Exam 1 Flashcards
What are some ways microorganism affect life?
Microbiome in gut, pathogens, foods, digest food, break down toxins, study, model for early life, source of all life, very diverse/abundant, grow everywhere, affect geosphere/climate, symbiotes, industrial - genetic engineering, source of enzymes
Meaning of ATCC
American Type Culture Collection
PAMPs and MAMPs
Pathogen Associated Molecular Patterns are now referred to as Microbial Associated Molecular Patterns
highlight that microbes can have beneficial or negative roles
Why are vertebrate immune systems more complex than invertebrates? (Margaret McFall-Ngai
They have a longer lifespan and have the opportunity and necessity to develop that way
Meaning of LUCA
last universal common ancestor
3 Domains of Life
bacteria, archaea, eukarya
Conditions on earth during heavy bombardment
no water, high temperatures, reduced gases in the environment
What are stromatolites? How old are they? Where are they found?
Fossils greater than 3.5 BYA found during the 1950s in intertidal marine areas
Mats of mostly photosynthetic organisms
Some are still found in Australia today
The oldest eukaryotes are __________
2.5 MYA
The oldest bacteria are _____________
3.5 BYA
The earliest branches of the Tree of Life contain _____________ bacteria
thermophilic
When did microbiology as a scientific discipline begin?
People began linking specific microbes to disease in the 1800s, partially due to the development of agar plates allowing separation of microbes
In the 1850’s people thought disease was caused by “bad air”
Three Eras of the Science of Microbiology?
Pre-Germ Theory, Golden Age, Modern Era
Contribution to Microbiology: Francisco Redi
cheesecloth over meat, disprove spontaneous generation
Contribution to Microbiology: Antoni van Leeuwenhoek
first microscope, discovered animalcules/microorganisms
Contribution to Microbiology: Edward Jenner
cowpox (cowpox victims were immune)
Contribution to Microbiology: Ignaz Semmelweis
childbed fever, pregnant women, handwashing
Women who delivered babies in hospitals
died more often
Contribution to Microbiology: John Snow
ghost map, cholera, father of epidemiology
Contribution to Microbiology: Louis Pasteur
disprove spontaneous generation, swan flask
Contribution to Microbiology: Joseph Lister
disinfectant before surgery
Contribution to Microbiology: Robert Koch
germ theory, 4 postulates, causative agents of anthrax and tuberculosis
4 Postulates and their purpose
Observe, Isolate, Infect, Reisolate
1st (Observe): Make the observation
Pts with tb have a particular microorganism associated with them
2nd (Isolate): Isolate that organism in pure culture
Possible with agar plates
3rd (Infect): Infect an individual with the purified organism
4th (Reisolate): Reisolate the same organism from the infected individual
Demonstrate that a disease is caused by a microorganism
Germ Theory
Germ Theory: A disease-causing microorganism should be present in animals infected by the disease and not in healthy animals
Contribution to Microbiology: Fannie Hesse
agar plates (instead of gelatin)
Contribution to Microbiology: Hans Christian Gram
gram stain (1st differential stain)
Contribution to Microbiology: Sergei Winogradsky
principles of chemolithotrophy, Winogradsky column
Contribution to Microbiology: Martinus Beijerink
virus and enrichment techniques
Contribution to Microbiology: Beatrix Potter
mycologist
Contribution to Microbiology: Paul Ehrlich
chemotherapy (salvarsan)
Contribution to Microbiology: AJ Kluyver
comparative biochemistry
Contribution to Microbiology: Alexander Fleming, Howard Florey, and Ernst Chain
penicillin, mold that grew on agar petri dish killed bacteria on the same agar
Contribution to Microbiology: Alice Evens
pasteurization of milk
Contribution to Microbiology: Rebecca Lancefield
serotyping streptococci
Contribution to Microbiology: Selman Waksman
streptomycin
Contribution to Microbiology: Oswald Avery, Colin MacLeod, Maclyn McCarty
identify deoxyribonucleic acid (DNA) as the “transforming principle” responsible for specific characteristics in bacteria
How do microscopes work?
