Microbiology 261 exam 1

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In what ways are microorganisms important to humans?

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In what ways are microorganisms important to humans?

Digestion, prod of vitamins, dairy products, biotechnology, environment - break down organic materials

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What is a bacterial colony and how is on formed?

formed through a process of binary fission, where a single cell divides into two identical cells

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How can you get a pure culture of bacteria and why are pure cultures important?

sterilization techniques such as heat or chemical treatment to eliminate all other microorganisms in the sample

Pure cultures are important in scientific research and industry because they allow for the study and characterization of specific bacteria strains without interference from other microorganisms

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Where do you find microorganisms and do they typically live in a pure culture?

Microorganisms can be found in a variety of environments such as soil, water, air, and even on human skin not found in pure cultures

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What cellular structures distinguish prokaryotic and eukaryotic cells?

Prokaryotic cells lack membrane-bound organelles while eukaryotic cells have these organelles.

eukaryotic cells have a nucleus while prokaryotic cells do not.

Eukaryotic cells are generally larger and more complex than prokaryotic cells.

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What are some differences between a cell wall and a cell membrane?

A cell wall is a rigid structure made of cellulose that provides support and protection to plant cells.

cell membrane is a flexible barrier made of phospholipids and proteins that surrounds all types of cells, controlling the entrance and exit of materials.

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In what types of organisms would you expect to find cell walls and or cell membranes?

Cell walls are found in organisms belonging to the domains Bacteria, Archaea, and in the plant kingdom

Cell membranes, on the other hand, are found in all living things, including those without cell walls, such as animal cells.

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How has the Earth changed over its history? How have microorganisms contributed to these changes?

From inhabitable to oxygen rich by cyanobacteria

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Name the three domains of life. Which of these contain eukaryotic life forms? How are they similar and different?

Archaea, Bacteria, and Eukarya

Archaea and Bacteria are both prokaryotic organisms,

Eukarya contains eukaryotic organisms

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Why were cyanobacteria so important in the evolution of life on Earth? What is a genus name of a cyanobacterium and what is unique about these organisms?

Cyanobacteria were important in the evolution of life on Earth because they were one of the first organisms to produce oxygen through photosynthesis. This oxygen revolutionized the Earth's atmosphere, allowing for the proliferation of more complex life forms.

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How do microbes contribute to the nutrition of animals such as humans and cows?

Microbes contribute to the nutrition of animals such as humans and cows by breaking down complex organic molecules into simpler compounds which can be absorbed by the animals' digestive systems

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Describe several ways in which microorganisms are important in the food and agricultural industries.

shelf life,vaccines for livestock

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What is wastewater treatment and why is it important?

Wastewater treatment is the process of removing contaminants from wastewater so that it can be safely released back into the environment.

untreated wastewater can contain harmful substances such as bacteria, parasites, and chemicals that can pollute the natural water sources

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What is the difference between magnification and resolution?

Magnification refers to the degree to which an object is visually enlarged, while resolution refers to the capacity to discern the details of the object being viewed

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What is the function of staining in light microscopy?

enhance contrast and visibility of cellular components or structures that are otherwise difficult to see

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What color will a gram-negative cell be after Gram staining by the conventional method? Gram positive? Why?

A gram-negative cell will turn pink or red thin peptidoglycan layer

A gram-positive cell will turn purple or blue due to thick peptidoglycan layer

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What are the steps of a gram stain and the function of each reagent?

1. Prepare a heat-fixed smear of the bacteria on a microscope slide.

2. Flood the slide with crystal violet stain and let it sit for 1 minute.

3. Rinse the slide with water and flood it with iodine solution and let sit for 1 minute.

4. Rinse the slide with water and decolorize with alcohol or acetone for a few seconds.

5. Rinse the slide with water and flood it with safranin stain for 1 minute.

6. Rinse the slide with water, blot dry, and observe under a microscope.

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What major advantage does phase-contrast microscopy have over staining?

visualization of live, unstained samples without altering their natural morphology or biochemical activity, whereas staining requires the sample to be killed, fixed, and stained

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How can cells be made to fluoresce?

Genetic modification or by labeling them with fluorescent dyes

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What are the major differences between electron microscopes and light microscopes?

