question

How is selective permeability achieved?

answer

-By the use of substrate-specific carrier proteins (permeases) in the membrane
-aid from dedicated nutrient-binding proteins that patrol the periplasmic space
-through the action of membrane-spanning protein channels, that discriminate between substrates

question

Facilitated diffusion

answer

Type of system that uses the concentration gradient of a compound to move that compound across the membran from high to low concentration.
ex. GLpF facilitates h20 and glycerol

question

Coupled Transport

answer

When a transport protein uses free energy from an ion moving down its concentration gradient to drive the transport of a second molecule against its concentration gradient

question

Symport and Antiport

answer

Symport- one molecule pushes another molecule down the concentration gradient, same direction
Antiport- the actively transported molecule moves in the opposite direction of the driving ion

question

ABC transporter

answer

"ATP-binding cassette" tranporter- a super family of energy driven transport systems that are critical for transporting nutrients, always against the gradient

question

Group Translocaton

answer

Chemically alters a substrate during transport so that it will go down the gradient into the cell.

question

Liquid Growth Media

answer

-organisms can move about freely
-useful for studying the growth characteristics of a single strain of a single species (pure culture)
-good for examining growth kinetics and microbial biochemistry at different phases of growh

question

Solid Growth Media

answer

-usually gelled with agar
-useful for trying to separate mixtures of different organisms as they are found in natural environment or in clinical specimens

question

Selective media

answer

Favor the growth of one organism over another

question

Differential media

answer

expose biochemical differences between two species that grow equally well

question

Fluorescence-activated cell sorter (FACS)

answer

an instrument that can measure cell size, identify, and count different populations of cells by detecting the light scatter of a laser passing through the fluorescent labeled cells

question

Formula for calculating number of generations (n)

answer

n=(log10(Nt/N0))/0.301

question

Formula for growth rate constant (k)

answer

k= n/t= log10(Nt/N0)/0.301t

question

Mean generation time (g)

answer

g= 1/k

question

Lag Phase

answer

time needed for bacteria to detect their environment, express specific genes, and synthesize components needed to institute rapid growth
a variety of factors determine the length, such as if they are damaged, if they are put on old or new media, complex or minimal media, etc.

question

The growth cycle

answer

in a liquid batch culture consists of lag phase, log phase, stationary phase, and death phase

question

Carl Woese

answer

discovered Archaea in hot springs in 1977, replaced the 5 kingdoms with the 3 domains bacteria, archaea, and eukarya

question

Genetic Recombination

answer

the ability to exchange genetic information by transduction, conjugation or transformation indicates a high level of DNA sequence conservation

question

Classical Taxonomy

answer

based on morphology, nutritional requirements (phototroph, heterotroph, lithotroph), oxygen requirement, spore formation, cell wall chemistry

question

Numerical Taxonomy

answer

uses classical traits to create a systematic grouping of related bacteria, system of dichotomous keys- separates species on hierarchical series of tests

question

Robert Hooke (1635-1703)

answer

first described microorganisms viewed with compound microscope, coined the term "cell" for basic unit of life

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Antoni van Leeuwenhoek (1632-1723)

answer

first person to see individual bacteria w/ normal microscope, his reports were so detailed we can even determine the species he observed, he used his own microscope with a single lense stronger than Hooke's

question

Carl Zeiss

answer

built microscopes that had lenses that corrected for chromatic and spherical abberation and provided good images at up to 1000x magnification

question

Francisco Redi (1626-1697)

answer

disproved the spontaneous generation of flies

question

Lazzaro Spallanzani (1729-1799)

answer

showed that infusions heated in a sealed glass flask did not produce microbial cells, shoed that microbial cells arose from existing cells by cell fission, (disproving spontaneous generation a little

question

Louis Pasteur (1822-1895)

answer

disproved spontaneous generation of microbes with his swan necked flasks experiments

question

John Tyndall (1820-1893)

answer

noticed he couldn't reproduce Pastuer's observations, hypothesized that there were heat resistant microbes, showed repeated boiling and cooling would kill them, process called Tyndallization, also disproving spontaneous generation

question

Ferdinand Cohn (1828-1898)

answer

discovered the bacterial structure called an endospore that is resistant to many environmental extremes, what tyndall was killing, disproving spontaneous generation

question

Theodor Schwann (1810-1882)

answer

proposed tranformations of matter including fermentation, putrefactions, and liquefactions were caused by microorganisms

question

Jacob Berzelius, Justus von Liebig, and Friedrich Wohler

answer

were against Schwann, insisted these were chemical reactions

question

John Pastuer

answer

solved their argument by showing specific organisms are associated with specific fermentations. discovered anaerobes.

