How are nutrients utilized by bacteria?
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In biosynthesis and energy production.
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How are nutrients utilized by bacteria?
In biosynthesis and energy production.
What is FtsZ?
The major cytoskeletal protein in the bacterial cytokinesis machine.
What is the most commonly used practical form of energy in living organisms?
Adenosine 5'-triphosphate (ATP).
What are viable counting methods used for?
To determine the number of viable microbes in a sample.
What happens to the membrane carrier after binding an external molecule?
It changes conformation and releases the molecule inside the cell.
How are the results of viable counting often expressed?
In terms of colony forming units (CFU).
Why might plate counts be ineffective for measuring microbial populations?
If the microbe cannot be cultured on solid media or if large colonies overgrow the plate.
What structure does FtsZ form during bacterial cell division?
The Z ring.
What amino acid is synthesized from Glutamic acid by E. coli?
Proline.
What is the state of the membrane carrier after releasing the molecule?
It returns to the outward oriented position, ready to bind another solute molecule.
What are the three main aspects of microbial metabolism?
Utilization of energy, nutrient uptake, and biosynthesis of important molecules.
What is the role of nutrients in bacteria?
They provide nourishment essential for maintenance of life and growth.
What is a Coulter counter used for?
To directly count microorganisms.
What does the cytoplasmic membrane allow regarding small molecules?
It allows the passive passage of certain small molecules and actively concentrates others within the cell.
What do viable counting methods count?
Only those cells able to reproduce when cultured.
What are the two main ways to measure microbial population size?
Directly or indirectly.
What are the two commonly used procedures for viable counting?
Spread plate and pour plate techniques.
What do bacteria require for growth and energy?
Nutrients and energy.
Why can't nutrient molecules frequently cross plasma membranes through passive diffusion?
Because they must be transported by one of three major mechanisms involving membrane carrier proteins.
What is the primary focus of nutritional uptake in bacteria?
The process by which bacteria absorb nutrients from their environment.
What is the function of the Z ring?
It constricts to initiate division of the cell.
What can be measured to determine growth rate constants and generation times?
Microbial growth.
What is the Most Probable Number (MPN) test used for?
To estimate microbial population size when plate counts are not applicable.
What is simple diffusion?
A process where a substance passes through a membrane without the aid of an intermediary, such as an integral membrane protein.
In what form is energy stored by microorganisms?
In the form of high-energy transfer compounds (ATP).
What is facilitated diffusion similar to?
Passive diffusion.
How do cells utilize ATP?
Cells 'earn' ATP through certain processes and 'spend' it in carrying out other processes.
What are the main types of nutrients that bacteria require?
Carbon, nitrogen, sulfur, phosphorus, and trace elements.
What is an example of polymer synthesis occurring outside the membrane?
Synthesis of cell wall peptidoglycan.
What do microbes do when only a few amino acids are present in the medium?
They convert other amino acids into those that are missing.
What leads to increases in both population number and mass?
Microbial growth.
What is the purpose of serial dilution in viable counting?
To prepare samples for pour plate and spread plate techniques.
How do small noncharged or lipid-soluble molecules enter or leave bacterial cells?
By passing between the phospholipids, moving from areas of high concentration to areas of low concentration.
What is another form of energy available to microorganisms besides ATP?
Proton motive force (electrochemical proton gradient).
What is ATP often referred to as?
The cell's energy currency.
What is the bacterial cell cycle?
The complete sequence of events from the formation of a new cell through the next division.
What technique is used to determine the number of bacteria in aquatic samples?
Membrane filter technique.
How do bacteria typically acquire nutrients?
Through various transport mechanisms such as passive diffusion, facilitated diffusion, and active transport.
How does a Coulter counter measure microbial cells?
By forcing a microbial suspension through a small hole and measuring electrical resistance.
What role do membrane carrier proteins play in bacterial nutrient uptake?
They facilitate the transport of nutrients that cannot cross the plasma membrane by passive diffusion.
What is MreB?
A protein found in bacteria that is a homologue of actin.