The major differences between electron microscopes and light microscopes are the type of radiation used for imaging and the resolution capabilities.

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What type of microscope would be used to view the three-dimensional features of a cell? Of the internal parts of a cell? Why?

A confocal microscope would be used to view the three-dimensional features of a cell,

electron microscopy uses beams of electrons to create high resolution images of internal structures within the cell.

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Explain how Pasteur disproved spontaneous generation.

Pasteur disproved spontaneous generation by designing experiments where he boiled the broth in a flask and then sealed it with a curved neck. This allowed air to enter but prevented microorganisms from reaching the broth. He observed that no growth of microorganisms occurred in the broth. However, when he broke off the neck of the flask, the broth became cloudy with microorganisms after a few days.

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Explain Koch’s postulates.

(1) the microbe must be present in all cases of the disease but absent from healthy individuals,

(2) the microbe must be isolated from a diseased individual and grown in pure culture,

(3) the same disease must result when the isolated microbe is inoculated into a healthy host,

(4) the same microbe must be isolated again from the diseased host

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What advantages do solid media offer for the isolation of microorganisms? What is an example of a solid bacteriological medium? Liquid growth medium?

Solid media offers advantages for the isolation of microorganisms by providing a stable surface for bacterial growth, as well as physical separation of individual colonies for easier identification and isolation

example nutrient agar

liquid growth medium (such as the tryptic soy broth) is more suitable for the cultivation of fastidious microorganisms or those that require specific conditions for growth.

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What is a pure culture?

population of identical microorganisms that are derived from a single cell or colony

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Describe Griffith’s transformation experiment.

Griffith's transformation experiment involved injecting mice with different strains of Streptococcus pneumoniae bacteria to observe the effects on the mice. Griffith discovered that a non-virulent strain of bacteria could transform into a lethal strain in the presence of a heat-killed virulent strain. This transformation occurred due to a transfer of genetic material from the virulent strain to the non-virulent strain. This experiment was significant in providing evidence for the concept of bacterial transformation and the role of DNA in genetic material transfer.

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What is a phylogenetic tree and what does it tell you?

determine the lineage and ancestry of different species, as well as to infer patterns of evolutionary change over time.

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What are the contributions to microbiology associated with the following people…Robert Hooke, Antoni van Leeuwenhoek, Louis Pasteur, Robert Koch, Frederick Griffith, Carl Woese

Robert Hooke is known for first using the term "cell" to describe the basic unit of life. Antoni van Leeuwenhoek is credited with the discovery of microorganisms and the development of the microscope. Louis Pasteur made notable contributions in the fields of vaccination, germ theory of disease, and pasteurization. Robert Koch was a pioneer in the field of medical microbiology and is well-known for his research on tuberculosis. Frederick Griffith conducted the famous Griffith's experiment which led to the discovery of DNA as the genetic material. Finally, Carl Woese is known for his significant contribution in the field of microbiology by discovering Archaea, a new domain of life.

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Define sterile in terms of microbiology. Name at least two ways to sterilize microbiological media.

sterile refers to the complete absence of all forms of living microorganisms, including bacteria, viruses, and fungi.

autoclaving and firation

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Why are Archaea more closely related to Eukarya than Bacteria are to Eukarya?

Archaea are more closely related to Eukarya than Bacteria are to Eukarya due to their genetic and biochemical similarities with eukaryotic organisms.

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How do cocci and rods differ in morphology? Give an example of a bacteria with each morphology.

Cocci are circular or spherical-shaped bacteria,

rods are cylindrical or elongated-shaped bacteria.

cocci morphology is Streptococcus pneumoniae

rods morphology is Escherichia coli,

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Using a microscope, could you differentiate a coccus from a spirillum? A pathogen from a nonpathogen?


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Draw the basic structure of a phospholipid bilayer and label the hydrophilic and hydrophobic regions. Why is the cytoplasmic membrane a good permeability barrier?

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How are the membrane lipids of Bacteria and Archaea similar, and how do they differ?