question

Girolamo Fracastoro (1478-1553)

answer

proposed that "spores" could transmit disease

question

Agostino Bassi (1773-1856)

answer

shoed that a fungal disease killed silkworms in 1836

question

Johann Schonlein (1793-1856)

answer

showed that a fungus causes ringworm

question

Miles Joseph Berkeley (1803-1889)

answer

showed that many plant diseases were caused by fungi

question

Florence Nightingdale (1820-1910)

answer

A British nurse who founded medical statistics. Showed that more soldiers have died of microbial infections than of wounds in battle

question

Ignaz Philipp Semmelweis (1818-1865)

answer

suggested physicians use hand disinfection between seeing patients. Reduced mortality of child bed fever from 35% to 1%, but observations were mostly ignored

question

Joseph Lister

answer

used pastuer's ovservations to initiate antiseptic surgery in which wounds and instruments were sterilized with carbolic acid

question

Robert Koch (1843-1910)

answer

Finally proved that bacteria caused disease, studied the disease anthrax, noticed that when transferring blood of infected mouse to healthy one they healthy one became infected. Grew the rod shaped bacteria in sterile serum and showed when put in healthy mouse, the mouse also became infected

question

Casimire Davaine (1812-1882)

answer

shown that the blood of infected animals contained rod shaped organisms

question

Friedrich Henle (1809-1885)

answer

proposed 4 criteria to establish that an agent caused disease, these would be called Koch's Postulates

question

Koch's postulates

answer

1. microbes must be present in every case of the disease
2. microbe must be isolated in pure culture
3. The disease must reappear when organisms from pure culture are injected into an uninfected animal
4. microbe then must be again recovered from the newly infected animal and shown to be the same organism

question

Golden Age of Microbiology (1850-1900)

answer

many bacterial diseases were identified, improvements in public health, studies on immunology by Pastuer
Discovery of viruses as agents of disease by Dmitry Ivanovsky and Martinus Beijerinck

question

Lady Mary Montagu

answer

introduced practice of smallpox inoculation to europe in 1717

question

Edward Jenner (1749-1823)

answer

deliverately infected patients with matter from cowpox lesions, this process would be called vaccination

question

Louis Pasteur (immunization)

answer

developed first vaccines based on attenuated or weakened strains, fowl cholera, ravies.

question

Development of Pure Culture techniques

answer

Koch developed these techniques to link specific bacteria to specific diseass
Pastuer and Charles Chamberland developed the autoclave which sterilized growth medium at 121 degrees C
Julius Petri invented the petri plate
Angelina and Walther Hesse used agar to make solid medium

question

Martinus Beijerinck and Sergei Winogradsky

answer

used enrichment culture techniques to isolate bacteria from environment. Found organisms that cycles nitrogen and sulfur
Winogradsky proposed concept of chemolithotrophy in which oxidation reduced inorganic compounds that can be used for energy

question

Pleomorphism vs. monomorphism

answer

Do a vew bacteria adapt to their environment in many shapes and forms or are their many bacteria with limited variability in form and function
The latter, monomorphism was shown to be true by use of pure cultures

question

Electron microscope

answer

developed by Ernst Ruska, reveals internal structure of cells

question

the ultracentrifuge

answer

developed by Theodor Svedberg
-a key tool of subcellular fractionation is the ultracentrifuge
-high rotation rate produces centrifugal forces strong enough to separate particles by size

question

Alexander Fleming

answer

discovered that Penicillium mold generated a substance that killed bacteria
In 1941 Howard Florey and Ernst Chain purified penicillin, the first commercial antibiotic to save lives

question

Definitions of Magnification, Resolution,and Contrast

answer

Magnification- the extent to which the image of an object is larger than the object
Resolution- quantitative measure of the closest distance between two points at which they are clearly separate entities
Contrast- the ability to distinguish an organism from the background

question

3 conditions for electromagnetic radiation to resolve an object

answer

1. Contrast between object and its medium
2. Wavelength smaller than the object
3. detector with sufficient resolution for the given wavelength

question

Resolution and Numerical Aperture equations

answer

Resolution = d = ?/N.A. and N.A. = N x sin ? where N is the refractive index of the medium

question

Microbial Size

answer

Eukaryotes 10-100 micrometers
Prokayotes 0.4-10 micrometers

question

Empty Magnification

answer

Increases the size of the image but the resolution isn't changed, no new information about the picture can be seen

question

Bright field microscopy

answer

light goes through the specimen to view it.