What happens to cells in batch culture after the stationary phase?
They enter the death phase.
Why is the synthesis of cell wall components significant?
Because polymerization takes place outside the cell membrane by enzymes on the membrane’s outer surface.
What are the processes by which ions or molecules cross the cytoplasmic membrane?
Various transport mechanisms involving membrane carrier proteins.
What is required for microbial growth in terms of biochemical building blocks?
The polymerization of biochemical building blocks into proteins, nucleic acids, polysaccharides, and lipids.
What types of molecules can pass through the cytoplasmic membrane by passive diffusion?
Water and some lipid-soluble molecules.
What is the first phase of the bacterial cell cycle?
A period of growth after the cell is born, similar to the G1 phase of the eukaryotic cell cycle.
What is facilitated transport?
A type of passive transport that uses carrier proteins to help move molecules across the membrane.
What are some biological purposes of the electrochemical proton gradient besides ATP synthesis?
Generating heat and rotation of bacterial flagella.
What happens to the carrier-solute complex during facilitated diffusion?
It moves between the outer and inner surfaces of the membrane, releasing one solute molecule on the inner surface.
What additional requirement is placed on microbial growth by coenzymes?
Coenzymes participate in enzymatic catalysis.
What is the structure of a counting chamber?
It consists of specially designed slides and coverslips that create a chamber of known depth.
What happens to nutrient concentrations during batch culture incubation?
Nutrient concentrations decline as they are consumed.
What method is used for measuring cell mass rapidly and sensitively?
Spectrophotometry.
Where does the sugar combine with enzyme II?
At the outer membrane surface.
What is the role of H+ ions in nutrient uptake?
They create a proton motive force that drives the transport of nutrients.
What are the components of the basal body in the flagellar motor?
M and S rings.
What occurs after the lag phase?
Cells begin to replicate their DNA, increase in mass, and divide.
What happens to the bacterial population during the long-term stationary phase?
It continually evolves, with actively reproducing cells best able to use released nutrients and tolerate toxins.
What is the result of the activities during the lag phase?
The number of cells in the population begins to increase.
What is marked by successive waves of genetically distinct variants?
The dynamic process during the long-term stationary phase.
What is required for sugar uptake and phosphorylation in the phosphotransferase system?
Participation of several soluble and membrane-bound enzymes.
What is still unknown regarding the flagellar motor?
The molecular events that cause the conversion of proton motive force.
What additional characteristics can be analyzed using flow cytometry?
Size, internal complexity, and other characteristics of cells.
Why is measuring dry weight especially useful?
It is particularly useful for measuring the growth of filamentous fungi.
What is a limitation of the dry weight measurement technique?
It is time-consuming and not very sensitive.
What are piezophiles?
Microbes that thrive under high pressure.
What type of diffusion is described in the text?
Facilitated diffusion.
What direction do molecules move during simple diffusion?
They move down their concentration gradient, from high to low concentration.
What type of membrane filter is used in the membrane filter technique?
Black polycarbonate membrane filter.
What happens to electrical resistance when a microbial cell passes through the hole in a Coulter counter?
Electrical resistance increases, causing conductivity to drop.
How does the electrochemical proton gradient contribute to microbial metabolism?
It results in ATP synthesis and can be used for other biological purposes.
What forms when the carrier molecule combines with the solute in facilitated diffusion?
Carrier-solute complex.
What is the principle behind counting cells in a Coulter counter?
Each time a microbial cell passes through the hole, it is counted based on the change in electrical resistance.
What activates the heat stable carrier protein HPr?
Transfer of a phosphate group from phosphoenol pyruvate (PEP).
What is the first step in the process of active transport?
Binding of a solute to a receptor site on a membrane-bound carrier protein.
What is a limitation of traditional counting methods for microbes?
They do not differentiate between live and dead cells.
What are the roles of Enzyme I and HPr in the process?
They are soluble proteins and non-specific components.
What is the third phase of the bacterial cell cycle?
Cytokinesis, during which a septum and daughter cells are formed.
What must be synthesized before growth can begin in the lag phase?