light bends as it passes through substances of different densities
Define resolving power
distance between two objects that can be separated by the lens in the formation of an image
Better Resolving Power = wavelength, refractive index, angular aperture
shorter wavelength (purple/UV)
high refractive index
higher angular aperture
Describe chromatic aberrations of microscopes
Different wavelengths focus at different places
Due to combining lenses of different shape and composition
Describe spherical aberrations of microscopes
Light rays at periphery focus at a different place from the rays at the center
Describe a darkfield microscope
dark background, structures of cells stand out
Describe a phase-contrast microscope
enhance contrast of cells and their medium
Denser objects appear darker (extremely dense is white)
More contrasts lends a 3D look
What is unique about fluorescence microscopy?
uses dyes and antibodies
Describe a confocal scanning microscope and what they are used for
See where cells are in tissues and how they move
Visual cells, 3D structures
Describe electron microscopes (general)
very high magnification, only dead organisms, need coating, black and white
What is a SEM microscope? How is it used?
Scanning electron microscope
Surface only
What is a TEM microscope? How is it used?
Transmission Electron microscope
3D, thin slice of material, internal structures
Describe a Nermaski microscope
Behaves like SEM
surface structures
3D appearance
Term for rod
bacillus
Term for round
coccus
Term for short rod (different from rod)
coccobacillus
Term for spiral
spirillum
Term for curved rod (different from short rod)
vibrio
Term for long, loose, helical spiral
spirochete
What would you call a joined pair of cocci?
diplococcus
What would you call a cube of cocci?
tetrad
What would you call a cluster of cocci?
staphylococcus
What would you call a chain of rods?
streptobacillus
Define inclusions
Structures inside the cell used for storage, detoxification, and movement
What is poly-beta-hydroxybutyrate?
a compound used for carbon storage that can be used for biodegradable plastic
What is the purpose of gas vesicles?
allow aquatic microorganisms to modify their density
What are stains used for?
Increase contrast, distinguish bacteria, see subcellular structures
What is the difference between acidic and basic stains?
Basic dyes stain negatively charged membranes, acidic dyes stain the surroundings of negatively charged membranes
What is the difference between simple stains and differential stains?
Gram stain is a differential stain, organisms act differentially in differential stains depending on the strain
What are specialized stains for?
Detect specific cellular components (such as flagella)
What are the four steps of a Gram stain? Which is most important?
1st Primary stain- prepare smear -> Both cells stained purple
Take cells and smear with water, then let dry.
Crystal violet stain first (stains every bacterial cell)
2nd Mordant- flood preparation
Iodine solution that intensifies the purple
3rd Decolorization- add ethanol -> Dye washes off gram-negative
4th Counterstain- stain with safranin
To see the gram negative bacteria (which are now clear), add safranin
3rd step is most important, will have controls to test the method
What are some functions of prokaryotic surfaces?
Cell-cell contact, non-specific binding, holding shape, cation/anion binding, protection, molecular sieve
What are pili/fimbrae?
rods that help bacteria attach to surfaces
What is a capsule/slime layer/biofilm? What is it for?
polysaccharide layers outside of the cell wall/membrane (also called glycocalyx)
Can help attachment to surfaces, prevent desiccation, or provide protection
What are some of the purposes of the cytoplasmic/plasma membrane?
Provide a selective barrier between the cell wall and internal structures
Site of photosynthesis (bacteria), DNA replication, and enzyme reactions
Small hydrophobic molecules pass through the best
Gram-Negative vs Gram-Positive: Peptidoglycan layer
thin in negative, thick in positive
Gram-Negative vs Gram-Positive: presence of lipoteichoic acid
absent in negative, present in peptidoglycan wall of positive
Gram-Negative vs Gram-Positive: presence of outer (secondary) layer
present in negative, absent in positive (more susceptible to attacks on peptidoglycan wall)
Gram-Negative vs Gram-Positive: presence of periplasmic space
present in negative (between 2 membranes), absent in positive
Gram-Negative vs Gram-Positive: tetrapeptide chain components
meso-diaminopimelic acid in negative, L-lysine in positive
Gram-Negative vs Gram-Positive: linkage between tetrapeptide chains
direct in negative, pentapeptide in positive
What are the special components of the outer membrane of gram-negative bacteria?
Outer membrane containing “lipid A”, which is linked by sugar to an O polysaccharide (repeating sequence, varies between cells)
Whole thing called a lipopolysaccharide (LPS)
Lipid A is toxic
What are the sugars that both gram-negative and gram-positive contain in their cell walls?
