.
What are the methods of asexual reproduction in Bacteria and Archaea?
Binary fission, budding, and filamentous reproduction.
How are bacteria trapped in the membrane filter technique?
Bacteria from aquatic samples are trapped on membranes.
What is the significance of understanding generation rates?
It helps in predicting microbial growth and behavior in various environments.
What happens to the dilution rate in a Turbidostat?
The dilution rate varies.
What is a replisome?
A group of proteins needed for DNA synthesis.
What is Acylhomoserine lactone (AHL)?
An autoinducer molecule produced by many gram-negative organisms.
What protein is a homologue of tubulin and is involved in Z ring formation?
FtsZ.
What structure does FtsZ polymerization form?
The Z ring, a meshwork of filaments.
How do MinC, MinD, and MinE contribute to Z ring formation?
They oscillate from one side of the cell to the other, preventing Z ring formation at the poles.
What is the lethal radiation dose for E. coli?
200 - 800 Gray.
What type of organism is D. radiodurans?
Non-spore-forming, obligate aerobic chemoorganoheterotroph.
What is the reaction catalyzed by peroxidase?
H2O2 + NADH + H+ → NAD+ + 2H2O.
What do strict anaerobic microorganisms lack or have in very low quantities?
Superoxide dismutase and catalase.
What are some environmental factors that influence microbial growth?
Salts, pH, temperature, oxygen concentration, pressure, and radiation.
Why is D. radiodurans significant in microbiology?
It has exceptional DNA repair capabilities.
Can microbes regulate their internal temperature?
No, microbes cannot regulate their internal temperature.
How many distinct phases does the growth curve have?
Five distinct phases.
What effect do high temperatures have on enzymes?
High temperatures may inhibit enzyme functioning and can be lethal.
What must all microbes do before division?
Replicate and segregate the genome.
What is done to the membrane after trapping bacteria?
The membrane is soaked in culture media.
Why is continuous culture important for studying microbial growth?
It allows study at very low nutrient concentrations, resembling natural environments.
What interactions can be studied in continuous culture systems?
Interactions of microbes under conditions resembling those in aquatic environments.
What happens to the daughter cells after binary fission?
They divide; some species separate completely while others remain attached, forming chains or doublets.
What is one mechanism of the acidic tolerance response in microbes?
Pumping protons out of the cell.
What types of proteins do some microbes synthesize for protection?
Acid and heat shock proteins.
What is an obligate aerobe?
A microbe that requires O2 for growth.
What is the radiation dose that is lethal to humans?
5 Gray.
What extreme conditions can D. radiodurans resist?
Cold, dehydration, vacuum, acid, oxidation.
What is the role of peroxidase in aerobic organisms?
It reduces hydrogen peroxide using NADH.
How are microbial counts reported in quantitative methods?
As Colony Forming Units (CFU).
Why is measuring generation time important?
It helps in understanding the growth dynamics of microbial populations.
What is the growth optimum pH range for neutrophiles?
Between pH 5.5 - 7.
What is the term for the density-dependent communication among bacterial cells in biofilms?
Quorum sensing.
What are the effects of ionizing radiation on organisms?
It can cause mutations and death (sterilization).
How do anaerobic microbes respond to the presence of oxygen?
Anaerobic microbes may be inhibited or killed by oxygen.
What state do microbes convert to as they replicate and communicate?
A competent state.
What type of microbes can tolerate varying oxygen levels?
Facultative anaerobes can grow in both the presence and absence of oxygen.
What role does natural selection play in the Prolonged Decline phase?
Natural selection drives the evolution of the bacterial population.
What happens to the population growth in the stationary phase?
Population growth ceases, and the total number of viable cells remains constant.
What do microbes release to form the extracellular polymeric substance (EPS) during biofilm formation?
Polysaccharides, proteins, and DNA.
What is synthesized completely through the cell center during binary fission?
The septum, resulting in two chambers.
What additional requirement do extreme halophiles have?
Extremely high concentrations of potassium.
In which direction does DNA replication proceed from the origin?
In both directions.
How do many microorganisms affect the pH of their habitat?
By producing acidic or basic waste products.
Name a method that uses technology to count cells directly.
Electronic counters.
What type of organisms live in deep sea environments with high hydrostatic pressures?
Some Bacteria and Archaea.
How many copies of its genome does D. radiodurans have during log growth?
8 - 10 copies.
What does pH measure?
The relative acidity of a solution, defined as the negative logarithm of the hydrogen ion concentration.
On what type of surfaces can biofilms be formed?
Any conditioned surface.
What are single colony isolates considered?
Pure strains.
What is the generation rate in microbial growth?
The time it takes for a population of microbes to double in number.
What do bacterial cells produce that increases in level as they replicate?
Small proteins.
What is the membrane filter method used for?
To count viable bacteria in aquatic samples.
What factors can affect the generation rate of microbes?
Nutrient availability, temperature, and environmental conditions.
What process occurs when bacteria reach a competent state?
DNA uptake.
What is the temperature range for psychrotrophs?
0 °C to 35 °C.
What is required for UV radiation to cause damage to microbes?