New components such as ATP, cofactors, and ribosomes.
Does passive diffusion involve specific interactions between substances in the membrane and solute molecules?
No, there is no specific interaction in passive diffusion.
What percentage of microbial cell dry weight is made up of major elements?
Over 95%.
What is flagellin and what is its enzymatic activity?
Flagellin is a component of bacterial flagella and has no detectable ATPase activity.
How does ATP contribute to the activity of locomotor organelles in bacteria?
It powers the movement of flagella.
What is a disadvantage of using counting chambers?
To determine population size accurately, the microbial population must be relatively large and evenly dispersed.
From where do organotrophs extract electrons?
From reduced organic compounds.
What is the relation equation of N and N₀ to n?
N = N₀ * 2^n.
What is the main function of the PTS system?
To phosphorylate and transport sugars into the cell.
How does Calcium (Ca2+) contribute to bacterial spores?
It contributes to heat resistance and many other functions.
What does VBNC stand for?
Viable but non-culturable state.
What type of transport does not require metabolic energy?
Passive diffusion.
How does the limiting nutrient affect growth rate in a chemostat?
Growth rate is determined by the rate at which sterile medium is fed into the growth chamber.
Why might it be necessary to centrifuge several hundred milliliters of culture?
Because bacteria weigh so little, a sufficient quantity is needed for measurement.
What is the carbon source for Chemolithoautotrophy?
CO2.
What type of growth do continuous culture systems maintain?
Exponential growth at a known rate and constant biomass concentration.
How is growth defined in microbiology?
As an increase in the number of cells.
In facilitated diffusion, where does the solute molecule flow from and to?
From higher to lower concentration.
Why are nutrients essential for microbial growth?
They are required for building proteins, structural membranes, and driving biochemical processes.
What is necessary for a species to be maintained in microbiology?
Continued growth of its population.
What is the driving force for molecules to enter the cell during facilitated diffusion?
The concentration gradient, where the concentration is greater outside the cell.
What happens to macromolecules in the cytoplasm of a bacterial cell?
They assemble into major cell structures.
What is often studied to analyze population growth in microbes?
The growth of microbes in liquid (broth) culture.
Where must the building blocks for microbial growth come from?
They must come preformed in the growth medium or be synthesized by the growing cells.
What governs the rate of inward flow of solute molecules during passive diffusion?
The difference in concentration of the molecule across the membrane.
What occurs during the second phase of the bacterial cell cycle?
Chromosome replication and partitioning, corresponding to the S and mitosis events of the M phase in eukaryotic cells.
Why might cells be depleted during the lag phase?
Cells may be old and depleted of ATP, essential cofactors, and ribosomes.
What occurs when one bacterial cell separates to form two cells?
One generation has occurred.
How do chemotrophs obtain their energy?
From the oxidation of chemical compounds (either organic or inorganic).
What is the role of bacterial flagella filaments in energy utilization?
They have no machinery for interconverting chemical and mechanical energy.
How does the etched grid in the counting chamber assist in counting?
It facilitates counting the cells.
What are the two sources of electrons for microorganisms?
Reduced inorganic substances (lithotrophs) and reduced organic compounds (organotrophs).
What principle does spectrophotometry rely on?
Microbial cells scatter light.
Which proteins are homologues found in comma-shaped cells?
MreB and FtsZ.
How do solutes enter the cell during group translocation?
As sugar phosphates.
Why are exponential phase cultures used in studies?
Because the population is most uniform in terms of chemical and physiological properties.
What happens to light transmission as cell concentration increases?
Less light is transmitted through the medium due to greater turbidity.
What factors influence the growth rate during the exponential phase?
Nutrient availability and environmental conditions.
What happens to the solute after the conformational change in the carrier molecule?
The solute is released into the cell interior.
What is one approach to measuring microbial cell mass?
Determination of microbial dry weight.
What happens to the growth rate as nutrient concentration increases?
The growth rate increases but eventually saturates, similar to enzyme kinetics.
What are vitamins in the context of growth factors?