NAG and NAM
What allows packaging of chromosomal DNA?
supercoiling
How are archaea different from bacteria (cell wall)?
Many lack a cell wall
Never contain peptidoglycan (also called murein)
May have pseudomurein or protein cell walls (S-layer)
What is the purpose of an endospore?
Formed due to lack of nutrients, toxins, certain types of cell-cell contact, and other types of stress
Protects from desiccation, heat, chemicals (including immune system), UV radiation, high refractivity
Metabolically inert
How are endospores produced?
A special type of asymmetrical reproduction called sporulation
Cell begins to reproduce asymmetrically → larger portion “engulfs” smaller portion → cell lyses → free endospore then removes a lot of liquid and produces proteins to make its exosporium, spore coat, core wall, and cortex
How can endospores be used in differentiating bacteria?
ability to make one, its size, its location
Describe the prokaryotic flagella
pure protein, solid/stable, very long, move by roatation
What are the parts of a prokaryotic flagella?
basal body, hook, filament
What is the term for a tuft of flagella?
loctricus
What is the term for flagella all over?
peritrichous
What is the term for two or more polar flagella?
lophotrichous
How do bacteria move? (general)
Without any stimulus bacteria will move until they reach equilibrium, stay near favorable areas and leave unfavorable areas, move by either tumbling or running
Describe a bacteria “run”. How is it used to move bacteria to a better location?
use flagella to move in a specific direction
If there is an attractant present they will extend their run and if there is a toxin they will shorten their run
Describe a bacteria “tumble”. Why do they do that?
throw out their flagella and float randomly
they have to keep sensing, bacteria are always trying to sense their environment
Describe a hemocytometer or a petroff-hausser slide
A special slide designed for counting the bacterial cells in a measured volume of sample
Easy to use, fast, inexpensive
What are the limitations of cell counting via hemocytometer?
Cannot distinguish live/dead, overlook small cells, imprecise (esp. low densities)
How does a coulter counter work? What are its limitations?
Counts cells by measuring change in resistance in a solution when a cell passes through a small opening
Rapid and accurate up to certain concentrations
Does not differentiate between live/dead cells
Describe the spread-plate method
Sample is pipetted onto agar and spread
Describe the pour-plate method
Sample is pipetted into plate, then medium is added
Volumes greater than .1 mL
What range of cells can be reliably counted?
30-300 cells/colonies, units are CFU/mL
What are the advantages and disadvantages of plate counting?
most accurate method (slightly low), but it requires a lot of plates, time, and effort
How are cells counted with a spectrophotometer?
Measured with a spectrophotometer with units as OD600
Rapid, can measure change over time easily, need a minimum concentration of cells
As long as above min, equally accurate at low + midrange
Usually plotted on a semi-log scale
Define growth
Increase in microbial mass indicates a change in the number of cells in a given locale
What is the equation to determine the number of generations needed to reach a certain population size?
Nn = N0 * 2^n
Nn is the number of cells at any generation n
N0 is the initial number of cells
n is the number of generations
What are the four phases of bacterial growth?
lag, exponential/lag, stationary, death
Describe the lag phase of cell growth
no cell division
Cells grow larger and are metabolically active, synthesizing proteins and making repairs
Describe the exponential/log phase of cell growth
generation time constant
Used for experiments to determine growth rate in prime conditions
Describe the stationary phase of cell growth
reproduction/death balanced
May have more cells (than exp/log), but many will be dead
Amount of viable cells remain the same
Describe the death phase of cell growth
death exceeds reproduction exponentially
Describe rich/complex media
Not all ingredients defined (yeast extract, peptone, tryptone), supports growth of a wide range of bacteria
Describe enriched media
contains added essential nutrients specific organisms need to grow
Describe enrichment cultures
preferred growth of desired microorganism followed by growth in selective media
Describe fastidious organisms
cannot make certain nutrients and require them to be added to their media
Describe chemically defined media
Identity/quantity of all contents known
Supports growth of fewer numbers of bacteria
Types dependent on carbon source
Describe selective media
Discourages the growth of specific types of organisms
Usually contains ingredients such as antibiotics, dyes, detergents, or salts
Define streak plating
procedure that uses inoculating loops to isolate a pure culture of a bacterium from a mixture
Describe differential media
Certain organisms will acquire a specific appearance
Usually contains pH indicator dyes or cleaveable color-changing substrates