Direct exposure on the microbial surface.
How can DNA damage from UV radiation be addressed?
Through several DNA repair mechanisms.
What does visible light generate at high intensities?
Singlet oxygen (1 O2), a powerful oxidizing agent.
Where does the highest concentration of MinC accumulate?
At the poles of the cell.
At what pressure do most microbes that live on land and water surface exist?
1 atmosphere (atm).
What can happen when biofilms form on medical devices?
Illness can result.
What are extremophiles?
Organisms that grow under harsh conditions that would kill most other organisms.
What happens to microbial cells in a hypotonic solution?
Water enters the cell, causing it to swell and possibly burst.
What is the reproductive strategy of Bacteria and Archaea?
They reproduce asexually and are haploid only.
What occurs during the final step of septation?
Constriction of cell and septum formation.
What is the wavelength of UV radiation most effectively absorbed by DNA?
260 nm.
What is a key characteristic of the nutrient supply in a Chemostat?
An essential nutrient is in limiting quantities.
What are halophiles?
Microbes that grow optimally in the presence of NaCl or other salts at concentrations above about 0.2M.
What two pathways function during the bacterial cell cycle?
DNA replication and partition, and cytokinesis (septation and daughter cell formation).
What are the reasons for entering the stationary phase?
Nutrient limitation, limited oxygen availability, toxic waste accumulation, and critical population density reached.
What is the name of the world's toughest bacterium?
Deinococcus radiodurans.
What is the role of the Z ring in bacterial cell division?
It initiates septation.
What is a critical factor that can lead to the stationary phase?
Reaching a critical population density.
What role does toxic waste accumulation play in microbial growth?
It can contribute to the transition into the stationary phase.
What technique involves analyzing cells as they flow in a stream?
Flow cytometry.
What are barotolerant organisms?
Organisms that are adversely affected by increased pressure, but not as severely as nontolerant organisms.
What are reactive oxygen species (ROS)?
They include superoxide radical, hydrogen peroxide, and hydroxyl radical.
What enzyme breaks down hydrogen peroxide into water and oxygen?
Catalase.
What types of radiation are classified as ionizing?
X-rays and gamma rays.
How do thermophiles stabilize their protein structure?
By having more hydrogen bonds, more proline, and utilizing chaperones.
What is a hypertonic solution?
A solution with a higher osmotic concentration than the cell.
How do most bacteria divide?
By binary fission.
What shape do most bacterial chromosomes have?
Circular (covalent loops).
What effect do changes in osmotic concentrations have on microbial cells?
They can cause water to enter or leave the cells, affecting their integrity.
What is the origin of replication?
The site at which replication begins.
What is the impact of oxygen on microbial metabolism?
Oxygen levels can significantly influence metabolic pathways in microbes.
What is cytokinesis in the context of the bacterial cell cycle?
The process of septation and daughter cell formation.
How is the number of bacteria in a sample determined using the membrane filter method?
By counting the colonies that grow on the membrane.
What happens as microbes reproduce in a biofilm?
Additional polymers are produced and the biofilm matures.
What role do carotenoid pigments play in microorganisms exposed to light?
They protect many light-exposed microorganisms from photooxidation.
What type of organisms primarily produce AHL?
Many gram-negative organisms.
What is one method of direct measurement of cell numbers?
Counting chambers.
What are aerotolerant anaerobes?
Microbes that can grow with or without O2.
What protective enzyme do aerobes produce to deal with superoxide radicals?
Superoxide dismutase (SOD).
What are the main phases of the E. coli cell cycle?
Growth phase, DNA replication phase, and division phase.
What machinery is assembled during septation?
Cell wall synthesizing machinery.
What is a key advantage of using counting chambers?
They are easy, inexpensive, and quick.
What are the distinct cardinal growth temperatures for organisms?
Minimal, maximal, and optimal temperatures.
What temperature range do psychrophiles thrive in?
0 °C to 20 °C.
What is a limitation of counting chambers?
They cannot distinguish living from dead cells.
What are extreme halophiles?
Microbes that require salt concentrations of 2M to 6.2M.
During which phase is the microbial population most uniform in terms of chemical and physical properties?
Exponential Phase.
In what fields is continuous culture used?
Food and industrial microbiology.
What are two ways to measure microbial growth?
Changes in the number of cells and changes in the mass of the population.
What are facultative anaerobes?
Microbes that do not require O2 but grow better in its presence.
How do barophilic organisms adapt to high pressures?
By changing their membrane fatty acids.
What is the growth optimum pH range for alkaliphiles?
Between pH 8.5 - 11.5.
What is the effect of high oxygen levels on aerobic microbes?
Aerobic microbes thrive and grow rapidly in high oxygen levels.
How does ionizing radiation affect the chemical structure of molecules?
It disrupts the chemical structure of many molecules, including DNA.
How does the length of the Lag Phase vary?
It can be very short or even absent.
What happens to microbial growth in low oxygen environments?
Microbial growth may slow down or be limited in low oxygen environments.
What is another name for the Exponential Phase?
Log phase.
What are released by bacteria during quorum sensing?