Small organic molecules that are part of enzyme cofactors and needed in very small amounts.
At what dilution rates does a turbidostat operate best?
At high dilution rates.
What is the relationship between log N, log N₀, and n?
n = (log N - log N₀) / log 2.
What does the equation 0.301 = 3.3 (log N - log N₀) represent?
It relates the difference in logarithms of N and N₀ to a constant factor.
How is the rate of nutrient exchange in a chemostat expressed?
As the dilution rate (D).
How can the increase in cell number in an exponentially growing bacterial culture be expressed mathematically?
Using a geometric progression based on the number 2.
What is the process called where nutrients move from an area of higher concentration to an area of lower concentration?
Diffusion.
What role does MreB play in bacteria?
It controls the width of rod-shaped bacteria.
What is active transport?
The transport of solute molecules to higher concentrations or against a concentration gradient using metabolic energy.
What alternative method is used when plate counts are not suitable?
Most Probable Number (MPN) determination.
Is there a single best technique for measuring microbial population size?
No, the most appropriate approach depends on the experimental situation.
How is much of the energy from ATP utilized in bacterial cells?
In the biosynthesis of new cell components.
What energy source is primarily used in biosynthetic processes?
ATP.
How is the yield coefficient related to biomass production?
It relates to the quantity of biomass produced per gram of substrate utilized.
What are energy-storage inclusion granules mentioned?
Glycogen and poly-β-hydroxybutyrate.
What is released by Enzyme II after the transport process?
Sugar phosphate is released and enters the cell.
What is the function of crescentin in comma-shaped cells?
It localizes to one side of the cell and slows the insertion of new peptidoglycan units.
What newer methods help improve direct counting of microbes?
Fluorescent dyes that differentiate between live and dead cells.
What does a higher yield coefficient indicate?
A greater percentage of the original substrate converted into microbial biomass.
What does the asymmetric cell wall growth in Vibrio lead to?
The inner curvature that characterizes the comma shape.
What is necessary for the maintenance of transmembrane gradients during microbial growth?
A source of metabolic energy.
How can the number of microorganisms in a sample be calculated?
From the chamber’s volume and any dilutions made of the sample before counting.
How many distinct phases are there in the bacterial growth curve?
Five distinct phases.
What is group translocation?
A process that alters the molecule being transported, often involving phosphorylation.
What change occurs in the carrier molecule during solute transport?
A conformational change that decreases its affinity for the solute.
How can the equation N = N₀ * 2^n be expressed in terms of n?
n = (log N - log N₀) / log 2.
What do the proteins in the phosphotransferase system catalyze?
The transfer of the phosphoryl group of phosphoenolpyruvate to the sugar molecule.
What is the role of Iron (Fe2+ and Fe3+) in microbial metabolism?
It is part of cytochromes and acts as a cofactor for enzymes and electron-carrying proteins.
How much do vitamins contribute to bacterial growth?
They are needed in only very small amounts to sustain growth.
What does CASP refer to?
Constant activity stationary phase.
How can cell mass be estimated aside from dry weight?
By measuring the concentration of some cellular substance, like total protein or nitrogen.
What is a continuous culture system?
A system that maintains constant environmental conditions through continual supply of nutrients and removal of wastes.
What are alkalophiles?
Microbes that prefer alkaline environments.
What are psychrophiles?
Microbes that grow best at low temperatures.
What is a limitation of using plate counts for microbial enumeration?
They can be inaccurate if colonies overgrow the surface of the plate.
What is the role of energy in microbial metabolism?
To drive many endergonic reactions required for the cell.
How many phases are there in the bacterial cell cycle?
Three phases.
What is the lag phase in microbial growth?
A period when no immediate increase in cell number occurs after microorganisms are introduced into fresh culture medium.
Which substances typically enter and leave cells by simple diffusion?
Oxygen, carbon dioxide, and most lipids.
What types of solutes are taken up by cells through active transport?
Sugars, amino acids, peptides, nucleosides, and ions.
Is the lag phase a time of inactivity for microorganisms?
No, cells are actively synthesizing new components during this phase.