Both have membrane lipids made of fatty acids with ester linkages

Archaea also have membrane lipids with ether linkages

Archaea have L-glycerol backbone

Bacteria have D-glycerol

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Describe the major functions of the cytoplasmic membrane.

controlling the movement of molecules in and out of the cell, providing support and structure to the cell, aiding in cell recognition and communication, and serving as a barrier between the cell and its external environment

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Why do bacterial cells need cell walls? Do all bacteria have cell walls?

need cell walls for protection and structural support

Not all bacteria have cell walls

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Why is peptidoglycan such a strong molecule?

due to its unique structure, which consists of a network of glycan chains cross-linked by short peptide strands

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Describe the major differences between the cell walls of gram-negative and gram-positive bacteria.

gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane containing lipopolysaccharides, while gram-positive bacteria have a thick peptidoglycan layer and lack an outer membrane

gram-negative often more antibiotic resistant due to the outer membrane acting as a barrier.

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Explain whether you expect the enzyme lysozyme to be equally effective against Bacteria and Archaea.

archaea and bacteria have significant differences that may affect the effectiveness of lysozyme

archaea have different chemical bonds in their cell walls than bacteria, which could make them more or less susceptible to lysozyme activity

so its hard to say

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What do the enzyme lysozyme and the antibiotic penicillin have in common?

lysozyme and penicillin are capable of breaking down the cell walls of certain types of bacteria

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Describe the major chemical components in the outer membrane of gram-negative bacteria.

lipopolysaccharides (LPS), phospholipids, and proteins

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What is the function of porins and where are they located in a gram-negative cell wall?

they regulate the concentration of small, hydrophilic molecules that are important for cellular processes.

located in the outer membrane of the gram-negative cell wall.

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What component of the gram-negative cell has endotoxin properties?

lipopolysaccharide (LPS) layer

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What is pseudomurein and where is it found?

type of cell wall that is found in certain species of archaea, specifically those belonging to the order Methanobacteriales

found in bacterial cell walls

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What is the value of a cell having a capsule? What is the capsule composed of and where is it found? Name a bacterium that has a capsule.

provides protection against environmental stressors, such as dehydration and phagocytosis by immune cells

composed of polysaccharides and is found outside of the cell membrane

Streptococcus pneumoniae

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How do fimbriae differ from pili?

Fimbriae are shorter, more numerous appendages used for attachment to surfaces and movement on surfaces, while pili are longer, less numerous appendages used for conjugation and twitching motility

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What is dipicolinic acid and where is it found?

chemical compound containing two pyridine rings and two carboxylic acid groups

found in the spores of certain bacteria, particularly Bacillus and Clostridium species

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What is formed when an endospore germinates? What causes a cell to make endospores?

forms a vegetative cell through a process called germination

triggered by environmental stressors such as nutrient depletion or exposure to extreme heat or toxins

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Name two genera that produce endospores and how are the different?

Bacillus and Clostridium

Bacillus endospores are larger and oval-shaped, have a prominent spore coat,

Clostridium endospores are smaller and round in shape and do not have a coat

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Cells of Salmonella are peritrichously flagellated, those of Pseudomonas polarly flagellated, and those of Spirillum lophotrichously flagellated. Using a sketch, show how each organism would appear in a flagellar stain.

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What is archaella and where are they found?

whip-like structures that protrude from the surface of some archaea cells

found exclusively in archaea and play an important role in cellular motility and chemotaxis

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What is positive and negative chemotaxis? When would you see each?

Positive chemotaxis - movement towards a chemical stimulus,

Negative chemotaxis - movement away from a chemical stimulus

Positive - White Blood cells moving towards an infection site

Negative - movement of cells away from toxic substances

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What are the gram reaction, morphology and arrangement of the following bacteria? E. coli, Bacillus, Staphylococcus, Micrococcus, Streptococcus, Vibrio, Treponema

E. coli: Gram-negative bacillus arranged singly or in pairs Bacillus: Gram-positive bacillus arranged in chains

Staphylococcus: Gram-positive cocci arranged in clusters

Micrococcus: Gram-positive cocci arranged singly, in tetrads, or irregular clusters

Streptococcus: Gram-positive cocci arranged in chains

Vibrio: Gram-negative curved or comma-shaped bacillus arranged singly or in pairs

Treponema: Gram-negative spirochete arranged singly or in bundles

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How big is E. coli? How big is Staphylococcus?