Bacteriocins.
What temperature range do mesophiles prefer?
20 °C to 45 °C.
At what dilution rates does a Turbidostat operate best?
At high dilution rates.
How does AHL function in quorum sensing?
It diffuses across the plasma membrane and induces expression of target genes.
What effect does the high concentration of MinC have on Z ring formation?
It prevents the formation of the Z ring at the poles.
What is the radiation dose that Deinococcus radiodurans can withstand without growth deficit?
5000 Gray.
What is visible growth on a streak plate called?
A colony of microorganisms.
During which phase does DNA replication occur in E. coli?
The DNA replication phase.
What phase do cells maintain in a continuous culture system?
Log phase at a constant biomass concentration.
Can damage from ionizing radiation be repaired?
Yes, if the dose is small, damage may be repaired by DNA repair mechanisms.
How does nutrient availability affect the E. coli cell cycle?
Nutrient availability can limit growth and division rates.
How do microbes prevent protons from entering their cells?
The plasma membrane is impermeable to protons.
What is the temperature range for thermophiles?
55 °C to 85 °C.
What happens to the origins during DNA replication?
They move to opposite ends of the cell.
Which system in E. coli regulates the positioning of the Z ring?
The MinCDE system.
How can cells be counted using filters?
On membrane filters.
What percentage of Deinococcus radiodurans remains viable at 15000 Gray?
37%.
What is the bacterial cell cycle?
A sequence of events from the formation of a new cell through the next cell division.
What is continuous culture of microorganisms?
Growth in an open system with continual provision of nutrients and removal of wastes.
What is the first step in the binary fission process?
A young cell at the early phase of the cycle.
What triggers the division of E. coli cells?
Completion of DNA replication and cell growth.
What happens to the parent cell during binary fission?
It enlarges its cell wall, plasma membrane, and volume, and DNA replication starts.
Which organism is known for its extreme resistance to DNA damage?
Deinococcus radiodurans.
How does a Turbidostat regulate the flow of media?
By maintaining a predetermined turbidity or cell density.
What characterizes the Exponential Phase of microbial growth?
The rate of growth and division is constant and maximal.
How do microbes initially attach during biofilm formation?
They reversibly attach to a conditioned surface.
What type of extremophile is Deinococcus radiodurans?
Polyextremophile.
What temperature range do hyperthermophiles thrive in?
85 °C to 113 °C.
What does AHL regulate once inside the cell?
A variety of functions through target gene expression.
What is an obligate anaerobe?
A microbe that is usually killed in the presence of O2.
What are barophilic (peizophilic) organisms?
Organisms that require or grow more rapidly in the presence of increased pressure.
In what systems can sloughing from biofilms contaminate water?
In drinking water systems.
What occurs during the Lag Phase of microbial growth?
Cells synthesize new components to replenish spent materials and adapt to new conditions.
What is the main function of a Chemostat?
To maintain a constant rate of incoming medium equal to the rate of removal from the vessel.
What occurs when microbial cells are placed in a hypertonic solution?
Water leaves the cell, leading to membrane shrinkage from the cell wall (plasmolysis).
What are the main stages of the bacterial cell cycle?
Growth, chromosome replication, and cytokinesis.
What type of mutations can UV radiation cause?
Thymine dimers in DNA, leading to mutations and potentially death.
What occurs as the chromosomes move during binary fission?
The septum begins to form.
What is the terminus in DNA replication?
The site at which replication is terminated, located opposite of the origin.
What occurs to active cells during the stationary phase?
Active cells stop reproducing or the reproductive rate is balanced by the death rate.
What do microbes exchange for protons to maintain pH?
Potassium ions.
What extreme conditions can Deinococcus radiodurans survive?
Cold, dehydration, vacuum, and acid.
How does nutrient limitation affect microbial growth?
It can lead to the stationary phase where growth ceases.
What is an aerobe?
A microbe that grows in the presence of atmospheric oxygen (20% O2).
What is a microaerophile?
A microbe that requires 2-10% O2 for growth.
What is the reaction catalyzed by catalase?
2H2O2 → O2 + 2H2O.
What is achieved using a continuous culture system?
A constant supply of cells in exponential phase growing at a known rate.
What internal pH do most microbes maintain?
Near neutrality.
What happens after the membrane is soaked in culture media?
Colonies grow on the membrane.
What is a significant difference between a Chemostat and a Turbidostat regarding nutrient limitation?
A Chemostat has limiting nutrients, while a Turbidostat does not.
Why do halophiles need high salt concentrations?
To maintain stability and activity of their cell wall, proteins, and plasma membrane.
What determines growth in different oxygen concentrations for microbes?
It depends on a microbe’s metabolic processes, electron transport chains (ETC), and the terminal electron acceptor used.
What is an anaerobe?
A microbe that grows in the absence of O2.
What is the lethal radiation dose for Tardigrades?
4000 Gray.
How many copies of its genome does D. radiodurans have in stationary phase?
4 copies.
What is the reaction catalyzed by superoxide dismutase (SOD)?
2O2* + 2H+ → O2 + H2O2.