What factors are noted when examining techniques for determining population size?
Advantages and disadvantages of each technique.
Which fluorescent stains are commonly used in the membrane filter technique?
Acridine orange or DAPI.
What is group translocation?
A process where a solute is altered chemically during transport.
What happens to the concentration gradient over time during passive diffusion?
It diminishes until equilibrium is reached.
Can the carrier molecule in facilitated diffusion bind to new solute molecules?
Yes, it returns to bind a new one on the outer surface.
What do biosynthetic polymerization reactions require for energy?
The transfer of anhydride bonds from adenosine triphosphate (ATP).
What is the time required for one generation in bacterial growth called?
Generation time.
Give an example of facilitated diffusion.
The entry of glycerol into bacterial cells.
What happens if the new culture medium is different from the previous one?
New enzymes are needed to utilize different nutrients.
How long can the long-term stationary phase last?
Months to years.
What do lithotrophs use as their electron source?
Reduced inorganic substances.
What is flow cytometry used for?
To directly count microbes and gain detailed information about them.
What types of enzymes are involved in liberating amino acids from proteins?
Intracellular and extracellular proteolytic enzymes.
What form do sugars accumulate in the cell during group translocation?
Phosphoenol pyruvate form.
What is the term for the extent of light scattering measured by a spectrophotometer?
Absorbance (optical density).
What drives the flagellar motor's rotation?
The inward flux of protons.
What is the logarithmic transformation of the equation N = N₀ * 2^n?
log N = log N₀ + n log 2.
What should be done if the absorbance sample exceeds 0.5?
The sample must be diluted before measuring absorbance.
What is a key characteristic of the culture medium in a chemostat?
It has a limited quantity of an essential nutrient.
What occurs at sufficiently high nutrient levels?
Transport systems become saturated, and the growth rate does not increase further with more nutrients.
What does the final cell density in a chemostat depend on?
The concentration of the limiting nutrient.
What happens to solute molecules during active transport?
They are changed.
What is the transport speed of active transport?
Rapid.
What is the specificity of passive diffusion?
No specificity.
What is the function of Enzyme II?
It is specific for a particular sugar and facilitates its transport into the cell.
What is the shape of the cells studied in Vibrio?
Comma-shaped cells.
How are microorganisms classified based on their source of carbon?
As either heterotrophs or autotrophs.
What is the yield coefficient (Y) based on?
The quantity of rate-limiting nutrient, typically the substrate converted into microbial product.
What is the primary method for direct measurement of cell numbers?
Using a counting chamber, such as the Petroff-Hausser counting chamber.
What are the two sources of energy available to organisms?
Light energy and energy from oxidizing organic or inorganic molecules.
What is primarily maintained through reactions leading to biosynthesis of macromolecules in bacteria?
The physical and chemical integrity of the cell.
What major cell structures are formed from macromolecules?
Cell wall, cytoplasmic membrane, flagella, ribosomes, enzyme complexes.
What do phototrophs use as their energy source?
Light.
What type of transport requires energy to move substances against their concentration gradient?
Active transport.
What type of harm do environmental changes cause to cells in the death phase?
Irreparable harm.
What role do micronutrients play in microorganisms?
They are part of enzymes and cofactors, aiding in catalysis of reactions and maintenance of protein structure.
What molecule provides energy for active transport?
ATP.
What is the long-term stationary phase in microbial growth?
A period where the population size remains constant after exponential death.
How is population growth of microbes plotted in a batch culture?
As the logarithm of the number of viable cells versus incubation time.
How is the proton motive force utilized in the cell?
To pump solutes into the cell.
What are macronutrients?
Elements required by microorganisms in relatively large amounts.
How do bacterial flagella differ from cilia and flagella of eukaryotic microorganisms?
Bacterial flagella are much simpler and lack the machinery for energy conversion.
Which six elements are the primary components of carbohydrates, lipids, proteins, and nucleic acids?
Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N), Sulfur (S), and Phosphorus (P).
What does PTS stand for in nutrient uptake?