question

Dark-field microscopy

answer

Uses scattered light to detect objects too small to be resolved by light rays
advantage- extremely small microbes and thin extracellular structures can be detected
disadvantage- shape of objects isn't resolved, dust particles can obscure image

question

Phage contrast microscopy

answer

super imposes refracted and transmission light to reveal differences in refractive index patterns
adv- live cells with transparent cytoplasm and organells of eukaryotes can be observed with high contrast
disadv.- phase contrast less effective for organisms with cytoplasm at low refractive index

question

Confocal Microscopy

answer

confocal laser scanning microscopy, both excitation light and emitted light are focused together
-can visualize cells in 3 dimensions
-allows observation of live microbes in real time

question

Electron Microscopy

answer

Sample is coated with heavy metal to absorb electrons
-electric beam and sample are in vacuum
-lenses are magnetic fields

question

cryo-EM

answer

sample is flash frozen so crystals aren't produced
cryo-electron tomography- generates high resolution models of viruses
-sample doesn't have to be thin-sliced

question

Atomic Force Microscopy

answer

measures van der Waals forces between electron shells of adjacen atoms of the cell surface and the sharp tip

question

X-ray diffraction analysis

answer

Samples are crystallized, beam is shot at sample and the position of atoms are computed based on the scattered X-rays
-shows 3d form of cell components at atomic level
-helps relate structure to function

question

How do double bonds affect fatty acid chains of membrane lipids?

answer

If the chain is unsaturated (contains one or more double bonds) and the double bond is cis it creates a "kink" in the oleic acid so that the chains don't pack as tightly and the membrane is more fluid
-some side chains can even form cyclopropane which will stiffen the membrane, this is usually in response to a stress like starvation or acidity.

question

What else do cells have that stiffen the membrane?

answer

Membranes use planar molecules that fill gaps between hydrocarbon chains to reinforce the membrane.
In eukaryotes these are called sterols, for ex. cholesterol
In bacteria the same function is done by pentacyclic hydrocarbon derivatives called hopanoids or hopanes

question

Archaea cell membranes

answer

use a ether link between glycerol and fatty acid instead of an ester link. Ether link is a lot more stable. They also are branched terpenoids. these help strengthen the membrane, but limit movement. Some may even have diglycerol tetraethers, which generate a lipid monolayer.

question

What can travel across the cell membrane without help from a protein transporter?

answer

Small uncharged molecules, such as O2 and CO2 easily permeate the membrane by diffusion.
Water can diffuse across the membrane through osmosis
Weak acids and weak bases can also diffuse across the membrane and change the pH of the cell.

question

Gram-positive cell wall

answer

Thick cell wall, contains multiple layers of peptidoglycan, interpenetrated by teichoic acids and a cytoplasmic membrane

question

Gram-negative cell wall

answer

Thin cell wall, has an outer membrane consisting of lipopolysaccharide and protein, periplasm, one to three layers of peptidoglycan and a cytoplasmic membrane

question

Peptidoglycan

answer

peptidoglycan makes up the cell wall, it helps confer the cell shape and also prevents osmotic lysis. The entire cell wall is a single molecule.

question

Lipopolysaccharide (LPS)

answer

on the outside membrane of gram negative cells, have short fatty acid chains, It acts as an endotoxin, and endotoxin is a cell component that is harmless as long as the pathogen remains intact, but when released by a lysed cell, endotoxin overstimulates host defenses.

question

Lipoproteins

answer

connect outer membrane to cell wall of gram negatives, the major one is called murein lipoprotein

question

Periplasm

answer

contains 30 to 50 different proteins in high concentration, hydrolytic proteins to process nutrients (nuclease, proteases, phosphatases)
Binding proteins which transport molecs across membrane
Chemoreceptors that signal to cytoplasm

question

S-layer

answer

sort of an outer membrane for gram positive bacteria, it is a rigid structure made up of proteins that forms a smooth layer around the cell wall. substances can pass through in either direction

question

Capsule

answer

firmly attached to cell wall, excludes small molecules, composed of polysaccharide or protein, protects cells from phagocytosis

question

Pili and Fimbriae

answer

Proteinaceous filamentous structures on the surface of bacteria
Fimbriae allow organisms to attach to surfaces including host cells in pathogen-host interactions
Pili are longer appendages, allow bact to mate (sex pilus) or move

question

Stalks

answer

attachment organelle, membrane-embedded extension of cytoplasm, the en of stalk secretes holdfasts, which are polysaccharides that firmly attach bacteria to an environment that has proved favorable

question

Flagella

answer

Organelle of mobility in bact., have a helical structure, spin to push or pull bacteria through liquid medium

question

How are flagellum powered?