E.coli - 2-6 micrometers in length and approximately 0.5-1 micrometer in diameter

Staph - diameter of around 0.5-1.5 micrometers

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Compare and contrast gram positive and gram-negative cells. Draw a diagram of each and label the structures. What components are unique to each.

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What value do gas vesicles give to bacteria?

providing buoyancy to bacteria by allowing them to regulate their position in the water column

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What is the function of flagella? What are flagella made of?

help free-living cells, such as bacteria, to move towards or away from stimuli.

made of the protein flagellin.

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Compare and contrast a prokaryotic and a eukaryotic cell. Give examples of both. What are the functions of each of the components?

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How do prokaryotic and eukaryotic cells differ when it comes to reproduction? In general, how do bacteria, fungi (molds and yeast), plants and animals reproduce?

Prokaryotic cells reproduce through binary fission,

Eukaryotic cells generally reproduce through mitosi

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Explain endosymbiosis.

suggests that mitochondria and chloroplasts were once free-living bacteria that were engulfed by larger cells and evolved to become symbiotic organelles

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Do bacteria have cilia?


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How do bacterial endospores differ from fungal spores in function?

Endospores formed as a survival mechanism during unfavorable environmental conditions, can remain dormant for long periods until environmental conditions become favorable

fungal spores are formed for reproduction, dispersed by air or water

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What is phototaxis?

movement or orientation of an organism in response to light

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How does a chemoorganotroph differ from a chemolithotroph? A chemotroph from a phototroph? What does troph mean?

Chemoorganotroph obtains energy from organic compounds by cellular respiration

Chemolithotroph obtains energy from inorganic compounds by chemosynthesis

phototroph obtains energy from sunlight by photosynthesis

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How does an autotroph differ from a heterotroph?

autotroph is an organism that is capable of producing its own food

heterotroph is an organism that cannot produce its own food and must consume other organisms or organic compounds for energy and nutrients

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What are enzymes made of? Why is that important when it comes to high temperatures?

made of proteins that are folded into complex shapes

changes in temperature can alter their shape and affect their ability to bind substrates and catalyze reactions

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Where on the enzyme does the substrate bind?

to the active site of the enzyme

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What is energy of activation?

minimum amount of energy required for a chemical reaction to occur

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How is catabolism different from anabolism?

Catabolism - breaking down complex molecules into simpler ones, releasing energy

Anabolism building complex molecules from simpler ones requiring energy input.

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How is respiration different from fermentation?

Respiration, the electron acceptor is an external molecule process yields a large amount of ATP.

Fermentation uses an internal molecule as its electron acceptor produces only a small amount of ATP

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What are some of the endproducts of fermentations?

ethanol, lactic acid, carbon dioxide, and acetic acid

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What yeast is commonly used for fermentations?

Saccharomyces cerevisiae

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What happens in glycolysis?

  1. six-carbon glucose molecule is split into two three-carbon pyruvate molecules involves the input of two ATP

  2. (4) ATP molecules and two NADH molecules.

  3. (2) molecules of water are produced as a result of the reaction.

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How does glucose get into a cell?

facilitated diffusion

Glucose transporters on the cell membrane act like channels

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Where is the most ATP produced? Glycolysis, Kreb’s cycle or in the ETC?

electron transport chain (ETC)

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What is the final election acceptor in aerobic respiration and what does it form?


forms water

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What is the final electron acceptor in anaerobic respiration?


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What is the carbon source for autotrophic organism? Energy source?

carbon dioxide (CO2) from the atmosphere or dissolved in water

energy source for autotrophic organisms is usually sunlight or inorganic substances

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Where do bacteria get their nutrients from?

from their environment

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What happens during nitrogen fixation and what types of organisms fix nitrogen?

atmospheric nitrogen (N2) is converted into a usable form for biological processes, such as ammonia (NH3) or nitrate (NO3-)

organisms - Rhizobium, Azotobacter, and Cyanobacteria, and some archaea

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Which four chemical elements make up the bulk of a cell’s dry weight?

carbon, hydrogen, nitrogen, and oxygen

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Which two classes of macromolecules contain most of a cell’s nitrogen?

proteins and nucleic acids

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Differentiate between trace metals and growth factors. How are these used by the cell?