Phosphotransferase system.
Where is the S ring mounted in the flagellar motor?
Rigidly on the cell wall.
What happens to the light when a cell passes through the laser beam in flow cytometry?
The light is scattered.
How is absorbance related to cell concentration at levels below 0.5?
Absorbance is almost linearly related to cell concentration.
What is a chemostat?
A device where the rate of sterile medium input equals the rate of medium containing microorganisms output.
What reflects the rate of nutrient uptake by microbial transport proteins?
The shape of the growth curve during the exponential phase.
Which transport mechanism is characterized by specificity?
Facilitated diffusion, Active transport, and Group translocation.
What energy source do Purple and green sulfur bacteria use?
Light.
Which transport mechanisms can move solutes against their gradient?
Active transport and Group translocation.
Which transport mechanism requires carrier proteins?
Facilitated diffusion, Active transport, and Group translocation.
Does facilitated diffusion require metabolic energy?
No.
What is the carbon source for Chemoorganoheterotrophy?
Organic carbon.
What must microorganisms do when the medium contains only inorganic sources of nitrogen?
Synthesize all the required amino acids from these nitrogen sources.
How does the number of viable cells change during the death phase?
It declines exponentially.
What role do transport proteins play in bacterial nutritional uptake?
They facilitate the movement of nutrients across the bacterial cell membrane.
Where is Enzyme II located?
It is an integral component of the cytoplasmic membrane.
Which bacterium is specifically mentioned for its comma-shaped cells?
Caulobacter crescentus.
Which micronutrients are commonly needed by most cells?
Manganese, zinc, cobalt, molybdenum, nickel, and copper.
What drives protons out of the cell during electron transport?
Energy released during the flow of electrons through the ETC or the splitting of the phosphate group from ATP.
What causes cells to enter the death phase?
Detrimental environmental changes such as nutrient deprivation and toxic waste buildup.
Do micronutrients usually limit microbial growth in nature?
No, they are ubiquitous and probably do not usually limit growth.
What does the movement of protons create across the cell membrane?
A difference in pH value and electric potential.
How are the stained bacteria observed after filtration?
Microscopically.
What are amino acids considered in relation to proteins?
Building blocks of protein.
What is the reaction that occurs involving Enzyme II?
Sugar + phospho-HPr → sugar-phosphate + HPr.
What drives the flagellar motor in bacteria?
The proton motive force.
What can fluorescent dyes help researchers determine in a microbial sample?
The number of live and dead microorganisms.
How does the growth rate behave during the exponential phase?
The growth rate is constant, with cells doubling in number at regular intervals.
What is a turbidostat?
The second type of continuous culture system that measures turbidity in the growth vessel.
What happens when protons reenter the cell?
The energy released drives the transport mechanism in the cell membrane.
How does a turbidostat maintain a predetermined turbidity?
By automatically regulating the flow rate of media through the vessel.
How does a flow cytometer create a stream of cells?
It creates a stream so narrow that one cell at a time passes through a beam of laser light.
What is turbidity related to in a turbidostat?
Cell density.
How does the concentration of a limiting nutrient affect microbial growth?
Final net growth increases with the initial amount of the limiting nutrient present.
What is the role of purines and pyrimidines in bacterial growth?
They are needed for nucleic acid synthesis.
How are cells collected for dry weight measurement?
By centrifugation, followed by washing, drying in an oven, and weighing.
What constitutes the energy currency in flagellar rotation?
Proton movements, not ATP.
What is SCDI in the context of microbial growth?
Stationary phase contact-dependent inhibition.
What is the speed of passive diffusion?
Slow.
What does the expression N = N0 * 2^n represent?
The relationship between the initial number of cells (N0) and the final number of cells (N) after n generations.
What characterizes the total number of viable microorganisms in the stationary phase?
It remains constant.
How can aerobic organisms be limited in the stationary phase?
By O2 availability.
What is examined to determine population size?
Commonly employed techniques.
What is ATP formed by in bacterial cells?
Energy producing reactions.
What are micronutrients?