answer

Proton motive force is the energy source for a flagellum, transport about 1000 protons for each revolution

question

The nucleoid

answer

DNA must be highly condensed to fit into cell, negative phosphate charges on DNA backbone must be neutralized b polyamine and Mg++, DNA is negatively supercoiled, this condensed form is maintained by small positively charged DNA binding protiens

question

Bacterial cytoskeleton

answer

Bacteria and archaea have cytoskeletal proteins, Tubulin homologs are found in both and are involved in cell division, actin homologs are found in both and again involved in cell division and shape

question

Specialized Structures: Thylakoids, Carboxysomes, and Gas vesicles

answer

Thylakoids- extensively folded intracellular membranes
Carboxysomes- polyhedral bodies packed with enzyme Rubisco for CO2 fixation
Gas vesicles- to increase buoyancy, filled with gases that are dissolved in cytoplasm, water cannot enter

question

Carbon Storage

answer

Polyhydroxybutyrate (PHB) is brroken down to acetyl-CoA when energy is needed, feeds into TCA cycle
Glycogen also used as storage, broken down into glucose-1-phosphate by glycogenolysis, which feeds into glycolytic pathway

question

Phosphate and sulfur storage

answer

Phosphate stored in the form of polyphosphate can be broken down for use in nucleic acid and phospholipid synthesis
Hydrogen sulfide is oxidezed to sulfur during chemolithotrophy, and stored in globules

question

Endospores

answer

highly resistant form of bacteria, dehydrated, dormant, resistant to many stresses

question

Autotrophs

answer

fix CO2 and assemble into organic molecules (mainly sugars)

question

Heterotrophs

answer

used preformed organic molecules

question

transport of nutrients

answer

ventry=Ventry[S]ext/KD+[S]ext
ventry is the velocity of entry, Ventry is the maximum velocity of entry, [S]ext is the external concentration of the nutrient, and KD is the dissociation constant of the permease for the nutrient

question

Facilitated Diffusion

answer

Permease required (transport protein), no energy required, goes down concentration gradient

question

Active transport

answer

uses permeases and energy source to move nutrients against concentration gradient

question

Siderophores

answer

specialized molecules secreted to bind ferric ion (Fe) and transport it into the cell
-iron is released into the cytoplasm and reduced to the more useful ferrous form

question

Balanced Growth of Bacteria

answer

state in which bacteria adapted to growth medium and are doubling in biomass accompanied by a doubling in all measureable properties of population (cell number, protein content, DNA, etc.)

question

what is MreB

answer

MreB determines cell shape is homologous to actin and forms a filament like cytoskeleton, also directs synthesis of peptidoglycan prior to cell divison

question

FtsZ

answer

Fts proteins form the divisome, FtsZ forms ring around the center of dividing cell, homolog of tubulin

question

Min proteins

answer

Min proteins align the divisome, others inhibit cell division by preventing stable association of FtsZ, as cell grows longer Min proteins spend more time at ends of cell and allow FtsZ ring to form in the center

question

Peptidoglycan growth

answer

Bactoprenol carries peptidoglycan subunits across membrane, Hydrolases make openings in murein wherethe subunits are added. Transpeptidases carry out crosslinking
good target for antibiotics since eukaryotes don't have peptidoglycan
Transpeptidase inhibited by penicillin

question

Petroff-Hauser counting chamber

answer

used to count total number of cells. averages the amount of organisms in each square to find total

question

Coulter counter

answer

Particle counter used for any cell, works by detecting change in electrical conductance of a small aperture as fluid containing cells are drawn though

question

Optical Density

answer

decreases absorbance due to light scattering from cells. light scattering depends on size of particle, standard curves must be prepared to compare OD to some other measurement of cell number

question

Nephelometry

answer

measure the scattered light by having the phototube at an angle to the incident light, scattered light is measured, more sensitive than absorbance

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