Trace metals cofactors for enzymes

Growth factors - regulate cell growth, proliferation, and differentiation.

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How is a complex medium different from a defined medium? What type of media is TSA and why?

complex medium contains a mixture of undefined components, while a defined medium has a precise formula with known amounts of nutrients and ingredients.

Tryptic Soy Agar, is a complex medium because it contains components such as enzymatic digests of soybean meal and casein, as well as sodium chloride and agar which are undefined

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What is meant by the word sterile? Why is aseptic technique necessary for successful maintenance of pure cultures in the laboratory?

sterile refers to the absence of all living microorganisms and pathogens

technique ensures that the cultures are not contaminated with any unwanted organisms during the transfer and manipulation processes

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Why is a viable count more sensitive than microscopic count? What major assumption is made in relating plate count results?

it considers only live and growing cells, whereas a microscopic count takes into account both living and dead cells

assumption made in relating plate count results is that each individual colony on a plate resulted from the growth of a single bacterial cell

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Describe how you would dilute a bacterial culture to 10-7.

mix one milliliter of the original bacterial culture with 999,999 milliliters of sterile diluent

then repeat this process six more times, each time taking one milliliter from the newly diluted culture and mixing it with 999,999 milliliters of sterile diluent.

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Explain the “great plate count anomaly.”

Observation - bacterial counts obtained through cultivation techniques on agar plates are lower than those estimated using direct microscopic counts of environmental samples

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Describe how you could use a turbidity measurement to tell how many colonies you would expect from plating a culture of a given OD.

first, measure the OD of the culture and then correlate it with the turbidity measurement

turbidity measurement can be used to estimate the number of colonies in a given culture by comparing it to the standard curve.

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What is meant by the term generation time? What is the average generation time of E. coli?

generation time refers to the time it takes for a population of organisms to double in size

20 minutes

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How do binary fission and budding cell division differ?

binary fission, the cell splits into two identical daughter cells.

Budding involves the growth and eventual detachment of a small "bud" from the parent cell, which eventually grows into a new, independent offspring

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In which phase of the growth curve are cells actively growing?

Cells are actively growing in the log or exponential phase of the growth curve.

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Under what conditions would a lag phase not occur?

A lag phase would not occur if the population being observed is already acclimated and in an optimal growth condition

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Why do cells enter stationary phase?

Cells enter stationary phase when they have exhausted their resources and can no longer continue to divide

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How do microorganisms in a chemostat differ from microorganisms in a batch culture?

Chemostat continually adapt to a steady flow of nutrients and adjust their growth rate through regulatory mechanisms.

chemostat is more stable and controlled

Batch culture are exposed to a limited supply of nutrients, leading to nutrient depletion and accumulation of waste products, ultimately leading to a decline in growth rate.

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Explain how to do a plate count? How many bacteria would be in the culture if you had 234 colonies on the 1/1,000,000 plate?

234,000,000 colonies

diluted sample is then plated onto an appropriate agar medium and spread evenly with a sterile glass rod. After incubation, the colonies are counted and the number of bacteria per unit volume of original sample is determined

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What are the stages and events that occur during biofilm formation?

Initiation bacteria begin to adhere to a surface and produce extracellular polymeric substances (EPS).

Attachment stage, the bacteria continue to produce EPS while forming microcolonies on the surface.

Maturation stage, the biofilm grows thicker and more complex as new bacteria continue to join in and the EPS matrix becomes denser.

Dispersal stage occurs when some bacteria detach from the biofilm and go on to form new colonies elsewhere.

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Why is biofilm formation such a major problem in human medicine?

can cause difficulties in human medicine due to the ability of the biofilm to serve as a protective barrier

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How does a hyperthermophile differ from a psychrophile?

hyperthermophile thrives in extremely high temperatures 80°C and 122°C,

psychrophile thrives in extremely low temperatures, typically below 15°C

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What are the cardinal temperature for E. coli? To what temperature class does it belong?

min - 7°C to 10°C

optimum growth - 37°C

max - 45°C to 47°C.


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