Nutrients required by microorganisms in small amounts, also known as trace elements.
What is required for the interconversion and biosynthesis of chemical substances in microbes?
The expenditure of energy.
What is the rate of cell death during the death phase?
Cells die at a constant rate.
What is the difference between passive and active transport in bacteria?
Passive transport does not require energy, while active transport requires energy to move substances against their concentration gradient.
Is energy required for facilitated diffusion?
No, there is no energy input required.
What are the advantages of using a counting chamber?
It is easy, inexpensive, and relatively quick, providing information about size and morphology of microorganisms.
What type of culture is typically used for cultivating microorganisms in broth?
Batch culture.
What macromolecules are continuously broken down and need replacement in bacterial cells?
Nucleic acids and proteins.
What other metabolic processes utilize ATP in bacterial cells?
Maintaining physical and chemical integrity, transport of solutes, and activity of locomotor organelles.
What is generated by the proton gradient?
Proton motive force.
What role does ATP play in the transport of solutes across membranes?
It provides the energy required for the transport processes.
How many amino acids are there?
20 amino acids.
Why is the determination of yield coefficient important?
It decides how productive and cost-viable the medium used is.
How is light scattering related to biomass in a microbial population?
It is directly proportional to the biomass of cells present.
How is the rod of the flagellar motor connected?
It is fixed rigidly to the M ring, which rotates freely in the cytoplasmic membrane.
What is not the immediate source of energy for flagellar rotation in bacteria?
ATP.
What role does Potassium (K+) play in microbial cells?
Required for activity by a number of enzymes, including those involved in protein synthesis.
Why are amino acids important for bacteria?
They are needed for protein synthesis.
How do turbidostats differ from chemostats?
The dilution rate in a turbidostat varies, while it remains constant in a chemostat.
What is the function of Magnesium (Mg2+) in microbial cells?
It acts as a cofactor for many enzymes, complexes with ATP, and stabilizes ribosomes and cell membranes.
What is the value of log 2 in terms of base 10?
log 2 ≈ 0.301.
What condition must be met for population size to be easily measured using turbidity?
The population must be high enough to give detectable turbidity.
At what dilution rates is a chemostat most stable and effective?
At lower dilution rates.
What is the formula for calculating the dilution rate (D) in a chemostat?
D = f / V, where f is the flow rate and V is the vessel volume.
What can be used to estimate the amount of living microbial mass?
The quantity of ATP.
What are halophiles?
Microbes that thrive in high salt concentrations.
What are the products formed in the reaction described?
Sugar phosphate and pyruvate.
What distinguishes facilitated diffusion from passive diffusion?
It involves a specific protein carrier molecule (porter or permease).
What type of transport does not require energy and occurs along the concentration gradient?
Passive transport.
What ion is required for the overall reaction?
Mg2+.
What is done to the bacteria after they are trapped on the membrane filter?
They are stained with nucleic acid fluorescent stains.
Why do traditional methods for counting microbes yield higher cell densities?
Because they do not distinguish dead cells from culturable cells.
What does Enzyme II combine with during the transport process?
It combines with the phosphate group carried by the activated HPr.
What cytoskeletal protein do vibroid-shaped cells produce?
Crescentin.
What is the role of ATP in biosynthetic processes?
To convert one chemical substance into another and to synthesize complex substances from simpler ones.
What does the equation x = Yx/s(S – Sr) represent?
It represents biomass concentration (x), yield coefficient (Yx/s), initial substrate concentration (S), and residual substrate concentration (Sr).
What occurs during the second step of active transport?
Translocation of the solute-carrier complex across the membrane.
What is an example of a system involved in group translocation?
Phosphoenol pyruvate dependent sugar-phosphotransferase system.
What occurs during the exponential phase of microbial growth?
Microorganisms grow and divide at the maximal rate possible given their genetic potential, medium nature, and environmental conditions.
What is the purpose of coupling translocation to an energy-yielding reaction in active transport?
To lower the affinity of the carrier protein for the solute at the inner membrane surface, allowing the release of solute to the cell interior.
In which organisms is the phosphotransferase system widely distributed?
Many bacterial genera.
What happens to the sugar after it combines with enzyme II?
It is transported to the inner membrane surface.
What happens if amino acids are not freely available in the medium?
Microorganisms may have to liberate amino acids from proteins using proteolytic enzymes.
What are growth factors?
Organic compounds essential for cell components that cannot be synthesized by the organism.
What are the five distinct phases of the bacterial growth curve?
Lag Phase, Exponential Phase, Stationary Phase, Death Phase, Long-Term Stationary Phase.
What are the three major classes of growth factors?
Amino acids, Purines and Pyrimidines, and Vitamins.
How many nutritional classes can microorganisms be placed into based on their primary sources?
Five.
What does GASP stand for?
Growth Advantage in Stationary Phase.
How is the number of cells in a sample determined using flow cytometry?
By counting the number of light-scattering events.
What is the nutrient condition in a turbidostat?
All nutrients are in excess, meaning none are limiting.
What is the carbon source for Photolithoautotrophy?
CO2.
What is often used to enhance the analysis of cells in flow cytometry?
Fluorescent dyes or fluorescently labeled antibodies.
What valuable information can flow cytometry provide?
Characteristics of the population of cells.
Which microbes are representative of Photoorganoheterotrophy?
Purple nonsulfur bacteria, green nonsulfur bacteria.
What can chlorophyll determinations measure?
Phototrophic protist and cyanobacterial populations.
What type of electron donor is used in Photolithoautotrophy?
Inorganic electron donor.
What does an increase in microbial population indicate?
Higher total protein levels.
What energy source do sulfur-oxidizing bacteria use?
Inorganic chemicals.
Which bacteria are examples of Chemolithoheterotrophy?
Some sulfur-oxidizing bacteria (e.g., Beggiatoa).
What factors influence the final population size in the stationary phase?
Nutrient availability, other factors, and the type of microorganism.
What may cause the stationary phase to occur?
A balance between cell division and cell death, or ceasing to divide while remaining metabolically active.
What type of electron donor is used in Chemolithoautotrophy?
Inorganic electron donor.
How can continuous culture systems model interactions between microbial species?
By simulating environmental conditions resembling those in a freshwater lake.
Why are continuous culture systems important for microbial research?
They allow the study of microbial growth at very low nutrient levels, similar to natural environments.
What do the variables N, N0, and n stand for in the growth equation?
N is the final cell number, N0 is the initial cell number, and n is the number of generations.
How is the generation time (g) calculated in an exponentially growing population?
g = t/n, where t is the duration of exponential growth.
Which types of microbes are included in Chemoorganoheterotrophy?
Most nonphotosynthetic microbes, including most pathogens, fungi, many protists, and many archaea.
What can lead to the cessation of population growth besides nutrient limitation?
Accumulation of toxic waste products.
What happens to population growth in a closed system like a batch culture?
Population growth eventually ceases and the growth curve becomes horizontal.
What two major types of continuous culture systems are commonly used?
Chemostats and turbidostats.
What type of electron donor is often the same as the carbon source in Chemoorganoheterotrophy?
Organic electron donor.
What is a significant reason for microbes entering the stationary phase?
Nutrient limitation.
What happens to the activity of DnaA in the stationary phase?
It becomes less active.
In what areas are continuous culture systems essential?
Microbial ecology, food microbiology, and industrial microbiology.
What is the significance of knowing the initial and final cell numbers in a bacterial culture?
It allows for the calculation of the number of generations (n) and the generation time (g).
What does the variable t represent in the context of bacterial growth?
The duration of exponential growth expressed in days, hours, or minutes.
What does the growth curve of bacteria represent?
The quantification of bacterial growth over time.
What are xerophiles?
Microbes that can survive in very dry environments.
What is the focus of Unit 2?
Metabolism of Prokaryotes.
What are the two main types of microbial metabolism pathways?
Non-biosynthetic pathway and biosynthetic pathway.
What are the three main types of bacterial recombination?
Transformation, transduction, and conjugation.
